|
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by Michael Meltzer

NASA SP-2011-4234
 Library of Congress Cataloging-in-Publication Data

Meltzer, Michael.

 When biospheres collide : a history of NASA’s planetary protection 

programs / by Michael Meltzer.

 p. cm. -- (NASA SP ; 2011-4234)

 Includes bibliographical references and index.

 1. Space pollution. 2. Space environment. 3. Outer space--

Exploration--Environmental aspects. 4. Environmental protection--

Moral and ethical aspects. I. Title.

 TL1499.M45 2010

 363.739--dc22

 2008005759
CONTENTS

List of Figures vii

List of Tables xi

Preface xiii

Foreword xv

Acknowledgments xix

Chapter 1: Why We Must Protect Planetary Environments 1

Chapter 2: In the Beginning: The Need for Planetary 

Protection Is Recognized 15

Chapter 3: Developing Effective Planetary Protection 

Approaches 77

Chapter 4: Back Contamination: The Apollo Approach 113

Chapter 5: Planetary Protection for Mars: The Viking Experience 247

Chapter 6: Small Bodies of the Solar System 301

Chapter 7: Return to Mars 359

Chapter 8: Do We Have the Right To Contaminate? The Ethical 

and Legal Aspects of Planetary Protection 433

Chapter 9: Conclusion 457

Appendices 461

A. Detailed Planetary Protection Requirements 461

B. The Impact of “Faster, Better, Cheaper” on Planetary Protection Priorities 471

C. Biohazard Identification: The Synergism Between Bioterror Prevention 

and Planetary Protection Research 474

D. Committees, Organizations, and Facilities Important to the Development 

of Planetary Protection 476

E. Timeline of Important Planetary Protection–Related Events 481

F. Planetary Protection Approaches Used on Various Missions 484

Acronyms and Abbreviations 493

The NASA History Series 497

Index 515

v
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LIST OF FIGURES

Image Page Description

2.1 17 Joshua Lederberg in a laboratory at the University 

of Wisconsin, October 1958. (National Library of 

Medicine BBBAAW)

2.2 17 Nobel Laureate Melvin Calvin. (Lawrence Berkeley 

National Laboratory image 96502090)

2.3 29 USSR scientist Anatoli A. Blagonravov, who helped to 

launch Sputnik and worked to establish cooperation 

in space between the United States and the USSR.

2.4 35 Carl Sagan with a model of the Viking Mars lander in 

Death Valley, California.

2.5 41 Abe Silverstein, NASA Director of Space Flight 

Programs and an advocate of spacecraft sterilization. 

(Glenn Research Center image 174771)

3.1 89 Estimating the quantity of contamination reaching Mars.

3.2 95 Typical probability distribution of viable organism (VO) quantities reaching and surviving on the 

Martian surface.

4.1 212 Flotation collar attached to the Columbia Command 

Module. (S69-21698)

4.2 214 The Apollo 11 crew, wearing biological isolation garments (BIGs), leave the helicopter that carried them 

from the Command Module and walk across the deck 

vii
When Biospheres Collide

of the USS Hornet toward the Mobile Quarantine 

Facility (MQF). (S69-40753)

4.3 216 President Nixon welcomes the Apollo 11 astronauts 

aboard the USS Hornet. (S69-21365)

4.4 217 Apollo 11 Command Module and its flotation collar 

hoisted aboard the USS Hornet. (S69-22185)

4.5 218 The first Apollo 11 sample return container is 

unloaded at the Lunar Receiving Laboratory (LRL). 

(S69-39996)

4.6 220 LRL functional areas. (S67-00696)

4.7 220 Sample operations area details. (S66-08384)

4.8 223 The first lunar sample photographed in detail at LRL. 

(S69-45025) 

4.9 224 Lunar material in a sieve from the bulk sample 

container being examined in an LRL glove box. 

(S69-40749)

4.10 232 Radiation counting laboratory. (S67-00689)

4.11 239 USS Hornet, prime recovery vessel for Apollo 12, 

moves toward the Command Module. (S69-22897)

5.1 249 Elements of the Viking Lander Capsule (VLC).

5.2 250 The Viking lander.

5.3 251 Viking spacecraft under assembly at Martin 

Marietta Aerospace near Denver, Colorado. 

(GPN-2000-001630)

viii
List of Figures

5.4 252 Joshua Lederberg with a model of the Viking 

spacecraft and launch vehicle. (National Library of 

Medicine and NASA file)

5.5 267 The Viking bioshield.

5.6 269 The Viking gas chromatograph mass spectrometer 

(GCMS).

5.7 272 Sterilization activity sequence.

6.1 320 A cutaway view of the possible internal structure of 

Europa. (PIA01082)

6.2 345 An artist’s concept of Stardust sample return capsule 

(SRC) parachuting down to Earth, bringing samples 

of comet particles and interstellar dust. (PIA03184)

6.3 346 The Stardust sample return capsule was transported 

by helicopter from its landing site at the U.S. Air 

Force Utah Test and Training Range. (PIA03671)

6.4 346 Mission staff prepare to remove an aerogel particle collection grid from the Stardust SRC. 

(KSC-98PC-1870)

6.5 347 A closeup view of a cometary impact into aerogel. 

(JSC2006-E-01008)

6.6 347 An artist’s concept of the Genesis spacecraft in its 

collection mode, opened up to catch and store samples of solar wind particles. 

7.1 391 Assembly of the Mars Climate Orbiter (MCO). 

(GPN-2000-000498)

7.2 399 Phoenix spacecraft assembly, with Lockheed Martin 

Space Systems technicians working on the science 

deck of NASA’s Phoenix Mars Lander. (PIA09203)

ix
When Biospheres Collide

7.3 408 Mars Global Surveyor evidence of recent liquid water: 

gully landforms possibly caused by geologically 

recent seepage and runoff. (PIA01034)

7.4 409 Gullies eroded into the wall of a meteor impact crater. 

(PIA01035)

7.5 415 Scientists have speculated that the tube-like structures in these electron microscope images may be 

microscopic fossils of primitive, bacteria-like organisms that lived on Mars more than 3.6 billion years 

ago. (PIA00284) 

7.6 416 An artist’s concept of the launch of a Martian sample 

back toward Earth. (PIA05488)

x
LIST OF TABLES

Table Page Description

3.1 84 Suballocations by nation—probability limits on 

contaminating a target planet during the period of 

biological interest.

4.1 139 Membership of the Interagency Committee on Back 

Contamination.

4.2 143 Candidate facilities for lunar crew quarantine.

4.3 160 Lunar Receiving Laboratory conceptual studies and 

site evaluations.

5.1 264 A comparison of nickel-cadmium (NiCd) and silverzinc (AgZn) batteries.

7.1 366 Summary of target body/mission type categories.

7.2 377 Planetary protection activities during different Mars 

Observer mission phases.

7.3 378 Mars Observer impact probability estimates and 

requirements.

xi
When Biospheres Collide

Reference Note

Many footnotes in this book cite Internet-based sources. Inevitably, 

some pages on the World Wide Web do not last forever. If you are trying 

to locate a source whose URL no longer works, you may contact the 

NASA History Program Office at NASA Headquarters for help (e-mail 

histinfo@hq.nasa.gov). Their Historical Reference Collection contains 

hard copies of many of the online sources cited in this book, and even 

if they do not have the one you are seeking, they may be able to assist 

you in locating it.

xii
PREFACE

Col. Ross: “Is there any point to which you would wish 

to draw my attention?”

S. Holmes: “To the curious incident of the dog in the 

night-time.”

Col. Ross: “The dog did nothing in the night-time.”

S. Holmes: “That was the curious incident.”

—The Memoirs of Sherlock Holmes 

by Sir Arthur Conan Doyle (1893)

Significant challenges abound in the astrobiological study of the 

solar system, similar to those faced by Sherlock Holmes in another context. In the search for extraterrestrial life, a negative result is nearly 

impossible to obtain, much less interpret. We are bathed in Earth 

organisms, which makes finding our own kind of life palpably easy and 

detecting indigenous life on other worlds much more difficult. We are 

not exploring the solar system to discover life that we have brought with 

us from home, and we are aware that Earth organisms (read: invaders) 

could very well erase traces of truly extraterrestrial life.

Likewise, we don’t know what would happen if alien organisms 

were introduced into Earth’s biosphere. Would a close relationship (and 

a benign one) be obvious to all, or will Martian life be so alien as to be 

unnoticed by both Earth organisms and human defenses? We really 

have no data to address these questions, and considerate scientists 

fear conducting those experiments without proper safeguards. After 

all, this is the only biosphere we currently know—and we do love it!

xiii
When Biospheres Collide

With this volume, Michael Meltzer details the fascinating history of 

our attempts at planetary protection and those who have worked to protect Earth from otherworldly organisms, while safeguarding other worlds 

from the all-too-pervasive life on Earth. Such a history is particularly 

important at this time, since it provides a point of departure for understanding the field as we undertake further explorations. Meltzer’s work 

will help us face what may well be a crucial topic in the future of the 

science of life and the future of humans in space.

John D. Rummel, Senior Scientist for Astrobiology

NASA Science Mission Directorate, Planetary Sciences Division

xiv
FOREWORD

The question of whether there is life on other planetary bodies became directly relevant to astronomy in the Renaissance, when 

Galileo made his observations confirming that the wandering “planets” 

might actually be objects similar to our own Earth, traveling around 

the Sun. (Previously, this question had been the purview of philosophers. In the fourth century BC, Metrodorus of Chios neatly summed 

up the attitude of his mentor, Epicurus, toward extraterrestrial life: 

“To consider the Earth as the only populated world in infinite space is 

as absurd as to assert that in an entire field of millet, only one grain 

will grow.”) In the 19th century, Schiaparelli’s description of “canali” 

(channels) on Mars encouraged Percival Lowell to depict canals, which 

might have been built by a dying civilization on a nearly dead planet. 

Such a Martian civilization was represented as hostile by H. G. Wells, 

who imagined that such a race would covet a warm and wet Earth, 

and might invade with the intention of conquering our more comfortable planet. In Wells’s fantasy, Earth fights back, and the Martians are 

themselves conquered by the least of Earth’s inhabitants: the microbes. 

Planetary protection addresses the real consequences that might 

result from an actual transfer of biological material between different 

planets if indeed life does exist on other worlds. We know, from many 

experiences over centuries of transporting organisms from one location to another on Earth, that such transfers are not always harmless. 

Fleas brought to Europe in the 1300s carried the Black Death plague 

that caused the most significant reduction of the global human population in documented history. Early interactions with native inhabitants 

of the “New World” by Columbus and subsequent European explorers inadvertently infected them with European diseases, engendering epidemics that caused the collapse of several civilizations before 

Europeans were quite aware that they existed much less had any 

opportunity to study or learn from them. Recently, the transport of 

“invasive species,” such as zebra mussels and purple loosestrife, has 

xv
When Biospheres Collide

been widely recognized to cause significant damage to local ecologies 

and economies, though not directly causing human diseases. These 

issues have been in the forefront of public consciousness throughout 

the last and the current centuries. It was in an effort to minimize the 

potential for negative consequences from space exploration that planetary protection was first initiated as this volume describes.

Being the NASA Planetary Protection Officer, it is my job to ensure 

that our space exploration efforts neither unintentionally contaminate 

other solar system bodies, nor Earth upon spacecraft return. However, 

my interest in planetary protection is much more personal. As part of 

my laboratory’s research on muscle atrophy, my first spaceflight experiment was flown on the last mission of the Space Shuttle Columbia

that tragically disintegrated during reentry on 1 February 2003. 

Surprisingly, when we opened our recovered hardware several months 

after the accident, many of our experimental animals had survived the 

crash. Inadvertently, our research had demonstrated that, if properly 

shielded, even multicellular animals could survive a meteoritic-style 

entry event, one of the key steps required for the natural transport of 

living organisms between planetary bodies. This recognition makes 

it even more critical that we don’t carry life from Earth with us on 

missions to search for life elsewhere—otherwise, if we find some, we 

might not be able to tell the difference!

When Joshua Lederberg first raised his concerns about planetary 

protection in the 1950s, we had no evidence that there was another 

place in the solar system where life could exist. We now know much 

more about our planetary neighbors, and from the data we have currently, we can say confidently that there are conditions present on 

or in other solar system bodies that do not exclude the possibility of 

Earth life surviving there. Although the surface of Mars is cold and dry, 

the subsurface is likely to be warmer and wetter, and we know that 

organisms on Earth survive kilometers beneath the surface, gathering energy from the rocks that surround them. Likewise, the surface 

of Europa, a moon of Jupiter, is frozen and exposed to high levels of 

hard radiation; however, the subsurface contains a thick (~100 km) 

layer of liquid water, overlaid by ice and at the bottom in contact with 

Europa’s rocky interior. Tidal stresses appear to keep Europa warm, 

which raises the possibility that hydrothermal vent systems, known 

to support abundant life on Earth, may also be present in a Europan 

ocean. With our increasing knowledge about life on Earth, and about 

xvi
Foreword

conditions favorable for life on other planets, our responsibility also 

increases to carry out solar system exploration in a manner that does 

not contaminate the target locations that we want to explore, nor 

Earth with samples of planetary materials that we choose to return.

When Biospheres Collide provides an excellent grounding in the 

history and fundamentals of planetary protection, as well as an overview of recent and ongoing activities within NASA’s programs. The 

public can be proud of the way that NASA has responded to planetary 

protection concerns, with its efforts to act responsibly, communicate 

openly, and address effectively the potential for contamination. Those 

who do not learn from history may be doomed to repeat it, but it is 

to be hoped that NASA’s future activities in planetary protection will 

demonstrate that those who do learn from history may also repeat at 

least some of the past’s successful efforts. This current volume is a 

valuable contribution to that capability. 

Cassie Conley, NASA Planetary Protection Officer

xvii
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ACKNOWLEDGMENTS

Many people gave me vital information for this book, and I want to 

thank them for their time as well as interest in the project. Some of 

these people include:

John Rummel, who shared many stories and articles from his 

decades in the planetary protection field.

Perry Stabekis for his insights on the evolution of the field. 

Craig Fischer, whose tour of the former Lunar Receiving Laboratory 

and whose many anecdotes were key in understanding the Apollo mission.

John Stonesifer for his memories of the Apollo mission.

Don Larson for a wonderful tour of Lockheed Martin spacecraft 

cleaning and assembly facilities. 

Ben Clark, for his perspectives on different types of Mars missions.

Margaret Race for her perspectives on the ethical aspects of the field.

Cassie Conley for her views on the importance of planetary protection.

Thanks also to the insights and data provided by Kent Carter, Judy 

Allton, Martin Favero, John Hirasaki, Richard Green, David Schultz, 

Wayne Koons, Roger Launius, Israel Taback, Linda Billings, James 

Young, Dennis Vaughn, Bruce Keller, Bob Polutchko, Tom Young, Brad 

Perry, and Bob Clark. Also thanks to Bob Fish for his tour of the USS 

Hornet. Several of the people who taught particularly instructive 

planetary protection-related classes include Jack Barengoltz, Michele 

Bahr, Amy Baker, Gary Coulter, Margaret Race, John Rummel, Perry 

Stabekis, and Dave Tisdale. 

Johnson Space Center and Langley Research Center archival personnel who helped on the research for this book include Shelly Kelly 

and Gail Langevin. At NASA Headquarters, thanks to Steve Dick for 

his guidance and support throughout the project. Archivists Colin 

Fries and Jane Odom were very helpful in finding key material from 

the NASA Historical Reference Collection. Steve Garber oversaw the 

book’s production process, while Nadine Andreassen was a valuable point of contact for all things NASA. Many thanks to the fine 

xix
When Biospheres Collide

individuals at Headquarters responsible for the finishing of this book: 

Stacie Dapoz and Andrew Jarvis carefully copyedited this volume; 

Chris Yates meticulously handled the layout; and Gail Carter-Kane 

oversaw this team with unwavering patience and support.

And finally, thank you to my wife, Naisa, for her spiritual advice 

and affection, and to my daughter, Jordana, for her inspiration. This 

book is also in remembrance of Robert Meltzer, who brought such joy 

to the world.

xx
1 WHY WE MUST PROTECT 

PLANETARY ENVIRONMENTS

The 20th Century will be remembered, when all 

else is forgotten, as the century when man burst his 

terrestrial bonds.

—Arthur Schlesinger, Historian1

From the time that humans first began sending spacecraft out from 

Earth, the possibility has existed of forever changing the extraterrestrial environments that we visit. If we irrevocably alter the nature of 

other celestial bodies, we compromise all future scientific experimentation on these bodies and may also damage any extant life there. By 

inadvertently carrying exotic organisms back to Earth on our spaceships, we risk the release of biohazardous materials into our own ecology. Such concerns were expressed by scientists from our country and 

from other nations shortly before the launch of Sputnik, and these 

concerns have continued to be addressed through the present day. Our 

human race has a great urge to explore the unknown, but this must be 

done in a responsible manner that considers the potential impacts of 

our actions on future exploration.

Exploration: A Basic Ingredient of Our Society

Since long before the founding of the United States, the need 

to explore has permeated our culture. The American colonies were 

 1. Arthur Schlesinger, Jr., quoted in, 

1
When Biospheres Collide

created by adventurers bent on finding and settling new, fertile places, 

and this spirit of discovery has continued through the years. From 

1840 through 1860, the United States spent one quarter of its annual 

budget on naval expeditions.2 And in the 1950s, a new frontier was 

added to those of land and sea exploration: space. 

The historian Daniel Boorstin has said that we humans are discoverers with a burning “need to know.”3

 It is part of what makes us 

human. But how we address this need is critical, particularly in our 

exploration of space, because the choices we make will affect the 

integrity of the data that scientists in the centuries ahead will use 

for their investigations. We thus have a responsibility to conduct our 

explorations of celestial bodies with as much wisdom and consideration of future generations as we can muster.

In the 1800s, land and sea exploration played an important role in 

maintaining the United States’ vitality. In the 20th century after the 

Space Age began, new imperatives were created. One of these was to 

investigate other worlds and contrast them with our own.4

Jerome B. Wiesner, a Massachusetts Institute of Technology (MIT) 

professor who advised Presidents Eisenhower and Kennedy on space 

issues, understood the critical nature of the space challenge. Wiesner 

chaired a transition team for space that wrote a key report in 1961 for 

President-elect Kennedy, which recognized the influence that space 

exploration would have in establishing our country’s place in the 

world. In the report’s section on “principal motivations for desiring a 

vital, effective space program,”5 the many expected benefits of exploring space were addressed, one of which was the major benefit to our 

nation expressed by the following statement: 

 2. Steven J. Dick, “Why We Explore,” 

2
Why We Must Protect Planetary Environments

First, there is the factor of national prestige. Space 

exploration and exploits have captured the imagination 

of the peoples of the world. During the next few 

years the prestige of the United States will in part be 

determined by the leadership we demonstrate in space 

activities.6

The author James Michener also understood the importance of 

space exploration. He believed that we as a culture have to express 

our need to explore or risk losing a vital momentum. He recognized 

that at different times in a nation’s life, different goals had to be 

pursued. In an address to Congress, Michener asserted that “there 

are moments in history when challenges occur of such a compelling 

nature that to miss them is to miss the whole meaning of an epoch. 

Space is such a challenge.”7

As our ability to explore other worlds developed, our “intent to 

travel in space [increased] with irresistible force.”8 At the heart of this 

endeavor was, in part, a yearning to establish that we Earthlings are 

not alone in the universe.9 In the words of Lawrence B. Hall (when he 

was NASA’s Special Assistant for Planetary Quarantine) and colleagues, 

“A most urgent, perhaps the most urgent, question to be answered by 

instrumented flights relates to the existence of life on the planets. An 

affirmative answer to this question has biological, medical, and even 

religious implications that far transcend the results to be obtained by 

mere geographical and physical exploration of the planets.”10

Randolph et al. expand on this theme in their paper examining 

the theological and ethical consequences of discovering life on other 

worlds, when they write about the types of life that might be found. We 

may one day discover a Martian life-form that is biochemically similar 

to life on Earth due to the large amounts of material that have been 

 6. Wiesner, 

3
When Biospheres Collide

exchanged between the planets from meteorite and asteroid impacts. 

This would indeed be a world-shaking event. But discovering life on 

Mars that had an independent genesis from life on Earth would have 

considerably deeper scientific, ethical, and religious implications. Such 

a discovery would suggest that if two independent forms of life could 

have arisen in just our solar system, and that if Earth-like or Marslike planets existed elsewhere, then life might well be commonplace 

throughout our galaxy.11 A discovery of such ubiquitous life, some of 

which might have high intelligence, would call into question how special our particular human life-form is. A traditional Judeo-Christian 

belief is that we humans were created in God’s image.12 This belief 

might be challenged if space exploration establishes that we are just 

one of many sentient species in the universe.

Exploring Without Disrupting Zones of Life

Planetary protection is a field concerned with keeping actual or 

possible “zones of life”13 pure and unspoiled. A planet’s biosphere is its 

complete zone of life, its global ecological system,14 and includes all its 

living organisms as well as all organic matter that has not yet decomposed. The term biosphere is frequently used today, but it is not a new 

concept. It was introduced by Eduard Suess, a professor of geology at 

the University of Vienna, in his four-volume treatise, Das Antlitz der 

Erde (The Face of the Earth), whose English version was published in 

1904.15 The Russian scientist Vladimir Vernadsky then popularized 

this term in his 1926 book, The Biosphere.16

 11.

4
Why We Must Protect Planetary Environments

Why Prevent Planetary Contamination?

A Necessary Condition for Good Space Science

Boorstin, Wiesner, and Michener recognized that exploration of 

new frontiers is a human imperative and that, at times, the health 

and vibrancy of our civilization may depend on it. But breaking new 

ground in the quest for human knowledge carries with it certain risks, 

and we explorers have a responsibility to understand those risks and 

address them intelligently. Planetary protection concerns itself with 

the quest to explore space responsibly under conditions of extreme 

uncertainty. This is no trivial matter, since the possible biospheres 

that we may encounter, and the impacts on them of our exploration 

efforts, are extremely difficult to forecast. John Burton Sanderson 

“J. B. S.” Haldane, the British geneticist, biologist, and popularizer of 

science, expressed the difficulty of envisioning another biosphere’s 

nature when he said, “Now my own suspicion is that the Universe 

is not only queerer than we suppose, but queerer than we can

suppose.”17 And yet we still have to act as best we can. John Rummel, 

NASA’s former Planetary Protection Officer (PPO), stated the problem 

of responsible interplanetary exploration like this: “Ignorance is not 

bliss. We don’t know what we’re doing, so let’s not do things that we 

can’t account for.”18

In trying to envision possible forms of life, or environments that 

could eventually lead to life, we are limited by a lack of perspective. So 

far, humans have only been able to study Earth life. Although this life 

can exist in wildly different environments, from volcanic ocean vents 

 17.

5
When Biospheres Collide

to the insides of ice formations, all of Earth life appears to be related, 

making use of the same basic biochemistry. In contrast, we have no 

data whatsoever on alternative chemistries that may also prove feasible for supporting life not as we know it, but of an entirely exotic, 

unrelated form. The space science community places high value on 

accurately determining what is currently unknown about other worlds. 

To accomplish this, we must protect extraterrestrial environments that 

may harbor undiscovered life-forms, at least until we have thoroughly 

examined those environments and analyzed any living organisms that 

exist within them.

Although we don’t know what we will find on other worlds, we can 

posit certain environmental conditions that appear critical to the origin of life-forms. These conditions include the following:

 A source of organic compounds.

While liquid water is typically mentioned as another essential for 

life—at least as we know it—some scientists have hypothesized that 

on very cold planetary bodies, liquid ammonia might have served in 

place of water to incubate life. Others have suggested that oceans 

of methane or other hydrocarbons on bodies such as Saturn’s moon 

Titan could have served that purpose.20

On Earth, the critical environmental conditions mentioned above 

might have converged and led to the formation of life in the following 

way: asteroids, comets, meteorites, and interplanetary dust carried 

organic compounds to Earth, which were then used in the formation 

of functional biomolecules, energy transference, and the development of cellularity. Such events should have been possible not only 

on Earth, but also on other bodies of the solar system. A second 

theory of life’s origins involves endogenous formation of organic molecules (i.e., without dependence on sources external to the planet), 

driven by either naturally occurring atmospheric energy discharges 

 19.

6
Why We Must Protect Planetary Environments

or through the processing of materials within hydrothermal environments. A version of this theory was espoused by Darwin over a 

century ago when he envisioned the growth of organic compounds in 

“some warm little pond.”21

A combination of these mechanisms could have contributed to the 

formation and development of life’s building blocks on Earth. Recent 

data such as those from Earth’s extremophiles suggest that once life 

did emerge, it would have used every available environmental niche 

and energy source, both photosynthetic and chemosynthetic, to support itself.22

We cannot expect to find many warm little ponds during our 

searches for, and attempts to protect, extraterrestrial biospheres or 

prebiotic environments. We need instead to conceptualize a range of 

exotic conditions that could lead to organic molecule development followed by the origin of life. Possible energy sources for these processes 

could range from the freeze-thaw cycles encountered on an ice world 

to tidal heating to the temperature variations that might be found in 

deep-sea hydrothermal systems.

Ethical Questions

Today’s planetary protection policy is dominated by a very practical consideration—the safeguarding of scientific investigations,23 and 

it is debatable to what extent ethical considerations affect the formulation of that policy. According to Pericles “Perry” Stabekis, a longtime NASA contractor who has served on the staff of every one of the 

Agency’s planetary protection officers,

Planetary protection does not have by policy an 

ethical component. So as it stands, it is not there to 

protect the planets for the planets’ sake. It is to protect 

 21.

7
When Biospheres Collide

the planets for preserving them as a target of biological 

exploration. [author’s italics]  .  .  . So clearly the 

mandate of planetary protection is not one that is based 

on the ethics of the question, but on preserving our 

ability to explore them biologically . . . to keep them . . . 

as pristine as warranted to protect that exploration. . . . 

It’s strictly to protect science. Planets for the sake of 

science.24

It could be argued, however, that the perceived need to conduct 

good scientific investigations is indeed an ethical position, and a 

strongly held one, given the amount of money and effort that NASA 

has spent on planetary protection.

Our desire to conduct space exploration and search for extraterrestrial life in a scientifically rigorous manner that will produce supportable results dictates that we protect planetary environments until 

the period of biological interest is over. But should we also protect 

planetary environments beyond that time, and for reasons that are not 

as pragmatic as conducting good science? Should we, in fact, preserve 

planets in their pristine state because it is the right thing to do?

Patricia Sterns and Leslie Tennen, two attorneys writing about 

celestial environmental protection, hold a view that resembles a physician’s commitment to do no harm, asserting that “purity of ecosystems throughout the universe must be respected in order to ensure 

the natural evolution of the heavens and their diverse planets.”25

Randolph, Race, and McKay stress the importance of protecting interplanetary diversity, writing that “from an ethical point of view, the 

need to preserve a life-form, however lowly, must be more compelling if that life-form represents a unique life-form with an evolutionary history and origin distinct from all other manifestations of life.” 26

 24.

8
Why We Must Protect Planetary Environments

Furthermore, finding a life-form whose origin is distinct from earthly 

life-forms, write Race and Randolph, has much more significant ethical implications than if the life-form’s genetics and biochemistry are 

closely related to Earth organisms. Exotic life-forms with different 

evolutionary histories than our own would necessitate that we “begin 

developing a broader theory of life”27 and its origins.

President Lyndon Johnson recognized the need to maintain the 

purity of ecosystems, although it is not clear whether protecting such 

ecosystems was based solely on scientific and political grounds or on 

ethical grounds as well. On 7 May 1966, Johnson issued a statement 

proposing a treaty that would govern space exploration activities in 

order to, among other objectives, “avoid harmful contamination” of 

celestial bodies.28 The United States submitted a draft of this treaty 

to the United Nations (UN) in June 1966. The language of the draft 

document was preserved in Article IX of the 1967 UN Treaty on 

Principles Governing the Activities of States in the Exploration and 

Use of Outer Space, Including the Moon and Other Celestial Bodies, 

or “Outer Space Treaty” (discussed later in the book), which called for 

avoidance of harmful contamination of the Moon and other celestial 

bodies, but did not specifically define what would constitute “harmful contamination.” Was it that which negatively impacted planetary 

ecologies, or just scientific endeavors?29

This ambiguity continued in more recent treaties. Article 7 of 

the 1984 UN Agreement Governing the Activities of States on the 

Moon and Other Celestial Bodies (the “Moon Agreement”) included 

a directive that specifically addressed the need to preserve nature’s 

equilibrium when it stated that all parties to the agreement “shall 

take measures to prevent the disruption of the existing balance of [the 

Moon’s] environment, whether by introducing adverse changes in that 

environment, by its harmful contamination through the introduction 

 27.

9
When Biospheres Collide

of extra-environmental matter or otherwise.”30 But this directive also 

stopped short of stating why the lunar environment must be protected, 

whether only for science’s sake or also to support an ethical position. 

The ethical position that the Moon Agreement does put forth is the 

right of all countries to have the same access to the Moon and to all 

planets, expressed in the statement, “. . . to promote on the basis of 

equality the further development of co-operation among States in the 

exploration and use of the moon and other celestial bodies.”31

The Soviet Union issued statements that also recognized the need 

to protect celestial ecologies. In its 1971 “Draft Treaty Concerning 

the Moon”32 presented to the UN General Assembly, Article VI called 

for “avoiding the disruption of the existing balance of the lunar 

environment.”33 Earlier, the USSR had proposed a clearly ethical position regarding space exploration. In March 1962, Chairman Khrushchev 

wrote to President Kennedy regarding “heavenly matters,”34 in which 

he urged that “any experiments in outer space which may hinder the 

exploration of space by other countries” should be discussed and agreements reached “on a proper international basis.”35 This and other Soviet 

proposals strongly linked the issue of contamination to the potential 

for interfering with the rights of states to achieve their own outer space 

explorations. The USSR focus was not on the negative impacts that 

might occur to a planet, but rather on the aspirations and objectives of 

other countries.36

These and other ethical concerns regarding the conduct of planetary exploration will be discussed in greater detail in Chapter 8.

 30.

10
Why We Must Protect Planetary Environments

For How Long and to What Extent Should Planets Be Protected?

Once the decision was reached by the United States, the USSR, 

and European nations to protect planetary environments, questions 

arose regarding for how long. According to Perry Stabekis, international policies speak of preserving pristine extraterrestrial environments for a period of biological exploration. In the 1960s, this period 

was set at 20 years—a length of time chosen under the belief that 

in 20 years, there would be a hundred missions to each of the planetary targets. Such an intensity of exploration did not happen, and the 

length of the protection period has been extended. For certain Mars 

orbiters, for instance, limits on their probability of impact with the 

planet extend up to 50 years after launch.37

The level of precaution to be taken in protecting a planetary target 

is another topic that has been intensely debated since the beginning 

of the space program. Biological interest in a target has been key in 

determining this level of protection, as has contaminatability. For target bodies on which the scientific community believed that terrestrial 

contamination would not survive or propagate, no special protection 

was deemed necessary.38

The level of protection that we should take in preserving a planetary environment also depends on whether we view it as we do our 

terrestrial environment. The United Nations Educational, Scientific 

and Cultural Organization (UNESCO) and space science researchers 

have posited questions in this regard such as the following: 

•	 Do we have an ethical obligation to preserve a planetary 

environment to the same degree that we seek to protect our 

Earth’s environment?

•	 Does this obligation hold, even if there is no life on a planet?

•	 Or, since environmental ethics seek to benefit and enhance life, 

do we have an obligation to see that terrestrial life expands 

onto lifeless planets?

 37.

11
When Biospheres Collide

•	 Does the type of extraterrestrial life we discover determine 

the appropriate level of protection? In other words, are 

exotic microbes deserving of the same level of protection as 

intelligent life?39

This last issue has been debated by many scientists. In 1980, Carl 

Sagan took a very protective stance toward all types of life, asserting that “If there is life on Mars, I believe that we should do nothing 

with Mars. Mars then belongs to the Martians, even if they are only 

microbes.”40 Christopher McKay, a well-known planetary scientist with 

the Space Science Division of NASA’s Ames Research Center, took an 

even more radical position, suggesting that the existence of life on Mars 

obligates us “to assist it in obtaining global diversity and stability.” To 

accomplish this, we must change Mars in order “to promote the biota’s 

emergence as a global biological system controlling the planet’s biogeochemical cycles.” Microbe protection is by no means a universally held 

view, however. Robert Zubrin and Richard Wagner take the position that 

if microbes are discovered on Mars, they should be treated no differently 

than similar life on Earth, which we do not hesitate to kill.41

Overview of the Book

Chapter 2 of this book discusses the beginnings of the planetary 

protection field and how it was perceived as a necessary response to 

the space race. The tremendously important parts played by the field’s 

pioneers, such as Joshua Lederberg, Melvin Calvin, and Abe Silverstein, 

and by the initial organizations (SSB, WESTEX, UNCOPUOS, CETEX, 

COSPAR, and others) are analyzed. Both international and U.S. policy 

 39.

12
Why We Must Protect Planetary Environments

development, which occurred in parallel, are included, and the key meetings and treaties that formed the foundations of the field are highlighted. 

Chapter 2 also addresses the difficulties that arose in implementing a 

policy of international scientific community cooperation, given the antagonistic military priorities of the United States and USSR.

Chapter 3 addresses approaches for implementing effective planetary protection, including the evolving procedures and technologies 

for sterilizing spacecraft as well as the probabilistic and other bases 

for determining appropriate procedures. The work of Abe Silverstein, 

Carl Sagan, Elliott Levinthal, and others is discussed, and probabilistic approaches for spacecraft contamination control are analyzed. 

The efforts of the international body, COSPAR, are examined, as are 

NASA’s planetary protection policy development and its methods for 

assigning acceptable risks to different missions. As an example of 

NASA’s approach, an analysis is included of contamination risks on 

a mission to Mars. This is followed by sections on sterilizing lander 

capsules and Soviet approaches to planetary protection, which differed 

markedly from those of the United States.

Chapter 4 considers planetary protection in the Apollo program. 

The main issue was prevention of back contamination and exposure 

of Earth to organisms or chemicals from the Moon. Lunar Receiving 

Laboratory (LRL) design, construction, and operation are discussed, 

along with the drawn-out struggle with Congress to secure funding. Influences of the U.S. Public Health Service and the Interagency 

Committee on Back Contamination are examined regarding LRL 

design and operation, as well as the conduct of the Apollo mission. 

Chapter 5 deals with planetary protection during the Viking Mars 

lander missions and the conflicts that arose between preventing contamination of Mars and conducting a rigorous scientific investigation, 

including a critical search for life. The question is addressed, “How 

much protection is enough?” COSPAR recommendations and NASA 

requirements are also discussed. The sterilization procedures used during lander capsule manufacturing are examined, including individual 

part treatments as well as terminal sterilization of the entire lander.

Chapter 6 focuses on planetary protection considerations for the 

solar system’s small bodies, including satellites, asteroids, comets, and 

meteoroids. The relevance of extremophile forms of life is considered, 

in addition to critical conditions on small bodies that could preserve 

metabolically active organisms.

13
When Biospheres Collide

Chapter 7 returns to Mars projects, examining the orbiter and 

lander missions of the 1990s and 21st century. Methods of estimating 

potential propagation of Earth organisms on Mars are discussed, as 

well as the designated “special regions” of Mars containing frozen or 

liquid water. The evolution of Mars planetary protection policy from 

the 1970s through the 1990s and to the present day is reviewed, and 

the problems inherent in Mars sample return are examined, including 

technologies for in-flight sterilization. Procedures that will be needed 

on human missions to Mars are discussed, and the question of how 

much damage we have already done to the once pristine Martian environment is examined.

Chapter 8 tackles ethical and legal questions related to planetary 

protection. Ethical positions such as the need to preserve or steward 

planetary ecologies are discussed as bases for planetary protection 

policy, in addition to the question of whether all life-forms, rather than 

only sentient ones, qualify for moral consideration and protection. The 

chapter also includes discussions of the statutes, regulations, and treaties that helped to determine U.S. and international contamination 

prevention policies. 

The appendices discuss topics that include the planetary protection policy’s various categories of missions, the impacts on planetary 

protection of NASA’s policy shift to prioritize missions that can be 

executed more rapidly and for far less expense, synergism between 

planetary protection research and biochemical terrorism prevention 

and response, and the organizations and facilities important to development of the planetary protection field. A timeline is also included in 

the appendices depicting dates of major planetary protection events 

from the 1950s through the present.

14
The Need for Planetary Protection Is Recognized 2 IN THE BEGINNING

The human species has a vital stake in the orderly, 

careful, and well-reasoned extension of the cosmic 

frontier. . . . The introduction of microbial life to a 

previously barren planet, or to one occupied by a 

less well-adapted form of life, could result in the 

explosive growth of the implant. . . . The overgrowth 

of terrestrial bacteria on Mars would destroy an 

inestimably valuable opportunity of understanding our 

own living nature.

—Joshua Lederberg, Nobel Laureate, Professor

of Genetics, and Advocate for Planetary Protection1

From the beginning years of space exploration, space scientists 

have taken the threat of contaminating celestial bodies very seriously. In 1956, predating the USSR’s Sputnik program by a year, the 

International Astronautical Federation (IAF) at its 7th Congress in 

Rome voiced its concerns regarding possible lunar and planetary contamination and attempted to coordinate international efforts to prevent this from happening.2 But the events that most strongly instigated 

the U.S. space program and, with it, our country’s planetary protection 

 1. Joshua Lederberg, “Exobiology: Approaches to Life Beyond the Earth,” 

15
When Biospheres Collide

efforts were the 4 October 1957 launch of Sputnik I followed by the 3 

November 1957 launch of Sputnik II. 

Although the successful Sputnik launches surprised most 

Americans, proposals and serious studies for such Soviet space missions had begun years before. In 1950, the young Soviet engineer 

Mikhail Tikhonravov had written a seminal paper on the potential uses of artificial satellites. In 1954, the USSR ordered studies of 

such projects, including a focus on various engine and propulsion 

approaches. In 1955 another Soviet engineer, Sergei Korolev, formed 

a group to coordinate with Tikhonravov in developing the first artificial satellite. The USSR’s first official plan for future spaceflight was 

issued on 30 January 1956, which called for orbiting satellites by 1958, 

human spaceflight by 1964, and reconnaissance satellites by 1970.3

The Sputniks’ successful space voyages informed the world that a 

new era in technological achievement had begun, one whose outcome 

had serious consequences for the balance of the Cold War. Sputniks’ 

achievements also “shone an unwanted spotlight on American science 

policy makers.”4 Senate Majority Leader Lyndon B. Johnson thought, 

after hearing about Sputnik while hosting a barbecue at his Texas 

ranch, that “somehow, in some new way, the sky seemed almost alien.”5

In response to the Sputnik program, the United States Congress, the 

military establishment, and much of the American public demanded 

immediate scientific and technical breakthroughs to match those 

of the Soviets. Sputnik made the conquest of space a new Cold War 

imperative for the United States,6 and with this imperative came concerns about planetary contamination.

 3. Asif Siddiqi, “The Man Behind the Curtain,” 

16
In the Beginning

Figure 2.1 Joshua Lederberg in a laboratory at the University of Wisconsin, October 1958.

Figure 2.2 Nobel Laureate Melvin Calvin.

17
When Biospheres Collide

Planetary Protection Visionaries 

and Key Organizations

Several scientists raised powerful alarms during the first years of 

space exploration efforts. As the superpowers of the world raced into 

space, these scientists feared that the exploration vehicles might well 

carry not only instruments, but also a mélange of Earth microorganisms. What effect would these bacteria and viruses have on the pristine environments that they invaded? 

Scientists such as Stanford geneticist and Nobel Laureate Joshua 

Lederberg (see figure 2.1), University of California at Berkeley chemist 

and Nobel Laureate Melvin Calvin (see figure 2.2), and British biologist 

J. B. S. Haldane identified a very specific danger—that the potential 

for scientific discovery could be forever compromised if space exploration was conducted without heed to protecting the environments 

being explored. What a tragedy it would be if living organisms were 

found on a celestial body, but it could not be determined whether they 

were of alien origin or from Earth, unwanted hitchhikers on the very 

spacecraft that were there to test for life. Lederberg feared that “the 

capacity of living organisms [such as from Earth] to grow and spread 

throughout a new environment” was a matter of the gravest concern 

in our management of space missions.7 We did not know if terrestrial 

organisms would indeed grow on, or within, another body in our solar 

system. However, if the number of terrestrial organisms on another 

body did balloon to Earth-like numbers, the effect on the body’s environment could be dramatic, changing soil characteristics, the ecologies of any existing life-forms, and even the oxygen, carbon dioxide, 

and nitrogen ratios in its atmosphere.8

After a meeting in November 1957, when another Soviet space 

spectacular seemed imminent, Lederberg worried about the extent 

 7. Joshua Lederberg, “Exobiology: Approaches to Life beyond the Earth,” 

18
In the Beginning

to which nationalistic motives to dominate the space race sometimes 

outranked scientific objectives, and he expressed concern that serious lunar and planetary biological contamination would result.9

 He 

believed that protection of scientific exploration and, in particular, of 

the ecosystems that might be encountered during voyages into space, 

was an ethic that should not be compromised. Lederberg articulated 

his concerns when he commented that “the scientific values of the 

space program, and the protection of its habitats for life (including our 

own) would be subordinated to geopolitics.”10

Lederberg’s warnings made an impression on members of the 

National Academy of Sciences (NAS), including its president, Detlev 

W. Bronk. NAS expressed apprehension that insufficiently sterilized 

spacecraft would “compromise and make impossible forever after 

critical scientific experiments.”11 NAS did not stop there, but adopted 

resolutions in February 1958 calling for the International Council 

of Scientific Unions (ICSU) to assist in developing the means of preventing harmful spacecraft contamination that “would impair the 

unique . . . scientific opportunities.”12 According to Lederberg, Bronk 

was careful to convey NAS concerns in a manner that left the issue in 

ICSU’s hands, “so it wouldn’t become an American proposal that had 

to be sold to the rest of the world, that it actually could be worked 

through on an international basis.”13

CETEX

On 8 February 1958, as a result of NAS’s expression of concern, ICSU established an ad hoc Committee on Contamination by 

Extraterrestrial Exploration (CETEX) to provide preliminary findings on 

lunar, Martian, and Venusian vulnerabilities to contamination. CETEX 

 9. Edward Clinton Ezell and Linda Neuman Ezell, 

19
When Biospheres Collide

held its first meeting at The Hague on 12–13 May 1958, with Marcel 

Florkin, Belgian biochemist, as its president and Donald J. Hughes of the 

United States representing the International Union of Pure and Applied 

Physics. Other organizations at the meeting included the International 

Astronomical Union, the International Union of Biological Sciences, and 

the Special Committee for International Geophysical Year. The CETEX 

meeting produced the following statements and recommendations 

regarding various aspects of lunar exploration:

The Moon’s Atmosphere. The Moon’s atmosphere contained such 

little matter (estimated at only 10 to 100 tons) that the release of tons 

of volatile material from a flyby spacecraft’s operations, such as the 

setting off of explosives for marking purposes, was likely to alter the 

atmosphere for very long periods. A landing vehicle would also almost 

certainly alter the Moon’s atmosphere radically, since landing requires 

deceleration and the release of tons of chemical propellants. CETEX 

thus recommended that the Moon’s atmosphere be studied in the initial phases by orbiting craft and that no flares be lit until extensive 

atmospheric data had been obtained. 

Moon Dust. Space scientists had great interest in the chemical 

characteristics of particles on the Moon’s surface and did not want 

them contaminated. CETEX thought that rocket impacts and other 

spacecraft operations would mainly lead to local contamination of 

lunar dust and thus not be that serious. Nuclear explosions, however, 

which might be planned in order to yield seismic data on the Moon’s 

interior, did present a danger of contaminating the Moon’s dust on a 

wide scale. Such explosions would release radioactive products that, 

especially in the extreme vacuum of the Moon, would likely behave as 

gases and thus be rapidly distributed over large areas through diffusion. Some of the radioactive products would be in a highly reactive 

form and might well combine with Moon dust to form nonvolatile compounds. The result of these processes could be that the entire lunar 

surface acquired additional radioactivity that interfered with radiochemical analyses performed to shed light on the Moon’s past history.14

Cosmic Dust. Scientists examined the possibility that valuable 

information regarding cosmic (interstellar and interplanetary) dust 

 14.

20
In the Beginning

would be lost if the Moon’s surface was disturbed during a mission. 

Cosmic dust contains a large percentage of low atomic weight elements 

such as hydrogen, carbon, nitrogen, and oxygen, and studying these elements and their relative abundances can potentially yield information 

about the evolution of the solar system. However, scientists believed that 

these low atomic weight molecules in cosmic dust are largely volatized 

by solar radiation, and thus little would be found on the Moon. Mainly 

the residues of high atomic weight elements in the dust would remain 

on the Moon, and this material was not particularly interesting, since 

similar deposits were found at the bottom of Earth’s oceans.15

Panspermia Hypothesis. The scientific community considered 

the possibility that Moon dust might be important in evaluating the 

panspermia hypothesis—that transport of tiny living spores in cosmic dust was responsible for disseminating life throughout the universe (panspermia is discussed in more detail later in the chapter). But 

scientists concluded that the same solar radiation that volatized the 

lighter molecules in cosmic dust would also decompose living spores 

in the dust. Thus, CETEX did not expect Moon dust to shed light on 

the panspermia hypothesis.16

Contamination of the Lunar Surface by Microorganisms. The scientific community decided that there was little chance that introducing living spores or other microorganisms from Earth would lead to a 

sustainable form of life on the Moon. No known cells on Earth could, 

the scientists believed, grow or multiply under lunar conditions of high 

vacuum and no water.17

Complex Molecule Synthesis. The emergence and continuance of 

life requires the synthesis and replication of complex molecules. To 

understand the mechanisms by which life might originate, it was necessary to discover processes by which such complex molecules (which on 

Earth are carbon-based) might be constructed and replicated. Space 

scientists thought that the analysis of Moon dust might conceivably offer 

clues regarding these processes. In fact, some processes might have 

been taking place on the Moon that could eventually, in the right environment, lead to the formation of life. These processes might have been 

 15.

21
When Biospheres Collide

similar to or different from those that took place on Earth. If such lunar 

processes were going on, then they could have been seriously upset 

through introduction of Earth chemistries to the lunar surface. While 

scientists considered the probability of such an occurrence to be remote, 

the damage done through contamination might conceivably have been 

very great. To lower the risk of this happening, CETEX recommended 

limiting the areas on the Moon in which spacecraft were allowed to land, 

thus localizing any effects of contaminants.18

At its May 1958 meeting, CETEX also examined the risks of space 

expeditions contaminating Mars and Venus. Since scientists believed 

that water, nitrogen, carbon oxides, and solar energy for photosynthesis were all available on Mars, they perceived a risk that terrestrial microorganisms would be able to grow there. CETEX therefore 

recommended that precautions be taken against space vehicles landing either accidentally or deliberately on Mars without first sterilizing 

them of all living organisms. Such precautions were considered for 

Venus as well. To not follow these safety measures was to jeopardize 

the search for extraterrestrial life on the planets. 

CETEX reasoned that future searches for extraterrestrial life could 

also be jeopardized by setting off nuclear explosions on Mars or Venus. 

Introducing a different level of background radiation on these planets 

might, it was feared, “greatly influence any form of life found there.”19

In its discussions, CETEX realized that there were inherent conflicts 

between certain types of experiments such that fulfilling the objectives 

of one would hinder the goals of another. For instance, an explosion of a 

thermonuclear device that would, as discussed above, provide valuable 

seismic data regarding a planet’s interior might subsequently ruin the 

opportunity to conduct meaningful radiochemical analyses.20 

One outcome of CETEX’s contamination concerns was the publishing of two articles that attempted “to set a tone for developing a code 

 18.

22
In the Beginning

23

of behavior in space research.”21 While CETEX did not at its inception 

have “sufficient scientific and technological data to enable it to propose 

a specific code of conduct,”22 it recognized that such a code needed to 

be drafted as soon as possible in order to safeguard future interplanetary 

research and achieve a suitable compromise between all-out planetary 

exploration and protection of extraterrestrial environments. CETEX recommended that ICSU gather “interested and expert parties”23 to address 

this issue as well as the statements and recommendations that were 

discussed above. ICSU did eventually gather such parties; what evolved 

is detailed in the section below on COSPAR.

Creation of the NAS Space Science Board

On 14–17 May 1958, immediately after CETEX’s initial meeting, 

a Satellite-Life Sciences Symposium recommended by NAS’s Detlev 

Bronk was held in Washington, DC. Lederberg wrote about his planetary protection views in a paper presented at this symposium, which 

was sponsored by NAS as well as the American Institute of Biological 

Sciences and the National Science Foundation (NSF). Lederberg’s 

views about biological contamination in space carried considerable influence and contributed to NAS’s establishment of the Space 

Science Board (SSB) on 4 June 1958. Lloyd V. Berkner served as 

SSB’s first chairman, and its initial members included Nobel Laureate 

 “The Moon and other celestial bodies shall be used by all States Parties to the Treaty 
When Biospheres Collide

chemist Harold Urey (who had conducted research on Earth’s primeval 

atmosphere and prebiotic evolution) as well as Lederberg himself. 

NAS tasked SSB with, among other priorities, surveying the scientific aspects of human space exploration and providing advice 

on all interplanetary contamination issues. Before the year was 

out, SSB had established the Panel on Extraterrestrial Life to “recommend approaches to the study of extraterrestrial life and, in particular, issues related to the problem of contamination.”24 NAS also 

directed SSB to “coordinate its work with the appropriate civilian 

and Government agencies, particularly the National Aeronautics and 

Space Administration [which was soon to be established], the National 

Science Foundation, the Advanced Research Projects Agency, and with 

foreign groups active in this field.”25

The Establishment of NASA 

On 1 October 1958, as a direct result of the political crises arising 

from Sputnik’s 1957 launch, the United States established the National 

Aeronautics and Space Administration (NASA). President Eisenhower 

named T. Keith Glennan, who at that time was the president of Case 

Institute in Cleveland, Ohio, to be NASA’s first Administrator.26, 27

The Establishment of COSPAR

Almost coincidental with NASA’s inception and after vetting the 

CETEX recommendations described above, ICSU at its Washington, 

 24.

24
In the Beginning

DC, meeting on 2–4 October 1958 established a Committee on Space 

Research (COSPAR) to encourage international collaboration and 

information exchange in interplanetary endeavors. This permanent 

committee worked and continues to work largely through organizing and sponsoring meetings and publishing scientific papers and 

information.28 ICSU stressed that COSPAR was to be concerned with 

fundamental space research rather technological problems (such as 

propulsion or construction of rockets).29 COSPAR’s purview included 

the biological aspects of interplanetary exploration, such as spacecraft 

sterilization and planetary quarantine.30

COSPAR held its first meeting on 14–15 November 1958 in Loudon, 

Switzerland, with the intention of fostering communication between 

scientists of different countries. It was meant to be an “organization 

as independent as possible from politics and governments.”31 Several 

months after the formation of COSPAR, CETEX held its second and 

last meeting on 9–10 March 1959 in The Hague. CETEX, an interim, ad 

hoc group, took the position that interplanetary contamination problems were now better addressed by COSPAR, which then took over 

CETEX’s functions.32 Also in 1959, the United States’ SSB endorsed the 

formation of COSPAR.33

From the beginning, a major objective of COSPAR was to open up 

a dialog between Eastern bloc space scientists and those from the rest 

of the world, most of whom were from the United States. There were 

difficulties in doing this. The Soviets objected to “the high proportion 

 28.

25
When Biospheres Collide

of Western representation”34 on COSPAR and insisted that countries 

within the USSR such as Ukraine and Byelorussia have independent 

memberships. The United States considered this similar to asking for 

Texas and New York to have independent memberships. But when the 

Soviets threatened to pull out of COSPAR, a compromise was reached, 

allowing any nation interested in and engaged in some way in space 

activities to be a member. In addition, COSPAR “agreed to accept 

on its Executive Committee a Soviet vice president and a U.S. vice 

president, thus assuring both countries of permanent positions on the 

executive body of COSPAR.”35 As a result of these changes, the USSR 

remained a member of COSPAR.

Two kinds of memberships in COSPAR emerged—representation from interested scientific professional organizations, such as the 

Unions of Geodesy and Geophysics, Scientific Radio, Astronomy, and 

Pure and Applied Physics: and representation from nation states. In 

the words of Homer Newell, who in 1961 became the director of NASA’s 

Office of Space Sciences,36 “the ultimate strength of COSPAR lay in 

the national memberships, for, as with the International Geophysical 

Year, the individual countries would pay for and conduct research.”37

One of COSPAR’s early actions was to ask the United States and 

the USSR to examine approaches for avoiding transfer of terrestrial 

organisms to other planets. As a result, NASA implemented a planetary quarantine program whose main aim was to protect planets 

of biological interest so that 1) life detection experiments would not 

be invalidated by contamination and 2) a planet would not get “overgrown by terrestrial life with consequent irreversible changes in its 

environment.”38

 34.

26
In the Beginning

COSPAR met every year in different venues so as to allow various 

nations to host the meetings. COSPAR typically divided its meetings 

into two parts: 1) a technical symposium on recent space science developments and 2) working group discussions on issues of importance to 

space exploration. Controversial discussions arose at these meetings 

regarding the undesirable impacts of space missions. In particular, the 

space science community voiced concerns over space research’s possible compromise of other scientific activities—for example, interference 

of ground-based radio astronomy by radio signals from satellites. To better address such concerns, ICSU passed a resolution in 1961 requesting COSPAR to analyze proposed space activities that adversely impact 

other scientific experiments and observations and to share the results of 

its studies with governments and the space science community.39

COSPAR responded to ICSU’s request by passing Resolution 1 

in 1962 that created a Consultative Group on Potentially Harmful 

Effects of Space Experiments. Vikram Sarabhai, a physicist who 

would later head India’s atomic energy agency, chaired this group. The 

Consultative Group also included delegates from the two major launching countries, the United States and the USSR, and from more neutral 

members. COSPAR’s president, H. C. van de Hulst, participated as well 

because of his belief in the importance of the Consultative Group’s 

mandate, which soon included addressing such issues as the effects 

of rocket exhausts on Earth’s atmosphere and of high-altitude nuclear 

explosions on Earth’s radiation belts.40

UN Committee on the Peaceful Uses of Outer Space 

(UNCOPUOS) 

Established by the United Nations General Assembly in December 

1958, UNCOPUOS reported the following year on contamination dangers to celestial bodies that could result from their exploration as well 

as on possible contamination of Earth from bringing materials back. 

UNCOPUOS is discussed further in Chapter 8.

 39.

27
When Biospheres Collide

SSB and NASA Planetary Protection Actions

In 1959, SSB focused its attentions on the life sciences as its 

members developed interests in studying “the viability of terrestrial 

life-forms under extraterrestrial conditions and the implications of 

contamination.”41 An ad hoc committee, chaired by Joshua Lederberg, 

concluded that sterilizing spacecraft was technically feasible and effective means of doing so could be developed. SSB then sent communications to NASA and the Advanced Research Projects Agency (ARPA) on 

14 September 1959, recommending the development of sterilization 

procedures. 

NASA Administrator Glennan told SSB that the Agency had 

indeed adopted the policy of space probe sterilization to the extent 

feasible for all craft intended to pass near or impact upon the Moon 

or the solar system’s planets. Moreover, NASA Director of Space Flight 

Programs Abe Silverstein requested that the Jet Propulsion Laboratory 

(JPL), Goddard Space Flight Center (GSFC), and Space Technology 

Laboratories42 initiate the coordinated development of sterilization 

techniques. Also in 1959, after studying CETEX’s research findings 

on the potential impacts of carelessly designed space missions, SSB 

decided to support the group’s recommendations to establish an international code of conduct that would protect against extraterrestrial 

planetary degradation.43

 41.

28
In the Beginning

Figure 2.3 USSR scientist Anatoli A. Blagonravov, who helped to launch Sputnik and worked 

to establish cooperation in space between the United States and the USSR. 

Tensions with the USSR

Although the focus of COSPAR’s Consultative Group on 

Potentially Harmful Effects of Space Experiments started as a scientific endeavor, political squabbles soon arose, notably due to 

harangues of the United States by the USSR. Such was also the case 

at UNCOPUOS gatherings. At the May 1963 meetings of the Scientific 

and Technical Subcommittee of UNCOPUOS, the USSR representative, Anatoli Blagonravov (figure 2.3), a scientist who helped launch 

Sputnik, complained about the U.S. West Ford experiment, which 

had injected large numbers of tiny copper needles into orbit in order 

to gauge their utility for reflecting radio signals from one ground 

sputnik/20fe.html (accessed 26 January 2011); David Darling, “Space Science Board,” in 

Encyclopedia of Astrobiology, Astronomy, and Spaceflight, http://www.daviddarling.info/

encyclopedia/S/SpaSciBoard.html (accessed 21 March 2005).

29
When Biospheres Collide

location to another. On 21 May 1963, Blagonravov submitted a paper 

recommending that COSPAR study the potentially harmful impacts 

of experiments that would contaminate outer space.44

COSPAR’s Consultative Group spent considerable effort addressing 

protection of the Moon and planets from biological contamination. Life 

scientists absolutely did not want contamination from Earth to compromise the search for and possible study of existing extraterrestrial 

life-forms, evidence of past life, or evidence of how the chemistry of a 

planet might evolve toward the formation of life.45

 The Consultative Group’s scientists understood that from economic and probably technical points of view, complete sterility 

of interplanetary spacecraft could not be achieved. Instead, the 

Consultative Group discussed probabilities of contamination and 

sought to arrive at acceptably low figures. “Acceptable” meant not 

setting the contamination probability so low as to make a spacecraft’s development costs prohibitively expensive, but setting it low 

enough to make the chances of compromising scientific research 

very small. A “low enough probability” is a very subjective concept, 

and not surprisingly, “there were a great many opinions as to what 

probabilities were reasonable and as to how to go about the engineering. . . . The interminable discussions of the scientists were a vexation to the engineers who had to translate prescribed standards into 

engineering criteria.”46

COSPAR did not agree on an international set of contamination probability objectives for years, although one number that its 

Subcommittee for Planetary Quarantine recommended in May 1966,47

which COSPAR reaffirmed at its 12th plenary session in Prague on 

11–24 May 1969, was to keep the probability of contaminating the 

solar system’s planets (and in particular Mars) to no more than one in 

1,000 during the anticipated period of biological exploration. COSPAR 

 44.

30
In the Beginning

estimated this period at 20 years, extending through the late 1980s, and 

envisioned approximately 100 missions launching during this time.48

Questions of how to translate evolving COSPAR planetary protection requirements into space vehicle engineering criteria were hotly 

debated by different nations. The United States attempted to facilitate this discussion by sharing the details of how its spacecraft were 

designed and constructed. The United States’ openness differed markedly from the USSR’s custom of giving few design details of its spacecraft, saying only that the craft were going to be decontaminated. The 

USSR’s close guarding of its spacecraft details resulted in considerable apprehension among other countries’ space scientists, because 

adequate planetary protection could only be achieved with the full 

cooperation of all spacefaring nations. Insufficient cleaning of even 

one nation’s space vehicles could greatly degrade the scientific opportunities available to all nations. And once these opportunities were 

lost, they would never be fully recoverable.49

Joshua Lederberg and WESTEX

Parallel to the efforts of COSPAR in developing the planetary protection field were some important achievements by noted scientists. 

One of these was Joshua Lederberg, who was instrumental in defining 

a role for the life sciences in space research. Although NAS leadership 

had intended its SSB to include life sciences in its oversight of space 

science, its initial actions focused on the physical problems of space 

exploration. Of its 10 original committees, only 1—the Committee on 

Psychological and Biological Research—focused on life science issues. 

The remaining 10 dealt with non-life-science issues such as geochemistry, astronomy, orbits, vehicle design, and meteorology.50

Joshua Lederberg put forth an admirable effort to alter NASA’s 

research priorities and bring exobiology to “the forefront of space 

 48.

31
When Biospheres Collide

policy.”51 Exobiology, a term coined by Lederberg himself, refers to the 

study of life’s origins on Earth and the development of instruments 

and methods to search for signs of life on other celestial bodies.52

Lederberg’s work was driven largely by his fears that the space 

program would result in irreversible contamination of the planets as 

well as Earth itself. The origin of his interest in outer space, according 

to Lederberg himself, occurred at a dinner meeting between him and 

British biologist J. B. S. Haldane in Calcutta, India, at which Haldane 

mused whether the USSR would set off a thermonuclear explosion 

on the Moon to commemorate the 40th anniversary of the Bolshevik 

Revolution. Haldane suggested that they might see a “red star”—a 

thermonuclear explosion—appear on the Moon. After considering 

such a possibility, both Lederberg and Haldane bemoaned the potential contamination that the Moon’s pristine environment might suffer from such a political demonstration. Lederberg took the situation 

as “a striking metaphor for the danger that scientific interests would 

be totally submerged by the international military and propaganda 

competition,”53 noting that science objectives had never gained first 

priority over military considerations and might get totally excluded.

Soon after his meeting with Haldane, Lederberg began his campaigns for international agreements as well as spacecraft sterilization 

procedures capable of protecting the Moon and other planets from 

both radiological and biological contamination. Lederberg felt the 

need to “assure that fundamental biological science was properly represented in the programs of space research that were just emerging.”54

In February 1958, Lederberg helped convince NAS to pass a resolution 

demanding thorough space mission planning to ensure that “operations do not compromise and make impossible forever after critical 

scientific experiments.”55

 51.

32
In the Beginning

Lederberg’s passion and deep concern for the well-being of scientific endeavors in space drew other scientists to his cause. From 

them, he formed the West Coast Committee on Extraterrestrial Life 

(WESTEX), a part of NAS’s Panel on Extraterrestrial Life,56 to address 

the protection and preservation of planetary surfaces during space 

exploration. Lederberg’s WESTEX first met at Stanford University on 

21 February 1959. Although a group of scientists that called themselves EASTEX (for East Coast Committee on Extraterrestrial Life, 

which was, like WESTEX, a part of NAS’s Panel on Extraterrestrial 

Life) had met earlier in Cambridge, Massachusetts, WESTEX was the 

more active of the two, convening at least five times between 1959 and 

1960. WESTEX, which focused on issues of planetary contamination, 

also differed from EASTEX in that the latter group concerned itself 

almost exclusively with the origin of life.

Lederberg brought high-profile scientists into WESTEX such as 

Melvin Calvin of the University of California at Berkeley, who would win 

the Nobel Prize for his work on photosynthesis; Harold Clayton “H. C.” 

Urey of the University of Chicago and University of California at San 

Diego, who, among many other efforts, conducted important origin-of-life 

experiments; geneticist Norman Horowitz of the California Institute 

of Technology (Caltech); molecular biologist Gunther Stent of the 

University of California at Berkeley; molecular geneticist Matthew S. 

Meselson of Caltech and Harvard; nuclear scientist turned biophysicist 

Aaron Novick of the University of Oregon; microbiologist C. B. Van Niel 

of Stanford; and a young astronomer, Carl Sagan.57 This group was 

purposely chosen so as to include a “diversity of interest . . . compactness of size, and convenience of assembly.”58

In 1958, ICSU’s CETEX had outlined potential contamination dangers to the Moon, Venus, and Mars. But Lederberg believed that CETEX’s 

work did not go far enough toward protecting planetary surfaces 

 56.

33
When Biospheres Collide

(including that of Earth). One of WESTEX’s initial tasks was to prepare 

scientific statements focusing on this area of concern for future CETEX 

meetings.59 WESTEX’s first meeting (held 21 February 1959 at Stanford 

University) was devoted to policy regarding “celestial contamination,”60

and concluded that rigorous decontamination of spacecraft was essential as well as feasible. This position was reaffirmed at WESTEX’s second 

meeting, which was held a month later at JPL in Pasadena.

Theories on the origins of planetary life. WESTEX’s desire to 

protect planetary surfaces from contamination made it necessary to 

consider the possible pathways for life to secure a foothold on those 

planets. One early 20th century theory, that of panspermia, held that 

life-bearing seeds were scattered throughout space and could germinate wherever conditions were favorable. In order to identify these 

seeds during a space mission’s quest to find life, scientists would need 

to distinguish them from substances of terrestrial origin as well as 

materials unrelated to life. Keeping planetary surfaces free from terrestrial microorganisms and other contaminants of human origin 

would aid greatly in isolating the panspermia seeds.

The newly evolving field of molecular biology raised serious misgivings on the likelihood of seeds of life floating endlessly through space 

and fertilizing previously barren planets. Lederberg did not categorically dismiss the panspermia theory but advised members of WESTEX 

that it was not a sound basis on which to justify stricter guidelines for 

space missions. A more current debate on mechanisms of life origination focused on abiotic synthesis as a means of forming organic molecules. Instead of embracing any particular theory of life origins, however, 

Lederberg chose to plead ignorance regarding a specific mechanism that 

was responsible. WESTEX proposed that the wisest course, and the one 

offering the best opportunities for scientific return, was simply to search 

for the existence of extraterrestrial organic molecules or bacterial organisms. WESTEX’s proposal was a politically savvy one, for it sidestepped 

arguments and disagreements regarding how life might have originated 

in favor of just identifying the existence of life, or potential building 

blocks of life, on a particular planet.61

 59.

34
In the Beginning

Figure 2.4 Carl Sagan with a model of the Viking Mars lander in Death Valley, California. 

Planetary protection for the Viking mission is examined in Chapter 5.

Prioritizing planetary protection. Beginning with WESTEX’s 

initial meetings in 1959–1960, Lederberg as well as Carl Sagan (figure 2.4) advocated that a high priority be placed on preventing planetary probes from carrying terrestrial contamination into space, and 

nearly as high a priority on the prevention of back contamination from 

sample return missions. Lederberg and Sagan lobbied to make these 

priorities NAS SSB’s official policy and to present them to COSPAR, 

which had become an important international forum for exobiology 

matters. Lederberg and Sagan’s lobbying efforts proved very effective 

at bringing planetary protection issues to the fore and incorporating 

them into space science policy at all levels. Allan H. Brown, a scientist 

on NASA’s Biosciences subcommittee, also advocated taking steps to 

prevent back contamination, underlining (as Lederberg and Sagan did) 

that even if the risk of such contamination was very small, the scale 

of harm could be huge indeed. In 1963, COSPAR agreed to form an 

anticontamination panel.62

 62.

35
When Biospheres Collide

A dissenting voice. Norman Horowitz was a WESTEX member 

who had quite a different view on back contamination. Although he 

gave some support to spacecraft sterilization as a means of preventing forward contamination, he considered the attention given to back 

contamination to be overblown. Belief in the supposed danger of back 

contamination, according to Horowitz, rested on three assumptions, 

each of which he thought was improbable:

•	 Microorganisms will be found on the planets.

•	 They will prove dangerous to humans.

•	 We would be unable to cope with them if they were brought 

back to Earth and escaped from quarantine.

The probability that the microbes would run rampant on Earth 

could be estimated by taking the product of the probability of each of 

the bulleted items (in other words, multiplying together the small probabilities of each of the above events should they occur). This would, in 

Horowitz’s mind, produce a very small overall probability of contaminating Earth—so small that he stated, regarding sample materials brought 

back from Mars: “I would be willing to run the risk involved in a premature return trip, if a less bold schedule meant that a sample of Martian 

soil could not be brought back to earth in my lifetime.”63

Horowitz argued that the slight risk of introducing a pandemic 

disease due to back contamination did not outweigh the “potential 

benefits to mankind of unhampered traffic with the planets.”64 By 

way of a historical example, he considered the back contamination 

resulting from Christopher Columbus’s voyages, which was severe, 

but made a case that even this was justified. If Europeans had known 

that Columbus’s crew would bring syphilis back with them and that 

it would plague Europe for centuries, the voyages might have been 

canceled. On the other hand, if Europeans had also been aware of the 

enormous wealth and resources that would be gained from the voyages, 

they would no doubt have approved Columbus’s travels.65

Lederberg countered Horowitz’s argument with the conviction 

that “we are in a better position than Columbus was to have our cake 

 63.

36
In the Beginning

and eat it too.”66 Caution and patience as well as modern analytical 

techniques, Lederberg believed, could allow planetary exploration to 

proceed in a manner that was also protective of Earth and its inhabitants. Other members of WESTEX concurred, but they were not nearly 

as polite as was Lederberg in refuting Horowitz. Aaron Novick of the 

University of Oregon grew angry, citing as an example the myxoma 

virus’s introduction to Australia’s rabbit population. Propagated in the 

1950s as a means of controlling Australia’s destructive rabbit hordes, 

it initially killed 99 percent of the population. Novick’s point was that 

the syphilis that Columbus brought back home might well have wiped 

out just as high a percentage of Europe’s population.67 And by extension, if a space expedition were to bring an extraterrestrial microbe 

back to Earth, it could have a similar effect.

Building respect for the exobiology field. One of Lederberg’s and 

WESTEX’s notable achievements was to garner a certain amount of 

respect and funding for the new field of exobiology, and this helped give 

planetary protection considerations more importance as well. This 

quest for respect was aided in part by Lederberg’s stature as a Nobelist 

as well as WESTEX’s strategy of linking exobiological work with the 

techniques of molecular genetics. According to WESTEX, since exobiology gave high priority to molecular-level analyses, it would eventually 

generate vital data for ongoing evolution, microbiology, and theoretical 

biology scientific debates. Exobiology was developing into a transnational field carrying out cutting-edge molecular genetics and biochemistry experiments concerned, among other things, with investigating 

the uniqueness of living systems based on nucleic acids and proteins,

and these endeavors gave the field prestige. They also helped make a 

strong case for implementing rigorous planetary protection measures 

on expeditions searching for extraterrestrial life, for these expeditions 

“demanded an especially cautious approach to the untouched surfaces 

of other planets”68 to be successful. Conversely, recognition by the scientific community of the need for planetary protection also helped 

 66.

37
When Biospheres Collide

raise support for exobiology programs. Lederberg effectively “used 

the fear of contamination—of earth and other planets—as a central 

argument for funding ‘nonpolitical,’ ‘scientifically valid’ experiments 

in extraterrestrial life detection.”69

Lederberg and his colleagues did well at selling a message of scientific as well as national prestige to NAS SSB and, as a result, reaped 

some rewards for their own research programs. In 1962, Lloyd Berkner, 

SSB’s first chairman, told the president of NAS that exobiology, rather 

than geology, meteorology, or radiation studies, was the “most important scientific research program in space.”70 NASA soon became the 

prime sponsor of exobiological research. Joshua Lederberg and his 

Stanford laboratory received grants exceeding $500,000 to carry out 

exobiological studies. 

Development of the planetary protection field has clearly involved 

the work of a mélange of different organizations, agencies, and facilities. The table in Appendix D lists some of these entities that have 

been important to planetary protection and briefly summarizes the 

nature of their contributions.

Development of NASA Planetary Protection Policy 

and Organizational Structure

NASA’s First Spacecraft Sterilization Policy Statements

NAS SSB, concerned with the possibility of planetary contamination due to space exploration, requested Joshua Lederberg to set up 

an ad hoc committee to study issues of spacecraft sterilization. This 

committee convened at Stanford University on 6–8 June 1959 and 

included representatives from NASA’s Goddard Research Center and 

Jet Propulsion Laboratory, General Electric Company, and the U.S. 

Army Biological Laboratories.71

 69.

38
In the Beginning

The Stanford meeting led to considerable debate on sterilization 

matters. One of the basic issues was just how clean a spacecraft must 

be for planetary protection purposes. In a 30 July 1959 memo, the 

atmospheric scientist Leslie H. Meredith, who was NASA Goddard 

Space Flight Center’s (GSFC) newly appointed Chief of the Space 

Sciences Division,72 asked just how clean a space probe must be, given 

the enormously larger size of a planet. Meredith also identified a major 

problem with attaining a useful state of sterilization, writing that 

“there are obviously some places which could only be ‘cleaned’ by a 

very major effort (i.e., the insides of resistors, transistors, relays, etc.). 

If it is assumed such places are left ‘dirty,’ how much point is there to 

making the remainder of the probe completely ‘clean?’”73 In a memo 

dated 3 August 1959, John W. Townsend, Jr., GSFC’s new Assistant 

Director, Space Science and Satellite Applications,74 also wondered 

whether devoting considerable levels of effort to spacecraft sterilization 

was a worthwhile endeavor. Townsend did not believe, as a scientist, 

that the state of knowledge was such as to even know if space exploration presented a danger of planetary contamination. Furthermore, 

he also saw “an almost impossible situation developing from a practical standpoint”75 if the space science community went ahead with 

attempts at space probe sterilization. Barriers he identified at GSFC to 

accomplishing useful sterilization included the following: 

•	 Lack of qualified biologists and chemists to supervise the program.

•	 Insufficient GSFC personnel to “handle the extra workload”76 of 

sterilization activities.

•	 The required cleanroom facilities were not available.

 72.

39
When Biospheres Collide

•	 None of GSFC’s construction or assembly people were familiar 

with hospital sterilization procedures.

•	 Added costs and personnel time would raise serious issues.

Even if these problems could be surmounted, Townsend was not 

sure that adequate sterilization could be achieved due to space vehicle 

procedures that resulted in “repeated opening of payloads and testing 

up to the final minute of launching.”77

On 14 September 1959, Hugh Odishaw, Secretary of NAS SSB, wrote 

to T. Keith Glennan, NASA’s first Administrator, declaring that the spacecraft sterilization recommendations of Lederberg’s ad hoc committee 

had SSB’s approval and requested that they be followed. Administrator 

Glennan answered a month later on 13 October 1959, pledging that NASA 

would indeed do its best to carry out the recommendations.

During the same month, Abe Silverstein, who was NASA’s Director 

of Space Flight Programs at the time, wrote letters to JPL and Goddard 

Space Flight Center stating NASA’s new policy, that space mission payloads “which might impact a celestial body must be sterilized before 

launching.”78 The letters listed the payloads of concern and recommended particular sterilization approaches. For instance, in a letter 

sent to the Director of Goddard on 15 October 1959, Silverstein mentioned the need to sterilize the P-14 Lunar Magnetometer Experiment 

payload and identified gaseous ethylene oxide as the sterilizing agent 

that NASA considered the most feasible.79 Some communications from 

Silverstein also suggested that the U.S. Army BioLabs at Fort Detrick, 

Maryland, which had experience with sterilization issues, be brought 

onto the team. These letters from Silverstein were the first official 

NASA policy directives on spacecraft sterilization. Weeks after they 

were written, on 12 November 1959, NASA transferred funds to the 

Army to support its cooperative efforts.80

 77.

40
In the Beginning

Abe Silverstein’s Approach to Spacecraft 

Sterilization and the Difficulties in 

Implementing NASA Policy

Homer Newell, the former Director of 

NASA’s Office of Space Sciences,81 considered Abe Silverstein (figure 2.5) to be “a 

hard-nosed, highly practical, boldly innovative engineer, with a solid conviction . . . that 

all research had to have a firm justification 

in practical applications to which it would 

ultimately contribute.”82 He was also seen as 

a powerful manager who got results. Former 

NASA Administrator Daniel S. Goldin called 

him “a man of vision and conviction” whose 

“effective leadership, both at Headquarters 

and at Lewis [NASA’s Lewis Research Center (LeRC)], directly contributed to the ultimate success of America’s unmanned and human space 

programs.”83 Silverstein’s letters put forth statements of NASA policy that 

were unqualified in their demand for sterilization of payloads that could 

contaminate a solar system body, with no room for equivocating. This 

NASA requirement articulated by Silverstein, however, proved very difficult to implement. Spacecraft were being launched by physical scientists 

and engineers with little experience in biological methodologies, especially sterilization techniques, and with almost no data on what these 

techniques might do to the dependable operation of the spacecraft.84

The typical model for sterilization was at that time drawn from 

the procedures used in hospitals to clean small instruments for surgical applications. These procedures employed autoclaving, involving wet steam at pressures 25 psi over atmospheric and carried out 

in small pressurized chambers. Autoclaving technologies were very 

Figure 2.5 Abe Silverstein, NASA 

Director of Space Flight Programs 

and an advocate of spacecraft 

sterilization.

 81.

41
When Biospheres Collide

poorly suited for sterilizing spacecraft.85 In addition, medical applications required that surfaces of instruments such as scalpels be 

devoid of bacteria, but not necessarily their interiors, which would 

never touch the patient. But a spacecraft might be subjected to a 

high velocity impact with a planetary surface, shattering the shell of 

the craft and its interior components. Unless the exterior and interiors of the craft had been adequately sterilized, such a crash might 

release viable organisms onto, or beneath, the planetary surface. In 

addition, resistors and capacitors, plastic components, ceramic components, indeed, all parts of the spacecraft, needed to be sterilized 

not only on their surfaces, but also within their interiors. Achieving 

this was an awesome task.86

The range of techniques employed by the U.S. Army BioLabs were 

much better suited for sterilizing spacecraft than those employed by 

hospitals. The Army BioLabs could sterilize objects as large as army 

trucks and as small as laboratory balances. The Lederberg ad hoc 

committee on spacecraft sterilization recommended that these capabilities be exploited, and this was repeated in Silverstein’s letters.

The Army BioLabs had refined the use of gases for sterilizing 

equipment, particularly ethylene oxide, which had several important advantages. It was noncorrosive to most equipment and could be 

stored in simple plastic containers at ambient temperatures and pressures. The gas consisted of small molecules that were soluble in many 

different materials, including rubber, plastic, and oil. It was quite a 

penetrating sterilant, able to work its way into the cracks and interstices of many components.87 One experiment showed that the gas 

 85.

42
In the Beginning

would penetrate to the inside pages of a New York telephone directory, 

even when an anvil was sitting on the book.88

But while gaseous treatment killed microorganisms on and sometimes in the cracks between surfaces, it could not reliably penetrate 

through solids such as the epoxy potting materials, ceramics, or plastics used to protect electronic components. Gaseous sterilants had difficulty penetrating the interiors of resistors and capacitors and even 

getting to the threads of installed screws and bolts. A hard landing 

of the spacecraft on a target body might expose these unsterilized 

regions, leading to contamination of the planet.89

But were microorganisms likely to exist within the interiors of 

spacecraft components? Might their manufacturing processes have 

accomplished what gas sterilants could not? Unfortunately, this proved 

not to be the case. In studies evaluating these concerns, the Army 

BioLab confirmed that some microorganisms survived plastic polymerization processes. In addition, many electronics components such 

as capacitors, resistors, and transformers were, the BioLab discovered, 

received from the manufacturer with viable microorganisms inside. 

When the component was crushed or cracked, these microorganisms 

were able to multiply, even in components that had received surface 

sterilization with ethylene oxide.90

Two other approaches—radiation and heat—were possibilities for 

effectively sterilizing buried or covered contamination, but each one 

had its problems. Penetrating radiation can be effective, although it 

has far less impact on microorganisms than on higher life-forms. This 

is because, to kill a unicell microorganism, the radiation has to hit and 

sufficiently damage a very small target—the structure of the single 

tiny cell comprising the organism—to the point where the cell cannot 

repair itself. To kill a higher life-form, however, only requires killing 

a small percentage of its many billions of cells. For instance, if radiation only damages cells in the intestinal lining of a mammal, but to 

the point where the intestine cannot take in water or nutrients, the 

mammal will likely die. Thus the probability is far greater that enough 

radiation will hit enough vital cells of a higher life-form to kill it. As 

 88.

43
When Biospheres Collide

a result of this situation, orders-of-magnitude more intense radiation 

dosages typically have to be used to kill microorganisms than higher 

life-forms. But the intense radiation levels necessary to kill microorganisms can damage many spacecraft components.91

Heat is effective in killing microorganisms, but only if it can reach 

them. Wet steam autoclaving is useful for sterilizing surgical instruments at temperatures of about 125°C and exposure times of 15 to 20 

minutes, but steam is no more able to penetrate into solid materials or 

screw threads than is ethylene oxide gas. Alternatively, dry heat can be 

used. Unfortunately, microorganisms are much more resistant to dry 

heat than to wet steam exposure, so temperatures of 160° to 170°C for 

4 or more hours were typically employed. Such high temperatures can, 

however, severely stress and damage sensitive equipment. In response to 

this situation, exploratory experiments at the Army BioLabs examined 

the effectiveness of lower temperatures applied for longer dwell times. 

The data that were generated suggested that 125°C and dry-heat exposure times of 24 hours might be sufficient for NASA’s needs.92

Sterilization Technology Development

At a 1962 conference on spacecraft sterilization, Charles Phillips 

of the Army BioLabs at Fort Detrick discussed the issues involved with 

low heat/long exposure approaches, noting that this method used to 

be considered highly impractical and was, until recently, poorly examined. Phillips explained the dependence of microorganism death on 

both time of exposure and temperature. He also discussed the abilities 

of spacecraft materials to withstand the sterilizing environment, noting that at certain temperatures, materials begin to decompose, and 

this defined an upper limit on the temperatures that could be used. 

 91.

44
In the Beginning

Phillips did believe, however, that many materials were available that 

could withstand 125°C almost indefinitely, whereas at this temperature, he thought that bacteria would be slowly killed off. Phillips was 

of the opinion that given sufficient exposure time, a spacecraft could 

be sterilized at 125°C.93

The Question of Viruses

Some space scientists believed that the sterilization techniques 

under investigation did not adequately address how to deal with 

viruses. The techniques, in fact, tended to ignore viruses as a class. 

Typical sterility tests did not determine whether viruses survived the 

sterilization procedures or not. Instead, scientists made assumptions 

that viruses would not present planetary contamination problems. 

Viruses, biologists believed, need a host cell to propagate. Viruses 

are also highly specific to particular types of cells. Thus, if the spacecraft was not carrying those types of host cells, the planet being 

explored would not get infected. Furthermore, to infect a planet, not 

only would the virus have to get to it alive, the virus would also 

have to find suitable host cells on that planet in order to propagate. 

Phillips believed that since the probability was very low that an 

appropriate host cell for an Earth virus existed on another planet, 

then it was also very unlikely that it could propagate on that planet. 

“The only organisms we are worrying about,” Phillips said, “are the 

husky, tough soil organisms which live on the very simplest kind of 

nutrient and media.”94

 93.

45
When Biospheres Collide

Clark Randt, who was appointed director of NASA’s Office of Life 

Science Programs in March 1960,95 did not totally dismiss viruses as 

a contamination risk. He commented to Phillips that “the question 

has arisen as to whether or not bacterial and mycotic [fungal] spores 

could not in themselves provide the cell on which a virus could survive.” Another attendee, Stanley M. Levenson of the U.S. Army Medical 

Research and Development Command, added that if a space mission 

introduced a virus on another planet, and if the virus found some way 

to survive, then any terrestrial animal [including humans] introduced 

to that planet’s ecosystem might get infected, and we wouldn’t know 

whether that contamination originated on Earth or on that planet.96

Randt’s and Levenson’s observations were important, for they identified potential pathways by which planets could get contaminated and 

the search for life could be severely compromised.

Sterilization Approaches for the Ranger Program

In developing the Ranger Lunar exploration program, JPL encountered significant difficulties meeting the terms of Silverstein’s directives to sterilize all of the spacecraft’s thousands of individual parts. 

Terms such as “sterilize to the extent feasible” began appearing in 

JPL correspondence.97 NASA remained firm, however, regarding the 

importance of adequate sterilization. A 23 December 1960 memorandum to program and field station directors that was signed by 

Hugh L. Dryden, NASA Deputy Administrator, for T. Keith Glennan, 

Administrator, affirmed that “effective decontamination and sterilization procedures for lunar and planetary space vehicles are essential”98

and called for a thorough study to attain this objective. No mission 

would be flown until adequate sterilization plans and procedures were 

developed. JPL initiated the requested studies, focusing in particular 

 95.

46
In the Beginning

on dry-heat approaches. NASA also supported a dry-heat research program being carried out by various contractors, beginning with Wilmot 

Castle Company in 1961. 

Sterilization issues were not the only serious problems besetting 

the Ranger program, but they were particularly thorny ones. NASA’s 

directives to sterilize its spacecraft came too late to build the requirements necessary for reliable sterilization into the Ranger spacecraft’s 

initial designs. Ranger engineers wondered how they would kill all 

microorganisms on the 326-kilogram (725-pound) craft and keep it 

sterile through assembly, testing, and launch operations until it ultimately reached the Moon. Killing all organisms on the craft without damaging sensitive equipment appeared especially difficult after 

Charles Phillips’s group at Fort Detrick showed that viable microorganisms existed that were embedded within electronic components.

On the basis of Phillips’s work, mission staff needed to assume that 

all materials and components of the spacecraft might contain internal 

contamination.99

George L. Hobby, a research biologist in JPL’s Space Sciences 

Division, commented at a 1960 meeting on decontamination techniques 

that several sterilization methods could be effective for spacecraft: dry 

heating, gamma ray irradiation, the sterilization of materials and components during their manufacturing processes, and the sterile assembly 

of individual parts. He viewed sterile manufacturing, however, as a difficult venture, since it would require that hundreds of different vendors 

go to great expense to initiate entirely new manufacturing processes for 

producing spacecraft parts. It would be far easier and cheaper if internal 

spacecraft sterilization could be achieved using one of the two standard 

technologies that existed: heat or high energy radiation. Heat treatment, 

in fact, appeared to be a promising technology for sterilizing most of the 

spacecraft, since Hobby estimated that approximately 85 percent of the 

electronic components and 90 percent of the nonelectric components 

presently on the craft would survive a 24-hour heat sterilization treatment at 125°C.100 Presumably, new designs could be developed for the 

components not able to survive this sterilization regime.

 99.

47
When Biospheres Collide

The effort to sterilize Ranger had two objectives: to prevent lunar 

contamination and to collect data for developing more effective and 

reliable methods for sterilizing spacecraft. Attaining this latter objective would be necessary for future planetary exploration.101 Under 

the direction of George Hobby, Ranger staff developed a three-step 

operation that addressed equipment fabrication, assembly, test, and 

transportation. All equipment components were to be assembled, then 

subjected to the dry-heating regime mentioned above: 125°C (257°F) 

for 24 hours. Choosing this environment was an attempt to walk a 

tightrope between two unacceptable results. At temperatures and 

times above these levels, electrical equipment often failed, while below 

these levels some organisms generally survived.

After heating, the sterilized components were assembled and the 

piece of equipment tested. Typically, assembly operations began on 

the Ranger spacecraft eight to nine months before launch. After initial 

assembly of the entire spacecraft, mission staff subjected it to multiple tests in various environments. During these tests, the spacecraft 

was “probed, changed in configuration, actuated, torn down repeatedly 

for repair, modification or recalibration and transported around from 

one test facility to another.”102 All of these operations made effective 

sterilization extremely difficult, even though mission staff rigorously 

cleaned the craft with alcohol and shipped it to Cape Canaveral in 

a carefully controlled environment. Procedures using other, possibly 

more effective, liquid and grease sterilants were under development 

but were not available in time for use in the Ranger project. Some of 

these other sterilants were also severely toxic.103

After completing prelaunch tests and shortly before the launch, 

mission staff inserted the Ranger spacecraft into the launch rocket’s shroud, or nose cone, which was a metal chamber with an aerodynamic configuration mounted on the upper end of the launch 

rocket and meant to protect the payload—in this case the Ranger 

101. F. H. Quimby, ed., Proceedings of Conference on Spacecraft Sterilization (Washington, DC: 

NASA Technical Note D-1357, 1962), p. 3; Craven, “Part I: Planetary Quarantine Analysis,” 

p. 20.

102. Quimby, Proceedings of Conference on Spacecraft Sterilization, pp. 5–6.

103. R. Cargill Hall, “Ranger’s Lunar Objectives in Doubt,” in Lunar Impact: A History of Project 

Ranger; Part I—The Original Ranger (Washington, DC: NASA SP-4210, 1977), Chap. 4, 

http://history.nasa.gov/SP-4210/pages/Ch_4.htm#Ch4_Top (accessed 26 January 2011).

48
In the Beginning

spacecraft—during ascent from Earth. The shroud’s base was biologically sealed using a plastic bulkhead to prevent contamination from 

outside reaching the spacecraft. A sterilant gas mixture containing 

450 milligrams per liter of ethylene oxide was piped into the nose cone 

cavity through an inlet port near its base and held there for 11 hours. 

An outlet port near the top of the shroud allowed expulsion of gases 

during the filling operation. This operation had to be carried out in an 

explosive-safe structure near the launch pad. Mission staff hoped that 

they had been able to adequately sterilize the craft during their previous cleaning operations, and since any subsequent contamination that 

the craft had acquired would have only occurred on its surface, this 

would be killed by the toxic gas.104

While ethylene oxide was effective at killing bacteria that it contacted, the gas had to be in residence in the nose cone for 11 hours, 

and this had to be followed by 2 hours of purging using filtrationsterilized nitrogen gas. Mission engineers worried that any repairs 

needed during countdown that required breaching the biological barrier isolating the spacecraft would necessitate repeating the gas sterilization process. If enough repairs and delays occurred, the launch 

window would be missed.

JPL submitted its proposed sterilization plan to NASA on 25 May 

1961, and NASA Associate Administrator Robert Seamans approved 

it in June 1961. Ranger Project Manager Jim Burke, however, did not 

give sterilization particularly high priority compared to other responsibilities of the Ranger staff. In listing 16 competing requirements for 

Ranger, Burke put reliability 1st in priority, while sterilization was 

ranked 14th.105

Protests Against Ranger Sterilization Procedures

During the early 1960s, performance problems plagued the Ranger 

spacecraft, and many in the space science community laid the blame 

on the sterilization procedures used. Ranger 1, launched in August 

104. Hall, “Ranger’s Lunar Objectives in Doubt”; Quimby, Proceedings of Conference on Spacecraft 

Sterilization, pp. 6–7. 

105. Hall, Lunar Impact.

49
When Biospheres Collide

1961, assumed a lower Earth orbit than planned. Ranger 2 failed at its 

November 1961 launch attempt. Ranger 3, which launched in January 

1962 and was to attempt a lunar landing, missed the Moon by 23,000 

miles and did not send back usable video images. Ranger 4 went out of 

control and crashed onto the far side of the Moon in April 1962, failing to send back video pictures. Ranger 5, which launched in October 

1962, missed the Moon due to a power loss and also did not send back 

video images. Three of these spacecraft, Rangers 3, 4, and 5, had been 

subjected to dry-heat and terminal-gas sterilization procedures.106

Vehement accusations followed these failures. Government entities as 

well as the media pointed fingers at the sterilization procedures as the 

root causes of at least some of the failed missions. Some members of the 

space science community adamantly insisted that lunar, unlike planetary, exploration did not require spacecraft sterilization. This position 

was somewhat supported by the Working Group on Biology at the July 

1962 NAS Iowa Summer Study, with Allan H. Brown as chairman. The 

group held that “contamination of the Moon does not constitute as serious a problem as is the case of the planets.” The group did, however, add 

that “lunar contamination should be kept at a feasible minimum.”107

This new, more lenient attitude toward contamination reflected 

to some extent the changing priorities of the U.S. space program. 

President Kennedy had committed the United States to landing a man 

on the Moon during the 1960s. Many space scientists had accepted the 

fact that wherever humans went, their microorganisms would have to 

go as well. The goal of attaining complete sterilization during lunar 

missions was being replaced, at least in part of the space science community, by the hope that contamination could be kept low enough 

such that it would not hinder the search for biological material within 

lunar samples returned to Earth.108

Those speaking out against spacecraft sterilization for lunar exploration attained some successes for their efforts. By November 1962, 

JPL was directed to cease applying dry-heat sterilization to Ranger 

space vehicle components. The requirement for terminal gaseous 

106. Phillips, “Implementation and Policy Directives,” in The Planetary Quarantine Program, pp.

25–33. 

107. Ibid., p. 30. 

108. Ibid., p. 30. 

50
In the Beginning

surface sterilization of the assembled spacecraft was eventually 

dropped as well. These policy changes became official on 9 September 

1963 when NASA’s Management Manual NMI-4-4-1, NASA Unmanned 

Spacecraft Decontamination Policy, was issued. The objective was to 

protect the Moon against “widespread or excessive contamination”109

until, in the eyes of NASA, a sufficient amount of data concerning the 

Moon had been obtained. In other words, the policy’s focus was on 

protecting the integrity of scientific exploration. Furthermore, NASA 

based its policy on prevailing scientific opinion that the Moon’s harsh 

surface environment would make reproduction of Earth microorganisms extremely unlikely, and that if viable Earth organisms were able 

to penetrate to the lunar subsurface and survive, any propagation 

would remain exceedingly localized.110

 NASA’s Management Manual NMI-4-4-1 did not lift sterilization 

requirements for planetary missions as it had done for lunar exploration. The planets were considered potentially contaminatable. The 

manual stated that NASA policy was to prevent planetary biological 

contamination “until sufficient information has been obtained . . . to 

ensure that biological studies will not be jeopardized.”111

Establishing Key NASA Life Science

and Planetary Protection Capabilities

One of the first people to whom NASA gave responsibility for spacecraft sterilization was Gerhard F. Schilling, a German rocket scientist 

who was brought to the United States after World War II and served as 

NASA Project Manager for the Atlas-Able Pioneer series of space probe 

launches and launch attempts that began in 1958.112 These probes 

109. Ibid., pp. 30–31.

110. Ibid., pp. 30–31.

111. Ibid, p. 32.

112. Charles R. Phillips, “NASA and Its Planetary Quarantine Responsibilities,” in The Planetary 

Quarantine Program (Washington, DC: NASA SP-4902, 1974), http://history.nasa.gov/SP4902/ch3.htm (accessed 26 January 2011); Sven Grahn, “The Atlas-Able Pioneers,” in “Jodrell 

Bank’s Role in Early Space Tracking Activities—Part 1,” http://www.svengrahn.pp.se/trackind/

jodrell/Able5.htm (accessed 31 January 2006). 

51
When Biospheres Collide

were key in helping to change the field of astronomy “from an observational to an experimental science,”113 and the field of life sciences to 

one concerned with, among other topics, “the quest for extraterrestrial 

life-forms.”114

T. Keith Glennan, NASA’s Eisenhower-appointed Administrator, 

realized early on that the new Agency needed to develop its own 

life sciences capabilities. This was necessary in order to reduce its 

reliance on military personnel and facilities to provide biomedical 

research for future human missions. It would also be necessary for carrying out the space agency’s planetary protection program, although 

even before NASA’s influence and Abe Silverstein’s first official NASA 

policy directives on spacecraft sterilization, the military did include, 

in response to science community recommendations, decontamination planning for its space probes.115

NASA had to expand its capabilities without alarming the military 

community or Congress, for the Agency needed their political support. The Agency also needed to address the expectations of the space 

science community, which was counting on it to carry out extraterrestrial biological investigations as well as biomedicine research. To 

help him with the delicate tasks of developing the new Agency while 

working effectively with the defense establishment, Congress, and the 

academic community, Administrator Glennan asked Clark Randt, a 

personal acquaintance and respected clinician, biomedical scientist, 

and medical administrator, to join NASA and serve as a special life 

sciences adviser. 

In addition, Administrator Glennan formed an ad hoc Biosciences 

Advisory Committee, naming Dr. Seymour S. Kety, a prominent neurologist and researcher with the National Institutes of Health, as its 

chair. Glennan instructed Kety to invite scientists with stature in 

the biosciences to serve on the committee. Glennan wanted these 

professionals to come from diversified backgrounds and to value 

113. R. Cargill Hall, “The Origins of Ranger,” in Lunar Impact: A History of Project Ranger

(Washington, DC: NASA SP-4210, 1977), Chap. 1, http://history.nasa.gov/SP-4210/pages/

Ch_1.htm (accessed 26 January 2011).

114. Hall, “The Origins of Ranger,” in Lunar Impact.

115. Charles R. Phillips, “NASA and Its Planetary Quarantine Responsibilities,” in The Planetary 

Quarantine Program (Washington, DC: NASA SP-4902, 1974), http://history.nasa.gov/SP4902/ch3.htm (accessed 26 January 2011).

52
In the Beginning

fundamental research as much as applied research and technical 

development. The Administrator needed a committee that 1) would 

provide specific guidelines for building a NASA life sciences program 

and 2) was responsive not only to the engineering community and 

the more applied scientific disciplines, but also to the interests of academia and other groups focused on basic research endeavors.116

The Kety Committee included among its advisers the strong planetary protection advocate Joshua Lederberg, as well as the chemist 

Melvin Calvin, another planetary protection pioneer.117 The committee 

carried out its study from June to November 1959, presenting its final 

report in January 1960. Besides urging increased emphasis on basic 

science (not a surprising conclusion, given Administrator Glennan’s 

guidelines for selecting committee members), the report cautioned 

against making NASA life science activities merely an adjunct to 

human spaceflight applications and operations. Instead, the report 

strongly recommended that an Office of Life Sciences be established 

as a major NASA division with two broad objectives: 

•	 Study of the biological nature of extraterrestrial environments, 

which was to include a serious search for extraterrestrial life. 

•	 Scientific investigations related to human spaceflight and 

exploration.

The Kety Committee report expressed complete support for a 

human spaceflight program, but stressed that its ultimate objective 

was to “expand opportunities for extraterrestrial science.”118

Planetary Protection and the Office of Life Science Programs

The NASA Office of Life Science Programs, which was formed on 

1 March 1960,119 included spacecraft sterilization and exobiology programs within its mandate. Administrator Glennan named his special 

116. Pitts, “The Human Factor,” Chap. 3; Phillips, The Planetary Quarantine Program, pp. 9–12; L. 

E. DeLisi, “Seymour S. Kety MD: The Man and His Accomplishments,” Psychiatric Genetics

10(4) (December 2000): 153–158. 

117. Phillips, “NASA and Its Planetary Quarantine Responsibilities,” 1974.

118. Pitts, “The Human Factor,” Chap. 3.

119. Mae Mills Link, “Office Of Life Sciences Established: 1960,” in Space Medicine in Project 

Mercury (Washington, DC: NASA SP-4003, 1965), Chap. 4.

53
When Biospheres Collide

adviser Clark Randt to head the new office. Randt was director of the 

neurology division at the medical school of Cleveland’s Case Institute 

(which became Case Western Reserve University in 1967 when it federated with Western Reserve University).120 He wanted to expand and 

strengthen biomedical studies within NASA, with an eye to the clinical applications that would hopefully result. He also enthusiastically 

supported human spaceflight and believed that a successful program 

required the cooperation of life scientists, engineers, and mission 

planners. Randt appeared to be “an excellent choice to bridge the gap 

between academic life scientists and NASA’s engineering—and physical science-oriented management.”121 In February 1960, Randt had 

recommended to Administrator Glennan that NASA’s life sciences 

program provide research, development, and training related to 1) biomedical requirements for human spaceflight, 2) biological effects of 

the space environment, and 3) the search for extraterrestrial life, outlining a schedule for accomplishing this work.122 

Memos and letters from Randt’s tenure with the Office of Life 

Science Programs indicate that he also gave importance to planetary 

protection matters. Several months after he was appointed, he wrote 

to Abe Silverstein, Director of NASA Space Flight Programs at the 

time, affirming the need to identify “adequate safeguards against contamination of celestial bodies” and proposing formation of a group that 

would “take positive action towards insuring that decontamination and 

sterilizing procedures are developed and effected.”123 George Hobby of 

the Jet Propulsion Laboratory offered to organize and lead this group, 

and JPL made plans, which Randt supported, for constructing a laboratory to investigate fundamental issues in decontaminating and sterilizing space probes.124 While Randt was pleased with JPL’s planetary 

protection research plans, JPL requested in an 11 October 1960 letter 

that Randt also make funding available from his office for the labora120. Case Western Reserve University, “Visiting Case,” http://www.case.edu/visit/about.html 

(accessed 10 March 2008).

121. Pitts, “The Human Factor,” Chap. 3; Phillips, The Planetary Quarantine Program, pp. 9–12. 

122. Pitts, “The Human Factor,” Chap. 3.

123. Both quotes in the sentence are from Clark T. Randt to Abe Silverstein, “Sterilization of 

Spacecraft,” 7 July 1960, folder 006696, “Sterilization/Decontamination Documentation,” 

NASA Historical Reference Collection.

124. W. H. Pickering to Clark T. Randt, 11 October 1960, folder 006696, “Sterilization/

Decontamination Documentation,” NASA Historical Reference Collection.

54
In the Beginning

tory. He was not able at that time to do so, although he thought that 

the matter should definitely be reexamined when his office developed 

its FY 1963 budget.125

Randt began efforts in 1960 to formulate a NASA policy on spacecraft decontamination.126 His Office of Life Science Programs also 

sponsored a study, related to both forward and back contamination, 

that sought to develop procedures and techniques for “sterilizing 

earth-launched objects so that they do not contaminate an extraterrestrial body with terrestrial micro-organisms and vice versa.”127

While Randt made grand plans for life science projects that 

included several important planetary protection efforts, his overall vision did not harmonize with NASA’s priorities at the time. The 

Agency closed the Office of Life Science Programs in August 1961 due 

to factors that included inadequate funding and inconsistent management and peer support. Randt’s programs met resistance from NASA’s 

engineers and physical scientists as well as from Congress and the 

military. They objected to such a broad, in-house life sciences effort. 

Randt’s agenda suffered from bad timing. During 1960 and 1961, 

NASA’s primary mission was to place a human in Earth orbit. The 

Agency had little interest in bioscience, the search for extraterrestrial 

life, or planetary protection, although it recognized that these areas 

would become important in the future, as they indeed did.128

The NASA Planetary Quarantine Program

By 1963, the importance that NASA gave to planetary protection matters had changed, largely due to the priority that was being 

given to lunar landing missions. (This change of attitude is discussed 

in detail in Chapter 4 on the Apollo program.) On 1 August 1963, 

125. Clark T. Randt to William H. Pickering, 27 October 1960, folder 006696, “Sterilization/

Decontamination Documentation,” NASA Historical Reference Collection.

126. Clark T. Randt to Carl E. Sagan, 2 November 1960, folder 006696, “Sterilization/

Decontamination Documentation,” NASA Historical Reference Collection.

127. Clark T. Randt to Commanding General, Army Medical Service Research and Development 

Command, 14 June 1960, folder 006696, “Sterilization/Decontamination Documentation,” 

NASA Historical Reference Collection.

128. Pitts, “The Human Factor,” Chap. 3.

55
When Biospheres Collide

the NASA Administrator asked the U.S. Surgeon General to detail 

Captain Lawrence B. Hall, a senior commissioned officer in the U.S. 

Public Health Service (PHS), to the space agency in order to develop 

a spacecraft sterilization program. Hall became NASA’s first Planetary 

Quarantine (PQ) Officer. NASA’s PQ Program operated from 1963 to 

1971 under the Agency’s Bioscience Programs, Office of Space Science 

and Applications.129

The PQ Office staff remained small and focused largely on directing research activities. NASA arranged with a variety of contractors to 

conduct a broad spectrum of necessary PQ research. Some examples 

of these efforts were as follows: 

•	 The Illinois Institute of Technology researched the survival of 

terrestrial bacteria under simulated extraterrestrial conditions. 

Of particular interest was the rate of germination of bacterial 

spores after exposure to a simulated Martian environment. The 

data helped in estimating contamination probabilities of Mars 

as well as other planets. 

•	 The Massachusetts Institute of Technology conducted a related 

study, evaluating microbial survival when exposed to the effects 

of ultra-high vacuum, extreme temperature, and ultraviolet and 

gamma radiation. 

•	 Wilmot Castle Company of New York conducted a study 

relating to effective spacecraft sterilization approaches, 

examining the dry-heat resistances of a range of spore-forming 

microorganisms. 

•	 Grumman Aircraft Engineering Corporation of New York 

carried out an experiment directly relevant to space travel, 

examining the growth and viability of terrestrial bacteria inside 

a closed, artificial environment. 

•	 Northrop Corporation of California researched envisioned 

sterilization issues on a Mars entry probe—in particular, “the 

ability of various spacecraft components or parts to withstand 

dry-heat treatments and ethylene oxide exposure.”130

129. Phillips, “Planetary Quarantine Program,” pp. 12–13. 

130. Charles R. Phillips, “Appendix: Planetary Quarantine Contractual Research,” in The Planetary 

Quarantine Program (Washington, DC: NASA SP-4902, 1974), http://history.nasa.gov/SP4902/appendix.htm (accessed 26 January 2011).

56
In the Beginning

•	 Florida State University developed probability models of 

decontamination strategies for individual spacecraft. 

•	 Stanford Research Institute (SRI) in California evaluated the 

probabilistic models of contamination that were currently being 

used in the PQ Program. SRI also worked on a more detailed 

model of expected microbial proliferation on Mars.

The PQ Office’s work proved important during the last half of the 

1960s in the Apollo program, when it was vital to collect and bring 

back Moon samples uncontaminated by terrestrial material and also to 

protect Earth against any Moon microbes on or inside samples taken, 

the spacecraft, and the astronauts themselves. The particular methodologies employed for accomplishing these objectives are examined in 

Chapter 4. 

The December 1970 Reorganization

By December 1970, several factors made it imperative that NASA 

reexamine its priorities, including those related to planetary protection. The Apollo program had been hugely successful and had achieved 

its major objectives. But President Nixon wanted NASA to implement 

“a reduced, multiple-objective, science oriented space program for the 

1970s,”131 and Congress’s interest in the space program was declining. 

As a result, financial support for space activities was reduced, leaving 

NASA with fewer space program options. 

In response to the situation, NASA adjusted its priorities. It limited 

human space exploration activities, which were extremely expensive, to 

Earth-orbital operations and research supporting unspecified and unapproved human missions. The Agency also prioritized science-focused 

robotic planetary exploration, including the search for extraterrestrial 

life. Exobiological studies and prevention of forward planetary contamination thus gained markedly in importance. 

Many NASA life scientists had been pushing for years for closer 

ties between the Agency’s biological programs, and NASA realized that 

131. John A. Pitts, “Toward an Integrated Life Sciences Program,” in The Human Factor: 

Biomedicine in the Manned Space Program to 1980 (Washington, DC: NASA SP-4213, 

1985), Chap. 11, http://history.nasa.gov/SP-4213/ch11.htm (accessed 26 January 2011).

57
When Biospheres Collide

this might be an appropriate time to make such changes. Associate 

Administrator Homer Newell requested the NAS Space Science Board 

to review the Agency’s life science efforts and identify their needs. 

NAS in turn appointed a special committee to do this, which found the 

space agency’s life science programs to be deficient in basic science 

and strongly requiring better coordination with each other. NAS also 

underlined the need for a NASA reorganization in the management of 

its life sciences programs. 

In December 1970, NASA responded to the above recommendations by announcing a reorganization, which resulted in certain advantages for the PQ Office. NASA considered the PQ Office’s coordination 

with planetary exploration activities important enough to give the 

PQ Officer access to top management. NASA reasoned that in order 

for planetary exploration missions to be carried out smoothly and 

effectively, it was critical for the PQ Office to conduct its regulatory 

responsibilities so as to avoid any conflict with the Agency’s planetary 

program operational responsibilities. To ensure this, NASA management gave its Director of Life Sciences an overall coordination role and 

provided the PQ Officer with a direct line of communication to the 

Associate Administrator, Office of Space Science.132

JPL Planetary Quarantine Efforts

In August 1959, JPL began to develop a small in-house biological group led by George L. Hobby, who had come from the National 

Institutes of Health. Since that time, many JPL personnel have conducted sterilization and planetary quarantine activities. Their efforts 

gained impetus after NASA Headquarters established its PQ Office, 

132. Phillips, The Planetary Quarantine Program, pp. 12–13; John A. Pitts, “Toward an Integrated 

Life Sciences Program,” in The Human Factor: Biomedicine in the Manned Space Program 

to 1980 (Washington, DC: NASA SP-4213, 1985), Chap. 11, http://history.nasa.gov/

SP-4213/ch11.htm (accessed 26 January 2011); Linda Neuman Ezell, “Organizational 

Charts,” in NASA Historical Data Book: Volume III—Programs and Projects 1969–1978 

(Washington, DC: NASA SP-4012, 1988), Appendix A, http://history.nasa.gov/SP-4012/

vol3/app.a.htm#436 (accessed 26 January 2011); NASA History Division, “Neat Stuff About 

the Right Stuff,” NACA/NASA Records at NARA, http://history.nasa.gov/nara/rightstuff.

html (last updated 21 January 2005, accessed 7 March 2006).

58
In the Beginning

which provided a centralized capability for program planning and 

funding. 

One large JPL research effort that began early in the space program sought to 1) determine which spacecraft components would survive various sterilization treatments and 2) develop new, more durable 

components when experiments revealed that heat or other sterilizing 

techniques damaged them. NASA’s PQ Office directly funded many 

JPL research efforts, although a good deal of JPL’s PQ and spacecraft sterilization research got intermingled with, and was difficult to 

separate from, other JPL activities associated with funded missions 

not directly related to planetary quarantine. For instance, trajectory 

computations for various missions served a dual purpose. They were 

critical for guiding the spacecraft where it was supposed to go and 

for keeping its components, including the payload, from inadvertently 

impacting a celestial body. Such computations were also critical in 

preventing planetary contamination due to such an impact.

133

International Scientific Cooperation vs. Military 

Priorities, and The Effect on Planetary Protection

The free exchange of technical data across international borders 

has always benefited scientific endeavors. Cross-border agreements are 

also key to the success of planetary protection, because keeping celestial bodies free of terrestrial contamination requires the cooperation of 

all spacefaring nations. During the Cold War, however, the open communication needed to implement broad technical and regulatory cooperation often ran afoul of military priorities. The Defense Department, 

for instance, regarded “space as a future setting for modern warfare”134

and thus opposed open exchange of data with the USSR.

The U.S. space program began as an outgrowth of military rocket 

development that took place during World War II and the following 

decade. While nonmilitary rocket research had been done earlier, 

133. Charles R. Phillips, “Planetary Quarantine Research,” in The Planetary Quarantine Program: 

Origins and Achievements 1956–1973 (Washington, DC: NASA SP-4902, 1974), Chap. 5.

134. Wolfe, “Germs in Space,” 203. 

59
When Biospheres Collide

and while our country would probably have eventually developed a 

space program without the military’s help, the ready availability of 

rocket engineering know-how and equipment greatly accelerated the 

program.135

The drivers for the space program included not only the direct strategic benefits and the scientific knowledge that could be attained by 

actual trips into space, but also the technological and political benefits that would indirectly help our position in the Cold War.136 As John 

Casani, the first project manager of NASA’s Galileo Mission to Jupiter 

once said, our country’s successes in space exploration conveyed to 

other states a powerful message regarding “how much technological 

capability . . . was represented here . . . if we could do that with a civilian enterprise, imagine what this would mean in a military” situation.137

Our space program, in other words, became a peaceful deterrent to 

future trouble by letting potentially hostile nations know, in a nonthreatening manner, that we were not a nation to be trifled with.

Exobiologists and planetary protection specialists in the United 

States as well as in other countries had to walk the tightrope between 

the open international exchange of scientific ideas and respect for 

military secrets and restrictions on information vital for national 

defense. Many U.S. scientists and engineers did not want their hands 

tied by such restrictions, because they knew that unfettered information exchange was important for creative advancements in their fields. 

They tried to retain their separation from military and political issues 

so as to protect their scientific objectivity and their right to uncontrolled trading of ideas and data. 

This tension between scientists and the military manifested in 

the continual struggles between SSB, NASA’s Office of Life Sciences, 

and the National Research Council-Armed Forces Committee on 

Bioastronautics (AFCOB). This committee, which was established by 

the NAS National Research Council in 1958 at the formal request of 

135. Phillips, The Planetary Quarantine Program, p. 1.

136. Jerome B. Wiesner, chair, Wiesner Committee, Report to the President-Elect of the Ad 

Hoc Committee on Space, 10 January 1961, NASA Historical Reference Collection and 

at Air War College (AWC) Web site, http://www.au.af.mil/au/awc/awcgate/report61.htm

(accessed 7 March 2006).

137. John Casani, recorded telephone interview by author, 29 May 2001.

60
In the Beginning

the Department of Defense,138 was populated largely by military advisers, but it also included scientists such as Melvin Calvin, an early figure 

in the planetary protection field who held membership on SSB as well. 

NAS attempted to combine its SSB with the military-oriented AFCOB, 

in order that the civilian and military branches of the space program 

might develop a unified front and also eliminate duplications of effort. 

Joshua Lederberg and his colleagues were among those strongly 

opposed to such an action, arguing that one committee was a group of 

civilians advising civilians, while the other consisted of military personnel studying military problems. Lederberg wanted the separation 

of tasks to be preserved. One clear advantage of doing so was to avoid 

the need for civilian space scientists who became engaged in military 

studies to obtain security clearances, for this would definitely restrict 

their ability to exchange scientific ideas and technical know-how 

across borders.139 Lederberg recognized that an effective international 

planetary protection network absolutely needed to be built, in part to 

protect the integrity of the field. If even one spacefaring nation failed 

to follow strict planetary protection procedures during its missions, 

this could result in irreversible contamination of target bodies and 

disastrous impacts to the exobiological studies of all nations. 

Exchange of state-of-the-art research data on, in particular, 

microbial survivability and effective sterilization approaches was key 

in building an effective international network. Western exobiologists 

thus carried out energetic efforts to engender international cooperation, hoping it would help prevent forward and back contamination. 

Their efforts could not, however, open the doors to free information 

exchange with the Soviet Union, partly because of the Russians’ own 

restrictions on scientific exchange. These were probably more strict 

than those put on U.S. scientists. According to Joshua Lederberg, 

official U.S. mechanisms of obtaining information were not able to 

identify critical details about Soviet sterilization techniques.140 What 

the West found out about Soviet actions and practices sometimes 

138. Mae Mills Link, “The Bioastronautics Mission Emerges,” in Space Medicine In Project 

Mercury (Washington, DC: NASA SP-4003, 1965), Chap. 1, http://www.hq.nasa.gov/office/

pao/History/SP-4003/ch1-3.htm (accessed 26 January 2011).

139. Wolfe, “Germs in Space.” 

140. Ibid. 

61
When Biospheres Collide

had to be obtained unofficially from personal contacts and gossip, 

as well from reading Eastern Bloc newspaper translations. But in 

general, Western exobiologists had to deal with a distinct lack of 

data from the Soviet Union on planetary protection, and this worried them. 

The USSR’s Luna II Mission

Western scientists grew especially concerned about the possibility of forward contamination when, in September 1959, the USSR 

announced that its Luna II probe had impacted the Moon’s surface. This was followed 30 minutes later by the crash of the third 

stage of Luna II’s launch vehicle on the Moon. Since the Soviets had 

kept their sterilization procedures largely secret, western scientists 

feared that science returns on future lunar missions might have been 

compromised by microbes released from the impacts. In a note to 

Eugene Kinkead of The New Yorker magazine, Lederberg discussed 

the USSR’s claim to have decontaminated Luna II, hoping that was 

indeed true. The Soviets had also claimed “to have ensured the safe 

landing of their marker plaques.”141 If they had accomplished this 

second feat but not thoroughly sterilized their spacecraft, a landing 

soft enough to preserve the marker plaques would likely not have 

destroyed the microorganisms on board. 

Lederberg considered Luna II’s mission to have been “more of a 

stunt and less scientifically valuable than a graze or an orbit around 

the Moon would be.”142 This supported his belief, discussed earlier in 

the chapter, that scientific research interests in space were likely to 

get deprioritized when there was a key strategic advantage to be had.143

Hugh Odishaw, Executive Director of SSB, also expressed concern 

about the uncertain level of contamination of the Soviet probe. He 

141. Joshua Lederberg to Eugene Kinkead, New Yorker, 16 September 1959, Correspondence/1959/

September (Chronological Listing), The Joshua Lederberg Papers, http://profiles.nlm.nih.gov/

BB/A/J/V/K/_/bbajvk.pdf (accessed 26 January 2011).

142. Ibid.

143. Joshua Lederberg, “How DENDRAL was Conceived and Born” (ACM Symposium on the 

History of Medical Informatics, National Library of Medicine, 5 November 1987), pp. 3–4, 

http://profiles.nlm.nih.gov/BB/A/L/Y/P/_/bbalyp.pdf (accessed 26 January 2011).

62
In the Beginning

noted in a letter to NASA and ARPA that “extra-terrestrial contamination could seriously interfere with proper studies of fundamental 

importance relating to biological developments in the solar system.”144

Odishaw suggested that because sufficient data were currently unavailable on actual contamination levels of space probe parts, SSB should 

initiate an immediate study to determine sterilization requirements 

compatible with present design and assembly processes. He further 

hoped that close international liaisons could be maintained so that 

other countries (i.e., the USSR) could have access to the study’s results.

Efforts by Individual Scientists To Determine USSR Planetary 

Protection Approaches and To Develop Alliances with Their 

Biologists

Lederberg, realizing that his personal connections with Soviet 

scientists might provide the best means of obtaining critical planetary protection data—in particular, the actual level of contamination control employed on Soviet spacecraft—took matters into his 

own hands on several occasions. He also strove to develop alliances 

with Soviet biologists, with the aim of attaining higher priorities for 

biological research goals on future space missions. Lederberg wrote 

to the microbiologist V. D. Timakov of Moscow’s Academy of Medical 

Sciences of the USSR in May 1958, stating that “the interest of U.S. 

biologists . . . will be futile unless we can make a common cause 

with our fellow-scientists in the biological sciences in the USSR.”145

Lederberg expressed concern that the eagerness to “demonstrate 

the capabilities of interplanetary vehicles,”146 as well as the emphasis in space research on collecting data for the physical over the 

life sciences, might well result in biological objectives being overlooked during the planning of interplanetary missions. He gave as an 

144. Hugh Odishaw (SSB) to T. Keith Glennan (NASA) and Roy Johnson (ARPA), 14 September 

1959, Correspondence/1959/September (Chronological Listing), The Joshua Lederberg 

Papers.

145. Joshua Lederberg to V. D. Timakov, 16 May 1958, Correspondence/1958/May (Chronological 

Listing), The Joshua Lederberg Papers, http://profiles.nlm.nih.gov/BB/G/C/W/G/_/bbgcwg.

pdf (accessed 26 January 2011).

146. Ibid.

63
When Biospheres Collide

example the “inadvertent contamination of a planet such as Mars by 

microorganisms carried from the earth”147 and added that the same 

danger applied to the Moon.

Similar sentiments were expressed by Lederberg in a July 1958 

letter to K. V. Kossikov of Moscow’s Institute of Genetics. Lederberg 

referred to his own deep interest in origin-of-life studies, and communicated his concerns that “programs of space exploration by various nations should not interfere with ultimate biological exploration of 

the moon and the planets.”148 In a letter sent at the same time to A. I. 

Oparin of Moscow’s Academy of Sciences, Lederberg articulated his 

view of the critical nature of space biological research and its vulnerability in the face of strategic considerations:

Unfortunately, although the experimental study of 

life on other planets is undoubtedly the most compelling 

scientific objective in space research, biologists have 

hardly begun to think about this problem in realistic 

terms. Since space-flight has become deeply entangled 

with the tragic political and military rivalry of our times, 

there is great danger that the fundamental scientific 

objectives will be overlooked . . .149

In 1959, Lederberg requested permission to directly contact a 

Soviet academician that he knew, N. D. Ierusalimskii, even though 

this was viewed by some in the government as a possible breach of U.S. 

security. Lederberg wanted to send Ierusalimskii copies of WESTEX 

meeting minutes, but the Executive Director of SSB, Hugh Odishaw, 

advised strongly against this course of action, which he felt would provide “the most advanced thinking of our senior scientists with regard 

to the many biological questions.”150

147. Ibid.

148. Joshua Lederberg to K. V. Kossikov, 1 July 1958, Correspondence/1958/July (Chronological 

Listing), The Joshua Lederberg Papers, http://profiles.nlm.nih.gov/BB/A/J/W/Q/_/bbajwq.

pdf (accessed 26 January 2011).

149. Joshua Lederberg to A. I. Oparin, 1 July 1958, Correspondence/1958/July (Chronological 

Listing), The Joshua Lederberg Papers, http://profiles.nlm.nih.gov/BB/A/L/D/C/_/bbaldc.pdf

(accessed 26 January 2011).

150. Wolfe, “Germs in Space,” 200. 

64
In the Beginning

In approximately 1960, Lederberg obtained a security clearance 

for A. A. Imshenetsky, director of the Institute of Microbiology of the 

Soviet Academy of Sciences, to visit restricted locales in California. At 

a Stanford University lunch meeting with Imshenetsky, Lederberg was 

able to glean possible indications of “the Soviet Union’s lack of progress in exobiology,”151 although this impression might have been due to 

Imshenetsky’s lack of understanding of the English language, or to his 

intentional evasion of questions. 

Other space scientists also used their personal influences to try to 

obtain information about Soviet spacecraft sterilization processes. In 

November 1959, Carl Sagan reported a personal attempt to augment 

official channels of information exchange by conducting a conversation with G. F. Gause of the Soviet Academy of Medical Sciences at 

the Darwin Centennial Celebration. Sagan’s aim was to obtain details 

on Soviet space probe sterilization procedures. Gause assured Sagan 

that mission staff had sterilized Luna II’s instrument package and its 

third stage carrier rocket, both of which had impacted the Moon. But 

when pressed for details, Gause said some curious things, claiming 

“that his knowledge of the sterilization did not exceed that published 

in Izvestia. He said that the sterilization methods were those known 

to every graduate student in microbiology at the University of Chicago, 

and to every manufacturer of canned food, but he would not be more 

specific than that. He explained his reluctance by the analogy that 

Abbott Laboratories in Chicago would not divulge trade secrets to 

competing pharmaceutical firms.”152 Sagan believed that Gause knew 

far more about the actual sterilization procedures used, but he could 

get little further information from him. 

Eventually, some encouraging data were obtained about Soviet planetary protection activities. Lawrence Hall, NASA’s Planetary Quarantine 

(PQ) Officer, wrote a memo in June 1972 referring to a presentation 

given at a recent COSPAR meeting153 by V. I. Vashkov of the USSR, in 

which he discussed a methyl bromide–ethylene oxide gas mixture used 

151. Ibid., 201. 

152. Carl Sagan, abstract of letter summarizing his conversation with G. F. Gause, November 1959, 

Abstracts (Chronological Listing), The Joshua Lederberg Papers, http://profiles.nlm.nih.gov/

BB/G/C/X/P/_/bbgcxp.pdf (accessed 26 January 2011).

153. This meeting was of the COSPAR Planetary Quarantine Panel, held in Madrid on 19 May 1972.

65
When Biospheres Collide

to sterilize Soviet spacecraft parts. After his presentation, Vashkov 

answered “with apparent frankness questions on the measures used to 

sterilize”154 Soviet Mars-bound spacecraft. Vashkov claimed that individual parts of landers were sterilized by heat (although he did not give 

the temperature or duration of the procedure) or by a radiation dose of 

2.5 millirads,155 depending on the characteristics of the part. The landers were assembled in cleanrooms, and individual parts were carefully 

cleaned, probably with hydrogen peroxide. UV light was applied during 

assembly as an additional sterilant. Finally, before launch, Soviet mission 

personnel exposed the entire lander to a methyl bromide–ethylene oxide 

gas mixture for 6 hours at 50°C.

Vashkov also stated that extensive bioassays were carried out on 

a model of the spacecraft in order to verify the effectiveness of the 

planetary protection techniques. These assays employed numerous 

samples taken by a technique called “mopping” that Hall believed was 

similar to NASA’s swabbing procedure (which is discussed in Chapter 

7 regarding Mars missions). To prevent recontamination of the Soviet 

lander, Vashkov mentioned it remained “enclosed in a plastic bag in 

which a low concentration of the sterilant gas was maintained until 

the spacecraft had left the earth’s atmosphere.”156

Hall’s confidence in the validity of Vashkov’s statements was 

enhanced by their agreement with several published documents. In a 

study by Vashkov, Rashkova, and Shcheglova,157 reference was made 

to experiments with electronic components such as diodes, triodes, 

capacitors, resistors, relays, sockets, and plugs, showing that they 

were effectively sterilized using 2.5 millirad of gamma radiation. The 

study mentioned assembly under sterile conditions, sterilization of 

some parts using hydrogen peroxide sprays, and final sterilization of 

154. Lawrence B. Hall, “Soviet Planetary Quarantine Sterilization of Mars 1 and 2,” 1 June 1972, 

NASA Historical Reference Collection.

155. A millirad (mrad) radiation dose is equal to one-thousandth of a rad, the dose causing 0.01 

joule of energy to be absorbed per kilogram of matter. Normal background radiation in the 

United States varies from about 50 to 200 mrad per year.

156. Hall, “Soviet Planetary Quarantine Sterilization,” 1 June 1972.

157. V. I. Vashkov, N. V. Rashkova, and G. V. Shcheglova, “Kavantin Planet: Printsipy, Metody, 

i Problemy,” in Osnovy, Kosmicheskoy Biolgii i Meditsiny, Chap. 4, vol. 1, part 3 (1970), 

pp. 3–156, and its English translation, “Planetary Quarantine Principles, Methods, and 

Problems,” NASATT F13, 769 (1971), 113 pages, a summary of which is attached to the 

above-cited Lawrence B. Hall memo of 1 June 1972.

66
In the Beginning

the spacecraft by filling it to excess pressures with methyl bromide–

ethylene oxide gas. Also described was a bioassay procedure, used as 

a means of verifying the sterility of spacecraft. 

Another study by Imshenetsky158 and Abyzov159 referred to 

experiments at the USSR’s Institute of Microbiology of the Academy 

of Sciences that sought to clarify the best procedure for sterilizing 

“infected” materials, and the result that reducing the temperature and 

lengthening the exposure period created “effective methods of sterilization for the spacecraft as a whole.” This was a result that NASA 

arrived at as well for terminal sterilization, which is discussed in detail 

in Chapter 7 of this book. Imshenetsky and Abyzov also mentioned the 

use of “radiation sterilization,” sterile assembly techniques, and final 

sterilization of the spacecraft using gas. Another study by Vashkov160

discussed heat sterilization performed at various temperatures and 

durations and specifically mentioned that this technique was used 

on Soviet Venus spacecraft. In addition, Vashkov referred to favorable 

analyses of UV-lamp, hydrogen peroxide, and gas sterilization techniques for spacecraft.

Impacts of U.S. Restrictions on Open Information Transfer

USSR limits on free information transfer regarding its planetary 

protection protocols have been discussed above. It is also important 

to mention that U.S. restrictions significantly limited data exchanges 

as well. This was especially so regarding the sharing of certain biohazard data. U.S. restrictions on information transfer definitely reduced 

the amount of data distributed from projects that involved the Army 

Biological Warfare Laboratories at Fort Detrick, Maryland.

158. The transliteration of his Russian name is alternately spelled “Imshenetsky,” “Imshenetski,” 

and “Imshenetskii” in various references. In this book, his name will always be spelled 

“Imshenetsky.”

159. A. A. Imshenetsky and S. Abyzov, “Sterilization of Spacecraft,” NASATT-710 (November 

1971): 230–252, a summary of which is attached to the above-cited Lawrence B. Hall memo 

of 1 June 1972.

160. V. I. Vashkov, “Modern Methods and Means of Sterilization of Spacecraft,” NASATT-710 

(November 1971): 207–219, a summary of which is attached to the above-cited Lawrence B. 

Hall memo of 1 June 1972.

67
When Biospheres Collide

Beginning in 1959, SSB had advocated cooperation between space 

scientists and Fort Detrick staff, whose experience and equipment for 

detecting and safely handling minute quantities of microorganisms, 

some of them extremely dangerous, were excellent foundations on 

which to develop spacecraft sterilization techniques as well as biological 

detection instruments. WESTEX also supported partnerships with Fort 

Detrick, especially for developing sterilization techniques based either 

on ethylene oxide gas or exposure to radiation. Lederberg was interested 

in Fort Detrick’s capability for testing bacterial survivability in hostile 

environments such as chemical explosions, for this would have direct 

applications for identifying effective sterilization techniques.161

The cooperative agreement with Fort Detrick produced powerful 

benefits, but it also raised barriers to the life science community’s 

repeated attempts to establish open, free exchange of data with other 

countries. Research undertaken at Fort Detrick biological warfare 

facility generated highly restricted, classified results that could not 

be openly shared with Soviet or other international colleagues, for to 

do so would have potentially given the USSR key information on very 

potent weapon systems.162

To What Extent Did Speculative Literature 

Influence the Planetary Protection Field?

 No technical field exists that is totally disconnected from the society 

around it and that society’s mores and fears. The priorities of the society 

in which a field of inquisition is embedded cannot help but have some 

influence on the field’s practitioners, whether through budget pressures 

or due to direct relationships with its members. The planetary protection 

field was no exception to this. 

The exploration of space is an endeavor whose success depends 

not only on good science, but also on good imagination. NASA scientists and engineers continually strive to do what has never been done 

before, and this requires originality of thought and leaps of creativity. 

161. Wolfe, “Germs in Space.” 

162. Wolfe, “Germs in Space,” 192–193.

68
In the Beginning

Science fiction writers, on the other hand, seek to create that which 

has not yet been envisioned. These writers, like space scientists, 

search for pathways to places as yet unexplored. Thus, it is not surprising that one field can inform and inspire the other. 

Several works of science fiction have resonated so powerfully with 

the psyches of their audiences, and have been so widely read or listened to, that they have strongly affected the public’s beliefs regarding 

space exploration and, in particular, the need for planetary protection. The earliest of these influential works was Herbert George “H. G.” 

Wells’s The War of the Worlds, written in 1898. Two decades before 

this book’s publication, the Italian astronomer Giovanni Schiaparelli 

had thought he saw a series of lines on the surface of the planet 

Mars that he called canali, an Italian word meaning “channels.” The 

astronomer Percival Lowell also observed these lines and, in his 1895 

book, Mars, mused that “Their very aspect is such as to defy natural 

explanation.”163 He concluded that they were artificial canals and that 

“upon the surface of Mars we see the effects of local intelligence.”164

Such a possibility inflamed the public’s imagination. Perhaps influenced by Lowell’s work as well as by major events of the time—in particular, German unification and the threat of a war that would engulf 

all of Europe165—Wells wrote a book that responded to the questions: 

What if intelligent creatures did indeed exist on Mars who had far surpassed our technological achievements, and what if those creatures 

felt hostile toward us?166

In The War of the Worlds, Martian life definitely was not benign. 

The creatures from the Red Planet destroy a large part of London and 

the English countryside, as well as many British citizens. Our planet’s 

163. Percival Lowell, Mars (Cambridge, MA: Riverside Press, 1895), http://www.wanderer.org/

references/lowell/Mars/ (accessed 26 January 2011).

164. Ibid.

165. Paul Brians, Department of English, Washington State University, introduction to “Study 

Guide for H. G. Wells: The War of the Worlds (1898),” http://www.wsu.edu:8080/~brians/

science_fiction/warofworlds.html (accessed 16 May 2005).

166. NASM, “Percival Lowell and Mars,” 12 September 1997, http://www.nasm.si.edu/ceps/etp/

mars/percival.html; “Exploring the Planets: Mars” Web site, National Air and Space Museum 

(NASM), http://www.nasm.si.edu/ceps/etp/mars/ (accessed 16 May 2005); John D. Gosling, 

“Herbert George Wells: A Biography,” on the Web site, “The War of the Worlds—Invasion: 

The Historical Perspective,” http://www.war-ofthe-worlds.co.uk/index.html (accessed 16 

May 2005).

69
When Biospheres Collide

bacteria, to which we humans have built up a resistance, eventually 

defeat and kill the Martians. The invaders bring along an insidious red 

weed that roots in Earth soil, but this too falls prey to Earth’s environment, dying from common plant diseases that don’t exist on Mars. 

Nevertheless, the Martian attacks scared many readers. H. G. Wells’s 

book planted fears in people that the ordinary life from one planet will 

be antagonistic, and even murderous, to those from another planet. The 

biggest impact of the book was not on its readership, however, but on 

those who listened to an Orson Welles adaptation of it for a radio play. 

Orson Welles and his theater company broadcast the play as a Halloween 

special on 30 October 1938 and aired it over station WABC and the 

Columbia Broadcasting System’s coast-to-coast network.167 The play was 

given the format of an emergency news program and listened to by over 

six million Americans. Almost two million of these thought that the play 

was the real thing and panicked at the supposed invasion. People who 

had heard the broadcast “packed the roads, hid in cellars, loaded guns, 

even wrapped their heads in wet towels as protection from Martian poison gas.”168

The public’s panic reaction to a radio adaptation of H. G. Wells’s 

classic was not limited to U.S. audiences. In February 1949, over 10 

years after Orson Welles’s broadcast, Radio Quito in Ecuador presented a similar play, but this time set in the Andean country rather 

than in the United States. A Saturday-night music program was interrupted in mid-song with “a long and frightening description of how 

Martians had landed twenty miles south of the city, near Latacunga.”169

The announcement told listeners that Latacunga had already been 

destroyed, and aliens were moving toward Quito in the shape of a cloud. 

This was followed soon after by another announcement claiming that 

an air base had been destroyed, leaving many dead and wounded. Then 

actors talented at imitating well-known public figures spoke, posing as 

the Minister of the Interior, the mayor of Quito, and others.

167. “Radio Listeners in Panic, Taking War Drama as Fact,” New York Times (31 October 1938), http://

www.war-of-the-worlds.org/Radio/Newspapers/Oct31/NYT.html (accessed 10 July 2008).

168. Ken Sanes, “War of the Worlds, Orson Welles, and the Invasion from Mars,” Transparency 

Web site, http://www.transparencynow.com/welles.htm (accessed 16 May 2005).

169. Don Moore, “The Day the Martians Landed,” Monitoring Times (October 1992), http://

members.tripod.com/donmoore/south/ecuador/martians.html (accessed 10 July 2008).

70
In the Beginning

Thousands ran from their homes, some in pajamas. When Radio 

Quito admitted its hoax, many in the panicked populace were enraged 

and converged on the El Comercio building where the radio station 

was housed. They stoned the building, then set it aflame. When the 

smoke finally cleared, the building was destroyed and, far worse, 20 

people had died in the fire. 

Panic reactions were also triggered following a broadcast of the 

Welles play in Santiago, Chile, in 1944, Providence, Rhode Island, 

in 1974, and in northern Portugal in 1988.170 Perhaps more than any 

other work of science fiction, The War of the Worlds left its listeners 

and readers with images of life’s dangerous fragility to exotic species.171

Such images strongly communicated the potential risks involved when 

one planet’s culture and ecology interfaces with those of another. 

Although radio stations, the news media, and the government 

quickly tried in each instance to convince the populace that there was 

no reality to an alien invasion, the fear that someday a real war of the 

worlds might occur did seem to linger. Such fears certainly flared up 

as the day approached for sending humans to the Moon to collect alien 

samples and then bring them back to Earth. The extreme measures to 

which the Apollo mission went to avoid back contamination of Earth 

(these are discussed later in this book) were certainly driven by scientific considerations, but also were needed to assuage the public fear of 

an extraterrestrial epidemic taking root on our planet. 

What the War of the Worlds broadcasts did was trigger a deep terror that may have resided in our collective psyches for many centuries: 

fear of the outsider whom we don’t understand and who wishes us 

ill. Because such a fear can be so easily activated and is periodically 

set off by disturbing stories in the media, both nonfictional and fictional, dealing with such terrors has to be an integral part of developing a planetary protection policy. In 1950, Ray Bradbury wrote 

The Martian Chronicles partly to counteract the War of the Worlds 

notion that Mars could be a menace to Earth. In Bradbury’s novel, it is 

humans from Earth who play the role of harmful “invaders from outer 

170. Robert E. Batholemew, “The Martian Panic Sixty Years Later,” Skeptical Inquirer (November/

December 1998), http://www.csicop.org/si/9811/martian.html (accessed 10 July 2008).

171. Audra J. Wolfe, “Germs in Space: Joshua Lederberg, Exobiology, and the Public Imagination, 

1958-1964,” Isis 93(2) (June 2002).

71
When Biospheres Collide

space,”172 wiping out a wise species of sentient beings from whom we 

could have learned a great deal. Although The Martian Chronicles did 

not instigate widespread panic or drive a large part of the populace 

into the streets, it appears to “have deeply affected [Joshua] Lederberg 

and his WESTEX colleagues.”173 One of the book’s similarities to H. 

G. Wells’s novel is the portrayal of exotic life-forms as terribly vulnerable to Earth microbes. In The Martian Chronicles, most of the Red 

Planet’s inhabitants get sick and die from a terrestrial disease resembling chicken pox, after which people on Earth destroy themselves 

through nuclear war. Although the documents produced by Lederberg 

and WESTEX do not explicitly refer to the above novels, “the themes 

of unintended consequences and self-annihilation echo throughout 

their discussions.”174

The War of the Worlds and The Martian Chronicles influenced many 

journalists reporting on the new field of exobiology, supplying them with 

the images and vocabulary by which to imagine and articulate the threats 

that could result from space exploration. Americans learned about exobiology from widely read periodicals such as Newsweek, Time, and Esquire,

as well as from local newspapers. Space scientists gave warnings that planetary exploration might result in back contamination of Earth, and these 

statements inspired journalists to write speculative pieces which often 

blended real science narratives with science fiction themes. A 1961 Time

article entitled “Danger From Space” reported that

The human species seems about to master the solar 

system. The contrary may be the truth. Last week 

Lockheed Aircraft Corp. announced that it has a team 

of scientists hard at work, hoping to find a way to foil 

invasions of the earth that may well start from space. 

The invaders most to be feared will not be little green 

Venusians riding in flying saucers or any of the other 

intelligent monsters imagined by science fictioneers. 

172. Paul Brians, Department of English, Washington State University, introduction to “Study 

guide for Ray Bradbury’s The Martian Chronicles (1950),” http://www.wsu.edu:8080/~brians/

science_fiction/martian_chronicles.html (accessed 16 May 2005).

173. Wolfe, “Germs in Space.”

174. Wolfe, “Germs in Space.”

72
In the Beginning

Less spectacular but more insidious, the invaders 

may be alien microorganisms riding unnoticed on 

homebound, earth-built spacecraft.175

In this story, Time effectively used science fiction themes to communicate real science issues. Many other popular articles about exobiology also began by evoking visions of alien life, sometimes dangerous, 

and then followed this with the actual scientific basis of the space 

exploration projects. Sometimes, though, the repeated implications—

that serious space science endeavors resembled fiction novels—damaged space scientists’ credibility. Journalists frequently chose titles for 

their articles that could have been applied to science fiction yarns. For 

instance, Esquire named a December 1963 article on space exploration, “Someone Up There Like Us?”176 while newspapers chose headlines such as “Invasion From Mars? Microbes!”177 and “Space Academy 

Board Warns of Microbe Attack From Space.”178 Lederberg and his colleagues struggled to legitimize the emerging field of exobiology, but 

their attempts continued to be plagued by news story lead lines such 

as, “A ‘war of the worlds’ is now conceivable.”179 This sensationalism 

was by no means limited to the United States. A cartoon in a Danish 

magazine, for example, lampooned Lederberg and exobiology in its 

depiction of three hospital patients afflicted with, respectively, Moon 

measles, Mars flu, and Venus warts.180

Although Lederberg expressed his chagrin with articles that linked 

the serious science of exobiology with popular culture and, in particular, the tropes of science fiction, many of these same articles communicated legitimate exobiological concepts to the lay public in a highly 

readable and entertaining manner, and by doing so helped to keep 

readers intensely interested in NASA’s space missions. The engaging 

narrative styles employed in these articles also helped achieve planetary protection goals by enabling exobiologists to widely publicize their 

175. “Danger from Space?” Time (17 November 1961).

176. Wolfe, “Germs in Space.”

177. Ibid.

178. Ibid.

179. Ibid.

180. Ibid.

73
When Biospheres Collide

pleas to implement dependable contamination prevention measures 

into space exploration.181

Michael Crichton wrote The Andromeda Strain in 1969 about a 

plague brought to Earth on a returning space probe. This book about 

the possible consequences of back contamination became a runaway 

best seller. Its sales certainly were not hurt by its release’s coinciding nicely with the first human Moon landing and the return of lunar 

samples to Earth. A gauge of the book’s effectiveness in communicating 

the potential dangers of back contamination to readers was that when 

it was first published, many people thought it was not a made-up story 

but was actually based on real events.182 The book elicited “a fear in the 

public mind that extraterrestrial specimens might introduce a new and 

unstoppable plague to the Earth.”183 Although events in the book were 

fiction, its premise has become a metric for worst-case scenarios resulting from back contamination. The Andromeda Strain is often referred 

to in this context by space science professionals and journalists as the 

outcome that everyone least wants from a sample return mission.184

Although The Andromeda Strain was hardly the first publication 

to address back contamination dangers, it put that issue in the public’s 

minds and, by so doing, in front of the scientific community as well. For 

example, Abigail Salyers, a professor of microbiology at the University of 

Illinois, wrote about efforts to find life on Mars and other planets. In her 

articles addressing the safety of bringing Mars samples back to Earth, 

she used The Andromeda Strain, as other space scientists have done, 

as the starting point of her discussion, then identified occurrences that 

were quite possible from those that were highly improbable. She asked 

whether a microbe brought back from a planet without humans could 

181. Ibid.

182. Michael Crichton, The Andromeda Strain, official Web site of Michael Crichton, http://www.

crichton-official.com/strain/ (accessed 20 June 2005).

183. Abigail A. Salyers, Department of Microbiology, University of Illinois at Urbana-Champaign, 

“Looking for Life on Mars and Beyond,” American Institute of Biological Sciences, August 2004, 

http://www.actionbioscience.org/newfrontiers/salyers2.html (accessed 20 May 2005).

184. Margaret S. Race and John D. Rummel, “Bring Em Back Alive—Or At Least Carefully: Planetary 

Protection Provisions for Sample Return Missions,” Ad Astra (January/February 1999), http://

www.astrobiology.com/adastra/bring.em.back.html (accessed 10 July 2008); “QED,” Telegraph.

co.uk, http://www.telegraph.co.uk/digitallife/main.jhtml?xml=/connected/2004/01/21/ecrqed18.

xml (accessed 10 July 2008); Brendan I. Koerner, “Your Planetary Protection Officer—What on 

Earth Does He Do?” Slate.com, Washington Post, Newsweek Interactive Co. LLC, 20 April 2004, 

http://www.slate.com/id/2099222/ (accessed 11 July 2008).

74
In the Beginning

cause serious infections in our species. Her answer was definitely yes. 

But would organisms that evolved in the low-temperature environments 

of Mars or Europa do well in the relatively high temperatures of our bodies? Probably not. The point is that The Andromeda Strain has become 

a touchstone for planetary protection specialists in discussing matters 

of back contamination and the dangers that they present.185

Red Mars, written by Kim Stanley Robinson in 1993, imagined 

possible colonization experiences on the planet and the conflicts arising from different visions of what was appropriate. The book articulated important questions about what on a planet should be protected. 

In the author’s words, “the question of whether or not to terraform 

Mars . . . [was] one of the great engines” of writing Red Mars and the 

two books in the series that followed it. The terraforming question is 

one that continues to be debated by scientists and ethicists. Do we 

have the right to someday transform Mars, or some other planet, into 

an Earth-like planet? Or only if we find no life there? Or should we 

leave Mars in its natural state even if it proves to be devoid of life? 

One of the views expressed in Red Mars pertained to “an awfully 

big and beautiful, sublime landscape”186 that turned out to be lifeless. According to this point of view, even if we should find that Mars’s 

vast deserts and enormous mountains and canyons contain no lifeforms, we still are not free to tear the planet apart and reconstruct it 

as we like. We need to keep the planet unspoiled. This is a position 

that Henry David Thoreau187 or John Muir, who both revered the wild 

places, might have taken. Muir once said that wilderness was a sacred 

area “that should be cherished because of its very existence.”188 This 

view was also articulated by David Brower, executive director of the 

Sierra Club from 1952 to 1969 and a founder of Friends of the Earth, 

185. Salyers, “Looking for Life on Mars and Beyond.”

186. Donna Shirley, “The Great Terraforming Debate-Part 7: Questions: The Martian Future,” 

Science Fiction Museum and Hall of Fame, Seattle, WA, 20 June 2004, http://www.

sfhomeworld.org/make_contact/article.asp?articleID=162.

187. Henry David Thoreau, “Walking,” Atlantic Monthly 9 (June 1862): 657–674.

188. Brian Manetta, “John Muir, Gifford Pinchot, and the Battle for Hetch Hetchy,” Ithaca College 

History Department, Ithaca College History Journal (spring 2002), http://www.ithaca.edu/

hs/history/journal/papers/sp02muirpinchothetchy.html (accessed 22 May 2005).

75
When Biospheres Collide

who believed that we must “save wilderness for its own sake, for the 

mysterious and complex knowledge it has within it.”189

The book Red Mars expanded the forum for discussing these ideas 

versus the views of those who say that we have a right, perhaps even 

a duty, to colonize and transform Mars into something good for our 

species. These various views continue to be discussed in the space science community. Christopher McKay,190 for instance, of NASA Ames 

Research Center, argued that “terraforming Mars would be permissible, 

provided the planet is sterile,”191 while the aerospace engineer Robert 

Zubrin took a giant step further, holding that “failure to terraform 

Mars constitutes failure to live up to our human nature and a betrayal 

of our responsibility as members of the community of life itself.”192 A 

more detailed discussion of the ethics of space exploration is included 

in Chapter 8.

Robinson’s Mars trilogy did something else besides bringing up ethical issues that was no less important an accomplishment. It gave Mars 

a reality in the mind of the reader, transforming the planet from a concept to an actual terrain that could be seen and almost felt—expanses 

of rust-colored sand, an endlessly rising volcano, enormous gashes in 

the surface, and a landscape bashed by “meteor strikes so large that 

pieces from the collisions flew all the way to our Earth and moon.”193

Making a planet more real allows the reader to think about issues such 

as contamination prevention in a different light, because the planet has 

become a tangible object, potentially worth protecting. Red Mars was 

a very widely read book. I believe its biggest contributions to the planetary protection field were to give the planet a bona fide existence and a 

beauty that will affect the decisions made about her in the future.

189. Tom Thomson, “David Brower,” http://www.netwalk.com/~vireo/brower.htm, from the Web 

site, “Earth talk!”—The quotations of over 200 American naturalists and scientists with brief 

biographies, http://www.netwalk.com/~vireo/ (accessed 23 May 2005).

190. C. P. McKay, “Does Mars Have Rights? An Approach to the Environmental Ethics of Planetary 

Engineering,” in Moral Expertise, ed. D. MacNiven (New York: Routledge, 1990), pp. 184–197.

191. Martyn J. Fogg, “The Ethical Dimensions of Space Settlement,” International Academy of 

Astronautics, IAA-99-IAA.7.1.07, 1999, http://www.users.globalnet.co.uk/~mfogg/EthicsDTP.

pdf (accessed 26 January 2011).

192. Robert Zubrin, The Case for Mars: The Plan to Settle the Red Planet and Why We Must (New 

York: Simon & Schuster/Touchstone, 1996), pp. 248–249. 

193. S. Troy, “Red Mars: Kim Stanley Robinson-Nebula 1993,” Award Winner’s Review, Sustainable 

Village Web site, http://www.thesustainablevillage.com/awrbooks/html/BooksinHTML/

redMars.html (accessed 23 May 2005).

76
3 DEVELOPING EFFECTIVE 

PLANETARY PROTECTION 

APPROACHES

There has been much concern . . . over the fact that 

sterilization procedures represent a hazard to the 

success of the total mission. . . . Approach it from the 

standpoint of not what should we do, but what can we 

do, and how should we do it.

—Freeman Quimby, Editor of 1962 Proceedings 

 of Conference on Spacecraft Sterilization1

Abe Silverstein, NASA’s Director of Space Flight Programs, issued an 

edict in October 1959 requiring that “payloads which might impact a 

celestial body must be sterilized before launching.”2 Sterilization, interpreted strictly, meant that every last microorganism in the space vehicle had to be either killed or removed. But NASA quickly realized that 

meeting this standard would be prohibitively difficult.3

In its effort to achieve absolute sterilization—the destruction or 

removal of all microorganisms—NASA mission staff attempted to walk a 

tightrope between two extremes: 1) subjecting spacecraft components to 

severe enough environments to remove all living material and 2) avoiding 

overly harsh conditions that would damage sensitive equipment and possibly cause a mission to fail. Accomplishing both objectives proved untenable. Even hospital sterilization procedures do not kill all living material. 

 1. Freeman H. Quimby, ed., 

77
When Biospheres Collide

NASA was developing its contamination control program under 

enormous time pressure. It had to meet President Kennedy’s directive 

to land a man on the Moon in the decade of the 1960s. The Agency 

saw that it needed to modify its standard for preparing a spacecraft 

to visit another world. NASA mission staff thus set a more realistic 

goal for dealing with spacecraft contamination: attain a sterilization 

level sufficient to avoid compromising biological studies of the Moon 

or a planet. In doing this, the Agency shifted its metric of successful 

planetary protection from a standard of absolute sterilization to one 

dependent on the limitations of biological sensing technologies.

4

Probabilistic Approaches to Spacecraft 

Contamination Control

As early as 1960, space scientists suggested that a probabilistic 

approach be used for designing contamination control procedures.5

During a NASA-sponsored conference held on 29 June 1960 entitled 

“Problems and Techniques Associated with the Decontamination and 

Sterilization of Spacecraft,” participants recommended that research 

be conducted to determine probabilities of accidental spacecraft 

impacts, coupled with statistical studies of viable organism implantations on celestial bodies.6

At another conference on spacecraft sterilization held 9 July 1962 

by NASA Biosciences Programs, participants considered tolerance 

levels for the probability that a single microbe would survive after 

sterilization of a spacecraft or one of its components. Discussion at 

this conference centered around studies conducted by L. D. Jaffe of 

JPL (but on temporary assignment to the NASA Lunar and Planetary 

Office). Jaffe’s studies considered various scenarios regarding 

 4. Phillips

78
Developing Effective Planetary Protection Approaches

permissible risks of a robotic expedition contaminating Mars. One 

of his reports, which he circulated at the conference, estimated the 

lowest probability level of microbe survival that could currently be 

achieved with the best sterilization methods available as 10–4. This 

was equivalent to no more than one in 10,000 landings or planetary 

impacts containing a microorganism. Conference participants adopted 

the 10–4 probability limit as a desirable goal for planetary flights.7

L. D. Jaffe spent considerable effort developing acceptable contamination risk recommendations for spacecraft landing on Mars. He estimated 

that on the basis of tests with terrestrial organisms under simulated 

Martian conditions, the probability of microbe growth if released on Mars 

was approximately unity. He also examined the engineering problems of 

spacecraft sterilization for robotic missions, as well as aseptic methods for 

spacecraft assembly and the dangers of recontamination. He concluded 

that the probability of introducing a viable microbe onto Mars should be 

held to 10–4, and techniques for accomplishing this were discussed.8

During this time, SSB was evaluating permissible probabilities 

of planetary contamination for flyby trajectories, as alternatives 

to sterilizing the spacecraft. In its 1962 study, A Review of Space 

Research, SSB recommended a probability of no more than 10–4 of 

an unsterilized flyby impacting (and potentially contaminating) the 

target planet.9

L. D. Jaffe’s work focused not only on Mars, but also on the degrees 

of assurance advisable for missions to the Moon and Venus. He held that 

sterilizing a spacecraft was probably not necessary for expeditions to the 

Moon, citing 1960 research by Carl Sagan as well as 1962 work by Soviet 

microbiologist A. A. Imshenetsky indicating only a remote chance that 

terrestrial organisms would grow and reproduce on or near the lunar surface. Sagan had discussed the “three major hazards for survival of terrestrial life on the Moon—temperature, corpuscular radiation, and solar 

 7. Morton Werber, 

79
When Biospheres Collide

electromagnetic radiation”10 as probably precluding microbial reproduction on the lunar surface. Nevertheless, Sagan believed that contamination of the Moon with terrestrial microbes and organic matter would 

constitute “an unparalleled scientific disaster,”11 interfering with research 

on the early history of the solar system, chemical compositions of matter 

in the remote past, and the origin of Earth life. He strongly felt that such 

contamination should be avoided. Lederberg and D. B. Cowie in 195812

had also suggested taking steps to avoid contaminating the Moon, so that 

any organic chemicals found there would not be confused with those 

transported from Earth. Jaffe accordingly recommended that the maximum probability of finding a terrestrial microbe on the Moon be limited 

to no more than 10–6 per square centimeter of surface. Rather than sterilizing lunar spacecraft, however, he thought that application of cleanliness 

procedures would be sufficient for meeting his recommendation.13

Regarding the allowable contamination probability assigned to 

Venus, Jaffe realized that he needed to take into account the likelihood 

that the planet’s surface, which was very hot, would be hostile to terrestrial organisms. The regions most liable to support microbe growth 

were in Venus’s upper atmosphere, but since Earth microbes did not 

appear to multiply in our own atmosphere, Jaffe thought “there was 

little chance they would do so in that of Venus.”14 He estimated the 

chance of a terrestrial microbe finding conditions suitable for growth 

on Venus to be about 10–3. Jaffe divided the desirable probability limit 

on a mission contaminating the target planet (10–4) by the probability 

of finding suitable growth conditions on Venus (10–3) to yield a recommended 10–1 probability limit on a mission releasing viable organisms 

into Venus’s upper atmosphere. 

Jaffe’s recommendations regarding Mars and Venus went through 

various revisions at NASA’s 1962 Conference on Spacecraft Sterilization 

as well as the Agency’s Iowa City Office of Space Science Applications 

Summer Study. The final guidelines included the following points:

 10.

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Developing Effective Planetary Protection Approaches

1. Spacecraft buses15 and booster last stages must either be sterilized or trajectories must be chosen for them that will ensure a 

probability of Mars impact no greater than 10–4 and a probability of Venus impact no more than 10–2.

2. A Mars entry capsule needs to be sterilized and afterwards handled 

aseptically, in order to limit the probability to no more than 10–4 

that a single viable organism will be released on the planet surface.

3. Lunar contamination, while it does not constitute as serious a 

problem as for the planets, still needs to be kept to a “feasible 

minimum” in order not to “seriously interfere with future biological and chemical surveys.”16

Note that these guidelines did not mandate a universal standard of 

planetary protection but were instead tied to the perceived likelihood 

that a particular celestial body could support life. Similarly, the NASA 

Unmanned Spacecraft Decontamination Policy (NMI-4-4-1), issued 

9 September 1963, stated that the Agency’s lunar policy was based on 

the prevailing scientific opinion that reproduction of terrestrial microorganisms on the Moon’s surface would be extremely unlikely.

COSPAR conducted its own deliberations on acceptable contamination levels at a meeting in Florence in May 1964, convening a study 

group chaired by C. G. Heden of the Karolinska Institute in Stockholm 

on spacecraft sterilization standards. Representatives from the United 

States, the USSR, France, Belgium, and the United Kingdom also 

attended. At this meeting, the participants formulated the first quantitative objectives for planetary protection. Each participant gave a best 

estimate for parameters used in the analytic framework for approximating acceptable levels of contamination.17 These discussions led to 

recommendations that were adopted by COSPAR’s executive council, 

resulting in Resolution 26.5. This resolution established a probabilistic 

framework for developing planetary protection standards, advocating “a 

 15.

81
When Biospheres Collide

sterilization level such that the probability of a single viable organism 

aboard any spacecraft intended for planetary landing or atmospheric 

penetration would be less than 1 × 10–4, and a probability limit for accidental planetary impact by unsterilized flyby or orbiting spacecraft of 

3 × 10–5 or less . . . during the interval terminating at the end of the initial period of planetary exploration by landing vehicles.”18

The term “sterilization” in the COSPAR resolution referred (and 

refers throughout this book) to reduction of spacecraft microorganism 

counts to defined levels, as distinguished from absolute sterilization—

the complete elimination of all microbes.19 In May 1966, the COSPAR 

Subcommittee for Planetary Quarantine recommended that the probability a planet of biological interest will be contaminated within the 

period of biological exploration be kept down to no more than 10–3 and 

that this standard be adopted by all states engaging in the exploration of 

space.20 COSPAR’s probabilistic approach was used until 1982, when SSB 

suggested a nonquantitative policy that is discussed later in this book.21

On 6 September 1967, NASA Policy Directive 8020.7 superseded 

the NMI-4-4-1 standard on robot spacecraft decontamination, specifying that the probability of terrestrial organism transport to planets be 

kept below certain levels. Furthermore, the directive recognized that 

viable microorganisms would land on the Moon and stipulated a management plan for them, ordering that they be “identified, quantified 

and, insofar as possible, located”22 in order that they could be recognized as terrestrial in origin if found in any return samples.

 18.

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Developing Effective Planetary Protection Approaches

NASA issued another directive based on probabilistic calculations on 

the same day as the above one, 6 September 1967. This second directive, 

NPD 8020.10, put forth a guiding criterion for exploration of planets and 

their satellites deemed important in the search for extraterrestrial life, precursors of life, or remnants of life. According to NPD 8020.10, the probability that a planet or satellite of interest will be contaminated by such 

exploration during the period of biological interest must not, as in the 

COSPAR recommendation of 1966, exceed one in 1,000 (1 × 10–3).23

Assessing Contamination Probabilities and Allocating Mission 

Risk Constraints

NASA developed mathematical models that aided in evaluating factors that could potentially contaminate a target planet. The Agency 

used data generated from these models to help establish appropriate 

mission risk constraints, P(N)s. These were limits on the probabilities 

that individual missions would contaminate the target planet, with N 

specifying the particular mission.24

Prior to 1966, COSPAR set the P(N) values for planetary missions. 

After this, however, COSPAR transferred some of the decision-making 

to the countries responsible for missions. COSPAR suballocated the 1 

× 10–3 overall limit on Pc, the probability that target planet “C” would be 

contaminated during the period of biological interest, to the different 

nations launching spacecraft. These suballocations are listed in table 3.1. 

Note that the United States and USSR each had a suballocation of 4.4 × 

10–4 while the total suballocation for all other spacefaring nations was 1.2 

× 10–4, adding up to a total allocation of 1 × 10–3. The NASA Planetary 

Quarantine (PQ) Officer, using data supplied by various consultants, 

 23.

83
When Biospheres Collide

Table 3.1 Suballocations by nation—probability limits on contaminating a target planet 

during the period of biological interest.

Nation Probability Limit

United States 4.4 × 10–4

USSR 4.4 × 10–4

All Other Nations (total probability of contamination) 1.2 × 10–4

Total 1 × 10–3

suballocated the U.S. probability limit on Pc, 4.4 × 10–4, to various individual missions, according to a schedule that considered the type of mission (planetary flyby, orbiter, lander, or lander-orbiter combination) and 

the anticipated number of similar missions that would be carried out.25

One of the PQ Officer’s consultants, Exotech Systems, Inc., performed the compilation of information necessary to maintain a database providing current summaries on the probabilities that missions 

already flown had contaminated the target planet, as well as calculations of projected suballocations to missions in the planning stages. 

The PQ Officer sometimes modified suballocation values for projected 

missions as new data became available. For instance, the two Viking 

missions each received initial suballocations of 7.2 × 10–5, but because 

of previous successful Mariner missions to Mars, this was augmented 

to a combined suballocation for the two Viking flights of 2 × 10–4.

26

A Planetary Protection Example: Analyzing Potential 

Contamination Sources in a Robot Expedition to Mars

During the 1960s, NASA developed plans for future Mars expeditions that included considerable thought on how to prevent planetary 

 25.

84
Developing Effective Planetary Protection Approaches

contamination. E. M. Cortright, who served as the director of Langley 

Research Center from 1968 to 1975,27 envisioned a robotic Mars expedition that involved two lander capsules containing surface analysis 

equipment and, in particular, equipment for biology experiments.28

Charles Craven and Robert Wolfson examined such a project through 

the lens of planetary protection, using systems analysis techniques 

and experiments to identify and evaluate potentially significant 

sources of biocontamination. Key to Craven and Wolfson’s approach, 

which was applicable to other target planets as well, was to divide up 

the difficult challenge of analyzing an extremely complex mission into 

a series of simpler tasks, including the following:29

1. Isolate every possible source of planetary contamination by 

thoroughly examining all aspects of the flight program.

2. Investigate each contamination source in order to build an indepth understanding of its mechanism.

3. Construct, where possible, mathematical models useful for calculating contamination probabilities.

4. In situations where meaningful mathematical models cannot 

be developed, estimate suitable bounds on the probabilities of 

contamination.30

Isolating and Examining Mechanisms of Contamination 

In carrying out the above tasks, Craven and Wolfson identified and 

analyzed these potential mechanisms of planetary contamination:

•	 Inadequate sterilization of a lander.

•	 Recontamination of a sterile lander.

 27.

85
When Biospheres Collide

•	 Accidental impacts of a launch vehicle or its components.

•	 Accidental impacts of unsterilized spacecraft components. 

•	 Accidental impacts of microorganism-bearing spacecraft ejecta.

•	 Inadequately sterilized propulsion systems.

Characteristics of each of these mechanisms are described below:

Inadequate sterilization of a lander. Planetary contamination 

could occur if viable organisms are present on the outside of the lander 

capsule or within the lander vehicle itself. In particular, organisms 

could be released due to 1) disintegration of the lander during impact 

or 2) erosion of the lander over time.

Recontamination of a sterile lander. This could occur 1) prior to 

launch due to improper handling; 2) during the launch or during the 

interplanetary voyage, by such occurrences as damage to the biological barrier isolating the sterile lander within the rocket’s nose cone 

shroud; 3) during release of the barrier; and 4) during lander release. 

Other spacecraft components such as the bus or orbiter craft could be 

the sources of recontamination. 

Accidental impacts of a launch vehicle or its components. Through 

improper maneuvering of the launch vehicle, failure of its propulsion 

system, or its detonation, the vehicle or components and pieces of it 

(such as clamps, rings, and bolts) could be accidentally propelled onto 

an impact trajectory with the target planet.

Accidental impacts of unsterilized spacecraft components. If mission staff lose control of the spacecraft after injection onto an impact 

trajectory with the planet, then all components of the craft will impact 

the body, including typically unsterilized components such as the bus 

that were not intended to do so. This scenario can also occur through 

a miscalculation in determining the craft’s trajectory. In addition, 

planetary environmental factors such as a thicker atmosphere than 

predicted may cause the spacecraft’s orbit around a planet to decay 

sooner than expected, resulting in an impact.31

Trajectory biasing is an approach for preventing accidental spacecraft impacts on a target body. In this technique, mission control staff 

deliberately offset (bias) the initial spacecraft trajectory in a direction 

that will ensure the craft misses its target by hundreds to thousands 

 31.

86
Developing Effective Planetary Protection Approaches

of kilometers, depending on the size of the target body. As the mission 

proceeds, mission controller knowledge of the spacecraft’s actual trajectory gets more precise due to continued radio tracking and optical 

navigation. The controllers then can employ the spacecraft’s propulsion system to reduce trajectory bias in progressive steps until the 

desired trajectory is attained. The advantage of trajectory biasing is 

that if mission staff lose the ability to control the spacecraft for any 

reason before the bias is removed, the spacecraft will not impact and 

contaminate the target body.32

Accidental impacts of microorganism-bearing spacecraft ejecta. A 

spacecraft typically releases certain types of ejecta during a mission 

that may carry microorganisms. These ejecta can include propulsion 

system gases, attitude control gas (generally far cooler than propulsion system gases and thus more likely to contain viable organisms), 

outgassing from spacecraft components, and particulates broken off 

the craft through micrometeoroid collisions or encounters with the 

planet’s atmosphere.33

For the Mars program, NASA initiated a major experimental effort 

to determine the sizes of the particulates likely to be ejected from 

spacecraft, as well as a comparison of the number of microorganisms 

projected to be killed by micrometeoroid impact versus those that 

would remain alive and continue on to impact Mars. To develop realistic projections, NASA built a micrometeoroid simulator facility to fire 

5 μm particles at average velocities of 30,000 ft/sec into targets inoculated with precise numbers of microorganisms. The targets were made 

of typical spacecraft materials including two types of aluminum, fused 

silica glass similar to that covering solar cells, and fiberglass-epoxy.34

Another study examined the various loose particles left on the 

spacecraft from its manufacturing process. These might escape the 

spacecraft during the mission and carry microorganisms to the target 

planet. The study analyzed the numbers and size distributions of particles likely to be generated during spacecraft fabrication and cleaning. 

Still another experiment investigated the attitude control gas system as 

 32.

87
When Biospheres Collide

a potential contamination source, employing a scaled-down version for 

the simulations. NASA staff placed filters of various sorts over gas nozzles in order to determine the extent to which microorganisms could be 

contained rather than ejected during firings. NASA staff also vibrated 

the attitude control system to simulate launch conditions. The aim was 

to determine whether launch environments resulted in viable organisms entering the system and getting expelled during firing operations. 

Some of these tests were performed using an actual Nimbus spacecraft 

attitude control system.35

Nonstandard ejecta of various types included such objects as the 

biological barrier on the launch rocket’s shroud, whose job was to isolate the lander capsule until launch; and debris such as bolts, clamps, 

rings, and so on. These could accidentally separate from the spacecraft at various times in the mission, such as during spacecraft maneuvers, and fall into an impact trajectory toward the target planet.36

Ejecta from propulsion systems. Interplanetary spacecraft engines 

weighed up to several tons. Developing and applying reliable sterilization procedures for them required considerable engineering and 

technical effort. During the 1960s, JPL conducted a research effort 

on sterilizing the propulsion fuels themselves as well as the rest of the 

onboard propulsion systems. The testing revealed that dry-heat sterilization at temperatures up to 145°C was possible for onboard liquid 

and solid propellant systems. Even though the propellants themselves 

were heat-producing and sometimes explosive substances, their autoignition temperatures were typically 250° to 300°C, which was two to 

three times higher than the envisioned sterilization temperatures. The 

main difficulties identified in thermally sterilizing them were such 

effects as chemical decomposition, degradation of ballistic properties, 

and high vapor-pressure buildup.37

Developing effective sterilization procedures required that the 

impact of engine exhaust on microbes be understood. For the Mars 

Voyager mission, the “previous incarnation of Viking,”38 General 

 35.

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Developing Effective Planetary Protection Approaches

Figure 3.1 Estimating the quantity of contamination reaching Mars. The matrix depicts 

various elements of the mathematical model used for predicting contamination carried to the 

Martian surface. (VO stands for viable organisms.)

Electric conducted a research project to determine the lethality of 

engine combustion to microorganisms. The program involved 22 test 

firings using three types of engines—solid fuel, monopropellant liquid 

fuel, and bipropellant liquid fuel—in order to estimate the survivability of microorganisms in the engine’s combustion chamber during firing. Engineers injected a measured quantity of germs into the engine, 

fired it into a test chamber, then surveyed the chamber to establish 

how many of the bacteria survived the firing.39

Test results indicated that lethality to microorganisms derived not 

only from combustion, but also because of the chemical compositions 

of certain propellants. For instance, liquid rocket propellants such as 

hydrogen and nitrogen tetroxide have chemical compositions that are 

toxic to microorganisms. These propellants are thus self-sterilizing 

within a few hours. As for solid-propellant rockets, few microorganisms 

are able to survive the high temperatures generated during firings.40

Scientists believed that the environments within cold-gas propulsion systems used for spacecraft attitude control might not be lethal 

to microorganisms, allowing some of them to survive. To avert this 

 39. Craven and Wolfson, Planetary Quarantine, pp. 8–9; Craven, “Part I: Planetary Quarantine 

Analysis,” 20.

 40. Ibid.

89
When Biospheres Collide

possibility, manufacturing and assembly of attitude control systems 

needed to be carried out so as to minimize internal contamination. In 

addition, gas supplies for these systems required thorough filtration to 

remove any microorganisms.41

Mathematical Modeling of Contamination Probabilities

The model attempting to calculate Mars contamination probabilities incorporated mathematical representations of the physical phenomena associated with various mechanisms of contamination. The 

matrix shown in figure 3.1 lists the various elements of the mathematical model and illustrates how the task of predicting a mission’s 

contamination probability was divided up into a collection of smaller 

tasks. A key factor in the probability calculations was the number of 

viable microbes initially present in or on each potential contamination 

source, several examples of which are listed in the left column of figure 3.1. Note that sources include parts of the spacecraft (i.e., “attitude 

control gas system”), loose particles, and exhaust gases.42

The model also calculated impacts on the microbes of the mechanisms that ejected them from the spacecraft and transported them to 

the Martian surface (see columns 3–4 in figure 3.1). Column 3 represents consequences of ejection processes. The calculations for each 

cell in this column drew on two types of data—the expected rate at 

which microbes were ejected from the spacecraft and the fraction of 

those microbes estimated to survive the ejection process. The environments associated with some contamination mechanisms were quite 

harsh, such that few microbes were expected to survive ejection. For 

instance, the second contamination source in the table, the “orbit 

insertion engine,” subjected ejecta to temperatures of 6,000°F.43

Column 4 calculations estimated the probabilities of ejected 

microbes achieving Mars impact trajectories. These calculations drew 

 41.

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Developing Effective Planetary Protection Approaches

from the orbital mechanics of particles leaving the spacecraft at a 

range of speeds and directions.44

Columns 5 through 9 identify calculations concerned with the 

impacts of various potentially lethal factors for the microbes. These 

included the vacuum of space, ultraviolet and other solar radiation, 

and atmospheric entry heating. Column 10 calculations focused on 

the probability that terrestrial microbes would survive and grow in 

the Martian environment. The Space Science Board periodically 

issued estimates of the ability of Mars to support terrestrial organism growth and proliferation. These were under constant review in the 

United States by the Planetary Quarantine Office (PQO). SSB regularly changed its probability-of-growth estimates to reflect the latest 

data that had been generated on planetary environments.45

For Column 11, the model calculated the total probability of contamination from each source and used the number in Column 1, the initial 

microbe loading, to estimate quantities of viable organisms from that 

source expected to survive on the Martian surface. Finally, summing the 

numbers in Column 11 yielded total numbers of viable organisms projected to survive on Mars for the particular mission under study.46

Developing Input Data for the Model

Determining the characteristics of the contamination mechanisms and sources in order to generate input data for the mathematical model was not a trivial task. It typically relied on subjective 

judgment by the field’s experts combined with analysis of whatever data were available from laboratory experiments and previous 

space missions. For instance, determining the quantity of microbes 

encapsulated within various materials or located between mated surfaces was very difficult due to inaccurate sampling techniques. This 

resulted in a large range of the microbe estimates for the landing 

 44.

91
When Biospheres Collide

capsule, running from less than 1 organism per cm3 to more than 

1,000 per cm3

. The variance in these densities meant that the total 

microbial burden in a Viking-type landing capsule might be as low as 

100,000 or as high as 1 billion, implying an uncertainty of more than 

20 hours in the required sterilization time.47

Note that each cell in the matrix corresponded to a contamination 

probability calculation for one aspect of the spacecraft that was considered a potential contamination source and one part of the voyage 

that a particle from this source might take en route to the Martian surface. For instance, the matrix cell that corresponded to “orbit insertion 

engine” and “survive vacuum” contained the results of probability calculations that a microbe would escape from the spacecraft’s orbit insertion engine in a viable state and also endure the vacuum of space.48

The Craven and Wolfson NASA study initiated an experimental 

program to generate needed input information for the model. The largest of their endeavors focused on determining whether the spacecraft’s 

orbit insertion engine, a bulky piece of equipment weighing five tons, 

presented a contamination threat if it was used near Mars. This was 

important information to obtain; if NASA had to sterilize the engine 

to protect Mars, a significant engineering effort and a considerable 

expenditure of funds would be required. Craven and Wolfson designed 

a test program that examined the exhausts from rocket engines using 

solid, monopropellant liquid and bipropellant liquid fuels. They inoculated these different types of engines with measured quantities of 

microbes, then fired the engines into a test chamber, which was bioassayed to determine bacterial survival rates.49

Another experimental program centered on the sizes of ejecta that 

would be broken loose from the spacecraft during a micrometeoroid 

impact, as well as how many viable organisms would be ejected, survive, 

and attain a Mars impact path. To answer these questions, the study 

used a micrometeoroid simulator facility that could fire 5 μm particles 

at 30,000 ft/sec. Micron-sized iron particles simulating micrometeoroids 

were smashed into targets made of spacecraft materials that had been 

 47.

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Developing Effective Planetary Protection Approaches

inoculated with known numbers of microorganisms. Ejected particles 

from the targets were caught in a trap, then bioassayed.50

The experimental program included analysis of the extent to which 

manufacturing techniques deposited loose particles on spacecraft surfaces. These particles could fly off the spacecraft during the mission 

and possibly carry bacteria with them. The study sought to estimate 

the number of particles deposited on spacecraft surfaces as well as 

their size distributions.51

The attitude control gas system, another potential source of contamination, was studied by covering the exhaust nozzles of a scaleddown model with special filters, which were then bioassayed. NASA 

did this in conjunction with vibrating the model in a manner simulating launch vibration levels. NASA aimed to determine whether launch 

vibrations released viable organisms within the attitude control gas 

system that would be expelled when it fired.52

Die-off rates of unprotected microorganisms in space. NASA conducted experiments in a space simulator meant to determine the rates 

at which unprotected microbes die when subjected to the extreme conditions of outer space. These tests generated vital input data because 

many of the scenarios for possible planetary contamination relied on 

viable organisms traveling for some distance through space, and the 

model needed as accurate information as possible on their die-off rates. 

The tests subjected Bacillus subtilis variety niger (also known as bacillus globigii, or BG) spores to ultra-high vacuum and temperature variations that simulated thermal-vacuum relationships observed on the 

Mariner 4 mission to Mars. The simulator for this work was a spherical 

high-vacuum chamber able to achieve a 10–10 torr vacuum.53 A molecular trap within the chamber captured up to 99.97 percent of the condensable molecules ejected from the test surface.54

Preparing input data. In developing the model, Craven and 

Wolfson debated whether to do the analysis using average values 

for input data such as the average number of microbes expected 

 50.

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When Biospheres Collide

to reside in a contamination source. They discarded this approach 

because it would lead to model outputs in terms of the average, and 

this would not represent the worst cases of planetary contamination 

that might occur. These worst cases were of particular interest to the 

planetary protection community, and so Craven and Wolfson considered doing the calculations based on worst-case data input. But this 

approach too was dropped because the final result would likely be a 

very improbable one. Instead, Craven and Wolfson decided that the 

approach yielding the most useful results would be to formulate input 

data as probability distributions. For instance, probability P1 might 

represent the chance that between 0 and 10 viable organisms were 

contained in a particular contamination source, while P2 through Pn 

would represent the probabilities that successively larger numbers 

of viable organisms were contained in the source. The output from 

the model would give a distribution of probabilities representing the 

chances that various quantities of viable organisms would survive on 

Mars. Such an output is depicted in figure 3.2. This approach allowed 

the probabilities of both worst case scenarios and more likely occurrences to be estimated.55

Challenges in Sterilizing Lander Capsules

Central to NASA’s planetary protection effort were its procedures 

to sterilize the part of a spacecraft most likely to contaminate another 

planet—the lander capsule. These procedures needed to be applied 

down to the basic component level, as well as to assemblies of these 

components and to the entire lander, in ways so as not to damage 

the spacecraft. Designing sterilization regimes to accomplish this and 

lander capsules that could withstand those regimes presented serious engineering challenges. In the words of Bob Polutchko, a manager in the Viking program, the rigorous sterilization requirements 

“made every component a brand new development. There was little or 

nothing off the shelf that we could buy that could meet the requirements we imposed on ourselves for planetary quarantine. From the 

 55.

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Developing Effective Planetary Protection Approaches

Probability

1.0

0 1 2 3

Number of VOs reaching Mars’s surface and continuing to survive

Total probability of 5 to 100 

VOs reaching and surviving 

on surface is about 10–5 Total prob. of 100 to 1,000,000 VOs 

reaching and surviving is about 5 × 10–7

4 5 100 1,000,000

10–4

10–5

10–6

Figure 3.2 Typical probability distribution of viable organism (VO) quantities reaching and 

surviving on the Martian surface. In this particular distribution estimate, the probability of 

three organisms surviving is about 1 in 10,000, while the total probability for 100 to 1,000,000 

organisms surviving is about 5 in 10 million.

smallest . . . everyday resistor or capacitor or transistor all the way to 

basic raw materials of thermal coatings or heat shields or parachute 

materials.”56 (A detailed account of the Viking experience is included 

in Chapter 5.)

The following sections describe some of the efforts to understand the 

impacts of sterilization procedures on the lander capsule and its microbial load, the development of sterilization approaches, and the identification of materials and components able to endure those procedures. 

Microbial Response to Thermal Sterilization Techniques

A difficult parameter to estimate in modeling the impacts of sterilization procedures was the probability that microorganisms would 

survive the process. Thermal resistance is in large part dependent on 

 56. Bob Polutchko, manager of the Viking lander support office and of numerous other groups in 

the program, telephone interview by author, 21 February 2006.

95
When Biospheres Collide

the characteristics of the microorganism. Microorganisms of the most 

concern were those that were most heat-resistant. 

The space science community decided to choose a bacteria 

representative of thermally resistant spores that would typically 

contaminate space hardware and use it as a standard by which to 

measure the effectiveness of sterilization approaches. The scientists 

settled on the spores of Bacillus subtilis variety niger, also known 

as Bacillus globigii, or BG, and employed it in the majority of their 

studies on sterilizing space hardware. BG also became the standard 

test organism mentioned in the NASA Handbook NHB 8020.12, that 

was to be used in biologically qualifying planetary flight program 

sterilization procedures.57

Other Factors Impacting Microbial Kill Rates

The level of sterilization attained is a function not only of the thermal resistance of the particular organism to be killed, but also of the 

characteristics and geometries of the materials on which the organisms are located. For instance, scientists have observed “at least an 

order of magnitude range in resistance to dry-heat sterilization for the 

same test species depending on whether they are on the open surface 

of a material, located between two mated surfaces, or encapsulated 

within a material.”58 BG spores encapsulated in methyl methacrylate 

and epoxy, a plastic, exhibited D-values (the time required to kill 90 

percent of the cells)59 of 210 to 300 minutes when exposed to flowing 

hot gas at 125°C. Spores from the same suspension that lay unprotected on metal surfaces exhibited D-values of only 10 to 30 minutes 

when exposed to the hot gas.

The physical characteristics of a spore’s surroundings that inhibit 

or accentuate water loss have a dramatic impact on its survivability. 

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Developing Effective Planetary Protection Approaches

As an example, if water movement is restricted around spores (such 

as when they are encapsulated in space vehicle parts), the spores 

exhibit higher D-values than in situations in which water can be 

easily lost or gained (such as when they are thermally exposed on 

external surfaces of a space vehicle). Furthermore, the rate of gas 

flow over an exposed surface on which spores exist appears to affect 

their destruction rate, probably because the gas flow impacts their 

moisture loss.60

Evolution of Sterilization Technologies

A critical factor affecting spore kill rates is the efficacy of sterilization technologies, which are constantly improving. The technologies 

that were available when spacecraft sterilization was initiated were those 

that could be transferred from biological weapons applications and from 

pharmaceutical, food canning, surgical supply, and other industries. New 

methods for applying heat and gases such as ethylene oxide needed to be 

developed that were better suited to spacecraft sterilization.61

The fundamental challenge of the food processing industry—to 

maximize the destruction of microbes that cause food spoilage while 

minimizing losses to the nutritional value and taste of the food—was 

somewhat analogous to problems faced in spacecraft sterilization—to 

maximize microbe destruction but minimize damage to spacecraft 

components. Thus, in the first years of the space program, the food 

industry’s analytic techniques for microbe kill rates were examined 

closely as models for analysis of spacecraft sterilization. An important 

difference, however, was that the food industry’s analyses as well as 

supporting data were based on moist heat processes. Moisture present 

during spacecraft sterilization negatively impacted some spacecraft 

components and equipment. NASA thus had to develop dry-heat sterilization approaches more appropriate to its needs.62

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When Biospheres Collide

Identifying Mechanisms of Contamination

Developing procedures for estimating the total surface contamination 

of a vehicle at different points during its assembly was essential in constructing reliable decontamination technologies as well as methodologies 

for avoiding recontamination. The approach for estimating contamination 

was to extrapolate from samples taken from the vehicles during assembly 

and before launch. Contamination samples were, and still are, taken by 

swabbing vehicle surfaces, analyzing environmental settling strips, and 

collecting air samples. These tests helped reveal important mechanisms 

of contamination that had to be dealt with, such as those resulting in 

contamination during transport operations of the flight-ready spacecraft 

to the launch pad. Contamination investigations disclosed a surprisingly 

high estimated microorganism count for the Surveyor II spacecraft of 40 

times the estimated counts for Surveyors I or III. The cause of this problem 

was traced back to high contamination levels on a shroud meant to cover 

the craft as space center staff moved it to the launch pad. Lunar Orbiter 5 

(whose mission launched in August 1967) also had a high microorganism 

count, and its source appeared to be a shipping canister used to transport 

the craft across country. Key in this determination were samples taken 

from the canister’s surfaces, which revealed large populations of microbes.63

The following sections examine specific types of lander capsule 

parts and materials, and the sterilization regimes to which they were 

subjected.

Electronic Components

NASA performed extensive research, notably at JPL beginning in 

1962, to identify heat-sterilizable electronic parts. NASA considered 

a part to be sterilizable if it was “serviceable and reliable after heat 

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sterilization preparatory to a trip to and landing on Mars.”64 JPL developed exhaustive experimental data on the longevity and reliability 

characteristics of the parts able to withstand heat sterilization regimes, 

as well as the ability of parts to survive ethylene oxide treatment, 

which the Agency was then considering for use as part of its sterilization protocols. Early testing in the JPL program focused on approximately 500 capacitors constituting 15 different part types. JPL then 

expanded its effort, analyzing nearly 43,000 resistors, diodes, capacitors, fuses, transistors, and other parts making up 262 part types. The 

JPL study generated over 400 million-part test hours of data. 

Electronic Packaging, Solder, Connectors, Wires, and Cables

Spacecraft electronics included not only the components mentioned in the previous section, but also the following:

•	 Soldered and welded joints.

•	 Wires and cables.

•	 Connectors such as for coaxial or multiconductor cables.

•	 Packaging materials.

All of the above needed to withstand three 36-hour, 145°C thermal 

sterilization treatments as well as ethylene oxide exposure.65

An individual spacecraft assembly operation often used a range 

of materials, each of which had to be thoroughly analyzed. Soldering 

processes provide a good illustration of this. Materials in typical soldered joints include the solder itself, various sizes of stranded or solid 

electric wire, terminals and connectors made from a variety of solderable materials, and flux—a substance made from rosin and acids, 

whose purpose is to help molten solder flow smoothly and form good 

joints. NASA expected that any degradation of the solder joint materials would manifest itself by degrading joint performance. To determine if this had happened, NASA conducted mechanical strength 

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tests, electrical resistance tests, electrical tests during vibration, and 

metallographic analyses of the joints.66

Polymers

Polymers were, and are, employed in a range of critical spacecraft 

parts and materials, including adhesives, electrical insulation, shrinkable tubing, circuit boards, module cases, conformal coatings, encapsulants, films, tapes, oils, and greases. Polymeric materials include 

many types of plastics and are typically composed of large organic 

molecules formed from combinations of smaller molecules (monomers) 

in regular patterns such as long chains. Types of polymers considered for spacecraft applications included epoxies, polyesters, polyolefins, polyurethanes, polysulfides, phenolics, polyimides, phthalates, 

silicones, and Teflons. Many of these materials were often found in a 

single electronic component of the spacecraft.

Polymers selected for use in a spacecraft needed to be compatible 

with NASA’s dry-heat sterilization and gaseous ethylene oxide regimes. 

NASA analyzed the effects of these regimes on over 150 polymeric 

products. The testing included a cycle of heat exposure of 36 hours 

at 145°C and then a more rigorous exposure to three 40-hour cycles 

at 149°C. Combined ethylene oxide and thermal exposures were also 

included in the testing. NASA examined materials subjected to these 

conditions for indicators of property changes, which included visual 

alterations in the material, volume and weight changes, and alterations 

in tensile strength. Polymers exhibiting gross changes were dropped 

from further testing.67

One particular polymer-related project conducted by Marshall 

Space Flight Center (MSFC) aimed to develop a tough, heat sterilizable, transparent potting compound intended for enclosing electronic 

modules and printed circuit boards. MSFC required that this compound withstand a more extreme environment than many other of 

the materials that were tested—200°C for 24 hours—without any 

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degradation in physical or electrical properties. The potting compound 

had to be totally compatible with the outer space environment and 

demonstrate adherence to exacting strength, hardness, adhesion, thermal expansion, moisture absorption, and dielectric standards. MSFC 

evaluated approximately 30 materials, including silicones, epoxies, 

and polyesters, and also discovered that subjecting materials to lowpressure molecular distillation68 improved their resistance to the space 

environment.69

Batteries

JPL initiated a program in 1962 to develop robust batteries capable 

of withstanding three heat sterilization cycles of 145°C for 36 hours 

each and still displaying good shelf life and energy storage characteristics. JPL deemed this battery development program necessary because, 

as with many other parts, no off-the-shelf battery could be found that 

would deliver adequate performance after being subjected to the heat 

sterilization regime and other stress tests. JPL conducted some inhouse battery development work, although NASA contracted out much 

of the research work to various vendors. These contracts entailed the 

following projects: 

•	 Electric Storage Battery Company (ESB) developed a copolymer 

of divinylbenzene and methacrylic acid that held up well to 

thermal sterilization procedures and was a candidate for battery 

separators, which were sheets of nonconducting material put 

between a battery’s many positive and negative plates to prevent 

short circuits caused by plates bending and touching.

•	 ESB received a contract in 1965 to fabricate silver-zinc and 

silver-cadmium batteries that remained sound after heat 

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sterilization (as well as after high impacts and vibration 

stresses). ESB studied all aspects of the batteries—electrodes, 

electrolyte solutions, separators, and case materials.

•	 Gulton Industries and Douglas Aircraft analyzed sterilizable 

battery components, but for batteries with inorganic rather 

than organic separators.

•	 Douglas Aircraft Company and The Eagle-Picher Company 

examined silver-zinc battery systems.

•	 TRW Space Technologies Laboratory had a contract with JPL to 

investigate battery characteristics after heat sterilization, with 

a focus on cells with nickel-cadmium electrodes.

•	 Electro-Optical Systems (EOS), a subsidiary of Xerox 

Corporation, developed a hydrogen-oxygen fuel cell (a device 

that converts the chemical energy in a fuel into electricity).70

Search-for-Life Instruments and Experiment Materials

Preparing instruments and experiment materials designed to 

search for life involved sterilizing them so as to protect the target 

planet and prevent contamination on the instruments from giving 

erroneous results. All components of the experiments had to be compatible with sterilization regimes which, in JPL’s 1965 study, included 

dry-heat and ethylene oxide environments.71 JPL’s dry-heat regime 

involved sterilization of planetary-impacting hardware in an inert 

atmosphere at 135°C for 22 hours.

Experiment materials that needed to be sterilization-compatible 

included chemical reagents and nutrient media, which were formulated 

to help nourish and grow extraterrestrial life-forms that might be found. 

Many types of hardware, from hand tools up to sophisticated instrumentation, also needed to be compatible with the sterilization regime.

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Impacts of Surface Roughness on Sterilization Operations

Spacecraft design engineers needed to know the relationships 

between the conditions of material surfaces throughout the lander 

capsule and the ease with which those surfaces could be sterilized. 

Tenney et al. pointed out that ordinary, machine-finished metal surfaces contained grooves and scratches that were typically “five times 

as deep as the diameter of streptococci or 50 times that of poliomyelitis organisms.”72 Some engineers thought that machining and polishing 

capsule surfaces to a high degree of smoothness would allow microbes 

to be more easily killed, although it would also add significantly to the 

program’s cost and complexity of operations. NASA’s biological testing 

showed, however, that fine machining and polishing of metal surfaces 

did not have the predicted reduction in the time required to sterilize the spacecraft. Marshall Space Flight Center and General Electric 

Company performed a series of tests using the standard BG microbe 

and samples of 2024 aluminum with varying degrees of surface roughness73 ranging from 4 to 125 microinches rms.74 Exposure of any of the 

surfaces to a temperature of 135°C rapidly and significantly reduced 

microbial spore levels. Highly machined or polished surfaces did not 

appear necessary for effective sterilization, given a dwell time of 24 

hours at the above temperature.75

Terminal Sterilization Approaches

In order to sterilize an entire planetary lander capsule during 

the terminal sterilization procedure, the capsule and its enclosing 

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canister would ideally spend a minimum of time at the elevated temperatures needed for resident microbes to be killed, resulting in the 

least impact on spacecraft materials and the least risk to reliability.76

Terminal sterilization procedures, however, had to walk a fine line in 

heating the capsule, using thermal gradients that were steep enough 

to elevate temperatures quickly but not so steep as to create thermal 

stresses capable of damaging the spacecraft. A 1964 study by Marshall 

Space Flight Center sought to identify capsule designs and materials 

that could be cycled between 25°C and sterilization temperatures of 

150°C as quickly as possible without warping or “adversely deflecting”77

spacecraft structures. The study determined such things as the best 

types of joining methods between components that would conduct 

heat as rapidly as possible, thus minimizing thermal gradients and the 

resulting stresses from different rates of expansion.78

A primary issue in developing a terminal sterilization regime was 

to choose the best way to apply heat. A range of heater blanket, radiant heating, and oven designs were examined by NASA engineers. The 

landing capsule had to be heated within its canister, which was not to 

“be opened within any portion of the earth’s atmosphere which might 

recontaminate the landing assembly.”79 NASA considered designs 

employing both evacuated sterilization canisters and those filled with 

gas at or near atmospheric pressures. In terminal sterilization simulations for a 1,200-pound lander, calculations showed that the times 

required for gas-filled canisters to reach a sterilization temperature 

of 150°C were almost 50 percent less than for the evacuated canisters, resulting in a 10 percent reduction of the total time required at 

elevated temperatures. Canisters filled with gas, which could conduct 

heat by convection, also reduced temperature gradients and their 

accompanying thermal stresses on spacecraft materials. Through the 

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use of gas circulation fans, heat transmission between the canister 

wall and the landing capsule, as well as within the landing capsule 

itself, could be even more accelerated. To maximize heat transmission 

rates, the locations of equipment, cables, wire harnesses, and tubing 

within the capsule had to be optimized so as not to restrict gas-flow 

paths any more than necessary. This was especially true for components with large thermal masses, which had longer response times and 

were typically “the limiting items in the heating and cooling portions 

of the sterilization cycle.”80

Requirements of the Canister

Fundamental to NASA’s policy for planetary landings was to 

enclose the capsule in a bacteriological barrier (the canister) that 

maintained both cleanliness and sterility. The canister had to be of 

minimal weight but provide a reliable barrier against all types of contamination—microbes, spores, dirt, and dust. This canister had to 

be compatible with the thermal sterilization regime. It could not be 

opened from the time of terminal sterilization until the capsule had 

ascended beyond Earth’s atmosphere and had separated from unsterile components of the spacecraft. Finally, the canister, whose exterior 

might not be sterile, needed to include the capability for being opened 

in space and jettisoned in a manner so as not to hit the target planet.81

Capsule Recontamination Issues

The aim of terminal sterilization procedures was to ensure that 

the landing capsule bioload was low enough so as to meet planetary 

protection requirements. Other parts of the spacecraft, however, were 

generally not sterilized and could potentially recontaminate the landing capsule at some point in the mission after terminal sterilization 

had been carried out. As mentioned above, the canister completely 

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enclosed the landing capsule, providing an effective biobarrier until 

such point during the mission that it was safe to remove the capsule. The chance of recontaminating it was minimized if the capsule 

remained within its biobarrier canister as long as possible—preferably 

until planetary encounter.

Recontamination probabilities were also reduced if mission control separated the capsule from the spacecraft engines while the 

capsule was still contained within its canister. Once the capsule 

and canister attained a distance from the spacecraft bus beyond its 

potential to recontaminate (which might occur, for instance, should 

its attitude-control jets spew out viable bacteria along with propulsive 

gases), mission control could then safely separate the landing capsule 

from its canister.82

A potential difficulty with the above separation strategy was that 

the ratio of canister mass to capsule mass was about 1 to 10, while the 

ratio of canister mass to that of the capsule and bus was roughly 1 to 

100. If the capsule separated from its canister after separating from 

the bus, the capsule could experience much greater perturbations to 

its velocity and orientation than if it had stayed anchored to the heavy 

bus while the canister lid was removed and discarded.83

This second strategy, removing the canister while the capsule 

stayed attached to the bus, had a downside as well. Unsterilized 

exhaust, dislodged dust, or other ejecta from the bus might contact 

the unprotected capsule, possibly resulting in microorganisms settling on its exterior and reaching the target planet. A way to prevent 

this was for NASA to program the capsule to carry out a slow rolling 

maneuver on its approach to the target planet, in such a manner as to 

expose all external surfaces to the Sun’s ultraviolet flux for 10 minutes 

or more. Typical bacteria cells cannot survive such radiation for more 

than one-half minute, while 10 minutes is sufficient to kill even the 

most resistant microbes.84

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Soviet vs. U.S. Planetary Protection Approaches

The nature of planetary protection is such that it cannot be accomplished by only one nation. Any country sending probes to other 

planets can contaminate those bodies and compromise the scientific 

investigations of all other countries. This was why U.S. and European 

scientists received the accounts of Soviet exploration of Venus with 

serious concern. On 1 March 1966, in a hearing of the U.S. Senate 

Committee on Aeronautical and Space Sciences, George Mueller, head 

of NASA’s Office of Manned Space Flight, reported an account from 

the Soviet Tass news agency announcing the landing of a spacecraft on 

Venus. NASA’s best interpretation of the event, however, was that this 

was not a soft landing, but an impact with the planet.85

Press reports from the USSR indicated that the payload capsule 

and bus from its Venera 4 spacecraft entered Venus’s atmosphere in a 

state described as sterilized. But there was no evidence at that time 

that the capsule had received anything beyond surface sterilization 

using gaseous germicides and high-energy irradiation of certain components, and the Soviets made no claims whatsoever about sterilizing 

the bus, which U.S. scientists believed to contain a circulating coolant. 

Although NASA gained some confidence in the 1970s in Soviet planetary protection approaches (see the discussion in Chapter 2 regarding 

USSR planetary protection approaches), the United States was quite 

worried at the time of Venera 4 that Soviet spacecraft might seriously 

contaminate other planets. 

Considerable data collected prior to the Venera 4 mission indicated that Venus surface temperatures were very high—perhaps too 

high to support life—but there were cooler environments above the 

surface that space scientists thought possibly capable of sustaining life. 

A worst case scenario: the spacecraft bus was internally contaminated 

with terrestrial microbes and had broken open in the dense Venusian 

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When Biospheres Collide

atmosphere, releasing those microbes into an environment in which 

they might be able to replicate.86

Protecting Against Unplanned Impacts

Studies by the U.S. space science community revealed important 

differences between our country’s planetary protection precautions and 

those of the Soviet Union. One of these was the variance in strategies 

for preventing an unwanted impact of the bus with the target planet. A 

spacecraft bus’s interior, and sometimes its exterior as well, are typically left unsterilized. One method for preventing a collision with the 

target planet is called a bus-deflection maneuver, in which mission control staff initially place the bus-payload capsule assembly on a collision 

course with the target planet. Days before arrival at the planet, a mechanism in the spacecraft separates the bus and capsule. The bus then 

uses its own propulsion system to deflect it onto a new course that will 

avoid planetary impact. If all systems operate as planned, this strategy 

effectively protects the planet from an unwanted impact. But if the bus 

propulsion system does not function correctly and does not change the 

bus’s course sufficiently, then it will crash into the planet and possibly 

contaminate it with terrestrial organisms.87

Payload capsule deflection is an alternate strategy that uses trajectory biasing and does not present the contamination dangers of 

bus deflection. In this approach, mission staff bias (aim) the capsulebus assembly on a near-encounter trajectory, then send commands 

to separate the capsule from the bus and give the capsule a velocity 

increment that will change its path to an impact trajectory with the 

planet. Meanwhile, the bus will continue on its nonimpact course. The 

importance of the payload capsule deflection strategy is that even if 

spacecraft systems fail to operate correctly, the bus assembly will not 

end up impacting or contaminating the planet. If the bus and capsule 

cannot be separated, then neither will hit the planet. 

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Payload capsule deflection is a more fail-safe strategy from a planetary protection point of view, but it is also a more complex and expensive strategy than bus deflection. To redirect the payload capsule onto 

just the right trajectory as to encounter the planet, the capsule needs 

to contain its own small propulsion system and propellant supply. Also, 

if the capsule is not equipped with its own internal stabilization and 

orientation system, then it must be spin-stabilized, which necessitates 

spinning it up before separating it from the bus. These requirements 

make capsule-deflection a significantly more difficult operation from 

an engineering point of view and more expensive due to the additional 

equipment costs.88

The cheaper bus-deflection approach can be employed in a manner 

that offers additional protection for the target planet by mounting an 

abort rocket on the bus as a backup system. The abort rocket would 

contain its own timing system that would initiate firing unless Earth 

sent an override command. Thus, if mission control lost contact with 

the bus or lost the ability to operate it before carrying out the deflection maneuver, the backup abort rocket would still fire and propel the 

bus away from an impact trajectory. The space science community 

analyzed this abort rocket strategy in great depth during plans for a 

possible 1969 Mars mission. The scientists came to the conclusion that 

this approach would sufficiently reduce the probability of accidental 

bus impact with the planet so as to meet the COSPAR recommendations discussed earlier in this chapter.89

The limitations of 1960s USSR planetary protection procedures 

can be illuminated by comparing Soviet planetary impact prevention approaches with those of the United States. It is telling that 

Soviet mission planners chose to use bus-deflection rather than 

capsule-deflection strategies, didn’t employ abort rocket capabilities on the buses, and did not heat-sterilize the buses, although they 

may have received other types of sterilization treatments. In addition, the Soviets may not have completely heat-sterilized the capsules that were intended to impact the planet itself. The USSR might 

have assumed that partial heat sterilization, possibly combined with 

gaseous sterilization and other nondestructive methods, adequately 

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addressed COSPAR’s recommendations. Alternatively, the Soviets 

may have decided that following the COSPAR recommendations 

would present such onerous restrictions as to prevent serious solar 

system exploration.90 Analysis of data from USSR and U.S. Venus and 

Mars missions revealed additional important differences between 

the Soviet and U.S. approaches to planetary protection. The Soviet 

Venus 2 mission launched on 12 November 1965 with the objective 

of passing as close as 40,000 kilometers (25,000 miles) from the 

Venusian planetary surface. In actuality, through calculations made 

from trajectory measurements once the spacecraft entered interplanetary space, scientists determined that the craft may have passed only 

24,000 kilometers from the planet’s surface. In contrast, the United 

States gave its Mariner 4 spacecraft an initial trajectory that would 

take it no closer than 600,000 kilometers from Mars, providing a considerably higher measure of planetary protection.91

The USSR’s Venus 3 space vehicle carried a landing craft that 

the Soviets claimed was thoroughly sterilized, although they never 

specified what procedures were used. No such claim was made for the 

spacecraft bus. Because the Soviets were not able to reach Venus 3 for 

the last scheduled radio contact, U.S. space scientists assumed that 

the planned bus-deflection maneuver was not executed. As a result of 

this loss of communication with the spacecraft, U.S. scientists believe 

that the unsterilized Venus 3 bus as well as the payload capsule, which 

also may not have been adequately sterilized, crashed into Venus on 1 

March 1966.92 Regarding this likely crash, British scientist Sir Bernard 

Lovell charged that the USSR “endangered the future of biological 

assessment of Venus.”93

In addition to the Venus 3 incident, the USSR also may have 

crashed a spacecraft into, and contaminated, Mars. Space scientists Bruce Murray, Merton Davies, and Phillip Eckman argued that 

the Soviet Zond 2 mission to Mars, which launched on 30 November 

1964, had a high likelihood of ending its life in an impact with Mars. 

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England’s Jodrell Bank Observatory for radio astronomy successfully 

tracked the course of Zond 2 until at least the middle of February 

1965. Tracking data suggested that the probe was traveling on a collision course with Mars. When Bernard Lovell asked a high-level Soviet 

scientist who was visiting the United Kingdom, M. V. Keldysh, if this 

was indeed the case, Keldysh responded that the probe would miss 

Mars by the slim margin of 1,500 km, within the range of uncertainty 

of the Jodrell Bank calculation. A characteristic of the Zond 2 trajectory suggested, however, that the Soviets intended to send the payload 

capsule on an impact with Mars, and it was only the bus, after a busdeflection maneuver, that was supposed to miss Mars by 1,500 km. 

When Western scientists analyzed the Zond 2 trajectory, they 

found that it was set up to minimize the relative velocity of approach 

at Mars. This gave an important clue as to the USSR’s intent for this 

mission. To achieve maximum scientific value, a payload on an impact 

trajectory needed to have adequate time to transmit all the data it 

could back to Earth before the moment that it crashed into the surface 

of the planet. The extremely thin Martian atmosphere did not provide 

the potential for atmospheric braking of the spacecraft that Earth’s or 

Venus’s atmosphere would have. Thus, a mission to Mars intending to 

impact with the planet’s surface needed a trajectory such as Zond 2’s 

that would reduce the relative velocity between spacecraft and planet 

as much as possible. Furthermore, the Soviet Union indicated that 

Zond 2 was the same type of spacecraft as Venus 3, which had a payload capsule intended for planetary impact.94

The above accounts indicate the possibility that Soviet missions 

have already contaminated both Venus and Mars with viable terrestrial microorganisms. If this has indeed happened, then the basis for 

the COSPAR Mars recommendations has been compromised, since the 

number of microorganisms already released on Mars would have considerably exceeded the total that COSPAR expected from all robotic 

exploration during the period of biological exploration of this planet.

U.S. space scientists expressed concern that the “expensive prophylactic measures”95 our country was investing in for spacecraft 

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When Biospheres Collide

sterilization might have to be reexamined if Soviet craft were already 

contaminating other planets. At the 10th annual COSPAR meeting in Prague, Czechoslovakia (now the Czech Republic), Richard W. 

Porter of the U.S. National Academy of Sciences (NAS) Space Science 

Board (SSB) stated that our planetary protection policies might 

need review, should the USSR land spacecraft on Mars having used 

the same sterilization techniques and precautions as in their Venus 

shots. Porter complained that the USSR had given no indication to 

the space science community of the extent of its spacecraft sterilization program and stressed that the “introduction of earthly bacteria 

into the environments of other planets . . . could spoil man’s first 

chance to make a pure investigation of biological evolution elsewhere 

in the solar system.”96 His strong statements did not only fall on the 

ears of those who agreed with him. Forty-seven Soviet scientists also 

attended the meeting, which was the first large COSPAR gathering 

to host both Russian and U.S. scientists since the USSR had invaded 

Czechoslovakia the previous August.

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4 BACK CONTAMINATION

The Apollo Approach

Apollo program objectives: 

•	 To make the United States preeminent in space 

by building a broad-based capability for manned 

space flight.

•	 To demonstrate this capability by landing men 

on the Moon, and returning them safely to Earth, 

within this decade.

—Hearings before the Committee on Science 

and Astronautics, U.S. House of Representatives1

On 25 May 1961, President John F. Kennedy challenged the nation 

to send a man to the surface of the Moon and bring him back him 

safely. He also asked that this be accomplished by the end of the 

1960s. President Kennedy considered such an endeavor to be a vital 

action in “the battle that is now going on around the world between 

freedom and tyranny.”2

Flying a human to the Moon and back would have tremendous 

scientific as well as political returns, but many in the space science 

community realized the potential danger that such a mission posed 

to Earth. In 1960, the National Academy of Sciences’ Space Science 

Board (SSB) had warned that life could theoretically exist on other 

 1. U.S. House of Representatives, 

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bodies of the solar system and advised NASA and other interested 

government organizations, including the Public Health Service (PHS), 

to establish an interagency committee on interplanetary quarantine 

that would develop safe policies for handling spacecraft and samples 

returning from planetary missions.3

The SSB, whose membership included 16 highly respected U.S. scientists, issued an important cautionary statement that at some “not very 

great distance below the lunar surface,”4 an environment of low temperature, high vacuum, and protection against destructive radiation existed 

that was ideal for preserving microbes. NASA management thanked the 

SSB for identifying this concern but did not take any immediate action. 

This lack of response was possibly due to the immediate organizational 

and technical problems that the new Agency’s management was struggling with that precluded any serious attention being given to possible 

infections from the Moon. In the initial years of NASA, the life sciences 

did not have the strong voice in Agency policy decisions that space physicists and astronomers had. Plus, few biologists of the day had much 

research interest in space; the focus of new research was on Earth. In 

addition, most space scientists believed that the risk to Earth from lunar 

contamination was extremely small.5

Policy Development for Preventing Back 

Contamination 

During 1962, as NASA struggled with the task of actualizing 

President Kennedy’s Moon challenge, some space scientists continued 

to raise concerns about the unlikely but possible prospect of back contamination and its potentially catastrophic impacts. In particular, Carl 

 3. William David Compton, 

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Back Contamination

Sagan warned that “there was a remote possibility that lunar explorers 

might bring deadly organisms back with them that could destroy life 

on Earth.”6 Sagan had not yet become well known through his books, 

articles, and public television series, and most scientists did not seriously think that toxic microorganisms, or life of any sort, were likely 

to exist on our barren, airless Moon. Sagan’s point, however, could not 

be ignored. The consequences of back contamination, while improbable, could be so dire that serious prevention measures needed to be 

implemented. This view was shared by others in the space science 

community. The SSB issued a warning in the June 1962 report of its 

Iowa City Summer Conference, advising that the introduction of alien 

organisms into the biosphere of our planet could cause “a disaster of 

enormous significance to mankind”7

 and recommended that “NASA 

do everything possible to minimize the risk of back contamination.”8

The SSB went on to suggest using quarantine and other procedures to 

manage returning astronauts, samples, and spacecraft. These warnings still had little impact on NASA plans.9

This situation changed as plans for Apollo missions progressed, and it 

became increasingly likely that shipments of Moon rocks and soil samples 

would soon appear on Earth. Finally, the voices of concerned politicians 

as well as biologists began to be heard. In April 1963, during budget hearings, Senator Margaret Chase Smith (R) of Maine raised questions about 

the potential biological threat posed by the Moon. NASA could hardly 

afford to ignore congressional concerns regarding its priorities. The 

Agency’s management quickly assured the senator that studies of back 

contamination issues would be made and appropriate actions taken to 

address her concerns.10 Nevertheless, NASA did not follow through with 

its promise, viewing the chances of back contamination harmful to Earth 

to be “too remote to warrant further attention.”11 NASA also decided to 

ignore a warning from the commercial sector. The Lockheed Missile and 

Space Company was interested in the business opportunities of establish-

 6. Carter, “Moon Rocks and Moon Germs,” 235.

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When Biospheres Collide

ing a permanent U.S. presence on the Moon, but its director of spacecraft 

sterilization also recognized the potential dangers of doing so. For many 

millions of years, extraterrestrial material that conceivably contained 

organic and even living bacterial components had been impacting the 

Moon. Isolating Earth from such potentially disease-carrying matter was 

thus a prudent course of action.12

What NASA was interested in was protecting Moon samples from 

getting contaminated by Earth’s environment, which would severely 

impair their scientific value. Space scientists in academia, outside of 

NASA, also needed the Moon rocks to be protected. Their own research 

agendas demanded that they obtain unspoiled lunar samples whose 

utility had not been destroyed by exposure to terrestrial contamination. In addition, these scientists understood that “reputations could be 

enhanced and prizes won from research on pristine lunar material”13

and vigorously supported sample handling procedures that would not 

compromise their analyses of lunar material. 

In late 1963, geoscientists Elbert A. King and Donald A. Flory from 

NASA’s Manned Spacecraft Center (MSC) in Houston (which was renamed 

the Lyndon B. Johnson Space Center [JSC] in 1973)14 proposed that the 

Agency take action to handle lunar samples under properly controlled 

conditions. In February 1964, King (who would, during the Apollo mission, become NASA’s first Lunar Sample Curator)15 and Flory constructed 

conceptual plans for a lunar sample receiving laboratory (LSRL) to appropriately handle samples from the Moon, and they presented the plans to 

Max Faget, MSC’s director of engineering and development.16

 12.

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Back Contamination

By February 1964, NASA’s Office of Space Science and 

Applications (OSSA) was putting together a committee of prominent scientists to choose the researchers and organizations “best 

qualified to carry out individual and different phases of the sample 

investigations.”17 NASA thus needed the capability to open sample 

return containers, analyze the contents, then repackage and distribute them to eager scientists around the country for more in-depth 

study, while maintaining the material in as near-pristine condition 

as when they were collected on the Moon.18

John Eggleston, who served as the chief of the Lunar and Earth 

Sciences Division at NASA’s Manned Spacecraft Center in Houston 

during the Apollo mission, stated in a February 1964 memo to 

Max Faget that appropriately managing the samples required construction of a central facility capable of handling lunar material 

“under precisely controlled, uncontaminated, sterile conditions.”19

This was the first formal statement by a NASA manager that the 

need existed for such a resource.20 The facility he envisioned 

would require a sterile vacuum chamber approximately 10 by 10 

by 7 feet that would be pumped down to a pressure of about one 

ten-millionth of Earth’s atmospheric pressure for extended periods 

and maintained at temperatures varying from –30°C to +25°C. The 

reason for vacuum processing was to preserve any loosely bonded 

lunar gases contained in the samples, and also to protect against 

the possibility that lunar samples might react with Earth’s atmosphere.21 The vacuum chamber would be kept as sterile as possible 

from microorganisms, as well as chemically clean, and would be 

 17.

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When Biospheres Collide

dedicated only to handling lunar samples.22 This chamber would 

have to contain remote-controlled equipment and manipulators 

able to open the sealed sample containers, divide up and prepare the samples as necessary, analyze them, then repack them 

in vacuum-tight containers suitable for transport to investigators. 

Eggleston believed that no existing facility even came close to fulfilling these requirements.

A more detailed vision of the required lunar sample facility was 

incorporated into an in-house MSC study entitled “Sample Transfer 

Facility,” which Aleck Bond, an MSC systems test and evaluation 

manager, enclosed in a 14 April 1964 memo. The envisioned facility 

needed the capabilities to check lunar samples for the presence of any 

viable organisms, perform some control testing of the material, and 

then repackage portions of each sample in accordance with the analytical techniques being used by each investigator. The facility also 

required the following:

•	 2,500 square feet of area, with an overhead 5- to 10-ton crane.

•	 Class 100 cleanroom conditions throughout.

•	 Approximately 200 square feet area containing no viable 

organisms (to be used for a virological laboratory).23

While design concepts for a central receiving facility continued 

to be examined by MSC engineers, several Apollo science planning 

teams, which had been established under the Space Science Steering 

Committee of NASA’s OSSA, were developing the technical requirements for such a facility and identifying issues involved in handling 

materials from the Moon. On 16 June 1964 at a MSC Lunar Sampling 

Summer Symposium, these teams gave their recommendations. The 

science teams envisioned a facility whose responsibilities would be 

much broader than the repackaging function originally conceived by 

MSC engineers. They recommended that the facility provide for biocontainment and that “all operations be conducted behind a biological barrier [underlining from cited document] to prevent any harmful 

 22.

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Back Contamination

organisms which might be contained in the lunar material from contaminating the surrounding environment.”24 They also recommended 

analyzing all lunar materials before release for the presence of pathogenic organisms. The facility would thus serve receiving and distribution as well as quarantine and bioanalysis functions.

Since certain experiments had to begin immediately after samples reached the receiving facility in order to ensure the generation 

of useful data, these experiments would need to be initiated within 

the containment facility while the samples were still being quarantined. Thus the necessary equipment would have to be built into the 

receiving facility. Examples of time-sensitive experiments included 

low-level radiation counting and investigations of gas contained in 

the samples, because such characteristics of the samples could decay 

quickly with time.25

By the summer of 1964, NASA realized that it was facing the 

complex task of constructing a multipurpose facility—one that could 

simultaneously keep terrestrial contamination out (to avoid degrading the lunar samples) and Moon pathogens in. Furthermore, NASA 

needed to do this while allowing scientists and technicians to enter 

the facility; conduct detailed, in-depth research on the lunar samples; 

and then leave without taking contaminants with them. Although 

biocontainment facilities such as Fort Detrick were in operation in 

the United States, no organization “had ever built or managed a facility which could do scientific research and biological containment 

and testing simultaneously.”26 Building and operating such a facility 

constituted a daunting technical and management task that NASA 

had to work through before the United States could fulfill President 

Kennedy’s challenge to land a person on the Moon. Adding to the challenge was the need to reconcile the demands of two powerful interest groups. Many in the scientific community considered the lunar 

samples invaluable as research material but also believed that quarantining them was unnecessary and expensive and could compromise 

the science analyses. The biological community, on the other hand, 

 24.

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When Biospheres Collide

strongly cautioned that lunar material was a potential source of deadly 

pathogens and needed to be contained until proven safe to release. 

On 29–30 July 1964, SSB hosted a Washington, DC, conference 

titled “Potential Hazards of Back Contamination from the Planets”27

in which rigorous discussions of back contamination issues took 

place. SSB invited agencies representing both the biological and physical science communities, including the Public Health Service, the 

U.S. Department of Agriculture (USDA), the National Institutes of 

Health, the National Academy of Sciences, the U.S. Army Biological 

Laboratories at Fort Detrick, and NASA. Representatives from the 

academic community also attended, including professionals from the 

University of Minnesota School of Public Health, the University of 

Pennsylvania Hospital Department of Medicine, and the University of 

Michigan Department of Zoology.

The assembled scientists recognized that the Moon was an extremely 

unlikely place to harbor living organisms, but that if the Apollo spacecraft did bring back lunar microbes, they could harm or even kill life on 

our planet or flourish in the terrestrial environment to such an extent 

as to overrun our biosphere. The conference thus supported quarantine 

procedures “no matter how slight the possibility of life might appear 

to be.”28 The conference made the following recommendations, which 

eventually became policy guides for the management of samples, vehicles, and personnel returning from the Moon:

•	 Alien life-forms, astronauts, spacecraft, and lunar samples 

returning from the Moon should immediately be placed in 

isolation.

•	 Astronauts should be quarantined for at least 3 weeks (some 

conference participants thought that 4–5 weeks would be 

preferable)

•	 Spacecraft, suits, and equipment should not be decontaminated 

until thorough biological studies have been conducted on them.

 27.

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Back Contamination

•	 Preliminary sample analysis should be conducted behind 

“absolute biological barriers, under rigid bacterial and chemical 

isolation.”29

•	 NASA should immediately develop the detailed operational 

procedures that would be necessary to carry out these 

recommendations.

•	 In preparation for missions, trial runs using nonpathogenic 

microbes should be made in order to test equipment and 

develop the best methods for minimizing contamination of the 

landing capsule.

•	 Postflight testing should include experiments designed to identify 

microbes harmful to terrestrial plants and animals. Protecting 

Earth’s biosphere must be a priority.

The conference also identified a moral and practical imperative to 

implement protective measures against back contamination and recommended that the United States take a leadership role in that effort. 

Since our country recognized the potential hazard of back contamination, and since we had the power to incur this hazard, we had to 

acknowledge the responsibility for doing what we could to avoid it.

NASA decided to accept the recommendations of its science planning teams, the SSB conference, and various interest groups, and it 

instructed the MSC engineering team to revise its plans and include a 

biocontainment function in the receiving facility.30

Incorporating Planetary Protection into the Lunar 

Sample Receiving Laboratory Design

King and Flory now envisioned a far more elaborate facility than 

they had before, exceeding 8,000 square feet (740 square meters) in 

 29.

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When Biospheres Collide

area and including offices for 30 visiting scientists and laboratories for 

chemical, biological, mineralogical, and petrological analyses as well 

as radioactive material measurements. The facility would have a vacuum chamber and also a cabinet filled with purified, inert nitrogen gas 

for processing lunar samples. In addition, the facility would contain a 

separate, sterile laboratory for biological investigations and measurement instruments for monitoring the atmospheric composition in the 

vicinity of the laboratory, so that investigators who received samples 

would know what contaminants were likely to be in them.31

The cost estimate for constructing the expanded facility reached 

$14 million as of 12 August 1964.32 King and Flory presented their 

conceptual plans to Bob Gilruth, MSC’s Director, on 13 August 1964, 

and Gilruth approved them. Max Faget then submitted MSC’s preliminary plans for the facility to Willis B. Foster, who headed NASA OSSA’s 

Manned Space Flight Division, asking for $300,000 to cover the costs 

of a detailed conceptual study.33

Foster did not favor MSC’s expanded laboratory concept, but 

thought that building a simple receiving laboratory without extensive analytical capabilities was the more appropriate action. 34 Foster 

had been expecting a total cost estimate for the receiving facility of 

about $2 million and was “understandably shaken when he realized 

the extent to which MSC plans had grown.”35 Foster supplied only 

$150,000 for the concept study and recommended that MSC meet with 

OSSA to resolve the two parties’ hugely different visions of what the 

facility’s mission should be and what it should cost.

 31.

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Back Contamination

Edward Chao’s Committee and the Prioritization of Planetary 

Protection

MSC and OSSA corresponded often over the next two months 

on appropriate models for the facility. Several statements of work for 

the conceptual study were also drafted and revised. On 23 October 

1964, Willis Foster sent MSC Director Gilruth a letter informing him 

of the formation of the OSSA Ad Hoc Committee on the Lunar Sample 

Receiving Laboratory.36 OSSA gave this committee the charter to 

investigate LSRL needs and establish general facility concepts and 

requirements. OSSA did not, however, specify the level of importance 

that planetary protection needed to have in the design.

Edward Ching Te Chao, an eminent U.S. Geological Survey (USGS)

geochemist on loan to NASA, chaired the ad hoc committee, which 

was often referred to as the Chao Committee. It met four times and 

functioned from 9 November 1964 until 15 March 1965. Membership 

included representatives from academia (the University of California, 

Harvard University, and the University of Minnesota), the Department 

of Energy (DOE)’s Oak Ridge National Laboratory, the National Bureau 

of Standards, the Army Biological Laboratories, and NASA.37 In the 

view of James McLane, MSC’s engineer in charge of the early planning 

of LSRL, Ed Chao seemed at the committee’s first meeting to have a 

preset agenda—to “keep the size and cost of the proposed lab to an 

absolute minimum.”38

The next meeting, held 11 December 1964, focused on LSRL performance parameters as well as a topic of relevance to planetary protection—the procedures for biological decontamination and testing. The 

third meeting on 15 January 1965 also involved discussion of issues 

related to potential living organisms in the lunar material, with the 

Chao Committee’s biological subcommittee giving its presentation.39

The wrap-up meeting took place on 26 February 1965, but by the 

beginning of March 1965, the Chao Committee had not yet completed 

 36.

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When Biospheres Collide

its final report. MSC personnel knew that adding quarantine capabilities to LSRL would significantly complicate its construction. Cognizant 

of the tight schedule that had to be followed to construct LSRL, MSC 

grew impatient to find out what Chao’s group recommended.40

Although the committee did finish its report on 15 March 1965, 

it did not immediately issue it. On 22 March, James McLane called 

Chao, who explained that a primary reason the report had not yet 

been released was that the committee had begun new discussions with 

various U.S. agencies and important issues had been raised. In particular, the U.S. Public Health Service (PHS) had aired its concerns 

regarding appropriate quarantine requirements and its envisioned role 

in planetary protection matters. These discussions with PHS, which 

eventually led to a long-term partnership between it and NASA, are 

examined in some detail later in this chapter.41

By 8 April 1965, McLane had finally received a draft of the Chao 

Committee’s report and had begun reviewing and circulating it. 

Planetary protection concerns had been very visibly addressed in the 

report’s first recommendation: Quarantine all lunar material while 

testing it for the presence of biological life or other substances that 

might be infectious, toxic, or harmful to humans, animals, or plants. 

The Chao Committee understood the importance of lunar sample biocontainment and defined a cardinal criterion for LSRL “to provide 

an absolute barrier between the lunar material and the world at large 

until the material is certified as biologically harmless.”42 The Chao 

Committee thus recognized planetary protection as a primary goal of 

the facility. 

Other recommendations included the following:

•	 Store, control, and package lunar materials and distribute them 

to scientists around the world.

 40.

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Back Contamination

•	 Conduct physical, chemical, biological, and radiological 

analyses that cannot wait until after the quarantine period.

•	 Protect all lunar material from terrestrial contamination in 

order to ensure the validity of later scientific investigations.43

The Chao Committee did not have the unquestioned support of 

MSC personnel, some of whom had reservations about the need for 

the committee to even exist. In a November 1964 meeting that took 

place between NASA OSSA’s Foster and MSC staff members Elbert 

King, James McLane, and Donald Flory, the MSC personnel expressed 

their belief that the ad hoc committee should function only in an 

advisory capacity and should definitely not have the final word on 

LSRL design criteria. MSC needed to own that function. In addition, 

they felt that the ad hoc committee should not determine where LSRL 

would be built.44

Various organizations tried to position themselves to host LSRL. 

Goddard Space Flight Center (GSFC) declared that it should be in the 

running, since other “data bank”45 facilities would possibly be constructed at GSFC as well. Several university laboratories expressed 

interest in having LSRL at their facilities and, in the opinion of John 

Eggleston, MSC’s Assistant Chief for Space Environment, Ed Chao envisioned locating LSRL at the U.S. Geological Survey facility in Flagstaff, 

Arizona. The Chao Committee, however, eventually recommended MSC 

as the best site for LSRL.46 The Chao Committee also reported the 

intense concern in the U.S. scientific community regarding NASA’s presumed intention to use LSRL “as the basis for a major in-house research 

program.”47 Such an action would have directly threatened the domains 

of scientists outside of NASA, who strongly wanted the detailed lunar 

sample analyses to be assigned to them.

 43.

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When Biospheres Collide

The Hess Committee’s Vision for a Receiving Facility

Homer Newell, NASA’s Associate Administrator for Space Science 

and Applications, decided that in order to design a suitable LSRL, an 

independent, non-NASA assessment was needed of the appropriate 

types of analyses to conduct on lunar samples upon their return to 

Earth as well as of the facilities and staffing required. In December 1964, 

Newell wrote to NAS SSB chairperson Harry H. Hess, requesting SSB’s 

judgment on these issues. Hess formed a committee composed of three 

SSB members and two scientists from academia. One of the scientists, 

Clifford Frondel of Harvard, also served on the Chao Committee. The 

Hess Committee (also known as the Ad Hoc Committee on the Lunar 

Sample Handling Facility) met in Washington, DC, on 14 January 1965 

to examine Newell’s concerns and considered four key questions:

•	 What types of analyses needed to be performed immediately 

upon return of samples from the Moon?

•	 What types of research were more appropriate to postpone until 

samples could be sent to the best available research laboratory?

•	 What types of LSRL capabilities would be needed for its 

analyses?

•	 What personnel would LSRL require?48

The Hess Committee gave recommendations in its 2 February 

1965 report on fulfilling both scientific and planetary protection objectives. The report concluded that the only critical scientific analysis 

that needed to be performed by LSRL, rather than by investigators 

to whom the samples would eventually be sent, was of the short-lived 

radioactivity induced in lunar samples by cosmic rays. This parameter 

would have to be measured soon after the samples arrived on Earth 

because induced radioactivity rapidly drops to a minimal level. No 

other measurements were as urgent as this from the point of view of 

fulfilling science objectives. From the planetary protection perspective, 

however, public health authorities needed to immediately examine the 

lunar material in order to identify any harmful biological properties. 

 48.

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Back Contamination

These biological examinations could be performed at LSRL, but they 

could also be performed at Army Biological Warfare Laboratories or 

U.S. Public Health Service facilities.49

The Hess Committee recognized a need that Newell had not asked 

it to evaluate: the requirement to quarantine lunar material until biological investigations could show them to be biologically harmless. In 

a letter written to Newell on 2 February 1965, Hess stated that the 

members of his committee had indeed determined that such isolation 

procedures were necessary. Notable in its absence was any recommendation that the quarantining be carried out at MSC. The report of the 

Hess Committee, in fact, stated that “we can see no inherently compelling reason why”50 LSRL should be in Houston. 

The report of the Hess Committee also estimated facility costs. Its 

recommended “relatively restricted-mission sample receiving laboratory for quarantine and biological measurement”51 coupled with the 

necessary low-level counting facility would, the committee envisioned, 

cost a comparatively modest $2.5 million. For all other sample analyses, 

the Hess Committee recommended using existing laboratories rather 

than building new ones. Besides the budget savings that could accrue 

from such a plan, potential political benefits may also have played a 

part in the committee’s recommendation. Hess chaired the SSB, a 

National Academy of Sciences organization concerned with the wellbeing and advancement of the U.S. scientific community. The SSB worried that NASA LSRL staff members might overstep their bounds and 

develop competing research programs with space scientists outside of 

the Agency. Thus, it was not surprising that the Hess Committee advocated a sample receiving laboratory with a limited mission.52

The committee held that the extensive analyses MSC was proposing would best be done by “our national scientific community”53 rather 

than by LSRL or any other single group. While the committee did 

not recognize any compelling reason for locating LSRL at MSC, it did 

 49.

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When Biospheres Collide

understand that doing so would add considerably to the capabilities 

of MSC, and this would not be a bad thing since MSC was to play a 

critical part in the Apollo program. But construction of a radiationcounting facility at MSC might prove to be more expensive than at 

other sites, due to the waterlogged soil and the need to locate such a 

facility deep underground to shield it from naturally occurring background radiation.

The committee recommended that LSRL, wherever it was located, 

be operated continuously rather than just during Apollo missions, 

so that it could conduct maximum research in as cost-effective a 

manner as possible. This, too, did not favor locating LSRL at MSC, 

because the committee suspected that MSC, with its “minimal scientific capability,”54 would likely have to shut down LSRL between 

lunar voyages.

The Hess Committee’s recommendation to NASA to quarantine 

all lunar samples until biological analyses showed that they contained no harmful living organisms surprised staff at both NASA 

Headquarters and MSC, who had not totally accepted that preventing 

back contamination was such a serious concern. Although NASA’s 

Director of the Biosciences Program in the OSSA had been communicating with NAS and PHS, he had not been expecting the importance that the Hess Committee gave to potential back contamination 

dangers presented by lunar samples. His surprise was in large part 

due to the generally held belief in the scientific community that the 

Moon was sterile.55

The U.S. Public Health Service Involvement 

in Back Contamination Issues

On 18 March 1965, a report published by PHS’s Communicable 

Disease Center (later renamed the Centers for Disease Control and 

 54.

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Back Contamination

Prevention [CDC]) in Atlanta, Georgia,56 added its opinion to the back 

contamination debate by recommending specific protective procedures 

for handling and quarantining lunar samples.57 In addition, the Surgeon 

General of the United States, whose office oversees PHS,58 met casually 

with NASA’s Administrator to discuss the two agencies’ relationship in 

preventing back contamination and had proposed the following actions:

•	 Continue to expand PHS’s space biology program.

•	 Assign a PHS liaison office to NASA.

•	 Develop, through a NASA-PHS partnership, an interagency 

committee to study and give guidance on matters of “outbound 

and inbound contamination problems.”59

The Administrator and Surgeon General reportedly agreed that 

negotiations between the two agencies needed to continue at the staff 

level. In order to kick off this process, Lawrence B. Hall, whom PHS 

sent on assignment to NASA’s Bioscience Program in the OSSA to 

serve as Special Assistant for Planetary Quarantine, drafted a proposal 

embodying the three items above as well as a NASA organizational 

structure that could meet the goals of both agencies.60

In April 1965, Hall examined another aspect of lunar exploration—

the jurisdictional issues of bringing extraterrestrial material into the 

country. In particular, Hall asked counsel for NASA’s Office of Space 

Medicine to advise him on the statutory authority of PHS, the Department 

of Agriculture, the Department of the Interior, and NASA itself to manage and control the import of extraterrestrial material into the United 

 56.

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When Biospheres Collide

States.61 This was an important matter to establish, because if an agency 

had such authority, it could refuse to admit lunar samples, the spacecraft, 

and possibly even astronauts into the country until they were subjected to 

required examinations and quarantines. During a meeting on 17 August 

1965, NASA and PHS agreed that PHS had the responsibility “for the 

health of the nation and for any potential threat to that health from extraterrestrial life, particularly from back contamination.”62 Furthermore, the 

Department of Agriculture had a similar responsibility in matters concerning U.S. crops and animals of economic importance. The Department 

of the Interior’s (DOI’s) Fish and Wildlife Service also had a potential concern with the matter but was not, NASA and PHS believed, interested in 

pressing for a part in planetary protection activities.

PHS’s Office of the Surgeon General agreed to submit a proposal to 

the Administrator of NASA outlining the planetary protection actions 

it deemed necessary to protect against extraterrestrial health threats. 

Furthermore, the chief of PHS’s CDC, James L. Goddard, affirmed 

that he “was prepared to staff any required quarantine activity”63 at 

LSRL. NASA initiated actions to bring PHS representatives into regular contact with the Headquarters Office of Manned Space Flight and 

Houston’s Manned Spacecraft Center, so as to provide needed planning 

input for the Apollo mission as soon as possible.

One of these contacts took place on 27 September 1965, when representatives from PHS as well as the Department of Agriculture met 

with those from the NASA Headquarters Office of Manned Space Flight 

and Houston’s MSC for “an informal exchange of views . . . on the subject of back contamination.”64 Elbert King of MSC’s Space Environment 

Division, after discussing quarantine issues with medical specialists 

 61.

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Back Contamination

from MSC, put forward a view that certain conditions on the Moon 

probably sterilized samples taken from its surface and rendered them 

less hazardous to life on Earth than samples taken from below the surface. These sterilizing conditions included the following:

•	 Intense ultraviolet radiation.

•	 High-energy protons from the solar wind.

•	 High surface temperatures.

•	 Low atmospheric temperatures.

•	 Absence of free water.65

•	 Hypervelocity impacts of small meteoroids.66

If the surface of the Moon was indeed sterile, then back contamination precautions could be altered. Astronauts and samples that had 

come into contact only with the lunar surface could be handled “less 

stringently than subsurface samples.”67 This would have placed fewer 

restrictions on the scientific research performed on the samples, 

which many scientists both within and outside of NASA would have 

appreciated. The cost of building LSRL might also have been lowered. But MSC’s opinion that samples collected on the lunar surface 

presented low risks was not shared by representatives from the other 

agencies. PHS representative and chief of the CDC James Goddard68

questioned King’s assumptions and suggested that there might be 

places on the Moon’s surface, such as in sheltered areas, where 

microorganisms could survive. Since no one at the meeting could 

refute this, Goddard pushed for strict quarantining of all lunar material. The importance of the issues, Goddard said, justified this action 

“even if it cost $50 million to implement an effective quarantine.”69

Goddard as well as other non-NASA personnel at the meeting agreed 

attachment to Aleck C. Bond to Deputy Director, “Lunar Sample Receiving Laboratory,” 30 

September 1965, JSC Historical Archives, “1 April–30 September 1965” folder, box 76-11, 

LRL Chron. Files 1964–1965.

 65. Kemmerer to Record, “Summary of Meeting”; Compton, Where No Man Has Gone 

Before, pp. 46–47. 

 66. W. W. Kemmerer, Jr., and E. A. King to Maxime A. Faget, “Proposed MSC Quarantine 

Policy for the Apollo Program,” 23 September 1965, JSC Historical Archives, “1 April–30 

September 1965” folder, box 76–11, LRL Chron. Files 1964–1965.

 67. Kemmerer to Record, “Summary of Meeting.”

 68. J. H. Allton, J. R. Bagby, Jr., and P. D. Stabekis, “Lessons Learned During Apollo Lunar 

Sample Quarantine and Sample Curation,” Advances in Space Research 22 (1998): 374.

 69. Compton, Where No Man Has Gone Before, p. 47. 

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When Biospheres Collide

that the general quarantine period for all samples brought back from 

the Moon needed to be at least 30 days, and more if LSRL found any 

biologic evidence.

Other points that non-NASA personnel agreed on included the 

following:

•	 Potential contamination of astronauts presented as great a 

hazard as lunar samples. Appropriate quarantine periods 

discussed were from 21 to 30 days.

•	 Astronauts needed to be trained in using sterile techniques and 

in the principles of microbiology.

•	 A high-hazard terrestrial pathogen was an appropriate model to 

use in designing LSRL’s protective systems.

•	 The LSRL quarantine area had to be capable of housing all 

personnel entering it should they become exposed to lunar 

material. LSRL also needed the capability to function as a 

hospital in the event personnel fell ill.

•	 Biologic findings were likely to result from accidental 

contamination with Earth microbes, rather than from detection 

of actual lunar microbes.70

The then-current concepts for an LSRL appeared adequate for conducting initial plant and animal testing involving exposure to lunar 

material, and the Department of Agriculture representatives thought 

that more extensive testing would not be necessary unless evidence 

was found of the presence of unusual organisms. If this happened, 

additional investigations could be carried out at other locations.71 In 

particular, Department of Agriculture representatives reached a consensus that LSRL did not need to provide large animal testing facilities, 

but that if life was detected in the Moon samples, a portion of them 

should be sent to the USDA Plum Island Animal Disease Center, which 

did have such facilities.72

 70.

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Back Contamination

Participants at the 27 September 1965 meeting came to a consensus that, in spite of precautions that might be taken, astronauts would 

not be able to “completely escape respiratory and dermal exposure to 

lunar contaminants and . . . the inside of the command module would 

receive a low but significant level of contamination.”73 A heated discussion ensued over the lack of plans up until that time for handling the 

astronauts after their return to Earth. Meeting participants examined 

in some depth the types of facilities that would be needed on the several recovery ships. The conferees also defined to a certain extent what 

was unacceptable treatment of returning space travelers by raising the 

hypothetical question: If Apollo astronauts were handled in the same 

way as the Gemini astronauts had been, would PHS permit them to 

enter the United States? Gemini 9 astronauts, for instance, who had 

not made a landing on another celestial body, did not wear biological 

isolation garments (BIGs) when they came aboard the prime recovery 

ship, the aircraft carrier USS Wasp.

74 This would not be acceptable for 

Apollo astronauts who had landed and walked on the Moon. PHS, after 

considering the question, “emphatically replied that they would refuse 

such entry”75 to the United States for Apollo astronauts if they only followed the precautions that Gemini astronauts had.

Those at the 27 September 1965 meeting also discussed the 

problem of contaminating the Moon with terrestrial microbes. NASA 

needed to avoid such an occurrence if possible because, in the view of 

the meeting’s participants, “this could lead to confusion in the examination of returned samples and possibly prolong the length of sample 

and astronaut quarantine.”76

Lawrence Hall, NASA’s Planetary Quarantine Officer, thought 

that one particularly useful result of the 27 September 1965 meeting was that it informed MSC staff of the points of view of U.S. regulatory agencies on planetary protection matters. He felt, however, 

 73.

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When Biospheres Collide

that those agencies still did not understand the reasons for MSC’s 

reluctance to address back contamination issues to the extent that 

the agencies wanted. One of the reasons was that MSC considered 

lunar surface material to most likely be sterile and thus not a source 

of back contamination. Another reason was that MSC’s and NASA’s 

main objective was to put an astronaut on the Moon before the end 

of the decade. They were much more focused on planetary exploration than on planetary protection and had concerns that excessively 

rigid planetary protection requirements could interfere with attaining their main objective. PHS’s chief purpose, on the other hand, 

was to protect health.77 Hall recommended that further informal 

exchanges between NASA and the regulatory agencies be scheduled 

to work out policies that were hopefully acceptable to both parties.78

Such meetings were held, but throughout much of the Apollo mission, MSC and PHS continued to differ on how extensive the quarantine needed to be. 

MSC staff came away from the 27 September 1965 meeting realizing 

that LSRL would need to be considerably larger and more expensive 

than had been projected. Although MSC questioned PHS’s strict position regarding planetary protection, MSC did not have the data at that 

time to justify a lower level of quarantine. Facilities would have to be 

constructed in which astronauts and support staff could be quarantined 

for at least three weeks. Postmission briefings, which would be numerous and extensive, would have to be conducted through a biological barrier. In addition, recovery operations for the spacecraft, the astronauts, 

and samples would have to be far more complex than MSC and NASA 

had hoped. PHS officials believed that from the moment the Command 

Module (CM) splashed down in the ocean, exposure of its interior to the 

atmosphere of Earth had to be prevented. Astronaut crews would need 

to be immediately isolated, even in the rubber rafts that the recovery 

crews used. Once the astronauts reached the recovery ship, they would 

have to go straight into a mobile quarantine chamber.79

George Mueller, NASA Associate Administrator for Manned Space 

Flight, paid a visit to MSC on 13 October 1965 and received a briefing 

 77.

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on the 27 September meeting. He directed MSC to propose a budget to 

Headquarters that incorporated the above-mentioned features of LSRL, 

including “isolation of astronauts and returned hardware during the 

quarantine period.”80

MSC’s Systems Engineering Division Chief, Owen Maynard, passed 

the word to all branches of his division that the Apollo missions had 

to implement a much stricter quarantine of spacecraft, astronauts, 

and samples than originally envisioned. It was unacceptable for his 

personnel to take the view that no changes could be made in Apollo 

mission plans, given present weight, cost, and schedule limitations. In 

Maynard’s words, all Apollo staff were “morally obligated to prevent 

any possible contamination of the Earth”81 and thus would have to 

find ways of conforming to PHS quarantine guidelines and incorporating additional planetary protection requirements into the mission. 

Preventing back contamination had become an ethical issue. It had 

also become a compelling political matter. Failure to take adequate 

planetary protection measures could seriously damage the public’s 

image of the Apollo program as well as of NASA in general, hampering 

the Agency’s future actions. These were additional reasons why NASA 

had to develop an effective quarantine program.82

PHS and NASA Roles and Actions

During the fall of 1965, United States Surgeon General William H. 

Stewart exercised his authority, demanding that Apollo mission astronauts and samples be quarantined. NASA decided that PHS needed to 

be given some responsibility in the matter and help design LSRL to 

effectively prevent back contamination. NASA and PHS initiated efforts 

 80.

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When Biospheres Collide

to “reach a formal agreement on cooperation.”83 On 15 November 1965, 

NASA Deputy Administrator Hugh L. Dryden wrote to the Surgeon 

General, expressing NASA’s wish that PHS, whose mission was to protect the health of the United States, “should assume a leadership role 

in the anticipation of problems that man-in-space flight may bring to 

the earth.”84 Dryden proposed assigning a PHS officer as a liaison with 

NASA and establishing an interdepartmental advisory committee that 

understood the potential impact of extraterrestrial contamination of 

our planet’s biosphere. Dryden’s hope was that the committee would 

be chaired by a senior PHS scientist-administrator. Dryden asked 

Stewart for recommendations concerning the characteristics of the 

facilities, equipment, and staff needed. He also asked Stewart for help 

“in justifying to the Bureau of the Budget the urgency and necessity of 

this program.”85

On 22 December 1965, Stewart responded directly to NASA 

Administrator James E. Webb, agreeing that a senior PHS officer be 

made a liaison between the two agencies and that an interagency committee be established to “guide NASA in the development and conduct 

of a program to avoid possible contamination of the earth biosphere 

by extraterrestrial life.”86 Stewart recommended that this committee 

be chaired by James Goddard, chief of the CDC. He also mentioned 

that PHS personnel were working with MSC to develop a Preliminary 

Engineering Report and budget materials for the envisioned LSRL and 

that he would be pleased to assist in justifying the envisioned planetary protection program to the Bureau of the Budget. 

 83.

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The Preliminary Engineering Report that Stewart mentioned 

had been initiated in late May of 1965. NASA had selected a Detroit 

architecture and engineering firm, Smith, Hynchman, and Grylls, to 

review MSC’s preliminary plans for LSRL and identify whether any 

alternatives existed to constructing a new facility. On 1 October 1965, 

this firm submitted a draft two-volume report, which concluded that 

modifying one or more existing facilities to satisfy both scientific and 

quarantine requirements would cost as much as constructing a new 

facility and take as long a time. Also, after evaluating 29 possible sites 

for LSRL, the report recommended MSC as the best location. This was 

the same conclusion that the Chao Committee and the Apollo science 

planning teams had come to almost nine months earlier.87

A Revised Plan for LSRL

The MSC Technical Working Committee for the Design of the LSRL, 

which had been established on 14 June 1965, was made up primarily 

of engineers who had been involved in LSRL planning since early 1964. 

This committee updated the Preliminary Engineering Report to reflect 

new requirements that had been implemented since the firm of Smith 

et al. had begun work on it and submitted it to NASA on 21 October 

1965 for approval as the Revised Preliminary Engineering Report. This 

report called for construction of an 86,000-square-foot facility at a 

cost of $9.1 million. An additional $7 million, approximately, would 

be needed to buy the equipment for the individual laboratories. The 

facility would require a staff of about 80 scientists and technicians and 

would cost $1.6 million per year to operate.88

Transport of Mission Components from Splashdown to LSRL

NASA awarded a contract to the MelPar Company of Falls Church, 

Virginia, to examine issues involved in transporting astronauts, 

spacecraft, and Moon samples from the planned splashdown point in 

 87.

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When Biospheres Collide

the Pacific Ocean to LSRL in a manner that would not contaminate 

Earth or the samples.89 MelPar also designed and oversaw construction of the Mobile Quarantine Facility that housed the personnel, 

equipment, and material returning from the Moon during their trip 

to LSRL.

Formation of the Interagency Committee 

on Back Contamination

In January 1966, NASA began setting up the multiagency board 

that Surgeon General Stewart had recommended, calling it the 

Interagency Committee on Back Contamination (ICBC). During the 

months that followed, NASA invited a range of federal agencies and 

organizations to bring their own points of view and expertise to the 

new board and eventually brought the organizations and individuals 

listed in table 4.1 onto it. In a letter from NASA Administrator Webb 

to Secretary of Agriculture Orville L. Freeman, Webb cited the importance of each group’s specialized knowledge and experience in helping to protect Earth’s living resources as well as the integrity of lunar 

samples and scientific experiments.90

 89.

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Table 4.1 Membership of the Interagency Committee on Back Contamination.91

Department of Health, Education, and Welfare—Public Health Service

David Sencer, ICBC Chairman and Chief of CDC 

John Bagby, Assistant Chief of CDC

Department of Agriculture

Ernest E. Saulman, Deputy Director of Science and Education

Archibald J. Park (alternate), Assistant to the Administrator, Agricultural Research Service

Department of the Interior

John Buckley, Office of Science Adviser

Howard H. Eckles (alternate), Assistant to Science Adviser

National Academy of Sciences

Wolf Vishniac, Department of Biology, University of Rochester

Allen Brown (alternate), Department of Physiology, University of Pennsylvania

NASA Ames Research Center

Harold P. “Chuck” Klein, Assistant Director for Life Sciences

Richard S. Young (alternate), Chief, Exobiology Division

NASA Manned Spacecraft Center (MSC)

Charles A. Berry, Director, Medical Research and Operations

Walter Kemmerer (alternate), Chief, Biomedical Specialties Branch

Aleck C. Bond, Manager, Systems Test and Evaluation

James C. McLane (alternate), Chief, Facilities Requirements Office of the Lunar Receiving 

Laboratory Program Office

G. Briggs Phillips, Liaison, Lunar Receiving Laboratory Program Office

NASA Headquarters

Leonard Reiffel, Apollo Program Office

Col. John E. Pickering, Director, Lunar Receiving Operations, Office of Space Medicine

James Goddard, the Surgeon General’s choice for chairperson 

of ICBC, got the opportunity to serve as Commissioner of the Food 

 91.

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When Biospheres Collide

and Drug Administration,92 and thus on 4 February 1966, Stewart 

selected the new CDC Chief, David Sencer, for the position. At that 

meeting, Sencer chose John Bagby, the Assistant Chief of CDC and 

the other PHS delegate on ICBC, to represent PHS’s views in support 

of LSRL during upcoming congressional hearings.93 Bagby’s argument to Congress to support construction of LSRL will be reviewed 

in the next section.

MSC assigned two regular delegates to ICBC—Charles Berry and 

Aleck Bond. Berry was concerned primarily with the biomedical and 

quarantine aspects of LSRL, while Bond focused mainly on the impact 

of quarantine measures on LSRL design, development, and operation.94

The prime objective of ICBC was to advise and guide the 

Administrator of NASA on planetary protection matters, with a charter to protect public health, agriculture, and other resources “against 

the possibility of contamination by hypothetical lunar organisms conveyed in returned sample material or other material exposed to the 

lunar surface (including astronauts) and to preserve the biological 

and chemical integrity of lunar samples.”95 ICBC was also to aid in 

protecting the validity of scientific experiments and ensure against 

compromising the operational aspects of the Apollo program. ICBC 

was formed to advise on policy, not on technical details, although the 

complexities of the Apollo mission required that it examine many 

technical matters. As plans for the Apollo mission developed, ICBC 

became intimately involved in many of the decisions regarding controls for preventing back contamination, quarantine protocols, and 

isolation facilities. It helped establish specific criteria for quarantine 

operations, determine the lunar material analyses needed in order to 

 92.

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Back Contamination

evaluate planetary protection risks, and design contingency plans to 

handle unintended releases from the quarantine facility.96

The MSC-PHS-Army “Apollo Personnel 

Quarantine Facilities Review”

Building quarantine capabilities into LSRL would, as the 

Preliminary Engineering Report drafts indicated, increase the facility’s cost by millions of dollars. George Mueller, head of NASA’s Office 

of Manned Space Flight, was concerned about the rising costs of LSRL 

and how to justify them to Congress. He recognized the need for quarantining, but still questioned whether a new, dedicated quarantine 

facility needed to be built, or whether a more cost-effective approach 

could be found.

On 22 November 1965, Mueller sent a teletype to James C. McLane 

of MSC’s LSRL Office requesting a survey of “existing US facilities 

with a potential for related personnel quarantine”97 that might possibly accommodate returning Apollo astronauts and their support crews. 

McLane responded the next day that MSC had already initiated the 

study, was conducting it in cooperation with PHS and the U.S. Army, 

 96.

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When Biospheres Collide

and would produce a final report by 3 December 1965.98 The title of 

the report was “Apollo Personnel Quarantine Facilities Review.”99

Other organizations assisting in the study—some of which owned 

facilities that were examined for their quarantine capabilities—included 

representatives from the military (the U.S. Air Force and Navy), the academic community (the University of Minnesota and the University of 

Notre Dame), industry (Pitman-Moore Division of the Dow Chemical 

Company), the American Medical Association, and the National 

Institutes of Health. Some of the facilities examined, including large 

environmental chambers, pharmaceutical industrial plants, and aerospace life science laboratories, were quickly rejected due to “grossly 

evident space or containment inadequacies.”100 The study committee 

selected for more careful evaluation 12 facilities that it felt had the best 

potential for personnel biocontainment. The committee analyzed these 

12 facilities using the criteria listed below as measures of suitability for 

quarantining Apollo astronauts, samples, and equipment:

•	 Presence of a barrier wall effective for biocontainment.

•	 Pass-through locks and autoclaves.

•	 Sufficient filtration capability for incoming air.

•	 Negative pressure maintenance of facility.

•	 Effluent heat treatment capability.

•	 Habitability for up to 15 people for 60 days.

•	 Sufficient area for medical examinations and specialized 

medical equipment.

•	 Layout compatible with security requirement.

•	 Observation provisions for debriefings and medical surveillance.

•	 Capability for handling and culturing high-hazard, pathogenic 

fungi, bacteria, and viruses.

 98.

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Table 4.2 summarizes the capabilities of the 12 facilities analyzed. 

The three hospitals in the table were those that provided the highest 

level of bio-isolation available in the country.101

Table 4.2 Candidate facilities for lunar crew quarantine.102

Facility Location

Cost To 

Modify 

Facility for 

Apollo Use Comments on Suitability

U.S. Army 

medical facility

Ft. Detrick, MD 1 Care facility for personnel working 

with high-hazard pathogens. Met 

most suitability criteria, but its use in 

the Apollo program would severely 

compromise its DOD mission.

Naval Biological 

Laboratory

Oakland, CA 2 Did not meet any suitability criteria.

Naval Institute 

of Health Clinical 

Center

Bethesda, MD 2 Primarily a hospital research 

facility. Had no biobarrier, passthrough locks; air filtration systems; 

negative-pressure capabilities; or 

isolated waste treatment.

U.S. PHS Hospital Staten Island, NY 2 Facilities for three people only.

Cook County 

Hospital

Chicago, IL 2 General hospital facility. Had no 

biobarrier, pass-through locks, air 

filtration systems, negative-pressure 

capabilities, or isolated waste 

treatment.

Belmont Hospital Worcester, MA 2 General hospital facility. Had no 

biobarrier, pass-through locks, air 

filtration systems, negative-pressure 

capabilities, or isolated waste 

treatment.

U.S. PHS Hospital Carville, LA 2 Leprosy facility that was not 

designed for highly infectious agents.

University of 

Notre Dame 

(Lobund germfree laboratory)

South Bend, IN 2 Animal facilities only.

 101.

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When Biospheres Collide

Cost To 

Modify 

Facility for 

Facility Location Apollo Use Comments on Suitability

National Institutes 

of Health National 

Center

Bethesda, MD 2 Designed to isolate single patients 

from environment; not designed to 

protect environment from patients.

Ames Research 

Center

Moffett Field, 

CA

2 Did not meet any suitability criterion.

U.S. Air Force 

School of 

Aerospace 

Medicine

San Antonio, TX 2 Animal facilities only.

U.S. Dept. of 

Agriculture

Washington, DC 2 Designed for animals only.

Legend

1 = Major cost

2 = Cost approaching that to build a new facility

Note from the table that some of the facilities had been designed for 

housing animals rather than people. Only one facility came close to the 

level of biocontainment and accommodations that were needed for Apollo: 

the Fort Detrick, Maryland, Army hospital. It was equipped to isolate and 

care for personnel who had handled highly risky microorganisms such as 

in Fort Detrick’s biological warfare facilities (which became the U.S. Army 

Medical Research Institute of Infectious Diseases [USAMRIID] in 1969). 

Converting the Fort Detrick hospital to accommodate the needs of the 

Apollo program would have required major expense and significant new 

construction, but this would have been cheaper than converting the other 

facilities listed in the table, which would have required expenses nearly 

equal to those for constructing a brand new facility. A downside of using 

Fort Detrick for the Apollo program, however, was that this would seriously impede the Army’s own occupational medicine research programs 

that it was conducting there. Thus, none of the existing sites in the MSC 

study could be used for LSRL without serious barriers to overcome.103

 103.

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Back Contamination

Different functions of LSRL could have been distributed among 

various facilities around the country, such as those examined above. 

But the “Facilities Review” pointed out that proximity of astronauts, 

samples, and spacecraft would make security and operational requirements far easier to attain and would minimize travel requirements for 

medical, engineering, and scientific staff. The “Facilities Review” also 

made a case for locating LSRL at MSC, arguing that this would allow 

monitoring and operation of the quarantine areas for samples, astronauts, and spacecraft by a relatively small resident group of NASA, 

PHS, and Department of Agriculture personnel and would eliminate 

considerable duplication of effort. This same argument could have 

been used, however, to justify locating all LSRL functions at another 

site. Nevertheless, the study’s findings gave Mueller some justification 

for seeking a budget from Congress to build a new LSRL facility rather 

than trying to use an existing site.

Winning Congressional Support

In February 1966, John Bagby, representing the points of view of 

PHS’s CDC and ICBC, wrote a strong statement to Congress providing reasons for including biocontainment capabilities in LSRL. This 

statement was included in the record of the 24 February 1966 hearing 

of the House Subcommittee on Manned Space Flight. Bagby acknowledged that the chances were extremely low that the lunar environment 

could support life as we know it, but he also stressed that we had no 

data assuring the absence of such life. His argument for biocontainment highlighted the dangerous lack of knowledge that space scientists 

had regarding the impacts of potentially life-bearing lunar material on 

our planet. There was the chance that if lunar organisms were destructive to Earth life and were set free in our ecosystem, they could cause 

a disaster of enormous proportions. Thus, the United States needed a 

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When Biospheres Collide

facility that could reliably keep any extant life in the lunar samples 

from contacting our biosphere.104

Bagby made the point that “the single most important scientific 

objective of the Apollo missions is the return of the lunar samples”105

and that the success of the experiments that would be performed on 

them depended heavily on preventing their contamination by terrestrial material. Thus, a quarantine facility was needed to prevent 

the flow of contamination in two directions—from the terrestrial 

environment to the samples and from the samples to Earth’s ecosystem. Bagby also summarized for Congress the recommendations 

of the July 1964 SSB conference for handling returning astronauts, 

spacecraft, equipment, and samples, as well as the 15 March 1965 

report of the NASA OSSA Ad Hoc Committee on the Lunar Sample 

Receiving Laboratory (the Chao Committee report),106 which covered the concepts, requirements, specifications, and operation of 

LSRL. Finally, Bagby’s presentation focused on the Preliminary 

Engineering Report that PHS as well as NASA MSC staff had worked 

on. This report identified necessary capabilities of LSRL, including 

the following:

•	 Microbiology testing of lunar samples.

•	 Isolation facilities for astronauts and potentially exposed 

personnel.

•	 Isolation capabilities for samples during all analyses.

•	 Isolated facilities for processing onboard camera film and data 

tape.

 104.

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Back Contamination

•	 Capability to perform time-critical analyses (such as radiation 

counting).107

Reduced Presidential and Congressional Support for the Space 

Program

NASA sought funding for LSRL during a time when support for 

human spaceflight was becoming increasingly difficult to acquire 

from Congress. This was in part due to the fact that President Lyndon 

Johnson was sinking large amounts of money into his Great Society 

social programs while at the same time trying to keep the U.S. budget 

under $100 billion. Meanwhile, the situation in Southeast Asia, and 

our country’s involvement in it, was heating up. As a result, the budgets of other U.S. programs, including our space program, were getting 

slashed. NASA had requested $5.556 billion for fiscal year (FY) 1967; 

the Office of Management and Budget (OMB) recommended that it be 

cut to $5.012 billion, and President Johnson accepted the opinion of 

his budget advisers. As NASA prepared for its annual presentation to 

Congress, the chances of receiving even the reduced budget recommended by OMB seemed questionable.108

The basis of President Johnson’s support for the Apollo mission 

had been strong but was steadily eroding. During the period from 1961 

through 1963, while he was Vice President under Kennedy, Johnson’s 

support for the space program rested heavily on issues of U.S. security. 

He made this position very clear in such statements as one he gave in 

May 1963, “I do not think this generation of Americans is willing to 

go to bed each night by the light of a Communist moon.”109 Johnson’s 

eagerness to surpass the USSR in the race for space and his support 

for the U.S. space exploration effort remained solid during the first 

year of his presidency—after Kennedy’s assassination in November 

 107.

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When Biospheres Collide

1963 until November 1964. Furthermore, in January 1964, Johnson 

told Congress that U.S. efforts to put a man on the Moon during the 

1960s continued unchanged. But various U.S. security-related events 

eventually reduced his eagerness to back NASA’s current space program. President Kennedy had emerged victorious from the Cuban missile crisis with the USSR in 1962; the United States steadily built up its 

own impressive arsenal of missiles; several nuclear powers—the USSR, 

the United Kingdom, and the United States—signed the Limited Test 

Ban Treaty in 1963, which prohibited nuclear tests in the atmosphere, 

underwater, and in space; and the USSR decided to de-emphasize its 

lunar landing program in favor of developing its near-Earth orbital 

capabilities.110

One of the main drivers for the race to the Moon had been the 

perceived threat from the USSR and its aggressive space program. But 

Johnson no longer worried that the Soviets were beating us in military might, especially missile capabilities, and the USSR was no longer 

threatening to land on and control the Moon.111 President Kennedy 

had concurred as well with Johnson’s view that the major danger had 

passed, especially regarding the space race. In fact, on the day that 

he was assassinated, Kennedy had prepared a speech that he planned 

to give at the Dallas Trade Mart, asserting that “we have regained the 

initiative in the exploration of outer space . . . the United States of 

America has no intention of finishing second in space,” and that “there 

is no longer any fear in the free world that a Communist lead in space 

will become a permanent assertion of supremacy and the basis of military superiority.”112

Congress, too, was changing its opinion of the magnitude of the 

Soviet threat. In the view of astronaut and later Senator John Glenn, 

appeals to the dangers presented by the USSR no longer swayed 

 110.

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Back Contamination

Congress, as they had in the past, to increase space spending. In 

Glenn’s words, “the anti-Russian theme had worn out.”113

The Competition for Limited Funds: NASA’s Struggle To Win 

Congressional Approval

In 1965, the war in Vietnam and its costs began to escalate sharply. 

Those costs as well as President Johnson’s antipoverty and Great 

Society programs had significant impacts on the 1965 and subsequent 

federal budgets.114 This made it increasingly difficult for NASA to get 

its budget requests passed. NASA had its first congressional hearing 

for its fiscal year 1967 budget request on 18 February 1966 in front of 

the Subcommittee on Manned Space Flight of the House Committee 

on Science and Astronautics. This committee had been authorized in 

1958 primarily to provide oversight of NASA and the nonmilitary space 

program.115

When NASA Administrator James Webb presented the Agency’s FY 

1967 budget authorization request, 60 percent of which was for human 

spaceflight, he found that the House subcommittee was actually sympathetic to most of the Apollo program’s funding requests. In spite of 

tight budgets, many seasoned politicians in Congress appeared to be 

“completely swept up in the pure romanticism of landing a man on the 

moon.”116 Nevertheless, the House subcommittee gave the proposed 

LSRL budget an exceptionally thorough examination. It was in this 

subcommittee that “the majority of the battle over funding for the 

receiving lab would be fought.”117

 113.

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When Biospheres Collide

NASA fortunately had a strong ally on the House subcommittee—

its chairman, Olin “Tiger” Teague, whose Texas district included MSC. 

Teague was a conservative Democrat and an ex-Marine fighter pilot 

who had been highly decorated in World War II. He was known for 

his directness, determination, and “heavy emphasis on educating the 

Congress and the public on the practical value of space.”118 He strongly 

supported human spaceflight and had been a major influence in 

Congress’s selection of Houston as the location of MSC. But the House 

subcommittee also included representatives not nearly so friendly to 

NASA’s endeavors and, in particular, to its plans for LSRL.119

The House Subcommittee on Manned Space Flight—18 and 24 

February 1966 Hearings

At the 18 February hearings, NASA gave a prepared statement on 

its budget request. This statement mentioned LSRL funding only once, 

indicating that this facility was meant to “house all activities and functions pertinent to receipt, processing and distribution of samples of 

lunar materials, as well as the quarantine of lunar exploration teams 

and spacecraft . . . ”120

The subcommittee briefly discussed back contamination issues, 

with NASA Deputy Administrator Robert C. Seamans assuring those 

at the hearing that NASA would take all precautions to prevent it. 

NASA reiterated and expanded on this position in response to questions that the subcommittee submitted for the record as part of its 24 

February 1966 hearings. NASA drew from the recommendations of 

the February 1965 NAS SSB conference, “Potential Hazards of Back 

Contamination,”121 which stated that although the probability of find-

 118.

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Back Contamination

ing viable organisms on the Moon was extremely low, the ecological 

balance of Earth was at risk, and so it was mandatory to take the necessary steps to prevent back contamination.122

No serious opposition to NASA’s planetary protection plans were 

presented at the February hearings. But that situation changed the 

next month.

The House Subcommittee—1 March 1966 Hearings

The House Subcommittee on Manned Space Flight hearings continued through March. At the 1 March 1966 hearing, NASA received 

its first direct challenge on constructing LSRL. This challenge was 

led by James G. Fulton of Pennsylvania, the ranking Republican on 

the subcommittee and a longstanding critic of the way that NASA 

managed its programs. A continuing complaint of Fulton was that 

NASA tended to concentrate its operations geographically around 

its Centers, rather than spread out the work through more areas of 

the country. Fulton mentioned several reasons why NASA was implementing the wrong strategy. One aspect was that of national defense. 

He worried that if the Agency centered too many capabilities in one 

place, they could all be wiped out with a single weapon. He also held 

that centering scientific talent in too few places would drain talent 

from every other area. He wanted the talent distributed in order to 

raise the cultural level throughout the country. He thus questioned 

the Agency’s intent to locate LSRL in Houston, already a Center for 

space programs. In addition, he suspected that LSRL would constitute an unnecessary duplication of existing facilities and actively 

tried to block its construction. 

Fulton’s position, as well as that of his Republican colleague on 

the subcommittee, Donald Rumsfeld of Illinois, was that NASA should 

make use of the already existing quarantine and scientific research 

 122.

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When Biospheres Collide

facilities in other parts of the United States. Fulton gave the example of the University of Pittsburgh, which had already established a 

department of Moon geology.123

Both congressmen were worried that by constructing LSRL in 

Houston, NASA was trying to use planetary protection as a springboard for building an extensive, costly in-house research program 

rather than relying on the talents of scientists outside of NASA. 

Rumsfeld in fact stated his concern that “next year and [in] succeeding years NASA will come before this committee and request funds 

totaling millions of dollars to beef up this capability which we are 

being asked to begin this year. The argument will be that we have to 

keep it an integrated program, and the capability exists in Houston. 

NASA will say: ‘We have this $9 million facility, therefore we need to 

add to it, add another $30, $40, or $100 million.’”124

Republicans also opposed Texas Democrats’ channeling still more 

federal funds into their construction projects, such as would be the 

case if LSRL was built at MSC.125 Fulton expressed the view that if an 

integrated LSRL was needed (and he was skeptical that it was), then a 

better location for it would be in a place that was not receiving its fair 

share of space exploration contracts, such as regions in the Midwest. 

Even though Fulton’s home state of Pennsylvania was not in the 

Midwest, his arguments highlighted the fact that members of Congress 

were motivated to obtain contracts and income for their home states 

and that NASA had to be aware of these motivations and perhaps play 

to them if they were to win congressional support.126

George Low, Deputy Director of MSC, and William Lilly, Director 

of NASA Manned Space Flight Program Control and a budget specialist, attempted to address the concerns raised by subcommittee members, but with little effect. Neither Low nor Lilly had come prepared 

with a detailed defense against the attacks. Low did point out that 

the Preliminary Engineering Report as well as the Chao Committee 

 123.

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Back Contamination

report both recommended MSC as the best location for LSRL. He also 

stressed that “there will be more than 50 scientific principal investigators who will get portions of the sample for their own investigations, 

and these will be mostly at universities throughout the country.”127

NASA’s arguments did not sway Fulton or Rumsfeld.The latter congressman expressed interest in a scheme that would send the lunar 

samples to one location and the astronauts to another. He believed 

that the astronauts were not going to be deeply involved in the packaging, distribution, or radiation counting of the lunar material, so why 

not use two locations? Low didn’t agree, insisting that the total cost of 

two facilities would far exceed the cost of the one planned LSRL. He 

gave one supporting example: If personnel working with lunar material 

got exposed to it (such as through a breach in the biological barrier), 

then at a single integrated facility, they could simply go into quarantine along with the astronauts. At two widely separated facilities, however, the situation would be more problematic.

Rumsfeld responded to this by asking if NASA had available a more 

quantitative analysis of the cost of developing two receiving labs using 

existing facilities. He wanted to see statistics and cost calculations in 

order to determine how the cost of enhancing two geographically separated, existing facilities—one for astronauts and the other for lunar 

samples—compared to the cost of building one integrated facility.128

 Low stated that NASA might not have such an analysis in the form 

that Rumsfeld wanted to see, but the Agency did have information on 

the various existing sites that were investigated. Acting subcommittee chair Emilio Daddario of Connecticut requested that NASA provide such information for the record, and Low agreed. NASA hastily 

put together a document titled “Additional Data Submitted Regarding 

the Lunar Receiving Laboratory,”129 which was added to the 1 March 

1966 hearing record. This document employed a shortened version of 

the term for the facility: Lunar Receiving Laboratory, or LRL, which 

was the name being increasingly used by NASA and other organizations. The “Additional Data” document included a written justification 

for NASA’s LRL plans, stressing that they outlined necessary actions 

 127.

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When Biospheres Collide

to meet the concerns of public health authorities in the retrieval 

of sample materials from the Moon as well as the time dependency 

requirements for certain types of testing. The “Additional Data” document made several important points, including the following:

•	 No existing U.S. laboratory was capable of performing all the 

required functions of LRL.

•	 The containment of all hazardous material and personnel 

within one facility significantly decreased the risk of 

contamination when transferring material from one functional 

area to another.

•	 The potential for contaminating surrounding areas was 

minimized if all sources of contamination were contained at 

one geographical location.

•	 Cost savings would result from using a single location for the 

operating and maintenance functions of quarantine areas.

Nowhere did the “Additional Data” document quantitatively compare the costs of two existing versus one new receiving facility, although 

reference was made to the Preliminary Engineering Report, which did 

compare several facility alternatives and showed that a cost saving 

would be realized by integrating all of the functions in one facility.130

Not all of the criticism during the 1 March 1966 hearings came from 

Republicans. Some came from the Democratic side of the subcommittee. 

Texas Democrat Robert R. Casey, for instance, asked for more explanation of LRL’s utility, complaining that “the ordinary layman is uninformed as to the necessity of this lab and what its purpose is going to 

be.”131 Casey’s comment indicated that if NASA expected subcommittee 

members to approve LRL funding as part of the Agency’s budget, then 

it had to do a better job of justifying the facility in ways that would 

be supported by the committee’s constituents. Up until the hearings, 

debates over LRL had taken place primarily within NASA and the scientific community as well as with other agencies. Little effort had been 

made to sell LRL to the public or to Congress. For instance, NASA’s 

256-page prepared statement on its overall budget request mentioned 

LRL only once. NASA needed to conduct a far-reaching campaign to 

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communicate the necessity of back contamination protection and the 

critical part that LRL would play in accomplishing this.132

The House’s Rejection of NASA’s Plans

The week following Lilly’s and Low’s hearing, the subcommittee 

expressed its position regarding LRL funding. Unsatisfied that NASA 

had adequately defended its plans for LRL, the subcommittee removed 

its funding from the authorization bill. One of the contributing factors to 

this action may have been the perception that NASA’s arguments were 

not objective, but were “after the fact”133 justifications for constructing an LRL and locating it at MSC. This opinion was supported by the 

fact that MSC staff had already developed conceptual studies for LRL, 

always assuming that it would be built in Houston. Critics believed that 

the focus of MSC’s analyses had been on identifying reasons why no 

other facility was suitable for LRL, rather than on logically determining 

what the best location within the United States actually was.134

Loss of LRL would have been a huge blow to the Apollo program 

and to MSC. Without the facility, the Apollo program could not meet 

all the requirements that had been imposed on it by the scientific 

community and PHS. Low stated the situation very bluntly: without 

the laboratory, NASA could not bring samples back from the Moon and, 

in fact, could not even complete the Apollo mission. This was not an 

exaggeration. Quarantine issues had become so important that a failure to have LRL ready for Apollo 11 would postpone the entire Apollo 

program. 

In response to this dire situation, Mueller called for a more detailed 

study of existing venues than he had ordered just a few months earlier, demanding that the study be ready in time to help secure FY 

1967 funding for LRL. This new study was to identify and examine 

additional existing facilities that could either provide quarantine 

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When Biospheres Collide

capabilities for the Apollo crews and lunar samples or carry out the 

necessary scientific studies.135

The Pickering Committee Study

To fulfill Mueller’s orders, MSC formed a site survey board led 

by Col. John Pickering, Special Assistant to the Director of Space 

Medicine in NASA’s OSSA. The Pickering Committee screened 27 

existing facilities and selected the following eight of them for in-depth 

assessment during the week of 16–23 March 1966:

•	 PHS’s CDC in Atlanta, Georgia. 

•	 Army Biological Center at Fort Detrick, Maryland.

•	 National Institutes of Health in Bethesda, Maryland.

•	 Oak Ridge National Laboratory in Oak Ridge, Tennessee.

•	 School of Aerospace Medicine, Brooks Air Force Base in San 

Antonio, Texas.

•	 Ames Research Center at Moffett Field, California.

•	 Navy Biological Laboratory in Oakland, California.

•	 Los Alamos Scientific Laboratories in Los Alamos, New Mexico.136

 The committee then developed criteria for an acceptable facility, 

based on the Apollo mission’s requirements. The facility needed to 

have the following capabilities:

Quarantine Capabilities

•	 Two-way biological containment.

•	 Treatment for liquid effluents.

•	 Sterilization for gaseous effluents.

Sample Handling Capabilities

•	 High vacuum sample handling with special chamber seals.

•	 Remote manipulators for samples and containers.

•	 Exceptionally clean pumping system.

•	 Low-level radiation measurement capability.

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Back Contamination

An acceptable facility also had to have available space, administrative and technical support services, ample utilities, and good logistics 

of travel to and from the site. In addition, the facility’s management 

had to be willing to accept the project and integrate it into the existing 

work schedule.137

On 24 March 1966, the Pickering Committee presented its results 

in a draft Site Investigation Study, Lunar Receiving Laboratory. 

This study was eventually made a part of House Subcommittee on 

Manned Space Flight hearings record. The study presented important 

findings regarding each of the eight sites, which helped the Pickering 

Committee and Congress to make decisions on LRL. These findings 

are summarized below:

Site 1: U.S. PHS Communicable Disease Center (CDC), Atlanta, 

Georgia. The CDC did not have adequate radiation counting facilities, quarantine laboratories with two-way containment capabilities, or 

crew reception facilities, all of which were vital to the envisioned LRL. 

In addition, laboratory support facilities at the CDC were being fully 

used and would not be available to LRL if it located there. No facilities 

were available that could be adapted to meet LRL needs. The conclusion was that all components of LRL would have to be provided by new 

construction at an estimated cost of $9.4 million, as compared to the 

$9.1 million estimated for building LRL at MSC. The additional cost for 

building it at the CDC was due in part to rock formations close to the 

surface that would have to be blasted or drilled away.

Site 2: U.S. Army Biological Center, Fort Detrick, Maryland. No 

acceptable radiation counting facilities existed. No laboratory facilities were available for LRL use, and no two-way quarantine facilities 

existed. Laboratory support capabilities were widely scattered and not 

adaptable to LRL use. A small Army hospital unit (20 beds) was at the 

site but was fully utilized in a respiratory disease research program 

and so was not available for a Crew Reception Area (CRA). Land was 

available to build an LRL, but doing so would require an extension of 

utilities into the area. The estimated cost of building an LRL at this 

site was $11 million.

 137.

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When Biospheres Collide

Site 3: National Institutes of Health (NIH), Bethesda, Maryland. 

Excellent radiation counting capabilities existed, but there were no quarantine facilities with two-way containment. Laboratory support capabilities were there but were committed to other use. The large clinical center 

on site could conduct tests on returning astronauts, but it was located 25 

miles away from where LRL would be constructed. Because LRL would 

not be able to be integrated into the existing NIH campus, LRL would 

require completely new construction at an estimated cost of $11.8 million. The land acquisition necessary would involve complex negotiations 

with city, state, and district planning commissions and would conflict 

with the development of a pathogen-free, large-animal farm at the site. 

Site 4: Atomic Energy Commission (AEC) Oak Ridge National 

Laboratory, Oak Ridge, Tennessee. Low-level radiation counting facilities existed, but not those with the specifications needed by LRL. No 

two-way containment facilities were at the site. An animal-virus laboratory was under construction, but use of it by NASA would impair its 

planned mission. Laboratory support facilities were present but were 

not adjacent to the potential sites of LRL. The region was not near a 

jet aircraft landing field. Conflicts with the weapons-development mission of the site were also envisioned. A necessary capital investment of 

about $9 million was estimated. 

Site 5: USAF School of Aerospace Medicine, Brooks Air Force 

Base, San Antonio, Texas. Radiation counting facilities existed, 

although not underground (which would have made it easier to reduce 

background radiation). No quarantine facility was present. No laboratory support facilities were available for use. Space was available for 

new facility construction, which would cost an estimated $11 million. 

The high cost was due in part to unusual soil conditions, which would 

require special foundations. 

Site 6: NASA Ames Research Center, Moffett Field, California. 

An above-ground radiation counting laboratory existed, although 

shielding would have to be greatly increased and a radon-removal 

system installed in order to reduce background radiation, which was 

necessary for the counting measurements to be as sensitive as possible. No two-way quarantine facilities were available. Existing facilities 

could be modified to provide some of the laboratory support capability 

needed. No crew reception facilities existed at the site. Land was available for construction of an LRL at an estimated cost of $10.3 million, 

with ready access to utilities and air transportation.

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Site 7: Naval Biological Laboratory, Oakland, California. No radiation counting or crew reception facilities existed, and laboratory support was not available. Considerable one-way quarantine capabilities 

existed, but not two-way. The availability and acceptability of commercially owned land adjacent to the site was questionable. A capital 

investment of $10.5 million was needed if the land could be obtained.

Site 8: AEC Los Alamos Scientific Laboratories, Los Alamos, 

New Mexico. Radiation counting facilities existed and could possibly 

have been used by an LRL for a period of several weeks, if scheduled 

in advance. Laboratory support capabilities were present as well. No 

suitable quarantine facilities existed. Land was available for new facility 

construction at an estimated cost of $10.3 million. The remote location 

of the site added to construction cost estimates. Residential housing in 

the area was severely limited. The site had limited air and road access.138

At the end of its intensive survey, the Pickering Committee reached 

conclusions similar to ones in previous studies:

•	 Without extensive modifications, none of the examined 

facilities could meet the criteria for even one of LRL’s main 

functionalities.

•	 None of the facilities could be economically adapted to meet all 

criteria of LRL.

•	 Using any one of the sites examined for LRL would result in 

the reduction or modification of another nationally significant 

research activity.

•	 To minimize public health hazards, one facility integrating 

several functionalities (rather than multiple specialized 

facilities) was advisable.

•	 The optimal location for LRL was MSC in order to attain the 

best operational characteristics and minimum operating costs. 

This was because efficient management of the Apollo mission 

would best be achieved by locating astronauts, spacecraft, and 

Moon samples in proximity to MSC engineers and physicians, 

especially in the weeks following recovery.

The Pickering Committee’s draft Site Investigation Study, Lunar 

Receiving Laboratory that was released on 24 March 1966 was 

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When Biospheres Collide

Table 4.3 Lunar Receiving Laboratory conceptual studies and site evaluations.

Date Study Summary Source 

Apr-1964 MSC “Sample Transfer 

Facility” in-house 

study

Identified need for the 

facility to check lunar 

samples for viable 

organisms. 

Aleck C. Bond 

to Chief, Office 

of Technical and 

Engineering Services, 

“Sample Transfer 

Facility.”

16-Jun-1964 NASA Lunar Sampling 

Summer Symposium 

Identified need for 

biocontainment to 

protect terrestrial 

environment, and 

for analyzing all 

lunar materials 

before release for 

the presence of 

pathogenic organisms.

Carter, The 

Prevention of Back 

Contamination, p. 13.

29–30-July1964SSB “Conference on 

Potential Hazards of 

Back Contamination 

from the Planets”

Advocated quarantine 

of astronauts, 

spacecraft, and 

samples. Called for 

astronaut quarantine 

of at least three weeks. 

Recommended that 

the United States take 

a leadership role in 

planetary protection.

Brown, “Potential 

Hazards of Back 

Contamination From 

the Planets.“

2-Feb-1965 Hess Committee 

report (NAS)

Recognized need for 

quarantining lunar 

material, but did not 

identify any reason why 

the isolation facility 

should be at MSC.

SSB, Report of the 

Ad Hoc Committee 

on Lunar Sample 

Handling Facility.

15-Mar-1965 Chao Committee 

report

Supported 

quarantining 

and testing lunar 

material for living 

organisms. Eventually 

recommended that the 

LRL be located at MSC. 

Ad Hoc Committee on 

the Lunar Receiving 

Laboratory.

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Date Study Summary Source 

18-Mar-1965 PHS CDC report Recommended 

specific protective 

procedures for 

handling and 

quarantining lunar 

samples.

Mangus and Larsen,

Lunar Receiving 

Laboratory Project 

History, p. 14.

1-Oct-1965 Preliminary 

Engineering Report

Concluded that 

modifying an 

existing facility to 

satisfy both scientific 

and quarantine 

requirements of the 

LRL would cost as 

much as constructing 

a new facility and 

take as long a time. 

Recommended MSC 

as best place for LRL.

Carter, The 

Prevention of Back 

Contamination, pp. 

22–24.

8-Dec-1965 MSC “Study of 

Existing Personnel 

Quarantine Facilities”

Concluded that 

no existing site 

was suitable for 

LRL without first 

overcoming serious 

cost, land availability, 

and other barriers. 

Study recommended 

one site rather than 

several distributed 

sites for LRL and also 

made case for locating 

it at MSC.

Deputy Director, 

Space Medicine, to 

James C. McLane, 22 

November 1965.

7-Apr-1966 Pickering Committee’s 

Site Investigation 

Study, Lunar Receiving 

Laboratory

Visited eight sites 

with existing facilities. 

None acceptable 

without expensive 

modifications. 

Recommended that 

LRL be built at MSC.

Carter, The 

Prevention of Back 

Contamination, p. 33.

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When Biospheres Collide

immediately read by at least some members of Congress, including 

Representative James Fulton of Pennsylvania. MSC distributed the 

final version of its study on 7 April 1966. The study underlined the 

point that from a project management perspective, Houston was the 

best location for LRL.

139

The House Subcommittee Rehearing—31 March 1966

Mueller appeared before the House subcommittee for a rehearing on 31 March 1966 devoted exclusively to LRL. The stated purpose of the rehearing was to “give NASA an additional opportunity to 

present other information in a complete way,”140 given the dissatisfaction that the subcommittee had with NASA’s justifications for LRL 

up until that time. Mueller, who was NASA’s Associate Administrator, 

Office of Manned Space Flight, brought several NASA witnesses with 

him to talk on the need for LRL. These included Lt. Gen. Frank A. 

Bogart, Deputy Associate Administrator (Management); Col. John 

Pickering, Special Assistant to the Director of Space Medicine; and 

Angelo P. Picillo, Facilities Engineer. Mueller began the proceedings 

by summarizing the envisioned LRL’s objectives and the evolution of 

LRL concepts and requirements, focusing in particular on the need for 

quarantine. He emphasized how identification of this need arose not 

only out of NASA’s ranks, but also from working in close cooperation 

with NAS Space Science Board members.141

Representative Fulton of Pennsylvania continued his attack from 

the 1 March hearing, pointedly criticizing the fairness of NASA’s intent 

to locate LRL at MSC. Fulton called into question the makeup of the 

Pickering Committee, noting that seven of the nine members were 

from NASA and five of those were from MSC. He commented that “If 

I were going to set up a site selection committee that would select 

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Houston as the site, I would then, of course, pick five out of the nine 

members from Houston.”142

Mueller was better prepared for Fulton’s attacks than Lilly and Low 

had been on 1 March. Mueller noted that the Chao Committee, which 

recommended at an earlier date than the Pickering Committee that LRL 

be located in Houston, was composed of members from a whole spectrum of organizations, including universities, Department of Defense 

facilities, a national laboratory, and the National Bureau of Standards, 

and was definitely not dominated by NASA. (A summary of the Chao 

and Pickering Committees’ findings, as well as those of other task forces, 

is included in table 4.3.) In fact the chairman himself, Edward Chao, 

was from the U.S. Geological Survey (USGS) and on loan to NASA.

Fulton then brought up many other questions, such as why the 

envisioned site for LRL was not an “isolated land mass or island”143

near the ocean pickup point for the spacecraft. Would not that have 

been a safer location that did not require the transport of potentially 

harmful material halfway around the world? Fulton also questioned 

why all functions of LRL should be located in one place rather than 

letting other parts of the country in on the action. At this point, acting 

subcommittee chair Emilio Daddario stopped any further questions 

and asked Mueller to complete his testimony on LRL plans, believing 

that many of Fulton’s questions would be answered during the course 

of the testimony.144

One of Fulton’s chief concerns was that the selection of the LRL 

site be handled fairly and objectively, and he questioned whether the 

heavy NASA makeup of the Pickering Committee would further this 

aim. Mueller responded by saying that the Pickering Committee was 

formed to make sure that the results of the earlier investigation conducted by the Chao Committee (which recommended Houston as the 

best LRL site) were sound and to investigate whether any existing facilities that could potentially serve as LRL had been overlooked. Mueller’s 

point was that the Pickering Committee was not meant to ensure that 

Houston got LRL, but rather to do what Fulton wanted done—conduct 

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When Biospheres Collide

an objective study to find the best site. The Pickering Committee 

was able to use results from NASA’s Preliminary Engineering Report, 

which gave it “a much more definite set of requirements that could be 

used to measure both the cost and the advantages and disadvantages 

of various locations.”145 The Pickering Committee thus employed the 

latest data to narrow down its investigation to the eight sites discussed 

earlier in this chapter as possible candidates for LRL. 

Mueller also defended the selection of Pickering Committee members by declaring that “These are the people who have been interested, 

intimately involved in trying to design the lunar receiving laboratory 

as a facility, so they were our experts as to what was required to carry 

out this program.”146 These people approached the task with the goal 

of finding another site that could more economically fulfill the necessary planetary protection requirements that were established by other 

agencies. They found that this could not be done. 

Mueller said that NASA’s original belief had been that every effort 

should be made to use existing facilities wherever they could be 

found in the United States. He stated that as little as a year earlier, he 

believed “there must be an existing facility somewhere in the United 

States . . . so that we would not have to . . . build a new facility. We 

therefore started with a bias against new facilities, and it was only 

after very careful study and very careful analysis that we came very 

reluctantly to the conclusion that a new facility had to be built . . . .”147

These remarks were borne out by a NASA internal document entitled 

the “Lunar Sample Receiving Laboratory Office Staff Paper,”148 which 

recorded NASA’s original intent to use existing or modified existing 

facilities. The shortcomings of existing vacuum systems, biological 

laboratories, containment capabilities, crew isolation facilities, and 

radiation counting laboratories forced the conclusion that new facilities were, in fact, required. 

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Back Contamination

After Mueller was finished, Col. John Pickering, the head of the 

site survey team, explained in considerable detail to the House subcommittee the assessments that his team had done and presented its 

findings. These findings, which were summarized earlier in the chapter, identified the many inadequacies of existing facilities and clearly 

showed that money would not be saved by modifying them into an 

LRL rather than constructing a new such facility.149

Fulton and Rumsfeld continued to oppose NASA’s plan for LRL. 

Fulton questioned the actual danger back contamination presented 

to Earth, commenting that it had been repeatedly hit by meteoroids 

containing “traces of life-giving substances in them.”150 Mueller agreed, 

but pointed out that the high temperatures those bodies reached while 

plunging through Earth’s atmosphere would have destroyed any complex molecules and viable organisms.

Richard L. Roudebush, a Republican representative from Indiana, 

raised a question related to one brought up by Congressman Fulton earlier in the hearings, asking if there would be a savings in locating LRL 

in an isolated area such as an island or a ship at sea. Mueller responded 

that NASA had carefully considered this and believed that a ship installation would markedly increase the cost, simply because a typical ship 

would by itself cost far more than LRL. As to locating the facility on an 

island, it was true that this could place it near one of NASA’s landing 

points, but the Apollo program required two such sites—a primary one 

in the Pacific Ocean and another in the Atlantic. If proximity to the 

landing site needed to be attained, two facilities would be necessary.151

Representative Roudebush questioned whether construction of 

LRL could be delayed a year.152 Roudebush’s inquiry was in line with 

recent concerns of President Johnson who, in order to curb rising 

inflation, wanted a slowdown in all federal construction. Mueller, however, made clear that NASA was up against a hard deadline. In order to 

meet the late President Kennedy’s goal of getting a man on the Moon 

within the decade of the 1960s, LRL needed to first be completed and 

fully operational, given the importance of preventing back contamina-

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When Biospheres Collide

tion from returning astronauts and lunar material. Mueller admitted 

that NASA should have recognized the need for an LRL far earlier than 

it had, in 1961 rather than in 1964. But if construction did not start 

immediately on the facility, it would prove extremely difficult to get it 

built and tested in time for the first lunar landing, and this would delay 

the entire Apollo program.153

Roudebush then asked if LRL could be scaled down in scope. He 

inquired as to why unprocessed lunar samples could not be sent directly 

to the university research laboratories that would examine them in 

depth, rather than first examining and testing the samples at LRL. He 

wondered if NASA was “going overboard”154 on the criteria for LRL. 

Mueller replied that LRL was to be the “minimum possible facility”155

to meet planetary protection requirements and that the equipment 

required by the facility did not at present exist anywhere else. He also 

pointed out that the earliest estimates for LRL added up to $23 million. 

Since that time, he and many others had done as much as they could to 

reduce those costs to the present estimate of $9.1 million. 

NASA’s 31 March presentations to the House subcommittee convinced most of its members that constructing a new LRL facility at 

MSC was justified, and the funds to begin this process were restored 

to the Agency’s authorization bill. The 1967 NASA Authorization Bill 

left the full Committee on Science and Astronautics on 4 April 1966 

and was sent to the House floor recommending a total NASA budget 

of $4,986,864,150 for 1967 operations, including the entire $9.1 million for constructing LRL. Fulton filed a Dissenting View to the House 

committee’s report, saying that not enough data had come to light on 

which to responsibly design and build the laboratory and restating all 

of the objections he had brought up during subcommittee hearings. He 

also tried to push through an amendment that would have gotten rid 

of LRL funding. Nevertheless, the authorization bill passed the House 

vote on 3 May 1966 by an overwhelming 349 to 10, with the LRL budget of $9.1 million entirely intact.156 

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Back Contamination

The Senate’s Review of LRL

The U.S. Senate Committee on Aeronautical and Space Sciences 

raised some similar concerns to those of the House subcommittee, but 

George Mueller, head of NASA’s Office of Manned Space Flight, had 

far less trouble convincing the Senate committee of the need for LRL. 

The Senate committee, in fact, discussed LRL only once during its 11 

days of hearings. Mueller explained briefly that LRL was an “essential 

part of the quarantine process”157 and necessary to meet the requirements of PHS. When asked by James J. Gehrig, the staff director of 

the committee, whether the requirement for LRL was placed on NASA 

in written form, Mueller referred to the statement written by John 

Bagby, Assistant Chief of the CDC, on the containment of lunar samples, astronauts, and personnel. As with the House subcommittee, this 

document was made part of the record.158

The Senate committee’s concern was not that LRL was needed, 

but that NASA had not done sufficient analysis to justify its estimated $9.1 million cost for constructing the facility. The committee 

took an action that was typical of the way Congress often responded 

to NASA budget requests: it recommended a reduction in the budget 

(of $1 million) in order to ensure that LRL planning and construction expenses would be minutely reviewed and carefully controlled. 

According to Carter,159 Congress frequently assumed that budget 

requests from NASA, as well those from other agencies with large 

Research and Development (R&D) programs such as the Department 

of Defense, had been expanded from what was actually needed. Most 

members of Congress did not have the capabilities to determine by 

just how much, and so arbitrary budget cuts were recommended. 

NASA and other agencies, aware of this congressional tendency, 

sometimes tried to circumvent the cuts by adding extra funding 

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When Biospheres Collide

to its initial budget requests. NASA may have done just that in the 

case of LRL, since nearly 11 percent of the requested budget was 

included in a rather nondescriptive category entitled “Acceleration of 

Construction.”160 Nevertheless, when NASA realized in May 1966 that 

the Senate meant to reduce LRL funding, the Agency took steps for 

lowering facility costs. On 9 May 1966, NASA approved two important 

groups to manage design and construction of LRL—a policy board and 

a program office, one of whose important tasks was to discover ways of 

meeting the reduced cost constraints that the Senate was attempting 

to impose while making sure that neither the biocontainment mission 

nor the research capabilities of LRL got compromised.161 In order to 

ensure that construction costs would not exceed $8.1 million, NASA 

eventually compressed the LRL area by 3,800 square feet, eliminated 

one of its two vacuum systems, and amalgamated all activities into 

one building rather than having a separate structure for personnel and 

Apollo crew quarantine.162

The Joint House-Senate Conference Committees

The Senate passed a NASA authorization bill on 24 May 1966 for a 

total amount of $5.008 billion, including the reduced amount of $8.1 

million for LRL. Since LRL budgets recommended by the House and 

Senate differed with each other, Congress formed a joint conference 

committee in order to work out an agreement. The joint committee 

came to a meeting of the minds on 19 July 1966, which was 19 days 

past the beginning of FY 1967. The joint committee agreed on a NASA 

budget of $5,000,419,000, with LRL receiving $8.1 million. The House 

accepted this budget on 21 July 1966 and the Senate on 22 July. 

The budget process was not yet completed, however. Congressional 

funding required a second step: the passing of a bill to actually appropriate funds for NASA. The House Subcommittee on Independent 

Offices of the Committee on Appropriations had begun this process 

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Back Contamination

on 5 April 1966, before the first bill had passed. The subcommittee 

agreed on a reduced appropriation, for a total NASA budget of only 

$4.95 billion, but with the LRL budget restored to $9.1 million. This 

appropriation bill passed the full House on 10 May 1966. 

The amounts approved in the corresponding Senate appropriations bill, which passed on 2 August 1966, again differed from the 

amounts in the House appropriations bill, and the matter once more 

went to a joint conference committee. The two houses of Congress 

finally reached an agreement on 18 August 1966 to give NASA a total 

of $4.968 billion. The compromise bill, which once again included 

only $8.1 million for LRL, was immediately accepted by the House; 

the Senate approved it on 24 August, nearly two months after the 

start of FY 1967.163

Designing, Constructing, and Outfitting LRL

Defining LRL Scientific Requirements and Physical Characteristics

During 1965, NASA Headquarters’s Manned Space Science 

Division worked on defining scientific requirements for LRL, while 

MSC in Houston focused on developing the facility’s architectural 

and engineering design requirements. By the end of the year, as 

mentioned earlier, MSC completed its Preliminary Engineering 

Report as well as quarantine requirements for crew and support personnel. The results of these efforts, which were presented 

to Congress in 1966, included plans for an 86,000-square-foot 

(8,000-square-meter) facility with a personnel isolation area, sample 

laboratories, and a radiation-counting capability, part of which was 

to be built 50 feet (15 meters) below ground and heavily shielded 

from outside radiation.164

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When Biospheres Collide

LRL had three major objectives:

1. To prevent the back contamination of Earth from any lunar 

organisms that might have been brought back from the mission.

2. To prevent lunar sample contamination from Earth’s atmosphere and microorganisms in order to protect the integrity of 

the scientific investigations on those samples.

3. To determine if and when it was safe for lunar material to come 

into contact with the terrestrial environment.165

To achieve these objectives, LRL required a complex design and 

integration of many functional areas: 

•	 Living and examination quarters for the astronauts, including 

the following:

•	 Medical and dental examination rooms.

•	 Operating room.

•	 Biomedical laboratory.

•	 Astronaut exercise, debriefing, office, and sleeping area.

•	 Support staff office and dormitory areas.

•	 Kitchen, dining, and lounging areas.

•	 Facilities for sterilizing and passing food and laundry in 

and out.

•	 Sample analysis laboratories of various types: 

•	 Radiation counting laboratory, a section of which was 50 

feet below ground.

•	 Gas analysis laboratory.

•	 Physical-chemical test laboratory for performing 

mineralogical, petrological, and geochemical analyses.

•	 Spectrographic laboratory and darkroom.

•	 Biopreparation laboratory for sample handling, preparing, 

weighing, and packaging for distribution.

•	 Bioanalysis laboratory for blood and other tests on mice.

•	 Holding laboratory for germ-free mice.

•	 Holding laboratory for normal mice.

•	 Lunar microbiology laboratory to isolate, identify, and 

possibly grow lunar microorganisms.

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•	 Bird, fish, and invertebrate laboratory for exposing animals, 

including shrimp, quail, cockroaches, and oysters, to lunar 

samples.

•	 Plant laboratory for exposing plants such as germ-free 

algae, spores, seeds, and seedlings to lunar samples.

•	 Microbiological laboratory for culturing lunar and 

astronaut samples.

•	 Crew virology laboratory for postflight astronaut 

examinations. 

•	 Biosafety laboratory to monitor all systems.

•	 Microbiology laboratory for clinical tests of quarantined 

personnel.

•	 X-ray room.

•	 Vacuum system for receiving and processing Moon samples. 

•	 Air conditioning system to sterilize air both entering and 

leaving LRL. 

•	 Two-way biological barrier for quarantining astronauts for more 

than two weeks and lunar samples for over a month.

•	 Apollo Command Module storage.

•	 Support facilities. 

•	 Staff offices.166

Oak Ridge National Laboratory, which was owned at the time by the 

Atomic Energy Commission (and later by the Department of Energy), 

designed and constructed LRL’s vacuum system and its related equipment.167 AEC also developed LRL’s low-level radiation counting equipment and the software (or “computer programs,” as they were referred 

to at that time) to analyze the radiation data.168

Contracting for LRL Construction and Equipment Installation

MSC envisioned that construction of LRL would be completed and 

the facility ready for practice-testing by the end of December 1967. This 

testing would be completed by January 1969, which would hopefully be in 

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When Biospheres Collide

time for the facility to analyze the first lunar samples. The delay in congressional approval of the LRL budget until nearly two months after the 

start of FY 1967, however, seriously threatened this tight schedule, especially since Congress insisted that MSC could only solicit construction bids 

but could not even open them until passage of NASA’s authorization bill. 

MSC was able to work around this problem by initiating some tasks 

early, before actually receiving congressional funding. Procurement 

rules during this time were more flexible than they are today, allowing a job to be initiated before official congressional authorization.169

Some of the correspondence between NASA managers in 1966 gave 

hints as to how preofficial work on a contract was defended by MSC. 

In a 16 May 1966 letter from NASA Headquarters, for instance, George 

Mueller advised MSC Director Robert Gilruth that LRL “must be operational by November 15, 1967,”170 and thus to “proceed with your plan 

toward the early award of a construction contract for the substructure, 

utilities and building shell.”171 This gave Gilruth potential license to 

get a head start on the work before congressional approval.172 He was 

under enormous pressure to construct LRL in time to support the first 

Moon landing, which NASA thought might be as soon as late 1968. He 

acknowledged this pressure in a 9 June 1966 letter to Mueller, mentioning that meeting the 15 November 1967 deadline to have LRL fully 

operational was “a very difficult task to accomplish”173 with a cost ceiling of $9.1 million, which ended up being cut to only $8.1 million. 

In an 8 July 1966 letter, Col. John Pickering, Executive Secretary 

of ICBC, also hinted at initiation of work before receipt of congressional funding. He wrote that the final LRL design effort was already 

under way and that “procurement actions for incremental construction are being readied for award on July 15,”174 even though he must 

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have known that congressional authorization and appropriation bills 

were very unlikely to be approved and signed by that date. 

In June 1966, two months before congressional approval, MSC did 

start work, contracting with S. H. Barrett and Associates of Houston 

for $15,000 to develop shop drawings and fabricate some of the structural steel that it would need for LRL. MSC purchased the steel for this 

task by borrowing the funds from another project.175 

On 5 July 1966, MSC chose Warrior Constructors, another 

Houston firm, to perform Phase I construction of LRL, which involved 

site preparation, excavation, pouring the foundation, and erecting the 

building’s steel framework. Although Congress had not yet approved 

NASA’s budget and the official contract with Warrior was not yet 

signed, the company agreed to meet a 1 January 1967 deadline for 

Phase I and initiated work on 11 July 1966. 

On 28 July 1966, George Mueller sent MSC approval from NASA 

Headquarters to open bids for Phase I construction on 1 August 1966—

somewhat before the FY 1967 authorization bill passed Congress, but 

later than the Agency had hoped. NASA officially signed a contract for 

Phase I construction with Warrior Constructors on 12 August 1966 for 

$1.69 million. The Mueller letter also instructed MSC to conduct final 

negotiations with a contractor selected for Phase II construction—finishing the LRL structure and installing and testing all laboratory equipment—but to execute no contract until after NASA Headquarters had 

authorized funding (which didn’t occur until 24 August). MSC complied 

with this guidance, selecting Warrior Constructors on 1 August for final 

Phase II contract negotiations.176 On 19 August, NASA picked WNN 

Contractors, a consortium of Warrior, National Electronics Corporation 

of Houston, and Notkin & Company of Kansas City, to complete Phase 

II. Phase I and Phase II contracts totaled $7.8 million.177

 175.

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When Biospheres Collide

During LRL construction, all communications between NASA personnel and their contractors were officially supposed to go through a 

NASA contracting officer, but because of the time-sensitive nature of 

the work, LRL Program Office staff began issuing assignments and 

guidance directly to the contractors. This informal line of communication was eventually accepted by all parties and supplemented with 

guidance through official NASA channels. The arrangement allowed 

contractors to respond rapidly to new issues and necessary changes 

in requirements. The open communication procedures helped Phase I 

construction activities to proceed smoothly, notwithstanding technical 

problems that included construction site flooding and a building material shortage. Warrior Constructors completed Phase I on schedule by 

January 1967 for $1.71 million—about 1 percent over the initial contract amount, due to NASA-requested changes. 

Phase II proved to be more challenging to complete on time. 

MSC staff had to reduce construction costs in order to stay within 

Congress’s condensed budget, but no time was available for a major 

redesign of the facility, for this would have meant a significant delay 

that the Apollo program could not afford. The solution that MSC came 

up with, as mentioned above, was to reduce the total LRL area by 

3,800 square feet, consolidate all operations in one building rather 

than constructing a separate crew quarantine facility, and reduce the 

number of vacuum systems from two to one in the area where Apollo 

staff would open sample containers.178

Phase II construction ran into other challenges as well, including labor disputes, late equipment delivery, and unceasing visits 

by congressional VIPs, which became so disruptive that program 

manager Joseph V. Piland eventually ordered the staff giving VIP 

tours to “remain out of the immediate areas of construction and 

refrain from any conversation with the construction personnel.”179

NASA had to extend its 1 August 1967 deadline for completion of 

the LRL building by 40 days. This was not quite enough because 

the contractors did not entirely finish the building until the end of 

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September, although Wilmot Hess held a press conference on 29 

June 1967 to officially open it.180

Dealing with late equipment problems had its own set of complexities. The root cause of the late equipment situation was that 

the scientists who were developing specialized, cutting-edge equipment for LRL were intent on making products of the highest quality 

and reliability, regardless of the cost or time spent. Although Piland 

repeatedly communicated the need to deliver the equipment on 

schedule and within budget, most of it ended up getting to LRL late 

and overrunning cost targets. WNN Contractors could not complete 

its installation of equipment until late 1967, and even then, technical 

problems with the equipment had to be worked through in order to 

render it operational.181

Preparing and Implementing Planetary 

Protection Operational Procedures 

Beginning months before Congress officially appropriated funds 

for LRL, the Interagency Committee on Back Contamination worked 

intensively with NASA to define procedures for the receiving facility 

that would minimize back contamination probabilities. These included 

various means of biologically isolating astronauts, samples, spacecraft, 

and personnel in contact with them during residence at LRL. In its 13 

April 1966 meeting, ICBC approved a plan to contract with the Baylor 

medical school in Texas, or a similarly qualified institution, to develop 

a biological analysis protocol for lunar samples that would include 

planetary protection considerations.182

 180.

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When Biospheres Collide

Federal laws required that “all precautionary steps be taken to 

prevent the introduction of pathogens [to the Earth’s biosphere] 

that are harmful or destructive to human, animal, or plant life.”183

Implementing such steps was complex and multifaceted because it 

involved spacecraft hardware, crew and support personnel, and many 

strict procedures and training requirements. NASA gave Charles A. 

Berry, a medical doctor and MSC’s Director of Medical Research and 

Operations, the responsibility for implementing effective measures 

at LRL and the rest of his Center to prevent back contamination as a 

result of lunar landing missions. He was charged with meeting regulatory Agency requirements and with approval of all protocols and 

specifications for back contamination prevention, including those 

employed on return flights and during recovery operations as well 

as those carried out at LRL. Berry worked closely with Walter W. 

Kemmerer, another medical doctor and the Assistant for Biomedical 

Operations in MSC’s Science and Applications Directorate. MSC 

would be under intense scrutiny when lunar samples were received, 

with regulatory Agency representatives expected to be in residence. 

PHS, for instance, appointed G. Briggs Phillips as its MSC agent. 

Berry and Kemmerer had the job of certifying to these personnel 

and their agencies that all quarantine measures were being executed 

according to the agreed-upon procedures.184

Charles Berry also worked closely with ICBC which, as discussed 

above, included representatives from several regulatory agencies in its 

membership. Berry and the chair of ICBC, David Sencer, agreed that 

ICBC needed to approve the quarantine protocols implemented at MSC 

as well as to develop schemes for the release of lunar samples, spacecraft, and personnel after analysis for potential back contamination 

risks. This could be interpreted as an expansion of ICBC responsibilities from the original one discussed by NASA and PHS management, 

which envisioned the committee to be only an advisory body to NASA 

that would, as mentioned earlier in the chapter, “guide NASA in the 

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development and conduct of a program to avoid possible contamination of the earth biosphere by extraterrestrial life.”185

ICBC’s original purpose was to give counsel on policy more than 

technical details. Now ICBC needed to approve the detailed and fairly 

technical quarantine actions that would be carried out at LRL as well 

as to formulate the decision trees to be followed for the release of people, equipment, and lunar material from quarantine.186 In addition, as 

a Memorandum of Understanding between NASA and ICBC member 

agencies stated, ICBC needed to certify that the established release 

protocols and criteria had been met before the Administrator of NASA 

authorized their release.187

In February 1967, ICBC developed guidelines for analyzing lunar 

samples during their period of quarantine. ICBC greatly simplified the 

envisioned analysis by not requiring a search for living microorganisms in general, but only for infectious microorganisms. The suggested 

analyses included aerobic and anaerobic culturing; inoculating tissue 

cultures, eggs, plants, amphibia, invertebrates, and other animals; and 

conducting biochemical analyses.188

The Baylor University Operating Procedures

On 16 June 1967, a team of biologists and physicians at Baylor 

University College of Medicine published a formal, in-depth set of 

procedures for operating LRL and quarantining lunar samples and 

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When Biospheres Collide

astronauts.189 Writing these procedures to test for lunar pathogenic 

organisms took far more time and effort than expected, because the 

personnel who envisioned the possible existence of Moon organisms 

could not agree on approaches for identifying them. Baylor alumnus 

Walter W. Kemmerer, a medical doctor who had been helping in the 

LRL planning process and, as mentioned above, was the Assistant for 

Biomedical Operations in MSC’s Science and Applications Directorate, 

oversaw work on the procedures. PHS exerted its influence on the 

development and testing of the procedures as well as on the selection of the staff that would carry them out. PHS wishes needed to be 

respected because the organization could refuse to certify the procedures, which might delay the entire Apollo program.190

The Baylor protocol attempted to identify the biological studies 

that could detect the presence of agents that might be infectious or 

toxic to humans, animals, and plants. Furthermore, the protocol 

sought to provide safety clearance for the Moon samples, if possible, 

within 30 days. The protocol included three elements:

•	 Crew microbiology that compared preflight microbiology 

profiles with profiles following a return to Earth in order to 

establish any new microbial burden carried by the astronauts 

and whether they were free from communicable disease.

•	 In vitro attempts to culture microorganisms from Moon samples.

•	 Placement of Moon samples into terrestrial living systems for 

biohazard testing.191

Lunar material could conceivably harm terrestrial organisms due to 

any inherent toxicity or to a capability to propagate within Earth environments. The types of possible toxic materials envisioned included the 

following:

•	 Radioactive materials.

•	 Inorganic polymers. 

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•	 Low-molecular-weight compounds that could act as cellular 

and metabolic poisons, mutagens, irritants, antimetabolites, or 

antivitamins.

•	 Metallo-organic compounds.

Harmful replicative materials might take the form of the following:

•	 Viral, bacterial, or fungal microorganisms carried from Earth to 

the Moon and returned in a mutated form.

•	 Plant materials of lunar origin capable of reproducing on Earth. 

•	 Xerophilic fungi (molds that do not require free water for 

growth) of lunar origin. 

•	 Living matter on the Moon at organizational levels above 

that of small metazoa (multicellular animals) or metaphytes 

(multicellular green land plants). The Baylor protocol excluded 

these from consideration because their probability of existence 

was estimated to be extremely low.192

The Maximum Biotesting Fraction

During the LRL planning process, controversies arose over the 

maximum fraction of material brought back from the Moon that the 

facility would be allowed to use to test for signs of life and potential 

hazards to Earth’s ecology. LRL was competing for access to lunar 

material with the rest of the space science community. There were 

disagreements between various stakeholders of the Apollo mission, 

including opposing groups within NASA, as to which types of analyses 

would be prioritized. In particular, questions were raised regarding 

the relative importance of planetary protection studies as compared 

to other scientific inquiries.

The 1965 NASA Summer Conference on Lunar Exploration and 

Science,193 known as the Falmouth Conference, had been attended 

largely by the scientific community outside of NASA, and it sorely 

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When Biospheres Collide

wanted maximal opportunity to analyze lunar material in depth. The 

Falmouth Conference recognized that a small amount of lunar sample 

should be used for quarantine testing but believed it important to limit 

this quantity so as to not unduly restrict the amount of rock available 

for a broad range of other experiments. Both the Falmouth Conference’s 

Bioscience and Geochemistry Group Reports recommended that no 

more than 5 percent of the total lunar sample (an expected quantity 

of 1.2 kg or 2.6 lb) be used for quarantine testing. A 9 September 1966 

NASA memo from Homer Newell to George Mueller strongly supported 

these recommendations, formally setting forth 5 percent as a “general 

guideline for the collection and handling of Lunar materials.”194

A memo written several months later on 18 January 1967 from 

Charles Berry, MSC Director of Medical Research and Operations, 

suggested a different limit for biomedical assessment—10 percent 

of the lunar sample. ICBC was involved in developing this new limit, 

which Berry explained was based on an analysis conducted by MSC’s 

Computations and Analysis Branch and “took into consideration the 

concentrations of organisms anticipated on the lunar surface, and the 

required probability of having an adequate number of organisms in 

each sample.”195

Scientists inside and outside of NASA took exception to this change 

in sample allotment. A memo from MSC’s Geology and Geochemistry 

Branch, for instance, asked that Berry’s Medical Research and 

Operations Directorate reduce the new fraction to remain within 

the established guidelines, arguing that “The great demand for these 

samples for approved scientific experiments requires . . . the maximum possible sample.”196 The memo also asserted that Berry’s claim of 

needing 10 percent of the lunar sample to furnish an adequate quantity of organisms for quarantine testing was highly speculative and 

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Back Contamination

the computations he referred to were not sufficient justification for 

increasing the allotment. 

G. Briggs Phillips, PHS-CDC’s liaison to NASA, responded to scientists’ concerns with the assurance that regulatory agencies on ICBC 

were committed to “not using any greater amount of sample for quarantine than is absolutely necessary.”197 He also presented a document 

summarizing his and ICBC’s position on the matter. This document, 

“Guidelines for the Selection of Protocol Tests,” did not include any 

quantitative sample requirements, although it did list the general types 

of testing recommended, such as in vitro analyses versus in vivo exposures to living systems, and broad spectrum rather than selective culture media tests. The document appeared to be written at least in part 

to provide additional assurance that the smallest possible quantity of 

lunar sample would be consumed for quarantine assessments.198

The controversy over required sample size continued throughout 

the year. At the 7 June 1967 ICBC meeting, Walter Kemmerer proposed an approach that focused on the actual mass of lunar rock 

needed, rather than some percentage of the total lunar sample. He 

came up with a mathematical method for determining this, based on 

the desired reliability of 0.999 in the bioassessment tests, the number 

of test systems being planned, and assumptions concerning the concentrations of viable microbes that might be contained in a unit of 

sample. Kemmerer arrived at an estimate of 1.2 kg as the minimum 

amount of lunar material that would meet the quarantine test requirements and mentioned that 5 percent of a 22-kg sample return from the 

Moon would just about supply this amount. ICBC discussions followed 

on developing a minimum, rather than desired, quarantine testing 

protocol for a situation in which a lesser mass of sample was all that 

the Apollo mission could return from the Moon.199

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When Biospheres Collide

In an 18 July 1967 letter to MSC Science and Applications Director, 

John Pickering also proposed resolving the argument over quarantine 

sample size by using mass rather than percentage of total sample as a 

measure, noting that the “desirable sample quantity for accomplishing 

the complete biological protocol of quarantine tests”200 was about 1.2 kg 

of loose lunar material. He reiterated this proposal in a 15 September 

1967 communication, indicating that the matter of sample size had still 

not been resolved and needed ICBC’s early attention for “some rather 

serious deliberations”201 on his proposed resolution. Nevertheless, the 

issue was still under debate in January 1968, when Charles Berry sent 

a memo to MSC Director of Science and Applications, arguing that 

from a quarantine testing point of view, a minimum sample size was 

absolutely necessary in order to “conduct an adequate protocol allowing unconditional release of the sample.”202 Berry held that at least 

this minimum amount of sample should be unconditionally dedicated 

to biomedical testing protocols, even if the total amount of sample 

obtained from the Moon was less than what was envisioned. Berry was, 

in essence, giving the highest priority to planetary protection considerations, arguing that they must not be ignored just because the quantity 

of returned lunar material was not enough to fulfill the needs of all the 

scientists who had planned experiments. Sufficient lunar material had 

to be tested in order to determine the following:

1. Whether there was valid concern about viable organisms coming 

from the Moon and potentially contaminating Earth.

2. What care and treatment the returning astronauts needed prior 

to their release from quarantine.

Although Kemmerer’s and Pickering’s proposals provided paths for 

resolving the controversy, the issue of a sufficient sample for quarantine testing was still on the table a year later in April 1969, just months 

before the launch of Apollo 11. In a letter to NASA Administrator 

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Thomas Paine, David Sencer listed “Adequate . . . sample for quarantine testing”203 as one of the requirements that needed to be met 

before LRL could be certified as a biologically safe containment facility and before any release of lunar materials could be effected. 

Sencer added a caveat that made his statement into a threat: PHS 

was currently proceeding with a fallback plan to use other facilities

than LRL for the lunar quarantine, “in the event that the LRL cannot be certified.”204 Sencer signed his letter not as the chair of ICBC, 

but with more weighty titles—the Assistant Surgeon General and the 

Director of the CDC. A letter of 2 July 1969 added additional clout, 

identifying an agreement between regulatory agencies to designate 

the MSC Director of Medical Research and Operations—Charles Berry, 

who had strongly advocated the use of up to 10 percent of the total 

lunar sample for quarantine testing—as their agent to “impose a quarantine during any phase of the Apollo 11 mission as it applies to the 

crew, spacecraft and/or the returned lunar materials.”205 The regulatory agencies and ICBC could thus, through Berry, hold up the threat 

of additional quarantine if they felt that an insufficient portion of lunar 

sample had been made available for biotesting.

Procedures for Release from Quarantine 

ICBC developed a fundamental framework for deciding when 

quarantine requirements had been met and when the release of astronauts and their support personnel, lunar samples, and spacecraft was 

warranted. Although the decision procedures took pains to envision 

all likely quarantine occurrences, they also included contingency 

provisions that gave ICBC as well as individual regulatory agencies 

“adequate opportunity to provide requirements and suggestions for 

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When Biospheres Collide

situations not covered in the formal plans.”206 For instance, the astronaut release scheme was based on the most likely occurrence, that 

Apollo crew and support personnel would exit the Crew Reception 

Area after 21 days if there were “no alterations in the general health of 

the quarantined people and no other indications of infectious diseases 

due to lunar exposure.”207 But if there were such occurrences, different 

branches of the decision tree would be followed (subject to review by 

ICBC and approval by NASA). Should an alteration in personal health 

occur, quarantine release would still not be affected if the medical 

team could show that it was noninfectious or of terrestrial origin. But 

if the incident could not be readily diagnosed, quarantine would likely 

be prolonged. The plans also required that LRL personnel exposed 

to potentially harmful lunar material due to a rupture of the vacuum 

cabinet system needed to be quarantined along with the astronauts.

LRL handled lunar sample release in a similar manner. If all the 

test protocols produced completely negative results, in that no viable 

organisms were isolated and no pathogenic effects were noted in the 

exposed animals and plants, then ICBC would recommend to NASA 

that the samples be released from quarantine after 30 days. If a replicating organism was detected in the samples but did not exhibit any 

deleterious effects on the life systems tested, then a series of analyses would be carried out to determine whether the organism was of 

terrestrial origin, unmodified by lunar exposure and nonpathogenic, 

or whether it was not readily classifiable and of potential danger.208

If “definite deleterious effects”209 were observed in one or more life 

systems, LRL personnel would carry out experiments to determine 

whether this was from chemical toxicity, a replicating microbe, or both. 

Quarantine would be prolonged for at least some of the lunar samples. 

Photographic film and data tapes from the spacecraft were to be 

sent to LRL in the same manner as lunar material and placed in quarantine. The film was to be processed inside the quarantine area but 

printed through the biological barrier so that prints could be handled 

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as noncontaminated. If, however, tests proved that the film could be 

sterilized without degradation using ethylene oxide, this would allow 

immediate release of the film.210

The spacecraft was to be quarantined in LRL next to the CRA and 

handled similarly to the lunar samples. It would also be available for 

extensive biosampling if required.211

Practice-Testing, Staff Training, Readiness Inspections, and 

Operational Simulations

LRL performed tasks that included sample receiving and distribution; geological, biological, and chemical analysis; and astronaut, 

sample, and spacecraft quarantining. Before LRL was ready to receive 

lunar samples and house the Apollo crew, the facility’s staff had to 

receive training in the use of all equipment, then test it to ensure that 

it functioned correctly. The staff also had to receive thorough training 

in the safety and quarantining procedures that ICBC and the Baylor 

study stipulated. The practice-testing and staff-training period was a 

stressful time for LRL staff, for they were under intense deadline pressure to complete their training and testing before the launch of the 

first Moon landing mission. If they didn’t finish this work on schedule, 

the concerns of ICBC and the agencies that it represented would not 

be satisfied and the Moon landing mission would have to be delayed.212

Many technical problems surfaced during the installation and 

testing of LRL equipment. This was not at all surprising, given the 

complexity of the facility and its operations. By mid-September 1968, 

however, the only serious problems that remained were with the autoclaves—pressure vessels for sterilizing tools and materials. These had 

been installed to sterilize items before they were transferred out of 

the biological containment area. They would present problems to LRL 

staff for many months.213

 210.

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When Biospheres Collide

Late in October 1968, Apollo science teams met at MSC to conduct training and simulation exercises on the operation of the sample 

receiving and processing sections of LRL. These exercises uncovered 

still more faults with the equipment, some of them major and affecting operation of the vacuum system in which lunar sample containers were to be opened. The vacuum chamber as well as most of the 

cabinets making up LRL’s primary biological barrier were glove boxes, 

enclosures designed so that a range of tools inside the chambers 

could be manipulated by staff through a pair of impermeable gloves 

attached to ports in the chamber wall. In LRL, these gloves had to be 

strong enough to withstand a pressure difference of about 15 pounds 

per square inch (psi) formed by a high vacuum within the chamber 

and normal atmospheric pressure without. The glove material thus 

had to be thick and tough and, as a result, was quite stiff, making it 

hard for operators to use small hand tools effectively. Another problem that was identified during simulation exercises related to visibility 

into the chamber. Operators looked through viewing ports to observe 

chamber operations and these ports did not allow full coverage of all 

parts of the chamber, but left blind spots in some corners. These and 

other issues resulted in over 80 major and minor modifications of the 

vacuum system.

By October 1968, enough of the problems had been ironed out to 

conduct an operational readiness inspection that would identify any 

final issues that had to be addressed. MSC Director Robert R. Gilruth 

appointed a team of 10 people from MSC, Langley Research Center, 

Fort Detrick (which LRL had been partially modeled after), and NASA 

Headquarters. This operational readiness team spent a month starting in November 1968 investigating LRL physical facilities, the staff 

selected, their level of training, and the operational procedures they 

were following. Each section of the LRL organization had to present 

detailed descriptions of its equipment and operational procedures to 

the operational readiness team, who reported back in mid-December 

1968, identifying 72 mandatory and 91 desirable modifications to 

make LRL ready to begin full operations. LRL staff responded quickly 

to these findings.214

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During this period, public interest remained high in the quarantine facility, and many people continued to seek tours of the facilities where astronauts would be isolated and Moon rocks examined. As 

mentioned earlier, managing these visitors was time consuming and 

drained MSC resources needed elsewhere, especially when visitors 

such as members of Congress made operational recommendations that 

they expected to be taken seriously.

When Apollo 8 successfully achieved lunar orbit during the 

Christmas season of 1968, it underlined the fact that LRL needed to 

become certified for full operation as soon as possible. On 15 December 

1968, quarantine testing trials involving biological agents as well as 

intensive, continuous personnel training activities were initiated at LRL. 

From this date until the end of quarantine following Apollo 11, LRL staff 

planned to operate the sample laboratory and Crew Reception Area as 

they would be during the mission. (These areas would not be officially 

certified as mission ready, however, until months later.) Wilmot Hess, 

MSC Director of Science and Applications, issued a notice limiting tours 

of the sample laboratory and Crew Reception Area only to “very special 

VIP visitors”215 and made sure this policy was followed by locking all 

entrances to the area except one, which he kept guarded.

As LRL activity ramped up in preparation for the first Moon landing, NASA Headquarters staff began to get more involved with MSC’s 

planetary protection program and needed to visit the receiving facility. NASA Apollo program director Sam Phillips traveled to MSC in 

early February 1969 for an in-depth review of back contamination 

prevention measures from splashdown of the Command Module until 

its release from quarantine. George Mueller, Associate Administrator 

for Manned Space Flight, whom NASA had just given full responsibility for back contamination control, visited LRL 10 days later along 

with a task force of advisers from various regulatory agencies. These 

advisers found equipment problems, a technician shortage, insufficiently trained staff, and inadequate biological testing protocols.216

Wolf Vishniac, the NAS representative on ICBC, also took issue with 

 215.

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When Biospheres Collide

the status of the quarantine program during this time. In a letter to 

Frederick Seitz, President of the National Academy of Sciences, he 

commented that “Routine apparatus does not seem to work properly, 

so for instance autoclaves tend to fill with water. This was still true on 

February 27.”217

During the early part of 1969, preparations for a critical 30-day 

simulation of the facility’s operations in March and April dominated 

LRL staff and contractor employee activities. This was the most complex test of the facility to date. Central to the simulation were exercises in the chemistry and geology areas, where LRL’s vacuum system 

sat. Simulated Moon materials went through the vacuum chamber 

during the simulation, from which they were dispersed throughout 

LRL. Other parts of the simulation involved the biological part of LRL, 

which ran back contamination experiments. 

LRL performed better during this full-scale simulation than it had 

in previous exercises, but many problems still surfaced. In a letter that 

David Sencer, chairman of ICBC, sent to the new NASA Administrator 

Thomas Paine on 7 April 1969, he listed what he considered to be 

disappointing results of the simulation, stating that LRL would not 

receive certification as a containment facility unless “rather drastic changes are made in the priority of activities and operations of 

the laboratory”218 In Sencer’s mind, the most glaring deficiency was 

malfunctioning autoclaves for sterilizing items moving in and out of 

the biological barrier that enclosed the sample laboratories and crew 

quarters. Sencer also complained that personnel were not sufficiently 

trained nor was “a scientific discipline apparent in the overall operation directed to the quarantine requirements.”219

Another important issue concerned the glove box system. Gloves 

for handling lunar samples kept developing holes, which could result 

in back contamination of Earth as well as terrestrial contamination of 

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the samples, reducing their scientific value. At the conclusion of the 

full-scale simulation, many in the Apollo program worried that LRL 

would not be operationally ready by the time of the first scheduled 

Moon landing.220

Sencer enclosed a list of requirements with his letter that would 

have to be met before LRL could receive certification as a biologically 

safe containment system. These included requirements on the following aspects of LRL:

1. Astronaut release from LRL. The Crew Reception Area needed 

to be certified as a containment facility. To achieve this, adequate staffing and infrastructure needed to be implemented 

for personnel and health needs, including diagnostic laboratory 

capabilities. Also, an approved protocol for an astronaut release 

decision needed to be developed. 

2. Vacuum chamber operations for opening lunar samples. The 

LRL vacuum system needed to receive certification as a containment facility. This required contingency plans for preserving the integrity of the Moon samples as well as emergency and 

disaster procedures for breakdowns in the vacuum system. 

3. Sample processing. All sample laboratories needed to be certified as containment facilities. This required procedures for 

sample transfer under approved quarantine conditions, an adequate biotesting protocol, a sample to be used for quarantine 

testing, samples for time-dependent studies, and fall-back procedures for abnormal and catastrophic events.

4. Sample release from LRL. LRL needed to develop timetemperature curves of sample sterilization characteristics 

and other test data for conditional and unconditional sample 

releases. LRL also had to furnish biotesting results needed for 

an ICBC decision.221

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The projected time of Apollo 11’s launch and attempted lunar landing was now during summer of 1969, and LRL preparations intensified 

as summer drew nearer. By April 1969, LRL preparations for receiving 

materials from the Apollo 11 Moon landing reached a state of urgency. 

NASA Headquarters staff and other personnel conducted a complete facility review on 17–18 April 1969, again examining all aspects of the facility 

and its equipment, personnel, and procedures.222 NASA’s John Pickering, 

executive secretary of ICBC, made up a projected schedule for ICBC of key 

LRL activities through the end of the Apollo 11 mission. Notable projected 

dates and actions from Pickering’s schedule included the following:

9 May–15 July 1969. Simulations of operations of each of LRL’s 

individual laboratories occur.

12 May–15 July 1969. Parts of LRL go into mission mode, performing actions vital for the safe and successful analysis of lunar materials. 

Examples include the following: 

•	 Testing Apollo lunar sample return containers. 

•	 Growing seedlings to proper levels of maturity for experiments 

with lunar samples.

19 May–15 June 1969. LRL closes its biobarrier as the facility goes 

into mission mode. The Apollo 10 mission flies during this time. While 

it does not land on the Moon, it includes a rehearsal for parts of the 

landing missions to follow, using LRL staff and facilities to conduct preand postmission crew microbiology studies.

14–26 July 1969. Based on the best guess, Apollo 11 flies during 

this period.

26–28 July 1969. Lunar samples enter LRL.

28–31 July 1969. Sample protocol begins. Note: if samples cannot 

be delivered within about a 5-day window, LRL biology staff need to 

restart the growth of cell lines and other test organisms. 

27–29 July 1969. Astronauts enter LRL’s Crew Reception Area. 

11–18 August 1969. ICBC decides, if possible, on the date for quarantine to end and astronauts to be released. 

30 July–1 August 1969. Spacecraft enters LRL.

1 September 1969. The first 30 days of spacecraft analysis end. The 

decision to release the spacecraft may be made.

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29 September–6 October 1969. The of 60 days of biotesting end. The 

release of lunar samples is possible.223

On 29 April 1969, George Mueller, NASA’s Associate 

Administrator for Manned Space Flight, distributed a memo referring to David Sencer’s 7 April 1969 letter and underlining the 

seriousness of the deficiencies that ICBC found during its evaluation of LRL’s 30-day operations simulation. The NASA memo gave 

details of the ICBC evaluation, which cited inferior laboratory procedures, unexplained plant and animal deaths, and what appeared 

to be casual concern for back contamination prevention. NASA’s 

memo stressed that ICBC was the certifying agency for LRL, as 

stipulated in Interagency Agreement NMI 1052.90, and that meeting ICBC’s requirements for certification would remain “high priority tasks.”224 In addition, NASA Administrator Thomas Paine wrote 

a letter on 9 May 1969 to David Sencer, who was also the Director 

of PHS’s National Communicable Disease Center in Atlanta. Paine 

told of LRL’s significant progress in meeting ICBC recommendations, 

including correcting the mechanical deficiencies in the autoclaves. 

Paine also wrote of the priority that LRL was giving to developing 

procedural documents and test plans and obtaining test results that 

would meet certification requirements.225

Certification and a Final Simulation

ICBC considered quarantine requirements to be absolutely critical 

to operating LRL and formulated a detailed certification process for 

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When Biospheres Collide

the facility to be deemed safe and ready to operate. One of the recurring problems that ICBC chairman David Sencer had with LRL staff, 

however, was that they seemed to view quarantining requirements as 

“an imposed operation to be done the easiest way possible while hoping 

that it would go away.”226 Sencer felt that LRL staff needed an enthusiastic commitment to meeting these requirements if they were to be 

reliably followed. 

ICBC repeatedly sent representatives to the partially completed 

LRL to monitor progress on it and ensure that planetary protection 

requirements were strictly followed. ICBC’s scrutiny was not particularly welcome to MSC staff, who worried that the committee would 

delay completion of LRL and the whole Apollo program. As LRL 

neared completion, basic differences between ICBC’s values and those 

of LRL staff became increasingly apparent. ICBC “tended to define the 

facility solely in terms of back contamination concerns and focused on 

developing quarantine requirements and biological testing protocols,”227

which clashed strongly with the research interests of the Apollo mission’s scientists, especially earth scientists such as geologists and 

geophysicists.

While LRL needed to pass the ICBC certification process in order 

to achieve readiness mode for receiving Apollo 11 samples, other organizations also wanted to be sure that the facility was prepared for full 

operation. PHS was one of these organizations. PHS management had 

researched in depth the legal issues governing quarantining actions 

and had concluded that the United States Surgeon General retained 

lawful authority over quarantine matters. In particular, G. Briggs 

Phillips, PHS’s liaison officer at MSC since mid-1965, determined that 

“the Surgeon General of the U.S. Public Health Service is empowered 

by law to make and enforce such regulations as may be needed to 

prevent the introduction and spread of communicable disease into the 

United States, its Territories or possessions,”228 and by right of this 

power, “returned lunar material, until free of possible pathogenic or 

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infectious materials and otherwise not harmful to man’s biosphere, 

should be controlled, quarantined, and tested in accordance with procedures approved by the Surgeon General or his representative.”229 In 

short, if PHS was not convinced that LRL and its quarantining actions 

were doing their job, PHS had a mandate to stop the Apollo program 

from completing its agenda.

Phillips also identified another organization, the Department of 

Agriculture, that had authority regarding quarantining. Parallel to PHS’s 

interest in potential dangers to human health and lives, the Department 

of Agriculture had a mandate to prevent harmful contamination risks, 

including lunar contamination risks, to plant and animal life. 

Both PHS and the Department of Agriculture were represented on 

ICBC. The ICBC chairman, in fact, was from PHS. These and other 

regulatory agencies had initially insisted on “exercising final approval 

authority over all phases of the program that might affect biocontainment.” It would have been quite a difficult situation for the U.S. space 

agenda, however, if one regulatory agency could have stopped work on 

the program because it didn’t approve the Apollo program’s planetary 

protection procedures.

NASA, not wanting to compromise its mission objectives, sought 

to limit this power of individual regulatory agencies to halt its activities. After more than 18 months of negotiations between NASA and the 

members of ICBC, they reached a compromise agreement, signed on 

24 August 1967, in which the regulatory agencies agreed “not to take 

any actions that might have an effect on the lunar program (such as 

refusing to let astronauts back in the country) without the ‘unanimous 

recommendation of the agencies represented on the [Interagency] 

Committee [on Back Contamination].’” This was a hugely important 

agreement. Since NASA was itself a member of ICBC, no actions could 

be taken without its approval. 

On the other hand, NASA had to agree that it would not take any 

actions of its own that might compromise biocontainment of lunar materials without first consulting ICBC, unless such actions were mandatory 

for the safe conduct of the mission. But NASA could, if pressed, have 

claimed that virtually any action it wanted to perform was necessary in 

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When Biospheres Collide

order to protect a crew or spacecraft, and so it was far less restricted in 

its actions than were the regulatory agencies on ICBC.230

Throughout spring 1969, LRL staff continued to work on bringing 

their facility, and especially its quarantine and back contamination 

prevention capabilities, up to full operational readiness. During this 

period, ICBC formulated a plan for certifying LRL. A team headed by 

G. Briggs Phillips, PHS’s liaison officer at MSC, would inspect LRL and 

prepare a report detailing any modifications to the facility that were 

still needed. NASA would make the recommended changes, then submit a certification to ICBC that it had done so, and ICBC would sign 

the certification. ICBC would not perform any further inspections to 

verify that NASA had actually made the modifications requested.231

The Phillips team inspected LRL on 26–28 May 1969 and prepared a report of its findings that it gave to ICBC on 5 June 1969. 

LRL management assigned area test directors the responsibility for 

implementing the Phillips team’s recommendations. After completion 

of the allocated tasks, each director signed a certificate of test-area 

readiness asserting that the area was “in a state of readiness to conduct the Apollo 11 mission.”232 NASA then forwarded the certificates 

to ICBC for concurrence. 

By June and early July 1969, LRL launch preparation activities 

reached their peaks of intensity, with “sixty to seventy-hour work 

weeks . . . the rule rather than the exception.”233 LRL conducted 

another mission simulation in order to refine sample handling procedures and smooth out the last remaining technical issues. In spite of 

the pressure and long hours imposed on personnel, however, reports 

indicated that they remained enthusiastic about the work and excited 

about the impending Moon landing. Scientists from academia who 

were part of the mission started to arrive during the weeks before the 

landing so that they would be fully prepared for the returning samples. 

LRL was scheduled to attain full readiness mode on 14 July 1969, just 

in time for the Apollo 11 launch, which was to be on 16 July. The last 

of the certificates of test-area readiness, however, was not officially 

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signed until less than 24 hours before the Apollo 11 Command Module 

splashed down in the Pacific Ocean.234

Planetary Protection Strategies 

from Moon Walk Until Arrival at LRL

The success of the Apollo program’s planetary protection efforts 

depended on controlling and carefully handling all extraterrestrial 

materials being brought back to Earth and isolating lunar samples and 

all potentially contaminated materials, astronauts, and parts of the 

spacecraft until they could be thoroughly analyzed and safely released. 

Critical planetary protection measures were executed starting on the 

Moon walk itself and continued on the return journey from the Moon 

to Earth, during the sensitive period after splashdown, and on the trip 

from the recovery ship to LRL.

Plans for Preventing Back Contamination from Moon Walks, 

Docking, and the Return to Earth

When the Apollo astronauts finished their Moon walks and prepared 

to reenter their ship, they took care to brush off as much loose lunar 

material from their spacesuits as they could and leave their outer shoe 

coverings and backpacks behind on the Moon, lowering the probability of transporting lunar contaminants back to Earth’s environment. 

Before docking their Lunar Module (LM) with the Command Module 

(CM) orbiting the Moon, the two astronauts who had visited the surface 

would clean the LM’s insides with a vacuum brush in order to minimize 

the quantity of material that they might carry into the CM.235

 234.

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When Biospheres Collide

Extensive cleaning of the LM would also be carried out while it 

was docked with the CM. This would be a shirt-sleeve procedure and 

would include LM cabin gas being continuously circulated through 

lithium hydroxide (LiOH) filter beds intended to remove virtually all 

particulate matter. A minimum of 5 hours was envisioned as available for LiOH filtration. NASA estimated that this time would be sufficient, assuming a uniform distribution of dust particles in the LM 

atmosphere, to reduce the original airborne particulate count to 10–15 

percent. The spacecraft would be under weightless conditions during 

this period. Past experience in 19 human spaceflights indicated that 

in weightless environments, dust, dirt particles, and small scraps of 

various materials tended to float around the cabin rather than cling 

to surfaces; this was expected to increase the likelihood that such 

particles would be carried into the LiOH filter and removed from the 

cabin atmosphere.236

To minimize airborne particulates floating from LM to CM during 

the time they were docked and crew and sample containers were being 

transferred, atmospheric pressure in the CM would be kept higher 

than in the LM so that gas would flow out of rather than into the CM 

and exit the spacecraft through the LM’s cabin relief valve.237

During the trip back to Earth, the astronauts would repeatedly vacuum and wipe the CM interior. Their vacuums were designed to pick 

up any Moon particles that had gotten into the module and trap them 

in chemical filters. In addition, the CM atmosphere would be constantly circulated through a series of LiOH filters. Tests demonstrated 

that these filters trapped particles as small as the size of bacteria. In 

discussions from 1966 and 1967, ICBC had come to the conclusion 

that if CM air was filtered through lithium hydroxide canisters prior to 

splashdown, sufficient lunar material would be removed from the vessel’s atmosphere such that no further air filtration would be required 

1966, in the package of letters and memos beginning with Col. J. E. Pickering to David J. 

Sencer, 28 October 1966, folder 4714, “MSC-Lunar Receiving Laboratory,” NASA Historical 

Reference Collection.

 236. Richard S. Johnston, Special Assistant to the Director of the MSC, Report on the Status 

of the Apollo Back Contamination Program, 28 April 1969, pp. 4–6, JSC Historical Archives, 

“April 1969” folder, box 76-24.

 237. Johnston, Report on the Status of the Apollo Back Contamination Program, pp. 4–6. 

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to prevent back contamination.238 ICBC based this conclusion on calculations of spacecraft system characteristics—in particular, the LiOH 

filter efficiency reported to ICBC, 43–50 percent, and the number of 

air filtrations a day, 180, performed by the CM air circulation system.239

MSC modeling predicted that after 63 hours of operation at the time 

of splashdown, 10–90 percent, or virtually none, of the original particulates would remain in the CM atmosphere. 

Questions arose as to what happened when carbon dioxide in the 

cabin atmosphere contacted the LiOH filters. Tests indicated that the 

reaction that followed would produce water and a sticky surface that 

would enhance the collection of dust particles. Other testing indicated 

that the environment inside the filters killed at least some varieties of 

microbes, which would tend to increase the filters’ capability to prevent back contamination.240

After Splashdown: Plans To Safely Transport the Apollo 

Astronauts, Command Module, and Samples to the Recovery Ship

One of the most difficult periods in which to prevent backcontamination was from the time the Apollo Command Module splashed 

down in the Pacific Ocean until the delivery of the module, its crew, 

and its lunar samples to LRL. If a significant quantity of contaminants 

escaped to Earth’s environment during Apollo CM recovery operations, 

the basic objective of the planetary protection program would be subverted and the value of LRL greatly reduced. Weighing the risk of such 

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When Biospheres Collide

an occurrence against astronaut safety became an issue of debate in 

1966. In its 13 April 1966 meeting, ICBC expressed “its concern with 

the possibility of uncontrolled out-venting of CM atmosphere following 

splashdown”241 and recommended prototype testing of the module’s 

return procedures along with the contamination control equipment to 

be used. 

ICBC wanted the CM, containing the crew and lunar samples, to 

be “hoisted aboard the recovery aircraft carrier unopened and placed 

inside a large van which would then be hermetically sealed. The sealed 

van would be transported back to LRL and attached to an airlock in 

the wall of the Crew Reception Area.”242 Deke Slayton, however, one 

of the original seven Mercury astronauts and now MSC’s Director of 

Flight Crew Operations, refused to support any quarantine protocol 

that put the safety of astronauts at risk. One of the major risks to astronauts was the thermal environment inside an unopened, unvented 

module. Wayne Koons, who was a supervisor in MSC’s Landing and 

Recovery Division and had responsibility for the design and operation 

of postsplashdown retrieval equipment, emphasized that after splashdown, the CM was “not really designed to be sealed up, because the 

first thing you have to do is ventilate in order to provide air and cooling for the crew. The basic plan is to be operating in equatorial waters. 

It’s going to get really hot really soon in there.”243 NASA calculations, 

in fact, indicated that astronauts could not survive in a poorly ventilated module during the postlanding phase of the mission unless supplemental cooling capabilities were added to the spacecraft.244

Another risk to the astronauts was associated with plucking an 

occupied CM from the ocean. During the Gemini program, NASA had 

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Back Contamination

tested the procedure of hoisting a module with its crew aboard up 

from the sea and had concluded that it was too dangerous.245 NASA 

doubted whether any aircraft carrier in the U.S. fleet could safely lift 

an occupied Apollo CM out of the Pacific and onto the deck with the 

astronauts aboard, especially in rough seas. 

According to John Stonesifer, JSC’s branch chief for recovery systems during the Apollo mission, this very issue “was roundly discussed 

over and over and over. I was the one in charge of giving the briefing 

to the managers—the pros and cons of lifting a spacecraft with astronauts in it versus bringing them back to the ship in the helicopter. We 

went through our evolution of how difficult it is to bring that spacecraft 

over along by the ship and hoist it aboard. Wave action, sea action—we 

practiced many recoveries out here in the Gulf of Mexico,”246 where 

conditions were far gentler than in the open ocean. And NASA conducted these exercises with a ship that was far smaller and more easily 

controlled than the aircraft carrier that would be used for the actual 

recovery. Even under these less dangerous conditions, it proved difficult to position the ship so that the CM could be safely hoisted aboard. 

In Stonesifer’s words, an aircraft carrier “is like a sail.” I’ve seen 

carriers drift down on the spacecraft. I’ve seen destroyers—which are 

more maneuverable than the carriers—I’ve seen them run into spacecraft. There’s just no good way, sure way of bringing a carrier up to the 

spacecraft and retrieve it in the open sea.”247

Another danger pointed out by Bob Fish, Apollo curator of the 

USS Hornet Museum (the Hornet was the recovery ship for Apollo 

11 and 12), was that if there was a high sea state, the onboard crane 

would need to lift the CM just at the moment when it was on top 

of a swell. If it was sliding down a swell when lifted, then the CM 

would swing back and forth like a pendulum and could crash into 

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When Biospheres Collide

the side of the recovery ship. This had happened on another recovery maneuver.248

NASA had an additional concern regarding the actual retrieval 

equipment the ship would use to haul the CM aboard. The shipboard 

cranes were primarily designed for dockside or sheltered-water procedures. The estimated dynamic loads that they might encounter lifting the CM in open-sea conditions with 8-foot swells were as high as 

44,000 pounds. But in order to provide a 50-percent safety factor, the 

cranes were prohibited from lifting loads more than 32,000 pounds. In 

addition, the Navy did not consider these cranes “manrated.”249

Because of the above dangers, NASA concluded that it would be 

much safer to bring the astronauts aboard an aircraft carrier recovery 

ship by means of a helicopter. By doing so, however, the Agency faced 

the different problem of limiting the release of lunar contaminants 

into the water and air while the CM was still floating in the ocean, 

after it had been opened and the astronauts had exited from it.250

Richard S. Johnston, special assistant to MSC Director Gilruth, 

believed that lunar contaminants could be reliably contained even if 

the CM was opened while in the ocean. He asserted that the planned 

cleaning activities described in the previous section, which involved 

extensive vacuuming and wiping of CM surfaces as well as filtration of 

the module’s atmosphere, would ensure that by splashdown, the spacecraft was sufficiently free of contaminants that its hatch could be ajar 

without endangering the terrestrial environment.251

Others did not share Johnston’s confidence. ICBC studied the back 

contamination potential of an ocean-exit recovery strategy and recommended that NASA install biological filters in the CM’s air vents. 

NASA studied such a plan in some detail, examining whether a filter could be put into place without significant modifications to the 

module’s venting fan or power consumption. The analysis showed that 

this would not be the case, unfortunately. Installing a filter with 99.9 

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Back Contamination

percent bacterial removal efficiency would dramatically reduce the 

atmospheric circulation rate within the module by about 83 percent. 

This would endanger astronaut survivability unless a supplemental 

cooling capability was added, such as through use of water-cooled garments. But the NASA study estimated that utilizing the current postlanding fan design and adding hardware to water-cool garments for the 

astronauts would result in a weight penalty for the Command Module 

of about 80 pounds, provide only marginally adequate thermal control 

for the astronauts, and result in an uncomfortable cabin humidity of 

98 percent. Alternatively, the module’s postlanding fan system could 

be redesigned. To achieve the same thermal cooling capacity that the 

module had without a bacterial filter, a large, 325-watt postlanding fan 

would be required (the current power requirement was only 15 watts), 

which would impose a weight penalty of approximately 470 pounds.252

NASA rejected both of these plans as impractical. 

At its 28 October 1966 meeting, ICBC accepted NASA’s decision 

and decided that if the CM’s atmosphere was continuously recirculated 

“without partition”253 through the craft’s LiOH canisters, no filter would 

be needed after splashdown for protecting Earth’s biosphere. ICBC 

reaffirmed this position at its 12 January 1967 meeting and again on 4 

October 1967. But this approach was not the committee’s first choice, 

and the matter was not yet closed. At its 8–9 February 1968 meeting, ICBC returned to its earlier recommendation for a biological filter 

and fan that would operate postsplashdown to remove any remaining 

contaminants from the CM, which would have to remain sealed for 

some period of time.254 The committee explained that its new action 

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When Biospheres Collide

was motivated by the need to “avoid what could be compromised and 

untoward decisions.”255

Wolf Vishniac, the NAS representative on ICBC, wrote a letter to 

Frederick Seitz, President of the NAS, outlining a plan that met ICBC’s 

recommendation, but did not subject astronauts to dangerous temperature extremes. Seitz forwarded Vishniac’s idea to NASA Administrator 

Thomas Paine. This alternate plan envisioned that after splashdown 

but before opening the exit hatch, swimmers from the recovery crew 

would “place a biological filter over the [CM’s] vent holes from outside 

and also provide a power pack to drive sufficiently powerful fans”256

that would draw the module’s atmosphere through the filters and 

decontaminate it. 

Vishniac strongly opposed venting the spacecraft in an uncontrolled manner, believing that it was “irresponsible to leave a 

large breach in the biological barrier in any part of the recovery 

procedure.”257 Opening and venting the spacecraft to Earth’s atmosphere after splashdown would, in his view, make the rest of Apollo’s 

elaborate quarantine program pointless. NASA did not follow 

Vishniac’s alternate plan, however, believing that its current approach 

would provide sufficient protection against back contamination. In 

addition, MSC recommended against Vishniac’s scheme because of the 

possible danger to recovery crew swimmers when trying to install the 

filter/fan package under open-sea conditions.258

Vishniac realized that he was fighting a losing battle on altering 

NASA’s recovery strategy,259 noting that “the Apollo Program is moving at a pace which we [ICBC] can not stop. It is equally clear that 

this irresistible progress is being used to brush aside the inconvenient 

restraints which the Interagency Committee has considered to be an 

essential part of the Quarantine Program.”260

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ICBC Chairman David Sencer understood this as well and felt that 

he had to add a strong statement for the record on the importance 

of preventing back contamination. In a letter to NASA Administrator 

Thomas O. Paine on 7 April 1969 (a different letter than the one he 

sent on that day regarding the disappointing results of LRL’s March 

simulation exercise), he asserted that NASA’s plan to open the CM 

after splashdown, allowing its crew to egress while the module was 

still bobbing in the ocean, violated the concept of biological containment. NASA had not responded adequately to ICBC recommendations 

and did not apparently recognize the necessity of protecting Earth’s 

environment against any possibility of extraterrestrial contamination. 

Nevertheless, Sencer agreed to NASA’s recovery plans, perhaps 

because he did not want to be remembered as the person who prevented the United States from meeting President Kennedy’s challenge 

of reaching the Moon during the 1960s. Speaking for ICBC, he said that 

although it wanted the recovery to be handled differently, the risk of 

back contamination could be made acceptably low if “strict ‘housekeeping’ procedures to minimize contaminating the environment . . . are 

written for and implemented by the crew.”261 This was not a new idea; 

ICBC had discussed such procedures as early as 1966 in conjunction 

with the use of “dust-settling sprays”262 prior to egress of the astronauts. 

Although ICBC agreed to recovery procedures allowing the CM 

to be opened while still floating in the ocean, and the astronauts to 

egress into a life raft, the committee did not give up on the idea of 

keeping the CM sealed during recovery. In its June 1969 meeting, in 

fact, ICBC decided that “there should be no abandonment of the earlier concept of picking up the Spacecraft with the crew on board,” and 

that the “MSC should actively pursue alternate modes for strict containment during recovery.”263 Louis Locke, a pathologist and veterinarian with the Fish and Wildlife Service of the U.S. Department of 

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When Biospheres Collide

the Interior, elaborated on the dangers of the present crew recovery 

procedure, warning that “should an astronaut fall into the water while 

making the transfer onto the raft, he would effectively nullify some 

important quarantine procedures as far as exposing of aquatic life is 

concerned.”264 Transfer of the crew from CM to raft, where they would 

be splashed with ocean water, was in his mind an extremely serious 

breakdown in proper bio-isolation.

Astronaut recovery scenarios. The nominal scenario for recovery 

was for the CM to splash down within helicopter range of the primary 

recovery ship. The helicopter would then drop swimmers next to the 

CM, who would install a flotation collar around it that would provide 

additional protection to it and its crew. The swimmers would attach 

a large raft, capable of carrying seven people, to the flotation collar. 

According to a scenario put forward in April 1969, the helicopter would 

lower a package of biological isolation garments into the raft. The BIGs 

were to help guard against infection of Earth during the astronauts’ brief 

trip from ocean to recovery ship. One of the swimmers would don a BIG 

and, after the CM hatch was opened, assist the astronauts in getting out 

and into the raft. The CM hatch would then be closed and the astronauts would put on the nylon, head-to-toe BIGs.265

This scenario was altered before the mission in an important way 

that increased the level of planetary protection. The new plan called 

for one of the recovery crew swimmers to don a BIG and, after opening 

the CM hatch, throw the BIGs inside for the astronauts, then close the 

hatch.266 The astronauts would put on their BIGs while still inside.267

Only after the astronauts had done so was the hatch to be reopened. 

The swimmer would then assist the astronauts in getting out of the CM 

and into the raft. 

The BIGs had respirators built into them designed to filter out 

exhaled particulates as small as 0.3 microns with a 99.98 percent 

efficiency. This, MSC’s Richard Johnston believed, would trap any 

organisms that the astronauts exhaled. The Crew Systems Division at 

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MSC had developed the garments and subjected them to human testing in a range of test chambers and at sea under recovery conditions. 

After the astronauts suited up in the BIGs and stepped into the raft, 

the recovery crew would scrub them with a decontamination agent. 

The astronauts would then be lifted into the waiting helicopter and 

transported to the ship. 

Once inside the shipboard quarantine unit, they would doff the 

clumsy suits and replace them with standard NASA flight suits.268

The recovery crew would scrub down the area around the module’s 

escape hatch, the flotation collar, and the raft (in which the astronauts 

had briefly ridden) with a strong acid disinfectant, then sink the raft. 

These recovery procedures were finally approved by ICBC quite late 

in the mission planning process, in a telephone conference on 19 May 

1969, only two months before the launch of Apollo 11.269

Lunar dust issues. What the ICBC analysis did not give importance to was the presence of any remaining lunar dust within the 

CM. Such dust might have been tracked in by the astronauts during 

their activities on the Moon, where it adhered to various surfaces and 

was missed during vacuuming and wiping procedures. Thus, the interior of the CM might still be contaminated. This possible occurrence, 

however, appeared quite solvable using the existing recovery strategy. 

After the astronauts left the CM and the recovery crew took the sample 

containers from it, the module would be sealed and its interior kept 

isolated throughout the period of quarantine. Only if LRL’s analyses 

determined that the returned lunar material was harmless would the 

CM be allowed out of quarantine.270

Astronaut safety vs. planetary protection. Central to NASA’s 

management of the Apollo program was, as discussed above, the 

importance given to astronaut safety. NASA simply would not put 

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When Biospheres Collide

its spacecraft crews in danger in order to meet quarantine requirements. Decisions based on this policy sometimes, as in the case of 

the Apollo CMs, ran contradictory to optimal planetary protection 

actions. It is important to note that when confronted with prioritizing either a very low-probability event with potentially global consequences (back contamination of Earth) or a much higher probability 

event with a limited potential consequence (injury to one or more 

of the three astronauts), NASA consistently chose to protect against 

the latter. 

Why was this? John Stonesifer thought it was because NASA did 

not believe that back contamination would actually occur, whether 

the Agency practiced planetary protection procedures or not.271 The 

astronauts, on the other hand, could be placed in real danger if they 

stayed in the CM while the USS Hornet attempted to maneuver close 

enough to connect its crane to the module and haul it aboard. The 

astronauts were people whom many NASA staff personally knew. 

What’s more, many people around the world considered them heroes 

for conducting the voyage to the Moon. Protecting their lives was, 

not surprisingly, something that NASA staff strongly wanted to do. 

By comparison, back contamination was a theoretical danger in 

that it had never, so far as space scientists knew, ever happened to 

Earth. Back contamination did not have the recognizable face of 

Neil Armstrong or Buzz Aldrin; it was a concept, not a human being. 

It was thus not unexpected that NASA chose to defend against the 

known, proven danger to several of its friends, rather than against an 

extremely unlikely risk to strangers. 

The Mobile Quarantine Facility

ICBC, recognizing the need to reliably isolate all potentially contaminated personnel and material from the time of spacecraft retrieval 

until delivery to LRL, developed preliminary concepts and recommendations for such a capability. Two concepts that survived initial critiques were for a mobile, self-contained facility or modification of a 

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cabin aboard the recovery ship. The tradeoff analysis between these 

two options considered the following objectives:

•	 Ability to maintain a consistent level of biological isolation. Use 

of several quarantine modes (shipboard cabin, aircraft cargo hold, 

transfer vehicles) would have difficulty meeting the objective. 

Also, each quarantine mode, and possibly the same mode on 

different vehicles (such as cabins on different ships) would have 

to be custom fit with quarantine capabilities, and this would be 

an expensive proposition. In contrast, if one mobile quarantine 

unit was employed from the time of recovery until delivery at LRL, 

it would provide consistency of isolation environment and would 

preclude the need for fabricating multiple isolation environments. 

•	 Flexibility of operations. Installing a quarantine unit in a ship 

would involve extensive downtime in a shipyard, precluding use 

of the vessel for a period of time and impairing its “readiness 

state . . . in the active defense forces.”272 It would also constrain 

use of a vessel for other applications during spacecraft recovery 

operations. Use of a mobile quarantine unit, on the other hand, 

would not require vessel downtime during construction of the 

unit, and it could be readily moved from one vessel to another, 

allowing rapid redeployment of a vessel if necessary. 

•	 Minimal dependence upon the United States Navy and Air 

Force. A completely self-contained and movable facility would 

not only reduce dependence on any one vessel, but also 

on Defense Department facilities and biological and waste 

management concurrence and control. In addition, such a unit 

would give NASA the maximum control of the quarantine effort. 

By August 1966, after considerable discussion, NASA decided that 

the best method of isolating crews and material was to build a wellequipped, self-contained mobile quarantine facility to house and transport the Apollo astronauts and their lunar samples from the time they 

boarded the Navy aircraft carrier recovery ship until they arrived at 

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When Biospheres Collide

and entered LRL.273 NASA and ICBC also decided that a savings in 

design and fabrication costs could be attained by using a “housetrailer” 

concept for the quarantine facility employing “basic household-type” 

equipment and appliances, rather than the initial concept of developing custom isolation units and equipment.274

NASA contracted with MelPar, a subsidiary of American Standard, 

to develop the MQF. In keeping with the housetrailer approach, MelPar 

subcontracted the actual construction to Airstream, Inc., a manufacturer of commercial travel and vacation trailers. Airstream fabricated 

four modified 18,700-pound trailers, each of which was meant to prevent the escape of infectious agents. Quarantine conditions were maintained on these MQFs through negative internal air pressure, filtration 

of effluent air, internal capture and storage of wastes in holding tanks, 

and a transfer lock system that could bring materials into or out of the 

facility without letting potentially infected air out. MelPar designed the 

holding tanks to be capable of containing the fecal and urine wastes 

of six people for at least five days. Each MQF had an internal backup 

power system, air conditioning, a communications system, and a medical diagnostic capability.275

Two externally mounted exhaust fans maintained negative pressure 

inside the MQF. All effluent air was passed through two filters capable 

of 99-percent efficiency in removing particles 0.45 microns (0.45 millionths of a meter) or larger. Airstream made the MQFs skid-mounted, 

double-walled structures with the outer wall designed to serve as the 

pressure vessel for preserving negative internal air pressure. Airstream 

installed insulation between the walls and made the interior wall mostly 

of durable, vinyl-covered aluminum. There were two doors—one in the 

rear and one in the side of the MQF. The side door was framed by a 

flange that provided a smooth surface for bonding to the flexible vinyl 

shipboard transfer tunnel, which was designed for maintaining biological 

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Back Contamination

isolation while conveying equipment to the MQF from the Command 

Module (once it had been lifted aboard the recovery ship). 

The procedures for transferring objects such as medical samples, 

lunar materials, flight tapes, flight film, and crew equipment out of 

the MQF while it was maintaining biological isolation required vacuum-sealing and heat-sealing the objects into Biological Isolation 

Containers. After this, MQF personnel put the containers into the 

MQF’s double-door, pass-through decontamination/transfer lock, 

where they were soaked in a 5,000-parts-per-million (ppm) sodium 

hypochlorite (bleach) solution for 15 minutes. After draining the 

solution, technicians outside the MQF opened the outer door of the 

lock and removed the item. Personnel also transferred items such as 

meals and various supplies into the MQF through the transfer lock, 

but decontamination procedures were not required since these objects 

were not contaminated with lunar material.276

In accordance with one of NASA’s objectives for the MQF—that 

it exhibit flexibility of operation—MelPar built into it the capability 

to employ a range of different power sources from the different environments in which it would be placed. On board the recovery ship, 

MQF engineers configured it to use 440-volt shipboard power to run 

its negative-pressure, cooling, lighting, and other systems. While it was 

being hoisted off the ship, an engine generator kept the MQF’s systems 

operating. While being flown in the hold of an Air Force cargo plane, 

the MQF ran on the craft’s 400-cycle, 115–230-volt system. And when 

the MQF reached LRL, it used the facility’s 120/240-volt, 60-cycle 

power. At no time could the MQF lose power, because its fans had 

to keep running in order to maintain the negative pressure within it. 

Loss of this pressure differential could have resulted in contamination 

of Earth’s environment with lunar microorganisms.277

NASA tested and confirmed the performance of one of the MQFs 

in January 1969 aboard the helicopter landing ship USS Guadalcanal, 

after completion of the Apollo 9 Earth orbit mission (which wasn’t 

expected to bring back any contamination since it never landed on an 

 276.

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When Biospheres Collide

extraterrestrial body). After the testing, NASA made plans to transport 

two MQFs, a primary and a backup, to Pearl Harbor, Hawaii, and put 

them aboard the USS Hornet, which was to be the primary recovery 

ship for the Apollo 11 Moon landing mission.278

The plan for the MQF used during Apollo 11 was to fasten it to 

the hangar deck of the USS Hornet, where it would sit from the time 

of the Command Module splashdown until the ship’s arrival at Pearl 

Harbor. The astronauts would remain inside the MQF while it was 

being hoisted off the ship, trucked in a motorcade to Hickam Air Force 

Base, flown in the hold of a C-141 cargo plane to Ellington Air Force 

Base in Houston, and then trucked to LRL. Once there, the astronauts 

would walk from the MQF to LRL through a plastic tunnel.279

The Need To Quickly Transport Lunar Samples to LRL

NASA scheduled the lunar dust, rocks, and gases taken from the 

Moon to arrive at LRL as soon as possible and significantly before the 

MQF and its astronaut passengers. The samples would be quickly taken 

to an airport and transported by jet to Ellington Air Force Base, then 

rushed by ground transport to LRL. This was critical in order to minimize any changes to them that began the moment they were taken from 

the lunar surface. In particular, the intensity of sample radioactivity 

caused by cosmic ray bombardment, off-gassing from the samples, and 

magnetism induced by a lunar field were all expected to decrease rapidly. Delays in analyzing the samples for these possibly faint characteristics might mean losing the chance to detect them.280

 278.

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Back Contamination

Planetary Protection Actions Taken During the 

Apollo 11 Moon Landing Mission

On 16 July 1969 at 9:32 in the morning, eastern daylight time 

(EDT), Apollo 11 lifted off from Kennedy Space Center with the Moon 

as its destination. It took the spacecraft a little over four days to get 

there, touching down in the Sea of Tranquility at 4:18 p.m. EDT on 20 

July. Shortly after astronaut Neil Armstrong stepped onto the lunar 

surface, he collected and stowed the first sample of lunar surface 

material to assure that “if a contingency required an early end to the 

planned surface activities, samples of lunar surface material would be 

returned to Earth.”281 Over the next 2.5 hours, besides emplacing their 

scientific instruments, astronauts Armstrong and Aldrin “acted like 

field geologists,”282 collecting many rock samples and taking two core 

samples. Obtaining the cores was not easy, since the astronauts found 

it difficult to drive their sampling tube into the lunar surface.

One of the challenges of the mission was to carry out sampling 

operations while dealing with forward contamination of the lunar surface with terrestrial materials. As the Lunar Module descended onto the 

Moon, its descent engine spewed out approximately nine tons of propellant exhaust. While most of this was lost into space, nearly a ton of 100 

different byproduct chemicals remained spread around the landing area. 

In addition, the astronauts’ suits were not entirely leakproof; significant 

quantities of gases exuded from spacesuit joints. According to NASA’s 

Neil Nickle, as the astronauts walked across the lunar surface, they were 

“virtually jets of gas.”283 To obtain samples as uncontaminated as possible, the astronauts took them from sheltered areas (although this was 

made more difficult since the landing was in a very flat region) and also 

used their core tubes to sample below the surface. 

 281.

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When Biospheres Collide

Figure 4.1 Flotation collar attached to the Columbia Command Module. The three astronauts 

plus a Navy swimmer sit in the recovery raft, awaiting pickup by helicopter. All four men are 

wearing BIGs.

Back Contamination Prevention on the Return Trip to Earth

The astronauts’ period of quarantine commenced when they sealed 

the hatch of the Lunar Module in preparation for lifting off.284 After 

liftoff and rendezvous with the Columbia Command Module, astronaut 

Michael Collins, sitting in the CM, slightly opened its oxygen supply 

valve and Aldrin adjusted the LM’s venting valve in order to make sure 

that the cabin atmosphere flowed from the CM into the LM. This was 

one of the strategies for minimizing back contamination buildup in 

the CM and possibly in Earth’s atmosphere as well after the return trip. 

Aldrin and Armstrong found that the amount of loose dust in the 

LM was less than NASA had expected, but the dust clung tenaciously 

to any surface that it touched, including the outsides of spacesuits. 

 284.

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Back Contamination

The astronauts used a vacuum cleaner, which had been fabricated by 

attaching a brush to an exhaust hose of the LM, to try and remove the 

particles from their suits. This vacuum setup turned out not to be very 

effective, making it more difficult than planned to thoroughly rid their 

suits of Moon dust.285

Recovery and Quarantine Operations After Splashdown

Early on 24 July 1969, eight days after launching, the Columbia

Command Module splashed down in the Pacific Ocean 812 nautical 

miles southwest of Hawaii and less than 13 miles from the USS Hornet

aircraft carrier, the Apollo 11 prime recovery ship. Recovery operations were directed from the Mission Control Center in Building 30 of 

Houston’s Manned Spacecraft Center (MSC), with support from recovery centers in Norfolk, Virginia, and Kunia, Hawaii. Within half an hour, 

recovery crews reached the CM, attached a flotation collar to it (see figure 4.1), and passed BIGs into the spacecraft. The recovery crew, which 

included swimmers, then applied Betadine, an iodine solution, around 

the postlanding vents in order to kill any microorganisms that might 

have escaped the inside of the module and might have adhered to the 

vent area (the Betadine would not, of course, have killed any organisms 

that had escaped into the atmosphere or the ocean). 

After the astronauts put on the BIGs, exited the CM, and boarded 

the recovery raft, swimmers wiped Betadine onto the hatch of the CM 

that they’d passed through. Astronauts and recovery crew decontaminated each others’ protective suits with a sodium hypochlorite (bleach) 

solution, which had performed better for this task than Betadine in 

NASA tests.286 The astronauts were then hoisted aboard a helicopter 

and taken to the USS Hornet recovery vessel. The helicopter crew 

wore oxygen masks at all times to guard against inhaling any germs 

 285.

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When Biospheres Collide

Figure 4.2 The Apollo 11 crew, wearing BIGs, leave the helicopter that carried them from the 

Command Module and walk across the deck of the USS Hornet toward the MQF.

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from the astronauts. The helicopter itself was later decontaminated 

with formalin.287

The cumbersome BIGs made it difficult for the astronauts to shed 

heat, and they grew quite uncomfortable during the short helicopter 

ride to the ship. Armstrong and Collins expressed concern that they 

had about reached their level of tolerance by the time the helicopter 

landed on the Hornet. They had to wait, however, until entering the 

MQF before they could strip off the BIGs and don clean flight suits. 

The BIGs, besides being cumbersome and uncomfortable, may also 

have leaked, since when the Apollo crew took them off, the suits contained saltwater.288

As the astronauts walked across the Hornet’s deck (see figure 4.2), 

television crews broadcast their images to millions of viewers around 

the world. NASA personnel then sprayed the path they had walked 

between helicopter and MQF with glutaraldehyde, a sterilant typically 

used in hospitals to disinfect equipment. This was yet another precaution against back contamination. Television commentators explained 

to the world that the chances of back contamination were miniscule, 

but that NASA had to take every precaution. 

Public concerns about contamination dangers. During this 

period of the 1960s, Michael Crichton’s novel The Andromeda Strain 

appeared on best seller lists. The book told a story about Earth in 

danger from microorganisms brought back on a space vehicle. The 

public response to the book resulted in additional pressure on NASA 

to implement strict planetary protection measures. Thousands of 

concerned citizens wrote NASA letters, worried that they were at risk 

from Moon germs. These fears of the public might today seem alarmist and naïve, but epidemics have occurred repeatedly in the past due 

to exotic organisms being introduced into an unprotected populace. 

 287.

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When Biospheres Collide

Figure 4.3 President Nixon welcomes the Apollo 11 astronauts aboard the USS Hornet.

One particularly devastating sickness occurred in the Pacific region, 

just a few thousand miles to the south of the Apollo recovery site. 

Early in 1875, the king of the Fiji Islands—a man named Cakobau—

returned from a visit to Australia suffering from a case of measles. 

His disease, rarely fatal to Westerners, took root in the Fijis and 

killed 40,000 of his subjects.289

 289.

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Back Contamination

Figure 4.4 Apollo 11 Command Module and its flotation collar hoisted aboard the USS 

Hornet. Astronauts have already exited from the craft.

Other examples concerned the native populations of the 

Americas, who lacked immunity to diseases that had propagated 

through Europe, Africa, and Asia for centuries. The diseases that 

explorers and settlers brought included smallpox, measles, chicken 

pox, typhus, typhoid fever, dysentery, scarlet fever, diphtheria, and 

cholera. These sicknesses ravaged native populations throughout the 

New World. Smallpox, for instance, arrived soon after Columbus did 

and wreaked havoc on Native Americans on the islands of Hispaniola 

and Puerto Rico, possibly wiping out entire tribes. The smallpox soon 

spread through many indigenous communities on the mainland as 

well. Cortez’s conquest of the Aztecs was made greatly easier because 

of the thousands from the tribe who quickly died of the disease. One 

lesson to take away from the Native American experience is that not 

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When Biospheres Collide

Figure 4.5 The first Apollo 11 sample return container is unloaded at LRL.

only do such epidemics exact an enormous human toll, they also dramatically disrupt existing political and social structures.290

President Nixon’s welcome to the astronauts. Only after the 

astronauts were safely sealed in the airtight MQF and the Hornet’s 

 290.

218
Back Contamination

deck disinfected did NASA allow President Richard Nixon, who had 

flown to the USS Hornet to welcome the space travelers home, to 

approach the large window at the rear of the MQF to give his congratulations (see figure 4.3). During the transfer of astronauts, President 

Nixon had been kept far away, a helicopter waiting to fly him off the 

ship should any leaks be detected in the MQF. The Hornet also contained a second MQF that could be used to quarantine any of the 

ship’s crew who might have been directly exposed to either astronauts or spacecraft. If a major biocontainment breach had occurred, 

the Hornet itself would have become the isolation unit and would 

have had to remain at sea for the entire astronaut and lunar sample 

quarantine period.291

Transporting Samples and Equipment from the Splashdown 

Point to LRL

After the astronauts were helicoptered to the Hornet, recovery 

crews hauled the CM aboard (see figure 4.4), then connected it by a 

plastic tunnel to the MQF. The film shot on the Moon and the lunar 

sample containers had to be carried through this tunnel into the 

MQF, since they, too, were potential sources of back contamination. 

In order to remove them from the MQF, the recovery crew had to 

first pass them through a decontamination lock. The recovery crew 

then packed one of the sample containers as well as the film and 

tape recorders in shipping containers. These were flown to Johnston 

Island, 200 nautical miles to the north, loaded onto a C-141 cargo 

aircraft, taken to Ellington Air Force Base in Texas, delivered to the 

nearby MSC, and received by LRL. The other sample container was 

flown to Hickam Air Force Base in Hawaii, and from there to MSC 

and its LRL.292

 291.

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When Biospheres Collide

Figure 4.6 LRL functional areas. Biological barriers quarantining certain areas are identified 

by the heavy black lines.

Figure 4.7 Sample operations area details.

Gas Analysis

Upper section of radiation 

counting lab (other 

section is underground)

Physical & chemical experiment cabinetry

Biological experiment 

cabinetry

Vacuum & magnetics lab

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Receiving and Handling Lunar Samples and Flight Film at LRL 

On 24 July 1969, NASA sent word to LRL that the Apollo 11 spacecraft had been successfully recovered, and the laboratory answered that 

it was fully operational and prepared to receive the spacecraft and its 

astronauts and lunar samples. The first Apollo Lunar Sample Return 

Container (ALSRC), weighing 33 pounds, 6 ounces, arrived at 12:28 

p.m. on 25 July 1969 (see figure 4.5). Accompanying it were canisters 

containing film records from Apollo 11’s voyage. The second ALSRC 

was delivered that night at 9:57 p.m. and weighed 52 pounds.293 It 

was because of the “extremely high scientific value and irreplaceable 

nature of the returned samples”294 that the each of the two ALSRCs 

were transported to LRL on separate aircraft. This provided additional 

assurance that at least one of them would reach the laboratory promptly 

and undamaged. Minimal transport time was especially important for 

the low-level gamma radiation counting experiment. Because of the 

expected rapid decay of sample radiation levels (the radionuclides of 

interest had half-lives as short as 15 hours), the sooner the lunar material could be delivered, the better the data would be.295

LRL (also referred to as MSC’s Building 37) included a sample operations area in its northwest corner, a Crew Reception Area in its southwest corner, and its administrative and support area in the eastern half of 

the building. These functional areas are depicted in figure 4.6; a detailed 

drawing of the sample operations area is in figure 4.7. The heavy black 

lines in figure 4.6 around the Crew Reception Area and sample operations area indicate that they were enclosed in their own biologic barriers. Several features made up these barriers, including sealed walls, floors, 

and ceilings; the control of leaks using differential air pressures between 

 293.

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When Biospheres Collide

the inside and outside of the isolated areas; special air conditioning features; biologic filters on both the air intake and exhaust systems of the 

areas; incineration of effluent air; and sterilization of liquid effluents. Staff 

had to transfer materials into and out of isolated areas using two-door 

sterilization cabinets, which employed steam and/or ethylene oxide gas.296

Film handling. Decontamination procedures for Apollo film canisters began immediately upon their arrival. One of the canisters was 

delivered covered with dust that was assumed to be of lunar origin. LRL 

technicians put film canisters from the mission into the two-door sterilization cabinets and exposed them to the ethylene oxide gaseous sterilant for several hours. Only after this treatment did LRL staff send the 

canisters to the photographic laboratory for processing. The sterilization 

process decontaminated the film as well as the canisters, which allowed 

technicians who were not behind the biobarrier to process the film 

without having to wait several weeks for the quarantine to be lifted.297

Handling the first lunar samples. After their delivery to LRL, 

facility staff brought the ALSRCs into the vacuum laboratory, where 

technicians gave them preliminary examinations, then passed them 

through two-stage sterilization consisting of ultraviolet light exposure 

and contact with peracetic acid, a biocide typically used for sanitizing 

equipment such as tanks, pipelines, and food contact surfaces.298 Next, 

they rinsed the ALSRCs with sterile water, dried them in a nitrogen 

atmosphere, and passed them through a vacuum lock into the main 

vacuum chamber glove box.299 LRL technicians pumped the chamber’s 

atmospheric pressure down to approximate that of the Moon. 

 296.

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Back Contamination

Figure 4.8 The first lunar sample photographed in detail at LRL. This was a granular, finegrained, mafic (iron- and magnesium-rich) rock, which appeared similar to several igneous 

rock types found on Earth.

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When Biospheres Collide

Figure 4.9 Lunar material in a sieve from the bulk sample container being examined in an LRL 

glove box by a lunar sample preliminary examination team member.

The technicians did not directly touch the samples, but worked 

from the outside of the vacuum chamber and reached into the interior by putting their hands in glove ports. The gloves and the rest of 

the vacuum chamber formed one of several lines of defense against 

contamination of LRL staff or the outside environment with Moon 

material. The LRL air conditioning system, which had the capability 

to sterilize all air leaving the facility, formed another contamination 

224
Back Contamination

barrier. The pressurization system, which maintained a negative pressure300 within LRL’s laboratories, formed yet another barrier.301

The staff did not immediately open the sample container because 

they could not stabilize the pressure in the vacuum chamber. Operators 

suspected that one of the gloves in the wall of the chamber through 

which samples were handled was slowly leaking, since they observed 

several small tears in one of the outer glove’s two layers, the Viton nonpressure-retention layer. However by midafternoon of the day after 

sample delivery, 26 July 1969, the leak had not grown any worse and 

the staff decided to examine the first ALSRC. Technicians began by 

puncturing the ALSRC, in order to analyze the pulse of gas that would 

be released. Later examination showed that the ALSRC had not been 

punctured sufficiently by the gas analysis probe. As a result, no gas sample was obtained. Procedures were put into place to ensure that a good 

sample would indeed be obtained from the second ALSRC.302

LRL Daily Summary Report records indicate that LRL staff 

opened the first ALSRC at 3:45 p.m. on 26 July 1969. What they 

initially saw was not terribly illuminating, since a fine lunar dust 

obscured the individual characteristics of the rocks. All that was 

apparent was that they were shaped irregularly with slightly rounded 

edges (see figure 4.8).303 Elbert A. King, NASA’s first Lunar Sample 

Curator, said of those first glimpses of Moon rocks, “The moment 

was truly history, but there was little we could observe or say. We 

counted the rocks and described the size and shape of each piece, 

but they looked like lumps of charcoal in the bottom of a backyard 

barbecue grill.”304 The first lunar rock examined in more detail, however, revealed a fine crystalline structure and an apparently igneous 

 300.

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When Biospheres Collide

origin. Analysis of the fines showed a substantial number of small 

glassy spheres 1 millimeter (1/25 inch) in diameter and smaller.305

The sample container also held two rock core tubes containing 

subsurface material and a sheet of aluminum foil that had been laid 

on the Moon’s surface to trap particles of the solar wind. Because the 

rock cores had received the least exposure to Earth contaminants of 

any of the samples, they provided the “bioprime”306 sample—a 100 

gram (3.5 ounce) portion of lunar material whose impacts on a range 

of Earth organisms would be carefully analyzed. MSC staff packed the 

rock core tubes and solar wind collector in stainless steel cans that 

they then sterilized and removed from the vacuum laboratory. 

Two teams of scientists—the preliminary examination team and 

the sample analysis planning team—inspected, characterized, photographed, and catalogued the samples. Through August 1969, specimens from the samples were allocated to 142 principal investigators on 

the project, but they could not immediately receive these specimens. 

That would have to wait until the quarantine period ended.307

Equipment Challenges and Malfunctions

The gloves through which technicians handled materials in the 

vacuum chambers needed to be quite strong since they had to withstand the very large pressure differential between the outside and 

inside of the chambers. As a result of this requirement, the gloves were 

also extremely stiff and unwieldy to use, especially for the delicate 

parts handling operations that were carried out. Nevertheless, LRL 

technicians grew amazingly proficient in performing those operations 

(see figure 4.9). According to Craig Fischer, a NASA pathologist who 

served as chief of clinical laboratories for the mission, “the technicians got very good at handling the rocks and apportioning the rocks 

 305.

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and milling the rocks and injecting the mice and exposing the fish and 

cockroaches and you name it.”308

On 28 July 1969, a sewage system malfunctioned and appeared in 

danger of breaking LRL’s biological containment, but the problem was 

corrected without such an occurrence. The torn glove on the vacuum 

chamber received a temporary fix—to reduce the leaking, technicians 

slipped another glove over it and taped the two together at the wrists. 

While this approach temporarily stopped the pressure fluctuations in 

the vacuum chamber, it didn’t last long. Within days, the glove ruptured. The 1 August 1969 LRL Daily Summary Report recorded that 

on 31 July 1969, “the webbing between the thumb and forefinger of the 

glove burst with almost no warning.”309 The strong flow of air into the 

chamber that followed the glove rupture exposed most of the samples 

in the vacuum system to LRL’s atmosphere. This incident also exposed 

two technicians to the Moon rocks, and these personnel had to go into 

quarantine. LRL suspended work in the vacuum laboratory until this 

tendency toward leaks could be solved.

LRL scientists decided to abandon keeping any samples under 

vacuum except those that absolutely required it, since leakage and 

subsequent contamination appeared unavoidable with vacuum conditions in the chamber. Instead of keeping the system under vacuum, 

which would have most closely resembled conditions on the Moon, 

LRL staff opted to introduce dry nitrogen—a chemically inert and 

noncontaminating gas—into the chamber. They also put the chamber 

through a sterilization heating cycle that started on 3 August 1969, 

when they turned on the chamber’s heaters. This sterilization cycle 

was a necessary part of a glove change operation, which entailed 

opening up the chamber bulkhead.310

 308.

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When Biospheres Collide

Quarantining the Astronauts

On the USS Hornet’s journey back from the recovery site to 

Hawaii, the astronauts shared the MQF with a doctor, William R. 

Carpentier, and a mechanical engineer and expert on MQF operation, 

John Hirasaki.311 When the ship reached Pearl Harbor, the MQF, with 

the astronauts aboard, was lifted from the deck onto a waiting truck. 

After the astronauts received greetings from the Honolulu mayor 

and thousands of local citizens, the truck transported the MQF to 

Hickam Air Force Base several miles away. There, the MQF was put 

into a C-141 cargo plane and flown to Ellington Air Force Base near 

Houston, where it landed just after midnight on 27 July 1969. A large 

crowd waited, hoping to get a quick look at the returning heroes. The 

MQF was transferred onto a special flatbed truck designed for it and 

was driven to the Crew Reception Area of LRL. The truck backed up 

to the CRA’s loading dock, and technicians taped a shroud tightly in 

place that effectively mated the MQF to the CRA and formed a sort 

of airlock that prevented outside air from being contaminated when 

the MQF was opened. 

Craig Fischer had this to say about the reception of the first lunar 

astronauts:

We were elated to see them, although it’s sort 

of interesting looking back at it. I didn’t have the 

sense of history that I do now. It was part of what we 

did. . . . Now . . . it has a totally different meaning than 

it did at the time. All of a sudden you realize that was 

the first lunar crew in the history of mankind, and we 

were privileged enough to work with them. But at the 

time, hey, it’s just Neil and Buzz and Mike and we’d 

Receiving Laboratory,” NASA Historical Reference Collection; Lunar Receiving Laboratory, 

“LRL Daily Summary Report No. 9,” 2 August, 1969, folder 012990, “Lunar Receiving 

Laboratory,” NASA Historical Reference Collection; Lunar Receiving Laboratory, “LRL Daily 

Summary Report No. 10,” 4 August 1969, folder 012990, “Lunar Receiving Laboratory,” 

NASA Historical Reference Collection; Lunar Receiving Laboratory, “LRL Daily Summary 

Report No. 11,” 5 August 1969, folder 012990, “Lunar Receiving Laboratory,” NASA 

Historical Reference Collection; Compton, Where No Man Has Gone Before, pp. 151, 268.

 311. John K. Hirasaki, project engineer for the certification and qualification of the MQF, 

telephone interview by author, 13 January 2006. 

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worked with them before on other missions and we 

were glad to see them. And they were glad to be there. 

But there wasn’t any hoopin’ and hollerin’ or huggin’. A 

handshake and in they came.312

At 3:30 a.m. on 27 July 1969, the Apollo crew and their companions were “successfully transferred to LRL.”313 Waiting for them in 

LRL’s Crew Reception Area was their support staff—a clinical pathologist (Craig Fischer), five laboratory technicians, a photographer, an 

MSC public affairs person, a logistics operations officer, and three 

stewards.314

Over the next weeks, medical staff kept a close watch on the astronauts for any sign of infection and illness, conducting frequent examinations and blood tests. The astronauts’ quarters had equipment for 

clinical tests as well as surgical and dental procedures. Doctors and 

dentists had been identified who could, if needed, enter the CRA and 

attend to its residents. These professionals would then, of course, have 

to remain in the CRA until the end of the quarantine.315

If a serious medical emergency had occurred that was beyond the 

capabilities of CRA equipment, NASA would have rushed the afflicted 

person from LRL to a hospital, regardless of quarantine requirements. 

Although such a situation did not occur, this was another example of 

NASA’s policy to prioritize the lives of its people above back contamination requirements. (A previously discussed example of NASA’s policy 

was its decision to have the astronauts exit the Command Module, due 

to concerns for their safety, before the recovery ship’s crane hoisted 

the module aboard the USS Hornet.)316

Apollo mission plans, which were in concurrence with the recommendations of ICBC, called for the astronauts to remain in quarantine for at least 21 days after their exposure to lunar material. The 

air exhaled by them and the other personnel under quarantine in the 

 312.

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When Biospheres Collide

CRA flowed through biological filters and then was heat sterilized in 

order to ensure that no microbes escaped to the outside world. The 

body wastes they produced received steam treatment, which heated 

them to a temperature of 260°F (127°C), while every piece of paper 

leaving the quarantine facility got exposed to ethylene oxide, a sterilizing gas, for 16 hours. The astronauts’ and their staffs’ periods of 

quarantine might have been extended if anyone had exhibited signs 

of infection by a potentially extraterrestrial organism. The release 

date from the quarantine would probably not have been altered, however, if the sick person was diagnosed as noninfectious or having a 

disease of terrestrial origin.317

LRL staff conducted extensive medical testing of the astronauts, 

their support personnel, and the technicians put in quarantine after 

the breach of the biobarrier in the vacuum laboratory. Staff conducted 

clinical observations and chemical, biological, and immunological 

analyses. These did not produce any indications of infections from 

exotic organisms or other ill effects from the mission. As a result, 

ICBC agreed to lift the quarantine of the astronauts and other personnel at 1 a.m. on 11 August 1969, one day early. ICBC did recommend, 

however, that all the personnel be kept under medical surveillance 

until completion of LRL’s biological analyses and release of the Moon 

samples. NASA chose an early morning hour for ending the quarantine 

in order to minimize the number of reporters and the scuffle that was 

expected as the astronauts emerged. After a month of confinement, 

however, the astronauts sought to get out as soon as they could, and 

so at 9 p.m. on 10 August 1969, after completing one more medical 

examination, they walked out of isolation, spoke briefly to the press, 

and were rushed home to their families.318

 317.

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Decontaminating the Command Module

NASA delivered the Apollo 11 CM to LRL at 6 p.m. on 30 July 

1969, where it was placed in the spacecraft storage room.319 Although 

the Apollo crew had executed CM cleaning procedures during the 

mission, NASA still considered the module to be potentially contaminated and thus subjected it to quarantine and decontamination. The aim was to release the CM with the flight crew on the 21st 

day of quarantine and return the module to the contractor, North 

American Rockwell Corporation. This would allow Rockwell to conduct postflight testing in ample time to use its data to support the 

next Apollo mission. 

LRL staff first conducted a detailed exterior inspection of the craft, 

including photographic coverage, and removed access panels to the 

interior. A recovery engineer entered the CM and removed and bagged 

all stowed equipment, including clothing, which had to be quarantined along with the astronauts and lunar samples. LRL staff finished 

removing spacecraft equipment on 2 August 1969. The following day, 

the recovery engineer completed preparations for decontaminating 

the craft’s water and waste management system by hooking up lines 

through which a piped-in formalin solution containing 40 percent 

formaldehyde would flow, remaining in the system for 24 hours. The 

engineer also opened all of the ship’s compartments and wiped them 

down with disinfectant. LRL staff subsequently heated the interior 

of the module to 110°F (43°C), evacuated its pressure to 8.5 psi, and 

filled it with formaldehyde gas for 24 hours. Because the recovery crew 

that performed the decontamination might have gotten contaminated 

themselves, they had to be quarantined afterward.320

 319.

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When Biospheres Collide

Figure 4.10 Radiation counting laboratory.

Moon Sample Quarantine and Analysis 

LRL staff conducted intense sample analysis work in August 1969, 

aiming at finishing their tests and releasing the samples from quarantine by mid-September. Completing the analyses was estimated to 

require 50 to 80 days after the samples entered LRL. 

Bioprime and biopool samples. LRL staff prepared two batches 

of lunar material—a bioprime and a biopool batch. They extracted 

the bioprime material—the sample that had least contacted Earth’s 

environment—from the two rock coring tools. They and the principal 

investigators subjected it to minute analyses that sought to find any 

evidence of “living organisms or their relics.”321

 321.

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LRL personnel made up two biopool samples from several hundred 

grams of fines and chips derived from Moon rocks in the bulk sample 

container. The mission scientists tested the biopool samples in a large 

range of living systems in order to determine whether Moon material 

was pathogenic or toxic, and to what extent.322

Gas and radiation counting operations. Scientists quickly performed the time-critical effluent-gas analysis and gamma-radiation 

counting experiments on the lunar material. LRL’s gas analysis laboratory staff strove to carefully analyze outgassing from the samples 

without the data being compromised by terrestrial contaminants. 

The vacuum-tight sample containers made this possible by providing a barrier against biological and chemical contamination during 

the trip from the Moon to LRL. Once they received the near-pristine 

samples, gas laboratory staff performed several closely related analyses of the following: 

•	 Gas from the sample containers. This provided data on the 

composition as well as quantity of gas released from the 

samples. It also provided a measure of just how effective a 

vacuum container’s seal was in keeping out terrestrial gases.

•	 Gas generated during the splitting and preliminary 

examinations of the lunar rocks. The same gases were expected 

to be observed as in the above experiment, except perhaps for 

interstitial and occluded gases323 released during cleaving of the 

lunar rocks.

•	 Gas evolved from heating the samples. These gases could have 

been adsorbed on rock surfaces or in interstitial spaces.

•	 Gas released or gaseous reaction products generated during 

atmospheric-reaction testing in LRL’s physical-chemical test 

laboratory.

Samples collected on the Moon, where no atmosphere or substantial magnetic field is present to shield or deflect cosmic rays and 

solar wind protons from bombarding surface rocks, were expected to 

contain induced radioactive nuclides in addition to the isotopes contained in terrestrial rocks. Analysis of the induced gamma radiation 

 322.

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When Biospheres Collide

in the rocks could yield valuable information on the sample’s composition as well as on the nature of the activating radiation that had 

bombarded it. Derived from this might be clues to the history of the 

Moon rocks. 

Gamma-ray counting experiments had to be performed in LRL 

as soon after receiving the specimens as feasible, before many of 

the short-lifetime nuclides possibly decayed to undetectable levels. 

Scientists suspected this decay would occur because lunar rock materials, they thought, might be similar to the materials in meteorites, 

and the extremely weak radioactivity levels in those were not able to 

be adequately analyzed using the capabilities of the time.324

Scientists measured the samples’ gamma-ray levels in the underground counting laboratory of LRL that had been constructed 50 

feet (15 meters) below ground (see figure 4.10). The overburden of 

earth plus 5-foot (1.5-meter) thick concrete walls eliminated most 

cosmic ray background from the laboratory. To shield the space from 

terrestrial background radiation sources that might also obscure 

faint signals from the rocks, the construction crew lined the laboratory’s walls with 36 inches (91 centimeters) of crushed dunite—

a material found in Earth’s mantle that consists mainly of olivine 

[(Mg,Fe)2SiO4

]—and held it in place with a 3/8-inch steel liner. A 

special ventilation system using chilled charcoal beds and other 

filters provided a radon-free atmosphere in the laboratory. Finally, 

special detector enclosures that employed a 26-ton lead shield further reduced the radioactive background reaching the detectors by 

another one to two orders of magnitude.325

Biologic examinations. Biological analyses sought to determine 

whether contamination of Earth environments with lunar material 

would or would not be harmful. LRL staff sought to determine the 

presence of any infectious and possibly hazardous lunar microorganisms by observing their ability to replicate in selected animal and 

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plant species.326 In these experiments, technical staff pulverized tiny 

pieces of Moon material and fed them to carefully raised colonies of 

insects, mice, birds, and plants that were bred to be germ-free and 

extremely sensitive to new forms of microbes. 

Some of these colonies proved quite difficult to raise. For instance, 

developing ordinary mouse specimens was fairly easy, but raising 

germ-free colonies delivered by Caesarian section under sterile surgical conditions presented many challenges. LRL lost three such colonies during its attempts.327

Biologic analyses included the following protocols:

•	 Direct sample observations. Optical microscopes using visible 

and infrared light sources as well as electron microscopes were 

used to search for life-forms.

•	 Bacteriology. Attempts were made to grow microbes from 

lunar samples incubated in air, carbon dioxide, and nitrogen 

environments, using cultural media that included blood agar, 

glucose yeast extract, and thiogycolate broth.

•	 Virology. Identification of viruses was attempted by observing 

lunar material’s ability to replicate in cell cultures, embryonated 

eggs, and other media.

 The lunar material was also tested to determine whether it contained life-forms capable of generating a disease or reproducing in 

specific categories of organisms. These categories, and the particular 

species used in the tests, included the following:

•	 Mammalian vertebrates: Germ-free mice. 

•	 Avian vertebrates: Japanese quail.

•	 Invertebrates and fish: Cockroaches, houseflies, wax moths, 

brown shrimp, commercial oysters, and fathead minnows.

•	 Plants: 33 varieties with economic importance.328

Physical and chemical analyses. Investigators subjected samples 

to physical and chemical examinations as well as biological tests. 

The physical-chemical test laboratory contained 36 linear feet of 

 326.

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When Biospheres Collide

double-sided, gas-tight, dry nitrogen atmosphere cabinets providing 

a biologic barrier, with glove ports for 20 different operator positions. 

Most of the minerologic,329 petrologic,330 and geochemical331 investigations during the quarantine period took place here. 

Equipment designed for operating through the biologic barrier 

included petrographic microscopes, stereoscopic binocular microscopes, balances, a gas comparison pycnometer (an instrument for 

measuring the density or specific gravity of materials), gas reaction 

equipment, x-ray diffraction and fluorescence units, photomicrography capabilities, and the hand tools, reagents, and other paraphernalia of a chemistry laboratory. Laboratory staff used microscopy 

to examine and characterize the different types of lunar material 

collected. They exposed the rock fragments to common Earth atmospheric elements, including nitrogen, oxygen, and water vapor. None 

of these elements would elicit a dramatic reaction from an Earth 

rock, but the lunar material might never have encountered water, 

oxygen, or nitrogen. Violent reactions could not be ruled out, such 

as rapid disintegration, sharp temperature rises, or, less likely, explosions. Significant changes in minerologic composition or physical 

properties were also possible. 

When such dramatic reactions to Earth elements did not occur, 

scientists subjected lunar rock chips to a battery of analyses that gave 

clues to the Moon’s history and origin, its surface materials and processes, the forces that formed the surface, and the period of the solar 

system’s history in which it was formed. Many laboratories throughout 

the scientific community outside LRL performed more detailed investigations once the quarantine was lifted. These experiments included 

comprehensive analyses of elements and isotopes, which generated 

mineral identifications and descriptions.332

When investigators could not determine the structures and characteristics of rock fragments using microscopes, they employed analytical methods such as x-ray diffraction or ignition of the sample and 

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analysis of the flame’s spectrum. This was useful because different 

elements can be identified by the characteristic spectral “fingerprints” 

they emit when burned.333

Releasing the Lunar Samples from Quarantine

LRL staff conducted intense testing throughout August 1969. The 

intention was to generate enough data on the lunar samples that they 

could be released from quarantine in mid-September with confidence 

that they would do no harm to Earth’s environment. 

None of the biological testing during August revealed any indication of the existence of lunar microorganisms nor any indication of 

hazards to Earth organisms. One result, however, was that lunar samples appeared to stimulate the growth of plants used in the testing. 

ICBC reviewed the extensive data from the testing and concluded that the lunar samples brought back by Apollo 11 presented 

no biological danger to Earth life. ICBC notified MSC Director Robert 

Gilruth of its finding and gave permission to release the samples on 

12 September 1969. The principal investigators (PIs) picked up their 

samples in person at LRL and began their in-depth, exhaustive studies 

of the lunar material.334

Apollo 12

The scientific community was satisfied for the most part with 

the way that LRL staff processed Apollo 11 samples, although many 

complained about the long delay in releasing samples to PIs, attributing this to inefficient procedures, inexperience, and problems with 

equipment. NASA wanted to correct these issues before the Apollo 12 

launch, which was scheduled for mid-November 1969. 

In order to meet this deadline, LRL began to work on the corrections and fixes while they were still completing their Apollo 11 tasks. 

 333.

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When Biospheres Collide

In early September 1969, NASA’s Lunar Sample Analysis Planning 

Team sent recommended changes to MSC’s new Director of Science 

and Applications, Anthony J. Calio, which covered procedures such as 

photographing samples and weighing and transferring material during 

quarantine as well as displaying data on each sample’s history, status, 

and location. Efficient display of current data was necessary because 

during Apollo 11, problems had emerged regarding where each sample 

was located and what operations had been performed on it. 

Staff who had handled Apollo 11 samples gave recommendations 

for reducing the number of personnel in LRL and streamlining sample 

preparation for quarantine testing.335 U.S. Department of the Interior–

Geological Survey personnel in particular developed sample handling 

procedures that they claimed would “drastically improve the speed 

and completeness of the preliminary examination.”336 One of these 

suggestions was to eliminate the biopool sample and use only a single 

bioprime sample. This would help to correct a serious bottleneck in 

Apollo 11 sample processing—the time-consuming preparation and 

handling of both bioprime and biopool samples. The U. S. Geological 

Survey personnel justified this proposed action by claiming that biopool sample testing was “merely a more extensive verification of the 

tests made on the bioprime sample.”337

The LRL vacuum system required significant modifications. As discussed above, problems had arisen regarding effective sample handling, 

and the glove boxes themselves had leaked, potentially contaminating workers and the outside environment. In addition, organic materials from the vacuum pumps had contaminated the vacuum system. 

Because of these issues, Lunar Sample Analysis Planning Team members thought it necessary to change policy and open at least one of the 

two lunar sample containers in a dry nitrogen atmosphere, avoiding 

the need for a vacuum system for that batch of samples.338

 335.

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Figure 4.11 USS Hornet, prime recovery vessel for Apollo 12, moves toward the Command 

Module. A helicopter from the recovery ship, which took part in recovery operations, hovers 

over the scene of the splashdown.

NASA officially decided many of these issues in late September 

1969. Richard Johnston reported in a 23 September letter that MSC 

was attempting, as suggested by USGS personnel, to develop an adequate sampling criterion that would permit the use of only a single 

sample for Apollo 12 bioprotocols.339 ICBC concurred with the use of a 

single pooled lunar material sample, as long as it was representative of 

the returned rock material from the Moon.340

NASA ultimately decided to prepare only one sample. Furthermore, 

the two lunar sample return containers would go through simultaneous processing, but this processing would be conducted for one container in a sterile nitrogen atmosphere and for the other in a vacuum. 

NASA refused, however, to fulfill an ICBC request to install a bacterial 

filter on the Command Module’s postlanding ventilation system, which 

would have given greater protection against back contamination but 

 339.

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When Biospheres Collide

would also have generated the problems discussed above regarding the 

Apollo 11 CM.341

In its 30 October 1969 meeting, ICBC studied whether results from 

the Apollo 11 mission warranted elimination of the BIGs during recovery operations on future Apollo missions. The Apollo 11 astronauts had 

found the BIGs oppressively uncomfortable. John Hirasaki, the MQF 

engineer on Apollo, commented that NASA had “a significant concern 

about the use of BIGs compromising the health of the crew because of 

thermal overload.”342 ICBC recommended eliminating use of the BIGs 

if “the Apollo 12 crew condition is normal at earth landing.”343 NASA 

concurred with this recommendation and implemented it for Apollo 

12. In lieu of BIGs, the recovery crew would provide astronauts with 

clean flight suits and oral-nasal respiratory masks to put on before 

leaving the Command Module. These masks were equipped with bacterial filters to prevent back contamination due to exhalations of the 

astronauts. BIGs would be available, however, “for use as a contingency 

in case of unexplained crew illness.”344

At 11:22 a.m. eastern standard time (EST), 14 November 1969, 

Apollo 12 took off from Kennedy Space Center, lifted by a Saturn 5 

launch vehicle. On 20 November, astronauts Pete Conrad and Alan 

Bean conducted a 4-hour Moon walk. At its conclusion, Bean and 

Conrad dusted each other off as best they could, but they had not 

taken any brushes or other equipment to help with the task. From this 

and the following day’s Moon walk, they carried considerably more 

lunar dust into the Intrepid Lunar Module than Armstrong and Aldrin 

did during Apollo 11. Conrad described himself and Bean as looking 

like “a couple of bituminous coal miners . . . .”345

The astronauts’ quarantine period officially began on the lunar 

surface the moment they closed the Lunar Module’s hatch.346 Once 

the Intrepid Lunar Module lifted off the Moon and attained lunar 

orbit, the dust carried in by the astronauts began to float throughout 

 341.

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Back Contamination

241

the cabin and was thick enough to be visible. After docking with the 

Yankee Clipper Command Module, the astronauts tried to vacuum the 

dust up, but had little success, so they removed and stowed their suits 

in an attempt to minimize the amount of contamination that would 

enter the CM. In spite of their efforts, the CM returned to Earth with 

significant amounts of dust clinging to every surface and remaining 

suspended in the cabin’s atmosphere. The filters in the ship’s environmental control system proved not capable of removing it from the 

ship’s air as thoroughly as NASA had hoped.347

The Apollo 12 CM splashed down in the Pacific Ocean on 24 

November 1969, 375 miles (600 kilometers) east of Pago Pago, American 

Samoa, and 2 miles (3.5 kilometers) from the USS Hornet recovery vessel, which then approached the CM (see figure 4.11). When the recovery 

crew swimmers arrived, they tossed respirators and coveralls into the 

module but, as mentioned above, did not furnish the astronauts with 

BIGs. Half an hour later, the crew reached the Hornet via helicopter 

and entered the MQF. The recovery crew removed lunar sample containers and film magazines from the CM, which were flown to Pago 

Pago and then on to Houston and LRL. The astronauts did not have 

quite so speedy a journey. They remained in their MQF during the 

4-day sea journey to Hawaii and the 9-hour cargo plane ride to Houston. 

Astronauts Conrad, Bean, and Richard Gordon finally reached LRL, and 

continued their quarantine, on the morning of 29 November 1969.348

Once again, problems arose with LRL’s glove box isolation system. 

During a preliminary examination of lunar samples, a small cut was 

found in one of the gloves. This potentially contaminated the area and 

sent 11 people into quarantine. Several scientists were among those 

isolated, and they were quite disappointed that they had been separated from their work. Other than the problem with the glove, however, LRL operations during Apollo 12 went quite smoothly. The staff 

finished inventorying and conducting preliminary examinations of all 

samples within a week after they had arrived at LRL. 

 347.
When Biospheres Collide

The astronauts and their companions spent a largely uneventful quarantine period. Periodic medical examinations showed no 

change in the conditions of any of the bio-isolated personnel. On 10 

December 1969, slightly before NASA’s official end of the quarantine 

period, they were released but kept under medical surveillance until 

data from the biological testing confirmed that they presented no 

threat to Earth.349

LRL’s intensive biological testing continued into January 1970. 

No evidence of living or fossilized microorganisms was detected. 

No indications of any sort of lunar-material-related pathology were 

observed among Apollo 12 astronauts, the personnel who had contact with them or with lunar material, or with any of the test species 

of plants and animals.350

After the release of the samples, outside scientists did find carbon and carbon compounds in the samples, but they did not find any 

indication of molecules that could “clearly be identified as derived 

from living organisms.”351 Investigators as well as the Lunar Sample 

Analysis Planning Team, however, recognized that only an extremely 

small fraction of the Moon’s surface had been sampled and understood 

the importance of obtaining materials from a diversity of terrains and 

locations. In the words of one scientist, “what I looked at was equal 

to the size of three postage stamps and a thimbleful of material . . . . 

Our results are based on the wanton destruction of two grams of lunar 

material.”352 NASA aimed in future missions to partially correct this 

problem by exploring a greater range of sites and terrains. This would 

be critical for drawing any conclusions about the Moon and its potential for back contamination of Earth.

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Apollo 13 and 14

In early 1970, ICBC used data from Apollo 11 and 12 to reexamine the need for quarantine on future missions. The environment 

that had been found on the Moon and that probably had existed for 

billions of years suggested to ICBC that quarantine was perhaps not 

needed. ICBC decided, after an extended dialogue, “to recommend 

to the NASA Administrator that crew quarantine be discontinued”353

and to advise the SSB of this recommendation. But in February 1970, 

the SSB examined this issue and did not agree that crew quarantine 

for Apollo 13, scheduled to launch in two months, should be discontinued. Apollo 13 was to land on a lunar highland site believed to 

be significantly different from the mare354 sites that Apollo 11 and 

12 sampled. Nonetheless, the SSB agreed with ICBC that crews on 

future missions need not be quarantined unless the anticipated differences in landing sites required it.

Apollo 13 launched on 11 April 1970, aiming to land at a spot on 

the Moon just north of the Fra Mauro crater. This would allow the astronauts to sample the Fra Mauro Formation, which scientists believed 

was made up of ejected material from the Imbrium basin caused by a 

large impact in the Moon’s past. Thus, the astronauts would be collecting samples from deep inside the Moon that had been forcibly excavated during the Imbrium event. Apollo 13 never landed on the Moon, 

however. Hours after launch, an oxygen tank in the Service Module 

exploded, resulting in damage to other systems and loss of most of the 

spacecraft’s electrical power and oxygen. NASA had to order the mission aborted; only a brilliant, real-time replanning of procedures by the 

mission operations team saved the lives of the crew.355

 353.

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When Biospheres Collide

After NASA had to abort Apollo 13, the Apollo site selection board 

almost unanimously agreed to send Apollo 14 to the previous mission’s 

target destination, Fra Mauro. Crew quarantine remained in place for 

Apollo 14 as well. The rationale given was the same as for Apollo 13: 

the mission was tasked to excavate a deep lunar core sample, whose 

material might differ from the surface samples of the mare sites taken 

by the previous lander missions.356

Apollo 14 took off on 31 January 1971 and, after mission commander Alan B. Shepard, Jr., and Lunar Module pilot Edgar D. 

Mitchell conducted two Moon walks, returned to Earth and splashed 

down on 9 February 1971. Recovery operations began with swimmers deployed to the CM to install the flotation collar, pass flight 

suits and respirators to the astronauts still inside the CM, then assist 

them from the module into the life raft. After this, the recovery helicopter flew the astronauts to the USS New Orleans helicopter carrier recovery vessel, where they entered an MQF. During the Apollo 

14 mission, however, they did not remain in this initial MQF until it 

reached LRL, but left it while it was still on the recovery ship, and 

they were helicoptered to Pago Pago, American Samoa, where they 

transferred to a second MQF aboard a C-141 aircraft. This aircraft 

flew them to Ellington Air Force Base near MSC.357

The new approach considerably shortened crew return time. 

During Apollo 12, the CM splashed down on 24 November 1969, but 

the astronauts did not reach LRL until 29 November. On Apollo 14, 

splashdown occurred 9 February 1971; the astronauts reached LRL 

about 60 hours later.358

NASA carried out its new return procedures over the strenuous 

objections of Charles Berry, who pointed out that within the MQF on 

the recovery ship, astronauts would remove their masks, allowing their 

exhalations to mix freely with the atmosphere inside the mobile facility. The entire recovery vessel and its crew would become exposed to 

lunar material when the outer MQF door was opened. Berry held that 

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Back Contamination

the procedures “clearly violate any pretext of maintaining an effective 

biological barrier.”359

The End of Quarantine

Life-detection experiments on Apollo 14’s return samples produced negative results, as had the samples from Apollo 11 and 12. 

Furthermore, no evidence emerged from any test system of any type 

of hazard associated with Apollo 14 samples.360 Thus after Apollo 14, 

NASA revisited whether quarantine procedures were needed on future 

lunar landing missions. 

Quarantining operations were very expensive. They were also 

troublesome and inconvenient to technical staff because they impeded 

postflight briefings and delayed the release of eagerly sought lunar 

samples to investigative teams. Considerable evidence suggested that 

quarantines simply were not required for the protection of Earth and 

that life had either never existed on the Moon, or at least appeared to 

have left no trace at the sites examined. On 26 April 1971, based heavily on the recommendation of ICBC,361 Acting NASA Administrator 

George M. Low discontinued the quarantine for future Apollo flights to 

the Moon, stating that

The analysis of quarantine information from Apollo 14 

has now been completed. On the basis of this analysis, 

as well as the results from the Apollo 11 and Apollo 12 

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When Biospheres Collide

flights, it has been concluded that there is no hazard to 

man, animal or plants in the lunar material.362

Although quarantine procedures were terminated, biomedical analyses of returned lunar samples would continue. In addition, the careful 

procedures for protecting lunar samples from Earth contamination on 

the return journey from the Moon as well as during transport to LRL 

would not significantly change.363

The Apollo mission was an extremely complex endeavor with many 

technical and political challenges. A concise summary of major events 

from this mission is included in the timeline in Appendix E. Specific 

planetary protection approaches employed by Apollo as well as other 

missions are summarized in Appendix F.

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5 PLANETARY PROTECTION 

FOR MARS

The Viking Experience

Landing on Mars was something nobody had ever 

done before. Looking for life on Mars is a pretty 

exciting venture. . . . It probably didn’t hurt that the 

science requirements and the planetary quarantine 

requirements somewhat overlapped.

—Tom Young, former Viking Mission Director1

The first United States effort to send soft landing spacecraft to 

another planet began with two Viking launches to Mars in 1975.2 These 

were our country’s most ambitious robotic space ventures up until that 

time. Furthermore, the Viking mission employed “the most stringent 

planetary protection requirements imposed to date on any U.S. flight 

project.”3 NASA estimated the probability of growth of an Earth microorganism in Mars’s environment to be relatively large. This necessitated rigorous sterilization procedures for the Viking Lander Capsules 

(VLCs), since they would directly contact the Martian surface.4

 1. Tom Young, former Viking Mission Director, telephone interview by author, 20 February 2006. 

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When Biospheres Collide

Bionetics Corporation (“Bionetics”) was of particular help in 

attaining effective planetary protection. The company had been 

founded in 1969 specifically to “perform planetary quarantine support for NASA Langley Research Center’s Viking Project”5

 and, in 1972, 

Bionetics was awarded a $1 million contract to manage Viking’s planetary quarantine and microbiological assay facility. Bionetics aided 

NASA in minimizing spacecraft contamination that could have led to 

false positive indications of life on Mars. Bionetics also assisted NASA 

and Martin Marietta, the manufacturer of the spacecraft, in developing 

cleaning approaches and verification procedures.6

Each Viking spacecraft consisted of an orbiter, or “VO,” and a 

lander capsule, or “VLC” (see figure 5.1). The VLC, in turn, included 

the actual lander (a detail of which is given in figure 5.2) that touched 

down on Mars, surrounded by the other components depicted in figure 

5.1: a descent capsule made up of an aeroshell–heat shield–parachute 

system that enclosed, protected, and slowed down the lander during 

its descent through the Martian atmosphere, and a bioshield cap and 

base assembly around the descent capsule that protected it from terrestrial contamination before and during launch. 

The Viking spacecraft journeyed 815 million kilometers (505 million 

miles) in approximately one year to land on Mars in the summer of 1976. 

The entire mission (i.e., the two craft’s journeys) cost approximately $1 

billion.7 JPL engineers used the knowledge they gained developing the 

Mariner spacecraft in the 1960s and 1970s to design and fabricate the 

VO, and they completed this task with relatively few technical difficulties. The VLC team, on the other hand, “was tackling a new field . . . 

[and] . . . breaking much new technological ground.”8

 The prime contractor for developing the VLC, Martin Marietta, had to work through a 

long list of engineering challenges before it produced a reliable capsule 

(see figure 5.3 depicting assembly of the lander).

 5. “Joseph A. Stern,” 

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Planetary Protection for Mars

Figure 5.1 Elements of the VLC.

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When Biospheres Collide

Figure 5.2 The Viking lander.

The Viking lander that touched down on Mars contained far more 

sophisticated equipment than NASA’s previous robotic lander, the 

lunar Surveyor, and weighed twice as much. The Viking lander had to 

carry out a soft landing on a celestial body many times farther away 

than our Moon, and its mission goals were more ambitious. The Viking 

lander performed studies in three basic areas—imaging, organic analysis, and life detection. The craft took extensive pictures of the Martian 

surface and contained state-of-the-art laboratories and instruments 

that conducted detailed scientific analyses.9

The Viking mission had a vital planetary protection goal as well—

to prevent biological contamination of Mars during the mission’s 

search for life. To satisfy international as well as NASA planetary protection agreements and guidelines, “all launch vehicle and spacecraft 

 9. Nicholas Panagakos and Maurice Parker, “Viking Mars Launch Set for August 11,” in 

250
Planetary Protection for Mars

Figure 5.3 Viking spacecraft under assembly at Martin Marietta Aerospace near Denver, Colorado.

hardware injected into a Mars flight trajectory [were] considered to be 

possible sources of contamination for Mars.”10 This was NASA’s first 

opportunity to protect the environment of a planet that many scientists thought capable of supporting life. 

Astronomers believed that Mars was the planet most like Earth. 

Data taken by Mariner 9 in 1971 and 1972 revealed possible evidence 

of flowing, liquid water on the Martian surface during some period in 

its past. The Mariner evidence included photographs of braided channels that were reminiscent of dry riverbeds, which suggested that water 

had flowed there and increased the chances that Mars might harbor, or 

might have once harbored, life.11 Carl Sagan and Stanford geneticist 

 10.

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When Biospheres Collide

Figure 5.4 Joshua Lederberg with a model of the Viking spacecraft and launch vehicle. This 

picture was taken in an exobiology exhibit at the 1975 pre-Viking “Earth and Mars: The Role 

of Life” symposium held at the Kennedy Space Center.

and Nobel Laureate Joshua Lederberg (figure 5.4) noted that organisms 

“which extract their water requirements from hydrated minerals [minerals whose molecules are chemically combined with those of water] or 

from ice are considered possible on Mars.”12

During the Viking mission, scientists needed to walk a tightrope 

between preventing contamination of Mars with Earth organisms 

and conducting a rigorous scientific investigation that would generate important data on the Red Planet. This was not an easy line to 

walk. Microorganisms exist in large numbers almost everywhere on 

Earth, and thus NASA had to take extreme protective measures to 

 12.

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Planetary Protection for Mars

minimize their transport to Mars.13 NASA scientists believed it inevitable that some microorganisms would survive on or inside the spacecraft and took special precautions to avoid introducing these entities 

to the Martian surface. If such organisms contaminated Martian soil 

and then multiplied and spread from the original point of entry across 

the planet’s surface, a later mission might detect and mistake them 

for indigenous forms of life. Such terran life-forms might also impact 

and even destroy any existing Martian organisms. A 1966 statement 

by the American biologist K. C. Atwood expressed what a tragedy such 

an occurrence would be:

It is possible that Mars may provide our only 

chance to study life-forms of an entirely separate 

descent. The importance of this opportunity outranks 

every prospect; the effect on world thought of the 

discoveries to be made on Mars may compare with 

that of the works of Copernicus or Darwin. A careless 

blunder would destroy the opportunity. The reasons 

for the sterilization of spacecraft are clear: we do not 

know enough about Mars to predict with confidence 

the outcome of microbial contamination of its surface. 

Regrettable and irreversible results can be imagined. 

The means of avoiding these results are known; hence 

we must employ such means.14

To protect against the scientific tragedy that K. C. Atwood warned 

of, spacecraft to Mars had to be thoroughly sterilized. But that was 

not the only reason to remove microbial contamination from the 

vehicles. Martin Favero, a microbiologist who headed CDC’s spacecraft sterilization and planetary quarantine activities from 1964 to 

1972,15 commented that “with Viking, there were two reasons to sterilize the spacecraft. One was to make sure that the life detection 

 13.

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When Biospheres Collide

systems didn’t detect self-contamination, and secondly to prevent 

contamination of the planet.”16 On the Viking project, life-detection 

experiments and planetary protection activities had overlapping 

needs, in that they both required extreme microbial contamination 

control. 

Probabilistic Contamination Control Guidelines

Although directives written in 1959 by Abe Silverstein, NASA’s 

Director of Space Flight Programs at the time, called for absolute 

sterilization of spacecraft, U.S. space scientists soon proposed more 

realistic guidelines using probabilities of contamination as the basis 

for designing planetary protection procedures (see Chapter 2).17

Instead of the “abstract concept of sterilization,”18 NASA required 

microbe burden reductions estimated as effective for planetary protection, but not so severe that attaining them would damage spacecraft reliability. 

During the first decades of the space program, NASA and 

COSPAR issued forward contamination control guidelines for Mars 

and other missions that followed this approach. For instance, in 1964, 

COSPAR issued Resolution No. 26, which called for a probability of 

less than 1 × 10–4 that a spacecraft intended for planetary landing or 

atmospheric penetration would contain even one viable organism. In 

May 1966, COSPAR issued a more attainable recommendation that 

the contamination probability of a planet of biological interest be no 

more than 1 × 10–3. COSPAR also recommended that this standard 

be adopted by all countries conducting space exploration. The United 

States adopted the standard on 6 September 1967. 

 16.

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Planetary Protection for Mars

COSPAR apportioned the contamination risk among different 

nations and gave the United States a maximum allowable risk of 

4.4 × 10–4. In other words, NASA had to ensure that during a planet’s period of biological interest (originally 20 years but eventually 

lengthened to 50 years), the total contamination risk from all U.S. 

spacecraft did not exceed 4.4 × 10–4.

19 It was NASA’s responsibility 

how to suballocate this risk among its various missions. See Chapter 

3 for a more detailed discussion of these probabilistic approaches to 

planetary protection.20 

To satisfy COSPAR and NASA planetary protection policies, all 

launch vehicles and all spacecraft hardware that were sent on Mars 

flight trajectories had to be viewed as potential contamination sources 

for the planet. For the Viking mission, vehicles of concern included 

not only the spacecraft (consisting of the VO and VLC), but also the 

Centaur upper rocket stage that carried the spacecraft onto a trajectory toward Mars. After the spacecraft separated from it, Centaur’s 

flight path needed to be such that it would not impact and possibly 

contaminate Mars.21

Apportioning Contamination Probability Limits for a Mars Mission

NASA suballocated maximum contamination risks to each U.S. 

mission to Mars in a manner to conform with the COSPAR guideline 

that the total contamination probability by all U.S. spacecraft not 

be greater than 4.4 × 10–4. NASA’s suballocations varied depending 

on the class of the mission. Landers, for instance, were assigned a 

larger maximum contamination risk than orbiters and flybys.22 For 

Viking launches, NASA further divided this risk probability into three 

 19.

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When Biospheres Collide

subprobabilities, each of which applied to a different mechanism of 

potential planetary contamination: 

•	 Large impactibles: Parts of the spacecraft that might, through 

errors in trajectory determination or malfunctions, hit and 

contaminate Mars. NASA designed its procedures for deflecting 

and making midcourse corrections and trimming maneuvers to 

the spacecraft’s trajectory23 to minimize the risk of accidental 

planetary impacts. 

•	 Ejecta-flux: Organisms that may get dislodged from the 

sterile surfaces of the spacecraft and directly impact the 

planet. Such dislodgings could result from collisions with 

micrometeorites or other events.

•	 Lander sources of contamination. Organisms on the VLC that 

survive terminal sterilization procedures on Earth or organisms 

such as from other parts of the spacecraft that recontaminate 

the VLC after it is sterilized.24

In order for terrestrial organisms to actually contaminate Mars, 

they had to survive 1) space vacuum and temperatures, 2) space ultraviolet radiation flux, 3) Mars atmospheric entry, and 4) landing and 

subsequent release from the spacecraft. After this, the organisms had 

to actually grow and proliferate on Mars. NASA calculated the probability of contamination of Mars that took into account its estimates of 

the probabilities of these occurrences.25

The probability that viable terrestrial organisms escaping from 

the Viking lander would actually proliferate and spread, forming 

infected microenvironments on the Martian surface, depended not 

only on the characteristics of the organisms but also on the characteristics of the planet’s surface and microenvironments that they 

encountered. First, a microbe ejected from the lander needed to survive the following conditions:

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Planetary Protection for Mars

•	 Exposure to UV radiation.

•	 Exposure to extreme diurnal cycles of temperature.

Second, it required some way of being transported into a microenvironment capable of supporting it. Third, that microenvironment, 

according to the opinions of a 1970 SSB study, needed to have the following factors occurring nearly simultaneously to support the propagation of a hardy terrestrial microorganism:

•	 Water activity.

•	 Temperature above 0°C for at least 30 minutes during a Martian 

day.

•	 Nutrients including small amounts of water-soluble nitrogen, 

phosphorus, sulfur, and carbon.

•	 Fairly neutral pH values (between 5 and 8).

•	 Attenuation of UV flux by at least a factor of 1000.

•	 Absence of antimetabolites.26

The probability of growth was a key factor in a long chain of factors making up the probability that a planetary surface would be contaminated.27 The SSB study estimated the probability at 3 × 10–9 that 

growth and spreading of terrestrial organisms released on the Martian 

surface would occur. For the Viking project, NASA in consultation 

with SSB adopted a more conservative value of 10–6.

28

Early Concepts for Sterilizing Robot Mars Vehicles

NASA performed exhaustive studies in order to choose the best 

sterilization approaches. The Agency weighed costs, engineering issues, 

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When Biospheres Collide

available technology, and the “biological assurance”29 of reliable planetary 

protection that could be attained with different technologies. When NASA 

and its contractors began designing Viking, they considered chemical 

sterilization, and, in particular, ethylene oxide sterilization, as a possible 

approach. Ethylene oxide had serious dangers associated with it, however, 

in that it was quite a toxic and corrosive material30 as well as flammable;31

its vapors could readily form explosive mixtures in air.32

NASA also examined heat sterilization approaches, whose impacts 

were more controllable but required heat-resistant, robust spacecraft 

parts. In the words of Israel Taback, a Bionetics Corporation engineer 

and consultant to NASA, heat sterilization was “a clean and relatively 

painless solution that produced no overpowering problems beyond . . . 

building components capable of surviving the qualification testing and 

the sterilization temperatures.”33

NASA eventually decided that heat was the most predictable, reliable, and overall best sterilization environment to use.34 Part of the 

reason was that sterilization temperatures could be closely managed 

and kept within the acceptable range of all the components installed 

in the spacecraft. Other methods such as gas sterilization involved 

“unknown degrees of risk for those components and might require new 

technologies that carry their own burden of compromise.”35

In the mid-1960s, NASA worked with other space science-related 

organizations to develop a multistep approach applicable to preventing 

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Planetary Protection for Mars

forward contamination carried by robot landers to Mars. The approach 

involved four steps:

•	 Selecting or developing materials for spacecraft components 

that were as heat-resistant as possible in order to resist damage 

from thermal sterilization techniques.

•	 Engineering manufacturing processes to minimize biological 

loads accruing on VLCs. 

•	 Applying sterilizing heat to a range of components and 

assemblies.

•	 Conducting terminal sterilization of the entire VLC, then 

hermetically sealing it in order to maintain sterility until it had 

launched and left Earth’s atmosphere.36

NASA eventually included all of these steps in its sequential 

approach to preparing VLCs for their mission to Mars. All personnel 

levels of the Viking project, including NASA upper management, space 

and research center staffs, contractors, and vendors, engaged in efforts 

to protect the Martian environment from contamination by terrestrial 

microbes. Their efforts were applied to individual components as well 

as to entire VLCs. Details of the NASA process are described in the 

next section.

The Incremental Sterilization Procedure for Viking 

Lander Capsules

NASA’s sterilization plan37 for reducing the bioburden on the complex Viking Lander Capsules were formulated to be consistent with 

the Viking ’75 Program Quarantine Plan (M75-149-0) and responsive 

to NASA regulation NHB 8020.12, Planetary Quarantine Provisions 

for Unmanned Planetary Missions. NASA’s approach for the VLC 

employed an incremental procedure to reduce bioburden (microbial) 

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When Biospheres Collide

levels. The procedure began with parts selection and development as 

well as clean manufacturing efforts. It also used a series of sterilization 

steps in order to minimize the severity of any one sterilization increment, thus lowering the chances of damaging Viking equipment. 

NASA and its contractors applied some planetary protection measures to the unsterilized Viking Orbiter (VO) such as using clean 

assembly procedures, conducting careful bioassays of VO surfaces and 

factoring the results into the total bioburden estimates for the spacecraft, and designing the VO trajectory to avoid impact with the target 

planet. But the lion’s share of NASA’s forward contamination prevention effort went into the VLC design and included procedures for the 

actual landers that touched down on Mars as well as their descent 

capsules’ aeroshell–heat shield–parachute systems and their bioshield 

cap and base assembly (see figure 5.1). 

Each Viking lander was itself a complex piece of equipment, containing approximately 61,000 parts, none of which could be allowed to 

carry terrestrial microbes to Mars.38 One of the first steps in NASA’s 

approach that it carried out years before the first Viking craft launched 

was to select or develop the most robust parts for the VLC that were 

able to withstand sterilization environments without incurring damage.

Selecting and Developing Heat-Resistant Materials and Parts

NASA, and in particular JPL, began a testing and development program in the mid-1960s to determine which off-the-shelf materials and 

components withstood sterilization heating environments and continued 

to function properly. JPL oversaw the examination of more than 40,000 

parts of 262 different types. In addition, several aerospace contractors, 

including Boeing, conducted their own research efforts in this area.39

When available parts and materials failed the testing, development 

efforts to produce better alternatives began. Serious product development efforts were an extensive part of the Viking project, for “in 

the engineering of Mars-mission payloads, sterility and reliability are 

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related so inseparably that the problems of reliability control appear 

in the management of sterility assurance and planetary quarantine 

programs as well.”40

NASA and its contractors sought to procure general-usage parts 

or develop new parts demonstrating high reliability and insensitivity 

to dry-heat sterilization temperatures of up to 135°C. Nevertheless, 

Viking engineers had concerns about post-sterilization performances 

of certain materials and parts. Among the most difficult parts to make 

more heat-resistant were batteries and tape recorders. It was also problematic to sterilize the insides of transistors, capacitors, vacuum tubes, 

switches, propellants, and igniters without damaging them.41

It became clear that sterilizing a spacecraft containing extensive 

electronics and a spectrum of different materials and subassemblies 

constituted “a significantly different task from the problem of sterilizing a surgeon’s instruments or canned foods.”42 Examples of sterilization-related issues encountered for particular materials and parts are 

discussed below.

Solder. At the temperatures employed for sterilization, the tensile 

strength of the eutectic43 solder used on Viking components was low 

enough to be of concern.44 Sterilization procedures could cause some of 

these solders to become brittle and crack. It was thus critical to identify 

types of solder that could withstand the heating environment.45

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When Biospheres Collide

Conformal coatings. The problem with conformal coatings46 was 

that they were frequently applied to components in layers that were too 

thick. When subjected to heat, the coating then expanded and deformed 

the components, potentially causing them to fail. To avoid this problem, 

NASA demanded standardized thicknesses of conformal coatings.47

Electronic parts. Materials used in electronic assemblies such as 

capacitors could explode or become damaged during sterilization procedures; qualification tests needed to ensure that the parts selected 

were not prone to this problem.48

Fasteners. Attachment fasteners such as bolts sometimes had different compositions and rates of thermal expansion than the nuts or 

holes into which they were threaded. Such bolts could “creep,” or in 

other words, loosen and back out. Thus, project engineers needed to 

fully understand “the amount of heat-induced elongation”49 of different alloys so that precision estimates of sterilization impacts on parts 

made of different materials could be predicted.

Gyroscopes. Project engineers worried about temperature-induced 

outgassing and decay of epoxy resins within gyroscopes, which could 

seriously degrade reliability and performance. Also of concern was the 

mechanical integrity of entire gyroscope assemblies due to internal 

pressure buildup. The fluid used in the gyroscopes presented issues as 

well. It had to be heat-tolerant, able to flow readily through gyroscope 

orifices at a range of different temperatures, and dense enough to float 

the gimbals of the device.50

Recorder. Viking managers decided to design a new recorder that 

would meet heat compatibility requirements rather than modify existing equipment. The development program tested various materials, 

assembly processes, and components. Testing activities included evaluations of electronic parts, seals, lubricants, ball bearings, magnetic tape, 

and heads. Organic materials were used only when unavoidable, and 

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Planetary Protection for Mars

then only materials that had low outgassing properties. NASA designed 

the flight recorder’s transport assembly so that it was virtually all metal. 

Motor housing and capstan were fabricated from titanium in order to 

eliminate differences in coefficients of expansion that could result in 

damage to the recorder during heat sterilization. Engineers chose metallic recording tape in order to achieve heat tolerance. Dry lubricants were 

used on the tape, bearings, and gears, which tended to be more resistant 

to degradation under high temperatures than oil-based lubricants.51

Computer. The memory medium of the computer included a 

densely packed matrix of plated wire with individual strands only twothousandths of an inch in diameter. This design made the memory 

easily impacted by heat. Engineers built a capability into the computer 

to recognize temperature-dependent behavior and employ temperature-compensation devices.52

Batteries. Project engineers initially considered two battery types 

for the spacecraft—nickel-cadmium (NiCd) and silver-zinc (AgZn). 

Whichever batteries they chose had to have several features, including 

the following:

•	 Capacity to be sterilized.

•	 Long life (about 22 months).

•	 Capability to survive an 80-percent discharge during terminal 

descent and repeated 50-percent discharges per day during 

operations on the Martian surface. 

Table 5.1 summarizes the positive and negative features of both 

battery types. AgZn batteries had continuing problems with leakage 

after being subjected to heat sterilization environments. NiCd batteries, 

although of heavier weight, had long lives and the ability to be charged 

quickly and cycled thousands of times, and they were relatively tough. 

As a result, NASA selected NiCd batteries for use on missions.53

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When Biospheres Collide

Table 5.1 A comparison of NiCd and AgZn batteries.

NiCd AgZn

Advantages Very long life, due to insoluble 

electrodes

Light weight for the amount 

of energy stored (high energy 

density)

Able to be cycled thousands of 

times

Low self-discharge rate

Capable of rapid charging

Robust, able to survive 

rough handling

Easily sealable

Disadvantages Relatively heavy for the amount of 

energy stored (low energy density)

Difficult to design these batteries 

to achieve a long life

Rapid self-discharge rate Typically doesn’t even get a few 

hundred cycles

Requires a minimum rate of 

change

Difficult to reliably seal; subject to 

chemical leaks

Problems 

Observed

Nylon parts disintegrated 

(successfully replaced with 

polypropylene)

Cellophane parts disintegrated 

(successfully replaced with 

polypropylene)

Plastic cases cracked

Epoxy seals leaked when 

exposed to sterilization 

environments

Bioshield. Integral to the VLC was a contamination control barrier 

impervious to microbes that provided a reliable impediment to recontamination after the sterilization process ended. This barrier, termed 

a “bioshield” (see figure 5.5), remained sealed during and after terminal sterilization of the VLC and was not breached until postlaunch. 

Otherwise, resterilization would have been required to kill any biological contamination deposited on lander or aeroshell surfaces as well as 

those of the bioshield’s interior.

NASA spent considerable effort choosing the most appropriate 

types of materials for the bioshield. The materials needed to withstand 

sterilization regimes and reliably protect the interior of the VLC from 

recontamination, which could lead to forward contamination of Mars. 

Both rigid and flexible materials were considered as well as combinations of the two.

NASA seriously examined flexible film materials for the bioshield. 

Thin-film bags were currently used to isolate animals in a germ-free 

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Planetary Protection for Mars

state for prolonged periods of time, and NASA thought they might be 

applicable to containing a lander as well. Film materials such as 0.01-

inch thicknesses of cellulose acetate or fluorinated ethylene propylene 

(FEP) fluorocarbon, for instance, were capable of withstanding 400°F 

sterilization temperatures or higher—far more than needed for sterilizing a Mars landing capsule. Transparent films had the advantage of permitting interior spaces to be viewed, and the films’ flexibilities allowed 

objects within to be manipulated. Furthermore, the weight of such films 

was very low—a distinct advantage for spaceflight applications.

These films were, however, susceptible to penetration and tearing, 

which could lead to recontamination of the lander. In addition, the 

remotely controlled separation and jettisoning of a thin-film bag from 

a complex-shaped object was a difficult operation to design. The problems associated with handling such films, as well as the possibility of 

compromising an entire space mission through damage to a thin-film 

container, argued strongly against using such a containment material 

as a bioshield.

The container in which the Ranger spacecraft had been sterilized 

was completely rigid (the Ranger lunar exploration program is discussed in Chapter 2). Although sterilization was accomplished on the 

Ranger through the use of gaseous ethylene oxide, a similarly designed 

container was also possible for VLC terminal sterilization. One of the 

challenges of designing any bioshield container for the VLC, however, 

was that the internal pressure that built up during heating could rupture it and expose the lander to microbes. A dependable venting system thus had to be included in the design. Additionally, after cooling, 

the pressure within the bioshield would drop, leading to its possible 

collapse unless sterile gas was pumped in.54

Another approach that NASA considered was the combined use of 

rigid and flexible materials, which offered certain potential advantages. 

Where access to the interior space was required, flexible work stations 

could be incorporated in the wall of a rigid canister, rendering it a sort 

of flying glove box.55

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When Biospheres Collide

NASA eventually chose a material for the bioshield that was somewhat pliable, but also very tough and heat resistant (see figure 5.5). 

The Viking team constructed the bioshield cap and base out of coated, 

woven fiberglass only 0.005 inches (0.13 millimeters) thick, which cut 

down on weight. It would not crumple like a thin-film bag, however, 

because it was supported by stays of aluminum tubes.56

To provide added protection against recontamination of the lander, 

a positive air pressure was maintained within the bioshield during and 

following terminal sterilization. During the actual launch ascent, when 

outside pressure rapidly dropped, excess pressure within the VLC was 

vented through a biofilter that did not allow microbes to reenter. 

The above parts and materials were critical for dependable VLC 

operations during the mission. Viking personnel were also concerned 

about proper operation of the mission’s science experiments after sterilization. A particularly vital piece of equipment for analyzing Martian 

substances was the gas chromatograph mass spectrometer.

Gas chromatograph mass spectrometer (GCMS). Viking’s organic 

compound analysis capability depended on the proper functioning of 

its GCMS. The mission’s GCMS experiment cost $41 million to construct, about 4 percent of the entire mission budget.57 When examination of the GCMS indicated that it would have difficulty meeting 

planetary protection heat sterilization requirements, the Viking team 

grew quite concerned. 

The team had designed the spacecraft’s GCMS to analyze the 

composition of the Martian atmosphere and to identify chemical substances emitted by Martian soil when heated.58 These analyses were 

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Planetary Protection for Mars

Figure 5.5 The Viking bioshield.

key to Viking’s search for life. The instrument drew vaporized chemicals into its gas chromatograph (GC) section, which separated them 

into individual compounds. These were then drawn into the mass 

spectrometer (MS) section of the instrument, where they were ionized, 

the constituent compounds identified, and their individual quantities 

determined. The GCMS generated profiles for each compound and 

sent these data to Earth. 

Results of the organic chemistry analysis gave scientists insights 

into chemicals that may have been produced by forms of Martian life 

as well as by purely chemical means. The major aim of the organic 

chemistry investigation was to help determine if any Martian life had 

existed or currently existed, or “if the right organic compounds were 

present for the evolution of life in the future.”59 The organic chemistry 

experiment constituted a critical cross-check on the biological lifedetection experiments.

The main thrust of GCMS work was to support organic chemical 

evaluations, but it had other uses as well. Its analyses also yielded data 

on concentrations of volatile inorganic compounds such as ammonia, 

carbon dioxide, carbon monoxide, nitrogen dioxide, nitric oxide, sulfur 

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When Biospheres Collide

dioxide, and hydrogen sulfide. It was thus extremely important that 

the instrument operate correctly during the mission.

The GCMS used on Viking was not an off-the-shelf item, and its 

development ran into some serious snags. Langley Research Center 

(LaRC) initially assigned the development of a GCMS prototype suitable for Viking’s needs to JPL in August 1968.60 But defects in the 

Viking project’s management structure led to a serious planetaryprotection-related problem with the instrument. JPL independently 

developed the GCMS for the mission without paying sufficient regard 

to prime contractor Martin Marietta’s specifications. An unfortunate 

result of this was that JPL constructed the GCMS prototype using sensitive electronics whose tolerances to Viking’s sterilization environment were questionable. 

NASA eventually made GCMS development a separate program 

that it could better control, but qualifying the GCMS for the planetary protection heat sterilization regime remained an ongoing issue.61

Recurring troubles included seals and gaskets that became unstable 

when heat was applied. The most significant development issue according to Klause Biemann, the GCMS/Molecular Analysis Team Leader, 

concerned the instrument’s potting compounds.

62 These repeatedly 

broke down under heat sterilization conditions. This resulted in parts 

pulling away from the potting compounds, creating a danger of arcing (high-voltage electrical discharge) that could have severely damaged the GCMS. The GCMS team eventually dealt with this problem 

by obtaining more stable potting materials from Hughes Aircraft.63 A 

schematic of the GCMS is depicted in figure 5.6.

NASA’s heat sterilization protocol was a likely cause of problems 

in both Viking GCMSs. These problems were not corrected before the 

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Planetary Protection for Mars

Figure 5.6 The Viking GCMS.

two Viking spacecraft launched and ended up impacting, although fortunately in a minimal way, the search-for-life investigation. The GCMS 

aboard Viking’s Lander Capsule 1 (VLC-1) had gone through the heat 

qualification procedure for individual components and did not appear 

at that time to have a problem. But later, during terminal sterilization of the entire spacecraft, the VLC-1 GCMS developed a leak in 

its vacuum system. NASA had to make a difficult decision—leave the 

GCMS in place and live with the leak, or open up VLC-1’s bioshield 

and change out the instrument, which would have required that the 

entire VLC go through terminal sterilization another time. This might 

have resulted in missing the launch window.64

Dale Rushneck, the GCMS Principal Technical Manager, calculated 

precisely where the leak was in the GCMS, based on his knowledge of 

the flow dynamics through the instrument. He determined where the 

pressure had to be in order to produce the observed leak and narrowed down the problem to a particular fitting. If that fitting could 

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When Biospheres Collide

have been tightened, Rushneck was confident that the leak would disappear. But this couldn’t be done without removing the GCMS from 

the spacecraft and disassembling it. Instead, Rushneck calculated the 

magnitude of the leak, its contribution to the background noise in the 

instrument, and its estimated effect on the atmospheric analysis that 

the GCMS was going to do on Mars. He determined that the leak was 

small enough that it would not compromise any but the most sensitive 

of measurements. Furthermore, NASA had installed another GCMS 

on Viking Lander Capsule 2 (VLC-2), which could obtain some of the 

data that the first lander could not. NASA concluded that it was best to 

leave the GCMS in place in VLC-1.65

This decision turned out to be sound. Although the VLC-1 GCMS 

was not able to make some of the most sensitive of its planned measurements, the GCMS in VLC-2 successfully carried out similar measurements. One lesson learned from this experience, in Rushneck’s 

view, was that having a second spacecraft with redundant instrumentation land on the planet (even in a very different location) can greatly 

lessen the scientific impact of an instrument failure in either craft. 

The GCMS in VLC-2 did not, however, perform flawlessly. Because 

VLC-2 landed much closer to the Martian northern polar region than 

VLC-1, it was subjected to wider temperature variations, and the 

GCMS on board eventually failed. The GCMS team traced the cause 

of the failure to a high-voltage arc discharge in the power supply of a 

pump that kept the instrument clean. Critical connectors on this component had been potted during their fabrication back on Earth, and 

Rushneck postulated that a failure somewhere in this potting material 

led to the high-voltage arc discharge. He also believed that this probably would not have occurred if the material had not been subjected 

to, and weakened by, NASA’s heat sterilization regime.66 Thus, NASA’s 

planetary protection procedures may have hurt GCMS performance in 

both Viking landers. It is important to emphasize, however, that this 

was never proven and that both GCMSs performed up to a high enough 

standard that NASA staff considered them key tools for organic compound analysis and, in particular, Viking’s search for life.67

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Planetary Protection for Mars

Reducing Biological Loads Through Improved Manufacturing 

Processes

An important step in the planetary protection process was to minimize the biological loads that accumulated on spacecraft components 

during manufacturing activities. The more successful these efforts were, 

the less heat sterilization of those components was required, which 

reduced the amount of thermal stress that they were subjected to. These 

potentially useful steps for improving manufacturing processes included

•	 Maximizing the cleanliness of the basic raw materials and parts 

used in the manufacturing process.

•	 Controlling contamination within the manufacturing environment—for instance, reducing dust and contamination from 

personnel.

•	 Using cleanrooms for manufacturing whenever feasible.

•	 Physically cleaning subassemblies on a regular basis—wiping 

down, vacuuming, and blowing off all accessible surfaces.68

•	 Applying standard spacecraft cleaning procedures to all 

surfaces prior to mating.

•	 Implementing component packaging requirements that 

preserved their level of cleanliness.69

VLC planetary protection and heat sterilization activities were carried out at multiple locations, including the following: 

•	 Subcontractor facilities, which supplied parts as basic as 

individual fasteners and as complex as the biology instrument.

•	 Martin Marietta Corporation’s VLC assembly site in Denver. 

•	 NASA’s Kennedy Space Center, which eventually launched the 

vehicles.

Details of the sterilization efforts and responsibilities of these different facilities are discussed below and depicted in figure 5.7. 

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When Biospheres Collide

Figure 5.7 Sterilization activity sequence.

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Planetary Protection for Mars

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When Biospheres Collide

Subcontractor Responsibilities

NASA required manufacturers of many types of flight hardware, 

including replacement parts, to subject their components to a flight 

acceptance heat cycle. This had dual benefits:

•	 Verification of parts’ abilities to withstand heat sterilization 

environments.

•	 Bioburden reduction, especially of the following: 

•	 Encapsulated microbes—those located in the interior of 

parts and completely surrounded by a nonmetallic, solid 

material impervious to water vapor transmission.

•	 Mated-surface microbes—those hidden within interfaces 

between two surfaces.

Vendor flight acceptance heat cycling became a key step for incrementally achieving the required bioburden reduction on the VLC, 

thereby helping to minimize the necessary exposure time, and thermal stresses, of the terminal sterilization activity. But component suppliers that performed the heat cycling needed the equipment and the 

staff to do so. This added to their products’ costs and reduced the 

control that the prime contractor, Martin Marietta, had over the manufacturing process. Martin Marietta thus needed to consider all the pros 

and cons of heat cycling at component vendor facilities. In its VLC 

integration proposal, Martin Marietta specified that nonmetallic loose 

hardware would not undergo the flight acceptance tests at vendor sites 

but would instead be heat-screened at its Denver facility. As will be 

discussed in the next section, Martin Marietta also performed many 

VLC component sterilization procedures in Denver, and this eliminated the need for bioassays by subcontractors and vendors.70

Prime Contractor Responsibilities

The major mission of prime contractor Martin Marietta Corporation 

was to assemble and thoroughly test the VLC, preparing it for shipment 

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Planetary Protection for Mars

to KSC. To render the VLC ready for shipment, Martin Marietta needed 

to include several key planetary protection activities, including heat 

sterilization of many of the components. 

While Martin Marietta mainly assembled different parts into a finished VLC, it also had some module manufacturing responsibilities, in 

particular building electronics assemblies, after which it subjected them 

to a heat sterilization environment followed by a post-heating checkout 

to verify that the modules were compatible with the sterilization. Martin 

Marietta also subjected loose, nonmetallic hardware received from subcontractors, as well as the VLC antenna, to heat sterilization.71

Further planetary protection measures involved the design of the 

manufacturing environment. Periodic surface cleaning of spacecraft 

assemblies were scheduled in order to aid in bioburden reduction. All 

cleaning, assembly, and test operations of VLC systems as well as of 

the capsule itself were conducted in cleanrooms with personnel working under strict handling constraints and procedures. This minimized 

the bioburden accumulation on the VLC prior to terminal sterilization. 

In addition, NASA’s sterilization plan called for a heat compatibility 

flight acceptance test (FAT) on the entire VLC before sending it to 

KSC, in order to verify that it operated properly after heat processing. 

The FAT was primarily an engineering test rather than one designed 

for planetary protection purposes, but it had the side benefit of further 

reducing the VLC bioburden.72

Martin Marietta also needed to closely monitor the activities of 

Viking subcontractors who were manufacturing key parts of the spacecraft. Martin Marietta was “responsible for really making sure that the 

subcontractors all produced and delivered essentially clean items like 

the instruments and the spacecraft components.”73 To help accomplish 

this, Martin Marietta developed an approved parts list that subcontractors had to follow and also assigned a cadre of personnel “that lived 

with the [sub]contractors when they needed it from time to time and 

overlooked all of their activities.”74

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When Biospheres Collide

Langley and Bionetics Roles: Management and Verification

Langley Research Center’s Viking Project Office was officially responsible for everything that was done on the mission but actually acted 

chiefly in a management function. Langley oversaw Martin Marietta work 

on the VLC, JPL’s design and fabrication activities on the VO, and the 

design work of Glenn Research Center in Cleveland (known then as Lewis 

Research Center) on the Titan-Centaur launch vehicles. But very little 

technical work was actually performed by Langley—that was the responsibility of other NASA Centers, Martin Marietta, and the subcontractors. 

Langley primarily tracked and oversaw other groups’ efforts.75

Langley was greatly aided in its monitoring efforts by Bionetics 

Corporation, a company that was formed in 1969 for the purpose of 

supporting the Viking mission and, in particular, its planetary quarantine function. Langley was the company’s first customer. Bionetics 

acted as an independent verifier, largely to ensure that Martin Marietta 

put together the spacecraft that NASA wanted. Bionetics provided 

much-needed expertise in spacecraft sterilization, contamination control, and microbial analysis.76

NASA and its contractors conducted continuing microbiological 

assays and monitoring throughout the VLC assembly and sterilization 

process (see the section later in the chapter on bioassaying). Project staff 

employed data from these assays to predict the interim and endpoint 

burdens on the VLC, using a bioburden model. The data also predicted 

potential trouble spots in the assembly process, where microbial samples 

especially needed to be taken. The bioburden-model calculation prior to 

terminal sterilization and VLC models of temperature distribution during 

terminal sterilization were used to help determine the required time that 

the VLC needed to undergo the terminal sterilization process in order for 

its microbial burden to be reduced to NASA limits.77

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Planetary Protection for Mars

Kennedy Space Center’s Terminal Sterilization of the Viking 

Lander Capsule

KSC received the first Viking flight components during November 

and December of 1974, including the Titan 3E liquid-fueled core 

launch vehicle, the solid-fueled booster rockets, and the Centaur upper 

stage. Shortly thereafter on 4 January 1975, the first of the Viking 

Lander Capsules (VLC-1) arrived. It and its sister VLC were subjected 

to a battery of verification tests.78 KSC staff disassembled, inspected, 

and functionally checked each of the two VLCs to confirm that they 

were ready for their mission. During reassembly, KSC staff performed 

detailed bioassays in order to estimate the microbe load on each of 

the VLCs. These assays were key in determining “the duration of the 

terminal sterilization cycle necessary to satisfy both PP [planetary 

protection] and scientific investigation requirements.”79

The KSC terminal sterilization procedure consisted of a dry-heat 

process using an inert gas atmosphere of 97 percent nitrogen, 2.5 percent oxygen, and 0.5 percent other gases. Thermal analysis of the VLC 

had indicated that its interior would heat very slowly during terminal 

sterilization if heat was only applied to its exterior. This presented a 

serious problem to the integrity of its systems. As the VLC’s interior 

slowly rose to sterilization temperatures, components near its surface 

would heat much faster and be subjected to extremely long heating 

times, endangering their reliability. 

The Viking team found a way to bring interior temperatures up 

more quickly by injecting the hot nitrogen gas mixture directly into 

the VLC, including into its heating and coolant lines. Viking engineers 

helped in this effort by designing effective gas flow paths within the 

VLC.80 Internal circulation of the hot gases was very effective at lowering the total length of the heating cycle and reduced prolonged temperature gradients within the VLC that could generate thermal stresses 

and damage electronics and structural materials. Nitrogen was excel-

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When Biospheres Collide

lent for internally conducting the heat because it is an inert gas that 

was unlikely to react with the materials of the VLC.81 Heat was also 

supplied to the VLC interior by the radioisotope thermoelectric generators meant to provide electric power during the mission, as well as 

through use of their cooling loops within the bioshield. The end result 

was to heat the entire VLC much more uniformly and quickly than if 

heat had only been applied from the exterior, avoiding stress to certain 

of its components or inadequate sterilization of others.

KSC staff performed the terminal sterilization procedure in a 

thermal test chamber within the Center’s Spacecraft Assembly and 

Encapsulation Building, with the VLC bioshield sealed and pressurized. 

The VLC contained no propellants or tanks filled with pressurized gases 

at this point, although gas fill lines as well as the line filters were placed 

in the thermal chamber so that they could be sterilized for future use. 

The parameters of a particular VLC sterilization cycle were in 

part derived from bioload results of the last assay done on the lander 

prior to encapsulation into the bioshield.82 Selecting the best temperature profile for sterilization meant walking a tightrope between 

temperatures high enough to be lethal to microorganisms aboard the 

VLC, but low enough so as not to damage equipment. Based on NASAfunded research, lethality could be achieved for temperatures of at 

least 104°C. NASA established sterilization specifications for the temperature range of 104° to 125°C. Viking project management (with the 

concurrence of NASA’s Planetary Quarantine Office) selected a value 

between these temperatures, specifying that each VLC be exposed 

to 111.7°C for 30 hours after the coldest contaminated point reached 

that temperature. Some parts of a VLC heated sooner than others and 

experienced slightly higher temperatures.83

KSC staff placed VLC-2 in the thermal chamber on 15 June 1975 and, 

including ramp-up and ramp-down, subjected it to terminal sterilization 

for over 43 hours. Temperatures within VLC-2 reached as high as 116°C 

(241°F). The sterilization procedure for VLC-2 ended on 18 June, and the 

Viking staff completed its software and hardware operational readiness 

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testing on 19 June, after which capsule verification testing began. NASA 

staff moved VLC-1 into the thermal chamber by 20 June, but terminal 

sterilization did not begin until the Viking project team confirmed that 

VLC-2 had survived the procedure and continued to function properly.84

VLC-1’s terminal sterilization spanned a longer time period than VLC-2, 

almost 50 hours, over a period from 20 to 22 June. 

Mitigating recontamination. While the insides of individual components of the VLCs should have been adequately sterilized during 

heating procedures at sub- and prime contractor facilities, NASA 

expected that some of the surfaces of these components would get 

recontaminated during handling and transport. The terminal sterilization environment, however, took care of such situations by reducing 

“the population of microorganisms accruing on the exposed surfaces 

during assembly and test of the VLC.”85

Preventing further recontamination of the VLC after final assembly. 

The lander within the VLC needed to get electrically and mechanically 

connected to the VO in order for the entire spacecraft to operate correctly during the mission. These connections had to be made using procedures that would not recontaminate any part of the VLC’s interior, 

including the lander. To prevent such recontamination, the lander was 

designed to never directly interface with the VO. Connections from the 

lander interfaced instead with the bioshield that surrounded it, and the 

bioshield then interfaced with the VO. 

A component called the bioshield power assembly, or BPA, assisted 

in isolating the interior of the VLC. The BPA, which was mounted on 

the outside of the bioshield, provided the power interface between 

lander and VO. The BPA remained attached to the VO after separation 

from the VLC.86

 84.

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When Biospheres Collide

To provide added protection against recontamination of the interior 

of the VLC, positive air pressure was maintained within the bioshield 

during and following terminal sterilization that continued until after the 

launch. The details of this procedure will be discussed later in the chapter, in the section on planetary protection procedures during flight.

Gas and propellant insertion. After the functional checkout of the 

VLC, NASA staff transferred propellants and pressurized gases into the 

capsule. These materials, which were used in VLC descent and landing engines as well for attitude control, needed to be loaded through 

fill lines that pierced the bioshield. Thus, NASA had to develop procedures that did not carry contamination into the spacecraft lander 

capsule, either in the fuel and pressurized gases themselves or in the 

equipment used for fueling.87

Pressurant gas fill lines for the VLC as well as the line filters had 

been sterilized at the same time as the VLC, within the thermal chamber. The pressurant gases themselves were sterilized by being passed 

through the filters. The hydrazine propellant was self-sterilizing, in 

that it was toxic to terrestrial microbes and thus did not need additional sterilization. 

RTG coolant treatment. Finally, after the VLC was mated to the 

VO and it to the launch vehicle, NASA introduced a sporicide into the 

coolant loop for the radioisotope thermal generators, a source of shipboard power. The sporicide was made up of an alcohol-formaldehyde 

mixture whose sterilization effectiveness had been previously identified in tests.88

Factors in Selecting Sterilization Temperature Regimes 

When Viking staff was setting sterilization temperature regimes, 

it had to weigh various considerations to arrive at the best values. 

Planetary protection requirements and existing test data indicated 

that component sterilization temperatures had to be at least 100°C, 

the minimum temperature at which microorganism lethality could be 

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achieved. Mission staff who researched specialized time/temperature 

regimes for qualifying Viking parts, however, proposed temperatures 

as high as 145°C. “We began with a temperature that anyone would 

consider safe,” commented G. Calvin Broome, the Project Lander 

Science Instruments Manager, in order to be “pretty sure there won’t 

be any microbes left alive in there.”89

Many of the mission’s engineers were opposed to such high temperatures. Electronics engineers in particular recognized the difficulty 

of finding or designing electronic components and circuit boards able 

to withstand such a sterilization environment. Materials engineers also 

worried whether some substances would stand up to the intense heat 

but could not always identify adequate alternatives. Materials of concern included nonmetallics such as coatings, adhesives, and rubberlike parts used in O-rings, gaskets, and other types of seals.90 Such 

materials might develop weaknesses and flaws during the rigorous heat 

qualification tests and end up failing prematurely, possibly compromising the mission. 

Some nonmetallics were also prone to outgassing (emitting volatile compounds). These gases would condense on cooler surfaces and 

could contaminate and corrupt the results of science experiments.91

Furthermore, different metals and other materials had different expansion rates when heated. High temperatures could lead to mechanical 

strains on the equipment and eventual damage. 

Lower temperatures can adequately sterilize parts and materials 

if longer exposure times are employed. Lower temperatures also make 

the technical challenges of meeting planetary protection requirements easier—in particular, finding reliable parts and materials while 

keeping the probability of planetary contamination acceptably low. 

Extensive analyses of the impacts of time/temperature trades on dieoffs of microbial populations identified the particular trades that could 

be made without compromising contamination control92 and led NASA 

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When Biospheres Collide

to an effective approach for killing microorganisms that also allowed 

low enough temperatures—104° to 125°C—to not damage hardware. 

The exact temperature selected was a matter of choice for the mission staff, but different temperature choices necessitated different 

heating times. Sterilizing at 104°C required an order of magnitude 

more time to attain a certain bacterial reduction than sterilizing at 

125°C. For instance, if at 125°C, an acceptable bacterial reduction 

could be achieved in 0.5 hours, it would take 5 hours at 104°C to 

attain the same reduction. 

Sterilizing the spacecraft at lower temperatures definitely had its 

advantages, but this practice also had a risk associated with it. The biologists on the project insisted that “we must be sure we don’t contaminate the biological instrument,”93 which had been built to detect the 

presence of life. Proper functioning of this instrument was central to the 

success of the mission, and concerns regarding its possible contamination (including by other parts of the VLC itself that had not received as 

rigorous a sterilization protocol as the biology instrument) led the biology instrument team to incorporate additional sterilization treatment of 

the biology package prior to the landers’ terminal sterilization.94

In the end, NASA decided on a temperature of at least 111.7°C 

for the Viking landers’ terminal sterilization.95 For the qualification 

of individual parts and components, however, the project used higher 

temperatures in the range of 125° to 145°C, depending on the heat 

sensitivity of the particular object.96

NASA engineers believed that their strategy would ensure a high 

probability of adequate sterilization and extremely dependable mission 

hardware performance. One aspect of this strategy was to implement 

long temperature ramp times—the periods employed to heat components from ambient to sterilization temperatures and to cool them 

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back down to ambient. The longer the ramp times, the less thermal 

shock was visited on the electronic components. The term “thermal 

shock” refers to the uneven expansion or contraction of a component 

resulting from rapid or uneven heating or cooling. Cracking and other 

damage can occur when one part of a component has been raised or 

cooled to a different temperature than another part and therefore has 

expanded or contracted by a different amount.97

Another factor on which adequate sterilization depended had to 

do with a part’s or a spacecraft’s thermal inertia, a measure of its 

response time to external temperature changes. The higher the thermal inertia, the slower the response to external temperature changes. 

Thermal inertia depends on factors such as density, thermal conductivity (ability to transfer heat), and heat capacity (amount of heat 

required to raise the object’s temperature one degree). The importance of these factors for planetary protection was that if the details of 

an object’s thermal inertia were not understood, a sterilization protocol could not be chosen that would dependably elevate temperatures 

in regions buried deep within the object to levels that would kill any 

microorganisms present.98

Engineering Planetary Protection into Viking Component Designs

Viking components needed to do more than perform well and survive sterilization environments; they also needed to perform without 

doing damage to the target planet. The workings of every aspect of 

the spacecraft had to be analyzed to verify that this was so. While 

microbiological contamination was the chief danger to be prevented, 

the spacecraft was also capable of visiting chemical and mechanical 

damage on the Martian surface, and these potential problems too had 

to be mitigated. Different areas of the spacecraft that required forward 

contamination prevention actions are discussed below.

Propulsive fuel. Planetary protection requirements limited the 

lander’s acceptable fuel options. A type of fuel was needed that was 

unlikely to harbor or, even worse, nurture terrestrial microorganisms. 

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When Biospheres Collide

NASA eventually chose hydrazine as the propulsive fuel, partly 

because of its toxicity to such microorganisms.

In its analyses of the lander’s exhaust plume chemistry resulting 

from hydrazine combustion, NASA initially found problematic substances that could potentially contaminate the Martian surface in the 

areas where samples were going to be taken.99 Bob Polutchko, a Martin 

Marietta engineer who worked on the Viking project from 1968 to 1978 

and led many of its task groups commented that the team detected 

hydrogen cyanide in the exhaust,100 which is often involved in amino 

acid reactions. Since Viking was going to Mars to look for life, mission 

engineers wanted the lander exhaust to be more pure. Examination of 

the hydrazine propellant manufacturing process revealed that small 

quantities of aniline had been employed to get the final amounts of 

water out of the fuel. When aniline was burned in the presence of carbon dioxide, which was the case in the lander’s combustion chamber, 

hydrogen cyanide was produced. To correct this situation, NASA separated out the aniline through a repeated freezing and thawing process 

that produced hydrazine ice cubes. 

Lander engine nozzles. Martin Marietta staff tested their lander 

engine concept at NASA’s New Mexico White Sands Test Facility. They 

envisioned using three rocket engines to control the Viking lander as it 

descended its final 5,200 feet to the Martian surface.101 Multiple engines 

were needed in order to control the craft’s pitch and yaw. But during 

their testing of just one of the engines, they discovered a very disturbing occurrence—one that did not contaminate the Martian surface 

with bacteria but did chemically contaminate and severely disturb the 

surface. The engine’s exhaust during the test impacted soil that NASA 

believed was similar to what would be found on Mars. As the engine 

fired, it dug a 4-foot crater—a totally unacceptable situation. The lander 

was supposed to analyze an undisturbed, pristine Martian site for the 

possible presence of life. A jumbled, cratered, chemically contaminated 

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Planetary Protection for Mars

site that had been made so by lander engine exhaust was hardly a pristine location in which to search for life. Furthermore, the lander was not 

capable of reaching out far enough beyond the cratering to examine an 

undisturbed section of soil. This problem “became a program-stopper 

for the whole Viking”102 mission. It simply had to be solved.

When analyzing the fluid dynamics of the engine exhaust, Bob 

Polutchko and his team determined that “in a vacuum like in space 

the plume of that engine expands broadly—almost to 130 degrees from 

the axis of the engine. So it’s not a focused kind of plume. But you fire 

such an engine with an atmosphere around it that has pressure—now 

the atmosphere focuses that plume and, like a launch vehicle taking 

off, you see . . . the flame coming out in a very directional way, [similar 

to] a Bunsen burner or a propane torch.”103 Even the thin atmosphere 

on Mars had enough pressure to focus the engine’s exhaust plume sufficiently to dramatically disturb the planet’s virgin surface. 

Martin Marietta personnel conducted an intense redesign effort 

aimed at minimizing the “impingement effects”104 of the engine’s 

exhaust plume on the Martian surface. They evaluated 10 different 

engine nozzle configurations by measuring impingement pressures on 

a flat blast plate fitted with pressure sensors and calorimeters. 

Martin Marietta designed seven of these nozzle configurations. 

Another of those examined was a conventional bell nozzle, and the 

others were supplied by Rocket Research Corporation and TRW. The 

best design turned out to be one that Martin Marietta had come 

up with—to change the exhaust nozzle from each of lander’s three 

engines into 18 small nozzles and point each one slightly outward. 

This approach cost the lander only 3 percent in engine performance 

but reduced disruption of the Martian surface by a factor of 20 or 

more. The team’s final design “disturbed less than a millimeter [of 

depth] of the surface. The plume hardly touched the native surface. . . . There was no churning action of that plume . . . the combustion products of the engine kind of moved horizontally along the 

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When Biospheres Collide

ground without disturbing the surface material. A little bit of dust was 

about all it ever kicked up.”105

Planetary protection issues and limitations for the biology package. The Viking instruments that conducted searches for life needed 

special scrutiny. Even a small number of terrestrial organisms that 

managed to stow away within these instruments could have caused 

false positive results for the presence of life on the planet. They could 

also have presented a higher contamination risk to Mars than terrestrial organisms within other parts of the lander that did not contact or 

operate in such close proximity to the surface. 

Not surprisingly, the Viking biology team chose to implement 

more stringent requirements than the planetary protection guidelines 

required for the biology package. The team decided that the probability of contamination of the biology experiments had to be kept below 

one chance in one million (1 × 10–6).106 This implied that if the standard was met, there would be no more than a 1 × 10–6 chance of the 

biology package depositing a living organism on Mars. Such a stringent 

standard required that the biology package be subjected to additional 

cleaning and sterilization that was not needed for the rest of the VLC.

TRW Systems of Redondo Beach, California, began development of the Viking biology package in 1970 under contract to Martin 

Marietta Corporation, the VLC prime contractor. Design, fabrication, and testing of the biology package took five years; it was delivered in the spring of 1975. The TRW team built the biology package 

under cleanroom conditions that possibly exceeded the cleanliness 

of Martin Marietta’s facilities when the VLC was being assembled.107

 105.

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Planetary Protection for Mars

Thorough removal of organic materials from all parts was exceedingly important, and it was accomplished largely by using plasma 

cleaning methods, in which the object was immersed in an ionized 

gas. Bombardment with energetic ions is quite effective for surface 

contaminant removal, especially for very thin films of organic materials that remain after conventional cleaning.108

After its construction, TRW sterilized the biology package in a 

120°C (248°F) dry-nitrogen-atmosphere environment for 54 hours. 

This was a higher temperature environment than the biology package 

and the rest of the VLC would experience during terminal sterilization 

(which is discussed below). While the biology package was not the only 

component to be heat-qualified by its subcontractor, the biology package and its accompanying sample-path hardware were the only components to be sealed in a biological barrier during their sterilization 

and transport procedures in order to lower the risk of recontamination.

All gases admitted to chambers in which TRW tested the instrument poststerilization were filtered through 0.45-micrometer membranes. Personnel handling the instrument wore sterilized caps, gowns, 

and gloves, and the instrument was shipped within a sterilized nylon 

bag to protect it from contamination sources such as airborne particles. Preventing recontamination required a very sensitive operation 

when the mission team had to take the package out of its biological enclosure and install it in the VLC. It was the time at which the 

instrument was most at risk of recontamination.109

Viking’s biology package cost $59 million, or 6 percent of the entire 

mission cost.110 The instrument included three automated laboratories, a computer, and sophisticated electronics, all contained in a 

“Mars Lander Successfully Completes Sterilization,” NASA news release no. 75-181, 20 June 

1975, record 5503, NASA Historical Reference Collection; Walter O. Lowrie, aerospace 

consultant and retired president of the Missiles and Electronics Group, Martin Marietta 

Corporation, Orlando, FL, interview in Bionetics, Lessons Learned, p. 3.10.

 108. Pamela P. Ward, “Plasma Cleaning Techniques and Future Applications in Environmentally 

Conscious Manufacturing,” Sandia National Laboratories, no date given, http://www.sc.doe.

gov/epic/docs/555.pdf (accessed 8 October 2007); Sebastian Deiries, Armin Silber, Olaf Iwert, 

Evi Hummel, and Jean Louis Lizon, “Plasma Cleaning,” Optical Detector Team, European 

Southern Observatory, Garching, Germany, 2005, http://www.eso.org/projects/odt/ODTnew/

documentations/docs/paper_sd_2005.pdf.

 109. Brown et al., “The Biology Instrument,” pp. 140, 143.

 110. Dick and Strick, The Living Universe: NASA and the Development of Astrobiology, p. 80. 

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When Biospheres Collide

box roughly 1 cubic foot in volume. The team considered the biology 

package so complex that they sometimes referred to it as a miniature 

spacecraft. There was a price to pay, however, for its strict heat sterilization protocol. One impact was that it prevented glucose, a simple 

energy source, from being included in the experiment, for the hightemperature sterilization environment would have caused the glucose 

to decompose. Glucose’s sensitivity to high temperatures was unfortunate because most known organisms—even algae—can use glucose as 

a nutrient. Biologists believed that glucose would have been likely to 

nurture the growth of any existing Martian life and would have proved 

very useful in Viking’s life detection experiments.111

Enzymes are another type of material that is not typically heat 

stable, and the biology package’s sterilization environment generally 

precluded experiments that required them as well. In particular, the 

“J-band experiment,”112 which sought to detect a reaction between an 

organic dye and Martian organic macromolecules such as proteins or 

nucleic acids, had been under consideration for the biology package 

but was dropped because it required the use of an enzyme.113

Assessing Microbial Burdens at Each Stage of the 

Sterilization Process

NASA and its contractors conducted a continuing microbiological 

assay and monitoring program from the start of VLC assembly up until 

terminal sterilization. Data from these assays were essential for two 

reasons relating to prevention of the forward contamination of Mars:

•	 The data were necessary in order to calculate the required 

parameters of the terminal sterilization process.

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Planetary Protection for Mars

•	 The data also were needed to confirm that the probabilities of 

Martian contamination arising from the Viking missions were 

within their allocations.

The Viking team needed to control, and monitor where appropriate, three types of microbial burdens on VLC hardware: encapsulated, 

mated, and surface burdens. Encapsulated bioburdens—those contained within a component (such as a resistor or capacitor) would have 

been extremely difficult to monitor. However, each VLC flight component, as well as spare replacement components, was subjected to 

flight acceptance heat compatibility tests. That procedure eliminated 

the need for bioassays at the component level,114 many of which would 

have had to be performed at vendor facilities, and saved a considerable 

amount of personnel effort and expense. 

Mated bioburdens are those VLC areas where contaminated 

surfaces are pressed together so that subsequent handling cannot 

increase the microbial level. The Viking team assayed VLCs by taking a minimum of 25 different samples from these surfaces just before 

they were mated. All flight VLCs were assayed as well as the proof test 

capsule (PTC), a complete VLC assembly fabricated from flight-style 

parts and used for system-level qualification tests.115

Surface burdens on the VLC constituted the major type of microbial contamination used for terminal sterilization planning and calculations. A total of 250 surface burden samples were required to be 

taken for each flight VLC or PTC each time that it was assayed. The 

Viking team was required to conduct bioassays of an assembled capsule at each of the following milestones:

Martin Marietta Operations

•	 Just before environmental testing.

•	 Just before preparations to ship the capsule to KSC.

KSC Operations

•	 During disassembly after dry-mating the capsule to the VO.

•	 During reassembly.

•	 During integration of the VLC and VO.

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When Biospheres Collide

•	 Just before the VLC-VO assembly was encapsulated in the 

spacecraft fairing (nose cone).116

Sampling procedure. In order to bioassay VLC hardware, the 

Viking team used the swab technique specified in the Viking Uniform 

Microbiological Assay and Monitoring Procedures, PL-3701042. 

Whenever possible, 4 square inches of VLC surface was sampled by 

each swab, which was typically a small piece of absorbent material 

such as cotton attached to the end of a stick. On areas less than 4 

square inches, the actual area sampled was estimated from component 

drawings or measurements on similar hardware.117

Viking Orbiter Bioassessment

NASA analyzed the forward contamination risks presented by the 

VO and decided that it did not need sterilization. The Agency estimated that the VO’s mated and encapsulated bioburden would not contribute significantly to Mars contamination risks, although ejecta from 

VO surface bioburden due to meteoroid flux and particle dispersion 

could conceivably cause planetary contamination. Because of this possibility, NASA decided that monitoring was necessary and designated 

the VO’s large, exposed areas as critical zones within which bioassays 

were to be concentrated. The critical zones included the following:

•	 Structural areas, such as the scan platform.

•	 Solar panels and devices.

•	 Thermal shields and blankets.

•	 High gain antenna.

These zones constituted the majority of the VO surface area. NASA 

required that at least 250 samples be taken from these zones using a 

swab technique.118

Because the VO was not subjected to terminal sterilization, 

microbes possibly survived within the craft, and in the unlikely event 

that it crashed onto Mars, could have been released. An SSB study 

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Planetary Protection for Mars

addressed possible bioburden within the VO’s interior,119 where most 

microbes were subjected to temperatures estimated at 10° to 38°C. 

Although some cell dehydration would have occurred due to high vacuum, the SSB study believed that a fraction of the microbes—perhaps 

1 to 10 percent—still survived.120

Sterilization of Bioassay Equipment and Materials

All equipment and materials used for bioassays had to themselves 

be thoroughly sterilized, or else they could recontaminate the parts 

of the spacecraft being analyzed. Viking staff sterilized equipment 

such as test tubes and their racks by autoclaving it at temperatures 

of at least 121°C (250°F) for 20 minutes or more. The nutrient media 

used within these test tubes also had to be certified as sterile. This 

was done by letting it incubate at ambient temperature as well as at a 

warmer temperature of 32°C (90°F) for several days, then inspecting 

the media for any signs of microbe growth. Viking staff sterilized the 

isopropyl alcohol used in the assays by passing it through a certified 

sterile 0.25-micrometer filter into a presterilized Teflon or polypropylene squeeze bottle.121

Side Benefits of Planetary Protection Procedures

While planetary protection heat sterilization procedures were 

necessary for the integrity of scientific investigations, they also 

 119.

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When Biospheres Collide

produced valuable side benefits. The severe requirements on VLC 

components that rigorous sterilization treatments imposed led to use 

of tougher materials with enhanced dependabilities. The end result 

was a robust, “uniformly and highly reliable spacecraft”122 with a 

longer useful lifetime. This was borne out by the strong technical 

and scientific performances of both Viking landers, as well as their 

longevities. The lessons learned in accomplishing these improvements helped to advance electronics and materials manufacturing 

techniques.123

Planetary Protection Measures Implemented 

During the Journey to Mars

During the period from launch until touchdown on Mars, NASA 

introduced several procedures, described below, that proved useful for 

preventing forward contamination.

The Launch

As mentioned earlier, positive air pressure was maintained within 

the VLC’s bioshield during and following terminal sterilization in order 

to prevent recontamination. During the actual launch ascent, when 

outside pressure rapidly dropped, excess pressure within the VLC was 

vented through a biofilter that did not allow microbes to reenter. This 

venting was necessary in order to avoid the danger of the bioshield rupturing due to the pressure differential between its interior and exterior.

The bioshields were kept in place during the launch ascent and 

while the craft was still in Earth’s atmosphere in order to prevent any 

possibility of recontamination by atmospheric microbes. The space 

science community proposed various altitudes at which the bioshield 

could be opened without fear of contaminating the lander with 

 122.

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Planetary Protection for Mars

microbes. Tenney and Crawford124 suggested that a conservative value 

was at least 300,000 feet (roughly 60 miles or 90 kilometers). 

The Cruise Phase

A Titan/Centaur launch vehicle lifted the spacecraft from KSC into 

a 115-mile-high (185-kilometer) parking orbit. After the craft coasted 

in this orbit for 30 minutes, the Centaur rocket reignited to inject the 

spacecraft onto a trajectory toward Mars. The spacecraft then separated 

from the Centaur, which was not a sterilized piece of flight hardware. 

Afterward, the Centaur was deflected off of its flight path in order to 

prevent an eventual impact with, and possible contamination of, Mars.

Subsequent to the spacecraft beginning its cruise phase to Mars, 

NASA sent the command for explosive bolts on the craft to eject the 

cap of its bioshield (see figure 5.1). This took place well above the 

minimum altitude for this action that Tenney and Crawford had recommended. The explosive bolts as well as other separation explosive 

devices had to be carefully designed to avoid generating shock waves 

through the spacecraft or creating flying fragments and shrapnel, all of 

which could damage sensitive equipment.125

An additional risk associated with opening the bioshield was 

whether the VO, which was unsterilized, would recontaminate the 

VLC. Particles, chemicals, and possibly biotic material from the VO, 

including from the propellants of its rocket engines and from the gases 

emitted by its coatings, greases, and paints, were all potentially capable of contaminating the VLC.126 Extensive calculations and experimental study indicated that this was not likely to occur, but mission 

staff planned an extra prevention measure just to make sure. Before 

the spacecraft reached Mars, mission control turned it so that the VLC 

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When Biospheres Collide

faced toward the Sun, allowing ultraviolet solar radiation to provide a 

sterilant function on the capsule’s exposed surfaces.127

The Descent to Mars

When the Viking spacecraft reached the vicinity of Mars, the lander, 

nested in its descent capsule, separated from its bioshield base and the 

VO and headed toward the planet’s surface. Following this action, the 

VO ejected the bioshield base into space.128 To ensure that the unsterilized VO did not eventually intercept, impact, and contaminate Mars, its 

trajectory had to be carefully calculated and controlled.129

As the lander-descent capsule assembly approached the Martian 

surface, it passed through an entry heating phase caused by friction 

with the atmosphere. During this heating phase, the descent capsule’s 

aeroshell protected the lander’s sensitive equipment from overheating. 

After the heating phase ended, at an altitude of about 20,000 feet (6 

kilometers), the descent capsule’s parachute opened and the aeroshell 

was ejected. The parachute itself was jettisoned at about 1 mile (1.6 

kilometers) above the surface. The radar-controlled terminal propulsion system’s three engines then fired for 30 seconds to slow the lander 

for a gentle touchdown on Mars.130

The lander’s biology package included instruments sensitive 

enough to detect a single microbe. After the lander’s touchdown but 

before it took samples, these instruments detected no trace whatsoever of contaminants within the biology package itself. NASA believed 

this to be an indication that its sterilization procedure, at least for the 

biology package, was entirely effective.131

 127.

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Planetary Protection for Mars

Viking Findings Pertinent to Planetary Protection

Estimating the likelihood of terrestrial organisms propagating on 

Mars required a comparison between known physical and chemical 

limits to terrestrial growth and known and inferred conditions present 

on or just below the Martian surface.132 The two Viking landers sampled only several square meters of the Martian surface, and these were 

located at subpolar (nonpolar) sites. The landers conducted searches 

for life on soil sampled during the Martian summer and early fall, but 

only as deep as 6 centimeters (about 2.4 inches) below the surface. In 

other words, the Viking sites were hardly typical of all Martian climates and surface and subsurface characteristics. Nevertheless, NASA 

staff made certain conclusions regarding quarantine issues that it 

extrapolated to other regions of the planet, greater depths, and other 

seasons of the Martian year. These are summarized below for the specified regions of the planet.133

Subpolar Regions Within 6 Centimeters of the Surface

Viking scientists concluded that no terrestrial organisms could grow 

within a few centimeters of the surface in regions lying between Mars’s 

two residual polar caps. They based this judgment on the following:

•	 The presence of strong oxidating chemicals in samples taken by 

both Vikings.

•	 The absence of detectable organic compounds, which the 

oxidants were assumed to have decomposed.134

 132.

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When Biospheres Collide

•	 The belief that conditions found by both Vikings probably 

prevailed throughout Mars’s subpolar regions, based on

•	 The similarity in findings at both widely separated 

Viking landing sites.

•	 The strong probability that the oxidants found were 

products of atmospheric or atmosphere-regolith135

reactions, which would have been very pervasive 

throughout other regions of Mars as well.

•	 The result of extensive infrared mapping of the Martian 

surface, which did not reveal thermal heterogeneities 

indicative of any regions whose temperatures were more 

favorable to growth of terrestrial organisms.136

Viking scientists did recognize the possibility that small “oases” 

of warmer climates existed with environments more friendly to life 

and that these had been missed by the thermal mapping. Such locations would also be accessible, however, to the oxidating chemicals 

that decomposed organic substances. While Mars’s subpolar regions 

do contain large channels that space scientists believe were carved by 

flowing liquid water, this probably occurred more than a billion years 

ago. Thus the channels would have little impact on the present suitability of the planet for supporting Earth organisms.137

Subpolar Regions Deeper Than 6 Centimeters

The supposedly lethal surface conditions observed by Viking might 

not extend to deeper layers. The necessary depth to escape lethal 

conditions on the surface was not known to Viking scientists, mainly 

because the relationship between oxidating chemical quantities and 

their depth below the surface was unknown. What was believed, however, was that maximum temperatures fell rapidly with depth. In the 

northern hemisphere of Mars, at depths of 4 centimeters, Viking scientists estimated that maximum temperatures were 20°C below the 

 135.

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Planetary Protection for Mars

“minimum confirmed terrestrial growth temperature”138 of –15°C for 

terrestrial organisms.139 And at a depth of 24 centimeters, the maximum temperature was estimated at –50°C, which was 35°C below the 

minimum confirmed terrestrial growth temperature. At increased 

depths, it became more likely that an ice layer would be encountered, 

but due to the temperatures, scientists did not believe that it or any 

liquid water present would support the growth of any known terrestrial organisms.

Thus, due to temperature alone, the prevailing opinion of the 

Viking team was that terrestrial organisms would not propagate at 

depths deeper than 6 centimeters, although scientists did admit the 

possibility that some anomalous subsurface regions could be warmer 

and that there was a remote chance of some unknown microbe growing at temperatures below –15°C.140

Residual Polar Caps

As with the subpolar regions, the low temperatures mapped in 

the residual polar caps by infrared surveys convinced most scientists 

that known terrestrial microbes would not grow. There were, however, 

some anomalous areas that, while still far below freezing, raised the 

remote possibility that other, yet undiscovered thermal heterogeneities might be warm enough to support life. But if warmer regions 

did exist, they would probably be drier regions as well because water 

would rapidly distill or sublime unless special conditions were present 

to allow water to liquefy, such as a freezing point depression due to 

electrolytes in the water. Such a water reservoir, however, would be 

too cold in the opinion of the SSB committee to allow growth of terrestrial organisms.141

 138.

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When Biospheres Collide

Note: The above conclusions were based on Viking results and theories of the 1970s on what habitats would support life. See Chapter 7 

on later missions to Mars to see whether these conclusions changed.

Recommended Quarantine Strategy for Future Mars Missions

According to the SSB study, post-Viking flights to Mars should analyze sites shielded from ultraviolet radiation and the strong oxidant 

chemicals found on the surface. Thorough analysis would require subsurface sampling, and thus future landers would need to have equipment 

to penetrate the Martian surface to greater depths than Viking. Of particular interest are sites at the interface between the regolith and ice strata.

Regarding forward contamination prevention actions, the SSB 

study concluded that the probabilities of terrestrial organism growth 

on Mars were so low that “for the mission that conducts the first 

exploratory phase”142 of a subpolar region, terminal heat sterilization 

of the lander is not necessary. Ben Clark, Lockheed Martin’s Chief 

Scientist of Space Exploration Systems, explained that this did not 

refer to missions whose primary aims would include the search for life. 

Such missions would indeed “trigger the Viking protocol,” including 

the need for terminal sterilization.143

The SSB study was not opposed to the sterilization of exploratoryphase spacecraft, provided that it did not increase mission cost and 

had no impact on the lander’s scientific payload. But an otherwise 

beneficial experiment for an exploratory-phase mission should not be 

eliminated or its performance degraded because of “the imposition of 

unessential sterilization requirements.”144 The SSB recommendation 

was important in designing planetary protection protocols for Mars 

missions of the 1990s and 21st century, as is discussed in Chapter 7.

The VLCs were the first planetary landers designed to be fully 

sterilized. To accomplish this, the Viking program had to make great 

strides in advancing space vehicle technology to be able to withstand 

 142.

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Planetary Protection for Mars

the heat sterilization environment. The Viking mission was, in many 

respects, “the trail-blazer and pathfinder for NASA’s important future 

[lander] missions.”145 It generated invaluable data and guidelines for 

the field of planetary protection. In the words of Jim Martin, Viking 

Project Manager, Viking “needs to be out in front as both a standard 

and a filter for systems-level implementation.”146

For a timeline of major events from the Viking as well as other missions, see Appendix E. For a summary of planetary protection methodologies used on the Viking as well as other missions, see Appendix F. 

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6 SMALL BODIES OF THE 

SOLAR SYSTEM

Deep within volatile-rich bodies, certain environments . . . 

might provide protection of dormant organisms . . . 

—“Survival of Life on Asteroids, Comets and Other Small Bodies”1

An ejected rock could cocoon viable microbes for 

millions of years, delivering them safely to another planet.

—Review of Looking for Life, Searching the Solar System2

The solar system’s small bodies include planetary satellites, asteroids, meteoroids, and comets as well as particles from sources such as 

interplanetary and interstellar dust and the solar wind.3 These bodies typically have little or no atmosphere4

 and thus cannot support a 

surface ecosystem likely to resemble that of our own planet. In fact, 

we have no direct evidence that a living organism evolved or currently 

exists on any small solar system body. Nevertheless, certain conditions, such as the presence of water on or under the surface of the 

 1. B. C. Clark, A. L. Baker, A. F. Cheng, S. J. Clemett, D. McKay, H. Y. McSween, Jr., C. M. 

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When Biospheres Collide

body, might make it possible for life to exist. Some of the solar system’s 

small objects also contain abundant organic material and hydrothermal processes. Speculation that such bodies could serve as reservoirs 

of life has become of increasing interest to space scientists because of 

the identification of material transfer mechanisms between them and 

planets.5 Thus, the need for planetary protection measures to prevent 

both forward contamination to and back contamination from small 

bodies must at least be considered when missions are planned.

The Task Group on Sample Return 

from Small Solar System Bodies

Advances in planetary science and technology in recent decades 

enable increasingly active space exploration, including the capacity 

to collect and return samples to Earth from all over the solar system. 

Recognizing this, NASA asked the Space Studies Board (SSB), formerly 

called the Space Science Board, of the National Research Council (NRC) 

to “assess the potential for a living entity to be contained in or on samples 

returned from planetary satellites and other small solar system bodies 

such as asteroids and comets.”6

 In response, SSB established the Task 

Group on Sample Return from Small Solar System Bodies, which extensively reviewed existing technical reports, interviewed NASA representatives and space scientists, and held a workshop to understand the wide 

range of perspectives. The Task Group attempted to identify the following:

•	 Detectable differences among small solar system bodies that 

would affect potential-for-life assessments.

•	 Scientific investigations that needed to be conducted to reduce 

the uncertainty in such assessments.

The Task Group asked the key planetary protection question: 

What risk do samples returned to Earth from spaceflight missions 

pose, as compared to “the natural influx of material that enters Earth’s 

 5. Clark et al., “Survival of Life,” 521.

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Small Bodies of the Solar System

atmosphere as interplanetary dust particles, meteorites, and other 

small impactors”?7 To evaluate this risk, the Task Group studied data 

from Earth, meteorites, the Moon, and astronomical and spacecraft 

observations to determine how samples returned from small solar system bodies should to be handled as opposed to those returned from a 

planet such as Mars.

The Task Group needed to identify necessary conditions for the 

origin and survival of living microorganisms, including dormant as 

well as metabolically active organisms. The group formulated six questions relevant to the search for life on small bodies:

1. Was there ever liquid water in or on the target body? 

2. Were metabolically useful energy sources ever present? 

3. Was there ever sufficient organic matter (or CO2

 or carbonates) 

in or on the target body to support life? 

4. After the disappearance of liquid water, was the target body 

subjected to extreme temperatures (i.e., >160°C)? 

5. Was sufficient radiation present to sterilize terrestrial-like 

life-forms? 

6. Is there, or has there been, a natural influx to Earth from the 

target body of meteorites or material equivalent to a sample 

returned?8

The Task Group answered these questions as best it could, given 

the existing scientific evidence. By so doing, the group defined the 

potentials for living entities to exist on a variety of small body types. 

Subsequent sections of this chapter describe these biological potentials, as well as others identified by NASA or international space organizations, and specify the planetary protection measures that need or 

will need to be put in place before these small objects are visited.

The Viability and Survivability of Microorganisms

Microorganisms have a far higher probability than multicellular organisms to remain viable on small bodies of the solar system 

 7. Ibid.,

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When Biospheres Collide

because they are able to adapt to a wider spectrum of environmental conditions, either as metabolically active organisms or as dormant forms. Single-celled microbes have successfully invaded every 

niche of our terrestrial biosphere and make up the majority of Earth’s 

biomass. Microbes grow on land and in fresh and salt water, within 

larger organisms, and in the extreme environments of deep-sea 

trenches and radically cold and icy, subzero locations that would kill 

other forms of life. Such robust microbes often have certain physiological tools facilitating their survival in their particular niche, such 

as the following:

•	 Protective layers of material and pigments that shield them 

from ultraviolet (UV) or ionizing radiation.

•	 Active, efficient DNA or other cell repair mechanisms.

•	 Spore-forming capabilities allowing them to remain metabolically 

frozen.

•	 Adaptability to desiccation (absence of water). Tychonema spp. 

for instance can survive where there is virtually no water.

•	 Halophilic capability—able to survive and even thrive in 

highly saline conditions (such as 30-percent sodium chloride 

solutions).

•	 Barophilic capability—able to propagate under high-pressure 

conditions, such as at the bottom of the deepest ocean 

trenches—11,000 meters (36,000 feet) below the surface.

•	 Acidophilic or alkalophilic capability—growth under extremely low 

or high pH conditions. Ferroplasma, for instance, grows at pH 0 in 

acid mine drainage. These extremophiles use various defenses such 

as reinforcing their cell membranes and removing hydrogen ions in 

order to keep their internal pH at a neutral 6.5 to 7.0.

•	 Autotrophic—able to use carbon dioxide as its source of carbon.

•	 Able to draw energy from various inorganic chemicals, such as 

sulfur, ammonia, and iron compounds. Thermoproteus spp., for 

instance, derives its energy from the reduction of elemental sulfur.9

 9. Mindy Richlen, “Microbial Life in Acidic Environments,” Microbial Life Educational 

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Small Bodies of the Solar System

For all their adaptability, metabolically active cells generally 

require several critical conditions for their survival:

•	 Presence of liquid water.

•	 Accessible energy source. These can be photochemical sources, 

which are available at the body’s surface, or various deeply 

buried sources.

•	 Temperatures generally no higher than 160°C (there are, however, 

ocean-vent sulfur-oxidizing bacteria communities that survive in 

volcanically heated water of 110° to 360°C [230° to 680°F]).

•	 Carbon source.

•	 Shielding from high-intensity or long-term exposure to ionizing 

or UV radiation.10

Dormant microbial life-forms do not require such stringent conditions for their survival. The capacity of many organisms to go dormant by forming cysts or spores permits them to survive greater 

temperature ranges for extended periods of times. Certain microbes 

show evidence of having survived for thousands of years, and possibly far longer, if they are protected from ionizing radiation fluxes. For 

instance, Streptomyces spp. as well as certain fungi have been isolated 

from a 5,300-year-old human corpse. In addition, one account reports 

microbes preserved in arctic and antarctic permafrost for 3 million 

years;11 another claims the cultivation of spore-forming Bacillus 

sphaericus taken from the abdomen of a bee entombed in amber that 

was 25 to 40 million years old.

12

 10.

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When Biospheres Collide

Surface Environments Hostile to Any Form of Life

Conditions on or near the surfaces of the solar system’s small, irregular bodies are typically unfavorable for metabolically active life to survive and may be unfavorable as well for sporulated life-forms. The space 

environment has characteristics that tend to sterilize the surfaces of 

small bodies. The three strongest sterilizing factors are as follows:13

•	 Ionizing radiation.

•	 Thermal inactivation.

•	 Vacuum.

Each of these factors significantly impacts the survivabilities of 

microorganisms. In combination, these factors greatly lower the probability of life existing on the surface of a small body. 

Ionizing Radiation 

Lack of an atmosphere implies intense exposure to damaging 

forms of radiation. Ionizing radiation from cosmic rays and solar particles consists of protons and ions of sufficient energy to directly destroy 

chemical bonds and inactivate molecular structures as well as to cause 

the formation of chemically damaging free radicals. Solar UV radiation, with its short wavelengths and, especially in the inner solar system, its high intensities, also damages molecules. 

Types of radiation with the highest energy transfer to a cell are 

especially destructive. A single high-energy particle, for instance, can 

cause a double-strand break of a DNA helix. Cosmic rays, in particular, 

are rich in damaging, high atomic number and energy (HZE) particles.14

Ionizing radiation degrades all kinds of matter, including organic 

molecules.15 The impact of ionizing radiation on living cells, how-

 13.

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Small Bodies of the Solar System

ever, is far from uniform. While it often causes cell lethality, its effect 

depends on cell size as well as DNA and RNA content, nuclear size, 

and ploidy (the number of sets of chromosomes).16

Some microbes have developed amazing tolerances to ionizing 

radiation. Deinococcus radiodurans, for instance, was discovered in 

1956 at the Oregon Agricultural Experiment Station in a can of ground 

meat that had spoiled despite exposure to radiation in the megarad 

range. The name of the organism literally means “strange berry that 

withstands radiation,”17 and it is the most DNA damage-tolerant 

organism ever identified. Its ability to survive extreme environments 

is attributed to its aptitude for quickly repairing damaged chromosome fragments, usually within 12 to 24 hours. Part of this process 

involves cutting usable DNA from another molecule and inserting it 

into the damaged strand. Marvin Frazier, who was the director of the 

Department of Energy’s Microbial Genome Program, which funded 

a project to sequence all of Deinococcus radiodurans’s genes, commented that this was the type of organism that might be able to survive interstellar journeys.18

Thermal Inactivation

Solar heating in our planetary system causes high temperatures 

on parts of a celestial body that are not shaded and may lead to thermal inactivation of any microbes on those surfaces. Inactivation comes 

about through damage to a cell’s constituent parts, including its membranes, metabolic equipment, and genomes, with the level of damage 

increasing rapidly as the temperature rises. 

Thermal inactivation of a cell may involve the disruption of a 

critical chemical bond in an essential molecule. DNA structures are 

 16.

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When Biospheres Collide

particularly vulnerable due to their reliance on relatively weak hydrogen bonds. All microorganisms, however, have built-in monitoring and 

repair mechanisms that can sometimes fix the above structures before 

they degrade enough that they cease to function.19

Most microorganisms that have been observed are quite vulnerable 

to heat, although there are exceptions to this. 

An organism designated “strain 121” was isolated from a water 

sample collected in an active, 300°C vent named Finn in the Juan 

de Fuca Ridge of the northeast Pacific Ocean. The microbe exhibited 

growth at 121°C, the typical temperature of an autoclave, which is 

employed in hospitals to kill microbes and their heat-resistant spores 

after an hour or so. Strain 121, in fact, doubled its numbers after 24 

hours at 121°C.20 The upper temperature limit for life is a critical 

parameter because it defines the boundary on organism survival in hot 

environments, either terrestrial or extraterrestrial. As mentioned earlier in the chapter, sulfur-oxidizing microbial communities have been 

found in hydrothermal vents emitting waters as hot as 360°C. Ironreducing microorganisms have been found in similar environments.

Vacuum

Unlike planets, most small bodies do not have strong enough gravitational fields to retain substantial atmospheres (Saturn’s moon Titan 

is an exception to this), leading to vacuum or near-vacuum conditions 

on their surfaces. In such environments, microbes cannot biotically 

employ atmospheric gases such as water vapor; hydrogen; hydrogen 

sulfide; carbon monoxide; carbon dioxide; and oxides of nitrogen, 

ammonia, or methane, as they do on Earth. Over an extended time 

period, high-vacuum conditions cause extreme desiccation of microorganisms, damage to DNA and membranes, and volatization of low 

molecular weight organic compounds.

Transformation of the microbes exposed to desiccating conditions 

into metabolically dormant forms—spores or cysts—is generally the 

 19.

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Small Bodies of the Solar System

most successful response for keeping the cell alive. This response also 

enhances its ability to withstand radiation and temperature extremes. 

Studies of Bacillus subtilis spores in space revealed an ability to 

survive up to six years if shielded from UV radiation. In fact, one in 

10,000 of these spores survived even when unshielded. Although this 

finding has potential implications for microbe survivabilities on small 

bodies, it would be unreliable to extrapolate these survivabilities to 

residence times of thousands or millions of years in space.21

Spore formation does not always protect the cells against extremely 

dry conditions. Research by Dose et al. suggests that at temperatures 

of around 20°C, dry environments lead to deleterious reactions of dormant cells’ structures and DNA, limiting half-lives of the organisms to 

only a few decades, unless their dormancy is interrupted by a metabolically active period and the presence of liquid water. This is because 

a transient period of such conditions allows cells to repair their damage. Spore half-lives may, however, reach geological time periods when 

temperatures remain low enough to slow down chemical reaction 

rates to near zero. This slowdown typically occurs at temperatures of 

around –130°C (–200°F) or lower.22

Initiation of Life on a Small Body: 

Endogenous and Exogenous Sources 

In spite of the hostile conditions discussed above, life may possibly exist on some small bodies of the solar system. If so, it might have 

arisen through endogenous sources—those within the solar system 

body itself. Life could also have arisen through exogenous sources, 

in that it began elsewhere and was transported to its present location. 

 21.

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When Biospheres Collide

Endogenous Sources

The probability of life originating on a small solar system body 

appears to be far less than the chances of it beginning on a planet. 

Small body surface areas and volumes are orders of magnitude less 

than those of planets and thus provide fewer possible microenvironments for prebiotic chemical processes. But more significant, planets 

(as well as some satellites) have a greater likelihood of providing abundant liquid water and a diversity of environmental conditions that may 

be critical for the initiation of life. Because of their stronger gravitational fields, planets can hold onto chemically reactive atmospheres 

with potentially important dynamic processes such as tides, streamflow, turbulence, convection, and variable weather.23

Although small bodies are less likely than planets to have harbored 

the beginnings of life, certain meteorites are rich in organic chemicals and also show signs of having been in contact with liquid water. 

Studies of carbonaceous meteorites revealed that they once contained 

moderate- or high-temperature water,24 while the Murchison meteorite 

(CM2) had over 600 different organic compounds, including proteinforming amino acids and DNA-forming nucleotide bases.25 These data 

suggest that although unlikely, it is at least conceptually possible that 

at some point in the solar system’s past, life may have arisen endogenously in its small bodies. 

Scientists have considered whether, if life did arise spontaneously 

on a small solar system body, but then was frozen and possibly desiccated, could it have survived to the present day? The three major 

sterilizing factors discussed in the previous section (ionizing radiation, 

thermal inactivation, and vacuum) would have made this unlikely, but 

if the organisms spent the eons buried deep enough to be shielded 

 23.

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Small Bodies of the Solar System

from ionizing radiation and protected by a layer of ice or other means 

of encapsulation from the impacts of a hard vacuum, then they might 

have survived. 

If such organisms were buried deep in the body, however, then 

the possibility of a spacecraft excavating and sampling them would 

be small indeed. A natural event could have recently (from a geologic 

perspective) excavated them to a location within a meter or so of the 

surface. But this would not have been a likely event except, perhaps, 

in the case of comets. When a comet passes through the inner solar 

system, ice layers sublimate and a blow-off of materials occurs. Most 

comets experience high material-loss rates when penetrating the 

inner solar system—as much as several meters of surface during each 

perihelion passage. Thus, comets experience a natural means of excavation independent of impacts with other bodies. Endogenous materials, including life-forms that had been protected since the early years 

of the solar system, could conceivably be exposed during one of a 

comet’s visits to the inner solar system region.26 Planetary protection 

measures for spacecraft exploring a comet have typically included 

the requirement to ensure a very low probability of accidental impact 

with the body.

Exogenous Sources

It is possible that by means of impacts between celestial bodies, 

biota were flung into space and traveled through the solar system. It 

would have been physically easier and perhaps more likely to remove 

biota from a body with weak, rather than strong, gravity and one with 

little atmosphere rather than a dense blanket of gases. It would also 

have required less energy to transport biota inward toward the Sun 

rather than outward. Biota could have been transported onto and carried by small bodies such as comets, asteroids, and meteoroids. 

An important planetary protection consideration that scientists 

have raised regarding small bodies is that, if some indeed do carry life 

and if such bodies have already impacted a target planet, then does 

 26.

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When Biospheres Collide

this not obviate the need for sterilizing spacecraft headed there? In 

particular, Gladman et al. examined the issue of whether expensive 

sterilization activities are justified for lander missions to Mars if meteorites from Earth, formed when some small body impacted our planet, 

have already found their way to Mars. Studying the orbital details of 

any terrene (Earthly) meteorites that exist has direct relevance to forward contamination questions such as this.27

Cross-contamination of materials among solar system bodies has 

been appreciable, according to existing data. The analysis of many 

meteorites, for instance, has revealed that they contain centimetersized clasts (constituents, grains, or fragments of sediments or rocks) 

from foreign parent bodies. Transfer of life-forms is thus conceivable. 

This possibility of cross-contamination among celestial bodies has 

“reduced the degree of confidence in the inherent safety of a sample 

returned”28 to Earth from a small solar system body. 

Missions to the small bodies of the solar system have already been 

conducted, while others have been proposed and are in the planning 

stages. Some of the missions involved or will involve sample return, 

requiring examination of planetary protection issues. Natural sterilizing factors have a range of expected impacts on such missions, 

depending on the locations, characteristics, and histories of the target bodies and the depths within them from which samples will be 

taken. Because of the radically different types of bodies and missions 

to explore them, each mission requires a separate assessment to determine the extent to which forward and backward contamination should 

be of concern.29

 27.

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Small Bodies of the Solar System

Our Moon Revisited: The Possibility of Ice Deposits

The elaborate quarantine and analysis procedures carried out at the 

Lunar Receiving Laboratory after the Apollo 11, 12, and 14 flights did 

not reveal any indication of life on our Moon. All return samples were 

certified as safe by the Interagency Committee on Back Contamination 

(see Chapter 4 on the Apollo program for a fuller discussion of this). 

Since the release of the lunar samples, “there have been no discernible 

adverse consequences for researchers or for Earth’s ecosystem.”30

No water was detected in lunar rocks. The SSB Task Group believed, 

given the existing data, that no special containment was needed for samples returned from the Moon. Hypotheses have been put forth, however, 

that ice could exist in lunar polar regions, accreted as a result of comet 

impacts.31 While most ice delivered by comets would sublimate into 

water vapor and escape into space due to high surface temperatures during lunar daytime hours, a small fraction of the ice could have reached 

permanently shadowed “cold traps”32 and remained stable over geologic 

time periods. Such traps may have formed near the Moon’s poles in craters whose walls perennially block the Sun’s light from reaching some 

sections of the crater floor.

Because solar radiation never directly illuminates cold traps, and 

because they do not emit much infrared or other types of radiation of 

their own, they are quite difficult to observe from Earth-based instruments. Frozen volatiles such as ice have a higher reflectivity to radar 

waves, however, than silicate rocks and also preserve the circular 

polarization sense of the scattered radar signal, and so under the right 

conditions ice at the lunar poles can be observable.

The Clementine mission, a joint endeavor between the Strategic 

Defense Initiative Organization and NASA, conducted numerous 

observations of the Moon in 1994. The Clementine spacecraft achieved 

 30.

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When Biospheres Collide

lunar orbit on 19 February and remained in orbit for 71 days, taking 

nearly 1 million images of the Moon at 11 different wavelengths, from 

the ultraviolet to the near-infrared parts of the spectrum.33 Some of 

these images yielded important data regarding the lunar polar regions. 

The lunar south pole is located within the South Pole-Aitken basin, 

an impact crater, and its relative elevation is likely several kilometers below the average radius of the Moon, resulting in areas that are 

always in shadow. Data from Clementine indicated that as much as 

15,500 square kilometers of south polar terrain, approximately twice 

the area of Puerto Rico,34 may be permanently in shadow, as well as 

a lesser area around the north pole.35 Clementine also generated data 

suggestive of polar ice, although Earth-based measurements from the 

Arecibo observatory36 raised questions about this.

More recent data from the Lunar Prospector, a NASA Discovery 

Mission that launched in 1998, provided compelling evidence of 

between 10 and 300 million tons of water ice in the Moon’s polar 

region (and a greater amount, surprisingly, near the north pole rather 

than the south pole).37 The existence of ice in lunar polar regions 

was by no means universally accepted, however. Based on what he 

considered more realistic water transport mechanisms and modeling approaches, R. R. Hodges of the Center for Space Sciences at the 

University of Texas held in a 2002 paper that “the concept of water ice 

at the lunar poles is insupportable.”38

In October 2009, NASA’s Lunar CRater Observation and Sensing 

Satellite, or LCROSS, may have “opened a new chapter in our understanding 

 33.

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Small Bodies of the Solar System

of the moon”39 when the impact of its Centaur upper stage rocket apparently uncovered water in the Cabeus crater, a permanently shadowed 

region near the lunar south pole. LCROSS findings indicated that water 

could be more widespread and in greater quantity than previously suspected. Then in 2010, Spudis et al. published data from NASA radar flying 

aboard India’s Chandrayaan-1 spacecraft that suggested the existence of 

ice deposits near the lunar north pole. The data, which were taken the 

year before, are consistent with the existence of more than 40 small craters ranging in diameter from 1 to 9 miles (2 to 15 kilometers) containing 

water ice. Although the total amount of ice depends on its thickness in 

each crater, scientists estimated there could be 600 million metric tons or 

more in the craters.40

If lunar polar ice deposits do exist and were delivered by comets or water-rich asteroids, they could have sublimated directly from 

solid to vapor phase upon impact and then back to solid when they 

condensed.41 Liquid-phase water likely never existed on the Moon, 

with its lack of an atmosphere. Nevertheless, if comet-delivered ice 

contained dormant microbes and if fragments of this ice reached cold 

traps on the Moon without sublimating, the possibility exists that 

such microbes could still be present. If ice deposits are confirmed 

on the Moon and samples are taken, planetary protection procedures 

would need to be strongly considered for preventing possible back 

contamination of Earth. Such regions may be declared by COSPAR 

to be special regions requiring additional care when studying them.42

Planetary protection measures may also be applicable if lunar ices 

were excavated and used as in situ resources for astronauts and mission operations.43

 39.

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When Biospheres Collide

Phobos and Deimos:

The Small, Rocky Satellites of Mars

The two moons of Mars—Phobos and Deimos—are rocky, irregularly shaped, and tiny compared to our Moon. Phobos has a maximum 

dimension of 27 kilometers (17 miles) and Deimos, only 15 kilometers (9 

miles). They are thus similar in size to many asteroids. One or both may 

in fact be captured asteroids, although such a mechanism would probably not have produced Deimos’s near-circular, near-equatorial orbit. A 

more probable history of the two moons may be that they coformed with 

Mars out of material left over from the planet’s creation.44

Phobos and Deimos are not likely locations in which to find biological 

organisms or evidence of past life. If biological material was at some time 

formed within the moons themselves, it would probably have been early 

in the bodies’ histories, and such life-forms would long ago have received 

enough radiation from natural abundances of uranium, potassium, and 

thorium within the moons “to eliminate the most radiation-resistant 

microorganisms known.”45 The top several meters of surface would also 

have received enough cosmic-ray and solar-flare proton flux to ensure 

its sterility. If, however, voids within the moons were filled with ice that 

contained microbes, these life-forms could have been effectively shielded 

from the radioactive element radiation as well as from proton flux.

There are compelling reasons why water ice probably does not exist 

today in near-surface niches on the Martian satellites. They are dark in 

color and thus fairly good absorbers of sunlight, and they also lie close 

enough to the Sun to be relatively warm objects with temperatures near 

their surfaces that are too high for water ice to persist. Ice could exist at 

greater depths, but it would be difficult to access for sampling.

Biological material could have been transported to the moons from 

an exogenous source, such as in the form of ejecta from Mars as a 

result of impacts that the planet experienced. Viking data indicated, 

 44.

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Small Bodies of the Solar System

however, that much if not most of the Martian surface and near-surface 

is quite hostile to life-forms. Also, meteorites of possible Martian origin 

have been extensively sampled and have not been found to contain any 

life-forms or, in fact, any materials harmful to Earth’s ecosystem.

Even if Mars ejecta did contain life and did at some time impact 

Phobos or Deimos, the odds would be miniscule of capturing such life in a 

return sample from the satellites, unless the biotic colonies that had been 

established were widespread. Still, the SSB Task Group recommended 

conducting remote sensing studies of Phobos and Deimos compositions in 

order to reduce uncertainties regarding their biological potential.46

The Soviet missions to Phobos. The USSR launched two missions in 

July 1988 meant to land on Phobos. If completed, they might have transported terrestrial organisms to the satellite. Neither mission, however, was 

successful. The Soviets launched both the Phobos 1 and 2 spacecraft from 

Baikonur Cosmodrome in Kazakhstan. Both were to study the surface 

composition of the larger of Mars’s moons, but both were lost en route.

A faulty command sequence sent from Earth on 29–30 August 

1988 resulted in a shutdown of the Phobos 1 craft. An error in the 

uploaded software deactivated the craft’s attitude thrusters, resulting 

in the loss of a lock on the Sun. This led to the craft’s solar arrays 

getting pointed away from the Sun, and thus the ship’s batteries ran 

down. Phobos 2 reached the vicinity of Mars on 30 January 1989, but 

it was lost while maneuvering for an encounter with the moon due to a 

failure of either the craft’s computer or its radio transmitter.47

The Icy Moons of Jupiter and Saturn: Life in Submerged Oceans?

Since the Galileo spacecraft sent back its data from its sojourn 

among the moons of Jupiter, space scientists have realized that 

 46.

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When Biospheres Collide

ice-capped oceans of liquid water may be widespread throughout our 

solar system. Strong evidence points to the existence of a salty ocean 

beneath the surface ice of Europa, and possibly within two of Jupiter’s 

other Galilean satellites: Ganymede and Callisto. Such oceans 

may exist on other satellites as well—notably the Saturnian moons 

Enceladus and Titan. 

The energy needed by life-forms may also be available in these 

oceans, originating from chemical disequilibrium48 conditions supplying molecular oxygen (O2

) and other oxidants. The processes that 

result in disequilibria would, however, be very different than those on 

our planet. On Earth, photosynthesis and organic carbon processes 

lead to oxidizing surface conditions and chemical disequilibria. Our 

planet’s ocean life depends heavily on the oxidants that filter down 

from the surface of the ocean. But significant solar energy cannot 

penetrate the kilometers of ice covering the surfaces of Jupiter’s and 

Saturn’s icy moons, and thus cannot drive photosynthesis in the 

oceans that possibly lie below. Instead, chemical energy could be 

derived from nonphotosynthetic sources of O2 and other oxidants 

available even to subsurface oceans. One pathway for a source of 

molecular oxygen is for gamma and beta radiation from potassium-40, 

a naturally occurring isotope of potassium, to decompose water into 

oxygen and hydrogen.49

Jupiter’s Galilean Satellites

The four moons of Jupiter that were discovered by Galileo—Io, 

Europa, Ganymede, and Callisto—are far larger objects than the planets’ other satellites. The compositions of the Galilean moons, as well 

as of Jupiter’s other satellites, are functions to some extent of the pressure and temperature environment in the material orbiting the planet 

during their period of condensation. Immediately after the Galilean 

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Small Bodies of the Solar System

satellites accreted from the primordial Jovian nebula, they were likely 

composed of some mixture of water ice and chondritic (i.e., having the 

structure characteristic of the class of meteorites called chondrites) 

nonicy material.

Assuming a radial temperature gradient in the primordial Jovian 

nebula, the amount of ice remaining in a satellite after condensation 

would have depended on the distance from Jupiter at which it formed. 

Data from observations of the Galilean satellites support such a scenario. Io, the closest Galilean moon to Jupiter, has a density suggesting 

a rocky composition that lacks even water of hydration, and no spectroscopic evidence of water has been found. Europa, the next distant 

Galilean moon, has a density consistent with a substantial amount of 

free water; its surface is also bright with ice. Ganymede and Callisto 

have densities indicating massive amounts of water—their bulk compositions are nearly 50 percent water by mass.50

While the outer three Galilean moons may have environments 

favorable to life, Io’s lack of water and other circumstances make it far 

less likely to support life. Virtually all of Io’s surface material appears 

to be volcanic, and thus was probably heated at one time to temperatures far too high for organic molecules to remain intact. Io is also subjected to a radiation environment more severe than any other body of 

its size in the solar system. This flux of high-energy charged particles 

from Jupiter’s magnetosphere powerfully inhibits any biological activity on or near Io’s surface.

This is not necessarily the case on other Galilean moons. The particle flux there would be significantly less intense due to their greater 

distance from Jupiter.51 If life is to be found in the Jovian system, it 

will probably be within one or more of those moons.

 50.

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When Biospheres Collide

Figure 6.1 A cutaway view of the possible internal structure of Europa. The rocky interior may 

be surrounded by a shell of liquid water, which is in turn contained in a shell of ice.

Evidence Suggesting an Ocean Under Europa’s Ice

In January 2000, NASA’s Galileo spacecraft approached the Jovian 

moon Europa while space scientists Margaret Kivelson, Krishan 

Khurana, and their team waited anxiously to measure which way its 

magnetic field pointed. They knew of two mechanisms that could be 

generating the field, and the implications for possible life on Europa 

were enormous. Internal processes and flows deep within the satellite could be generating the magnetic field, much as Earth’s molten 

core does. If such were the case, then the field should point the same 

direction, regardless of which way the parent planet Jupiter’s field was 

pointing at the time. Alternatively, an external magnetic field such 

as that of Jupiter might be acting on an electrically conducting layer 

within Europa and inducing a field from it. If the Europan field was 

indeed induced by its parent planet’s massive field, then the direction 

of the Europan field should be determined by that of the Jovian field.

Europa and the Galileo spacecraft had moved into a region of space 

in which the Jovian field pointed opposite to where it had pointed 

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Small Bodies of the Solar System

during previous flybys. If Jupiter was inducing Europa’s field, the 

opposite polarity of the Jovian field should cause an opposite polarity 

of Europa’s field. When Galileo’s measurements showed that this was 

exactly the case, the Kivelson team knew that they were seeing strong 

evidence of an electrically conducting layer hiding under Europa’s icy 

exterior. The layer’s most likely composition was water, warm enough to 

be liquid, and with dissolved salts in it that would make it a conductor. 

Exhaustive data from repeated Europan flybys demonstrated that 

the observed field, which flipped along with that of Jupiter, could 

indeed be explained by a subsurface global reservoir of water with a 

salinity similar to that of Earth’s ocean (see figure 6.1). And if liquid 

water does exist under Europa’s ice, so might life.52

Galileo’s Planetary Protection Approach vs. Those of Voyager 

and Viking

During early planning for the Galileo mission, which was to make 

many flybys of Jupiter’s icy moons, NASA staff began developing planetary protection protocol. They used the protocol from the Voyager mission, which in 1979 had conducted far more distant flybys of the Jovian 

system, as a baseline for developing Galileo’s plan. Voyager’s contamination control program utilized the same class 100,000 cleanrooms as 

did the Viking Mars lander, whose bioload was reduced to a very low 

level. But contamination-prevention controls for Voyager, which only 

flew by planets and did not orbit or land on any, were significantly 

more relaxed than for Viking. Different contamination control characteristics and requirements of the three missions are compared below:

Particulate contamination. Galileo and Voyager were expected 

to be less vulnerable to damage from particulate contamination than 

Viking and its sensitive life-detection experiments. Critical Galileo 

instruments were purged and covered but not subjected to the rigorous sterilization regimes that Viking’s instruments were.

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When Biospheres Collide

Alcohol cleaning. Galileo, like Voyager, was not able to be cleaned 

with alcohol, which would have damaged certain parts.

Personnel control and access restrictions. Galileo’s construction 

operations required fewer controls on personnel clothing than did 

Viking and did not employ any access restrictions that were exclusively meant for contamination prevention.

Terminal sterilization and encapsulation. Unlike Viking, the 

Galileo spacecraft was not subjected to terminal sterilization. It was 

also not encapsulated prior to mating with the Space Shuttle, from 

which it was launched. Encapsulation would have seriously impacted 

the spacecraft’s weight as well as its mission performance and budget.

Launch-related contamination sources. NASA considered Galileo–

Space Shuttle prelaunch and launch environments to be greater 

sources of contamination than the environments for the Viking and 

Voyager missions, since those missions employed Titan robotic launch 

vehicles instead of the Shuttle, with its human crew.53

Preventing an Accidental Impact Between Galileo and Europa or 

Another Icy Moon

The Galileo mission had an interesting approach to planetary protection that Jack Barengoltz called “a flexible PP plan.”54 The mission 

initially had an obligation to generate planetary protection documents 

that included prelaunch, postlaunch, and end-of-mission reports and 

to document the contamination control procedures implemented, 

probabilities of impacts with other bodies, and “the disposition of all 

launched hardware at the end of the mission.”55 But otherwise, the 

mission had no hard planetary protection requirements. Galileo faced 

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Small Bodies of the Solar System

the possibility, however, that its investigations would reveal the need 

to upgrade biological interest in one or more of Jupiter’s satellites. 

With this possibility in mind, the mission’s planetary protection plan 

included an agreement that if Galileo made such discoveries, then the 

project would modify its end-of-mission planning to reflect the new 

circumstances.

This is indeed what happened. The science return from the mission 

indicated that Europa most probably had liquid water under its layer 

of ice and that Callisto and Ganymede might also have such water layers. And if there were layers of water inside these moons, there was 

the possibility of life existing within them. The Galileo orbiter had not 

been sterilized and could have contained terrestrial organisms. Thus, 

NASA recognized the need to prevent the orbiter from accidentally 

impacting one of these moons. 

Discussions between Galileo mission staff and NASA Planetary 

Protection Officer John Rummel ensued. In March 2000, Rummel made 

a verbal request, followed by a letter in April, to the National Academies 

Space Studies Board Committee on Planetary and Lunar Exploration 

(COMPLEX) to provide advice on this matter. Specifically, Rummel 

addressed the final disposition of the Galileo orbiter. In addition, Torrence 

Johnson, Galileo’s project scientist, briefed COMPLEX in March 2000 on 

the “risks associated with the last phase of Galileo’s operational life.”56

In its deliberations, COMPLEX balanced planetary protection considerations with the unique scientific opportunities provided by various end-of-mission scenarios. A June 2000 letter from COMPLEX to 

Rummel expressed the following conclusions:

•	 No planetary protection-related objection existed to the 

“disposal of Galileo by intentional or unintentional impact with 

Io or Jupiter.”57

•	 Serious objections existed to the intentional or unintentional 

disposal of Galileo on Europa.

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When Biospheres Collide

•	 Disposal on Ganymede or Callisto had implications 

“intermediate in the broad range between those for disposal on 

Io and for disposal on Europa.”58

COMPLEX concurred with NASA that the best means available for 

disposing of Galileo was to send it on a collision course into Jupiter. 

The scientific benefits of this plan were that it would allow a close flyby 

of the small Jovian moon Amalthea and possibly one or more polar flybys of Io before the spacecraft’s final encounter with Jupiter. 

NASA had not developed quantitative estimates for COMPLEX of 

spacecraft-failure probabilities as functions of time, and thus the committee could not calculate the risks of an accidental Europa impact 

should additional flybys be planned. COMPLEX recommended that 

Galileo staff do this calculation. COMPLEX did have the data to analyze the probable effects of additional Jovian radiation absorbed by 

Galileo during an extra year of operations. Estimating the increase 

in radiation to be only about 20 percent, and taking into account the 

redundancy of all of Galileo’s essential operating systems and the fact 

that radiation effects to date had not handicapped the spacecraft, 

COMPLEX estimated that the probability of total loss of control of the 

craft during an extra year of operation was relatively small. And if a 

major Galileo control system did experience trouble, the spacecraft 

could be quickly retargeted onto a Jupiter-bound trajectory and away 

from any collision with a moon. Pending NASA’s completion of failureprobability calculations, COMPLEX reached a consensus that the best 

course of action was to defer the destruction of Galileo until after it 

completed its Io polar flybys. This would maximize the science returns 

from the mission, especially as related to the study of the Jovian system’s magnetic fields and plasma phenomena.59

On Sunday, 21 September 2003, after polar passes of Io and a 

flyby of Amalthea, Galileo plowed into and disintegrated in Jupiter’s 

60,000-kilometer-thick atmosphere, avoiding any chance that the 

craft might eventually strike and contaminate Europa or another icy 

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Small Bodies of the Solar System

moon.60 This was the first time that a mission had been “purposefully 

crashed into a planet to protect another solar system body.”61

Setting an Appropriate Planetary Protection Policy for Future 

Europa Exploration

For the last 40 years of the U.S. space program, Mars has been the 

focus of NASA’s search for extraterrestrial life. NASA developed forward contamination prevention protocols that reflected its understanding of Mars’s biological potential. Although these policies were derived 

from protocols developed for the 1970s Viking missions to Mars, NASA 

applied them to other solar system bodies as well. But given the distinctly different features of Europa (as well as other icy moons) from 

Martian characteristics, NASA eventually recognized that a different 

set of planetary protection criteria needed to be formulated. Toward 

this end, in the 1990s NASA’s planetary protection officer requested 

the Space Studies Board (SSB) of the National Academies’ National 

Research Council to analyze present policy and recommend necessary 

changes. Particular SSB tasks were to include the following:

•	 Assess the levels of spacecraft cleanliness and sterilization 

needed to protect Europa from contamination.

•	 Identify the necessary modifications to existing protocols.

•	 Identify the scientific investigations required to reduce the 

uncertainties in the above assessments.

In response to NASA’s request, the SSB created the Task Group on 

the Forward Contamination of Europa, which began its study in April 

1999 and drew its members from both academia and the aerospace 

industry. The core of the Task Group’s work was to determine whether 

present planetary protection procedures, which drew heavily from 

those originally formulated for the 1970s Viking Mars lander missions, 

were appropriate for Europa missions.62

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When Biospheres Collide

Current contamination prevention techniques included cleaning 

spacecraft surfaces with isopropyl alcohol and sporicides and sterilizing by means of dry heat. These approaches were derived from Viking 

procedures, but the current protocol also included sterilization using 

hydrogen peroxide. In addition, NASA staff envisioned Europa’s highradiation environment contributing to sterilization.

The Task Group concluded that the present procedures were “satisfactory to meet the needs of future space missions to Europa,”63

although they could be improved in certain areas. For instance, the 

Task Group recommended that the current spore-based culturing procedures for estimating bioloads be supplemented with screening tests 

for extremophiles, including radiation-resistant microbes. 

The Task Group was also aware of the significant cost penalties and 

operational complexities of carrying out current procedures. More modern analytical methods such as those based on the polymerase chain 

reaction (PCR),64 which is a molecular biology technique for replicating DNA, could cut down on time and add to sensitivity for identifying 

biocontamination. PCR employs DNA-copying enzymes and is typically 

used for finding genetic fingerprints and diagnosing infectious diseases.65

In addition, the Task Group recommended the following actions for 

improving planetary protection approaches:

•	 Analyze the ecology of cleanrooms and spacecraft assembly 

areas, focusing on extremophile microbes.

•	 Compare current bioload assay methodologies.

•	 Investigate the characteristics of desiccation- and radiationresistant microbes that could contaminate spacecraft during 

assembly.

•	 Examine techniques for detecting autotroph contaminants—

microbial organisms capable of synthesizing their own food 

using light or chemical energy.

•	 Research Europa’s surface environment and, in particular, its 

hydrologic and tectonic cycles.

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Small Bodies of the Solar System

The Task Group could not agree on the particular planetary protection standards appropriate for Europa, although most members 

believed that investigating the satellite could be key to understanding 

the origins of life and that current planetary protection protocols were 

not easily applied to Europan missions. Scientific understanding of 

terrestrial organisms’ abilities to survive under extreme conditions was 

very limited, and so a conservative approach to forward contamination 

prevention was called for. The first lander mission to Europa needed 

to meet “the highest reasonable level of safeguard”66 through severe 

bioload reduction in order to ensure a very low probability that a viable 

organism would be delivered to the satellite’s subsurface ocean. One 

particular concern was that over geological time scales of 10 million to 

100 million years, any surface contamination was likely to be carried 

into Europa’s deep ice crust or into its underlying ocean.

NASA’s 2005 document, Planetary Protection Provisions for Robotic 

Extraterrestrial Missions (NPR 8020.12C),67 promulgates mandatory 

requirements for preventing forward and back contamination on a range 

of mission types, including those to Europa. Requirements for Europa 

flyby, orbiter, or lander missions were aimed at reducing the probability 

of inadvertent contamination of a Europan ocean to less than 1 × 10–4

per mission, and they addressed the following factors:

•	 Microbial burden at launch.

•	 Cruise survival for contaminating organisms.

•	 Organism survival in the radiation environment adjacent to 

Europa.

•	 Probability of landing on Europa.

•	 Mechanisms of transport to the Europan subsurface.

•	 Organism survival and proliferation before, during, and after 

subsurface transfer.

Preliminary models suggest that microbial reduction will likely be 

necessary for Europa orbiters as well as landers. Implementing this will 

require precision-cleaning of all parts before assembly, cleanroom technology for spacecraft assembly, careful monitoring of processes, and 

a thorough understanding of the bioload and its microbial diversity, 

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including specific problematic species. NPR 8020.12C requirements are 

discussed further in Chapter 8, which addresses legal and ethical considerations of planetary protection.

Ganymede and Callisto—Abundant Water, But Are the 

Conditions Right for Life?

Ganymede, which is larger than Earth’s Moon, Pluto, or Mercury, 

and is nearly as large as Mars, would be considered a planet if it orbited 

around the Sun rather than Jupiter. It has a crust that is probably 

a thick layer of water ice and that likely covers a salty, liquid water 

ocean beneath. The presence of a submerged ocean would be the best 

way to explain the magnetic readings taken by Galileo during flybys in 

May 2000 and earlier. 

In addition, mineral characteristics and infrared reflectance data 

on Ganymede’s surface suggest that salty water may have emerged in 

the past from below or melted at the surface. Reflectance spectra from 

Galileo’s near-infrared mapping spectrometer (NIMS) provided evidence 

of possible hydrated materials similar to those found on Europa’s surface—in particular, frozen magnesium sulfate brines and possibly sodium 

sulfate as well, both derived from a subsurface briny layer of fluid.68

According to Dave Stevenson, a planetary scientist at the California 

Institute of Technology, natural radioactivity in Ganymede’s interior 

should provide enough heating to maintain a stable layer of liquid 

water between two layers of ice, about 150 to 200 kilometers (90 to 

120 miles) below the surface. That would be a different situation than 

found in Europa, where cyclic deformation from the tidal effects of 

Jupiter’s gravity could provide much of the internal heat.69

While life-forms may exist within a Ganymede ocean, less evidence has been found than on Europa of biologically important 

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Small Bodies of the Solar System

chemistry. For instance, magnesium salts and other materials significant for exobiology appear to be present on Europa in greater variety 

and abundance than on Ganymede, according to Ron Greeley, a professor at Arizona State University and head of the NASA Astrobiology 

Institute’s (NAI’s) Europa Focus Group.70 But because of the possibility 

of life, similar planetary protection precautions will need to be taken 

for the exploration of Ganymede as for Europa. 

Jupiter’s second largest moon, Callisto, may also have a liquid water 

ocean hidden under its icy, cratered crust, based on interpretations of 

Galileo data. According to Margaret Kivelson, space physics professor 

at UCLA and principal investigator for Galileo’s magnetometer instrument observations, this finding was quite a surprise. She commented 

that “Until now, we thought Callisto was a dead and boring moon, just a 

hunk of rock and ice.”71 But the analysis of Galileo data obtained during 

Callisto flybys in November 1996 and June and September 1997 indicated the presence of a magnetic field fluctuating in time with Jupiter’s 

rotation. Thus, it was most likely a field induced by that of Jupiter. 

The question was, where were the induced electric currents flowing to produce Callisto’s magnetic field? The moon’s icy surface was a 

poor electrical conductor, and its atmosphere, which lacked charged 

particles, was not a serious possibility for the medium in which a field 

could be induced. The best explanation for the observations was, once 

again, that Jupiter’s magnetic field was inducing electric currents 

within a salty ocean beneath Callisto’s icy surface.72

Thus, like Europa and Ganymede, exploration of Callisto would 

have to include planetary protection procedures taking into account 

the possibility of life within a salty water ocean. This is not to say that 

the existence of life on Callisto is a likely occurrence. The presence 

of a Callisto ocean is not sufficient for life to exist or have existed 

there. Energy to support such life is also needed. An ocean on Callisto 

would probably be heated almost completely by radioactive elements, 

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When Biospheres Collide

whereas Europa has tidal sources of energy as well, due to its greater 

proximity to Jupiter. Europa may be a more likely satellite to harbor 

life simply because it is the warmer of the two bodies.73

Enceladus: Saturn’s Bright, Surprising Moon

The Cassini spacecraft’s exploration of Saturn yielded unexpected 

data regarding its small satellite Enceladus. Space scientists once 

believed the moon to be too modest in size—only 314 miles in diameter—to be so active, but Cassini data have shown it to be “one of the 

most geologically dynamic objects in the solar system,”74 exhibiting a 

watery, gaseous plume reminiscent of Yellowstone National Park’s Old 

Faithful geyser (although far more diffuse),75 a geothermally heated 

spot in its southern polar region (20°C hotter than expected), deep 

canyons, and evidence of thick flows and periodic resurfacing on its 

exterior. In fact, amorphous and crystalline ice deposits may be only 

hours to decades old in some places. Partial melting and even a subsurface ocean may also exist within the moon.

According to Robert H. Brown of the University of Arizona, leader of 

the Cassini visual and infrared mapping spectrometer team, “The kind 

of geophysical activity we see is quite likely being driven by liquid water 

below the surface.”76 Tidal heating related to the parent planet’s gravitational field is a probable energy source for Enceladus’s activity; radioactive 

sources may play a part as well. The moon has two of the important factors for sustaining life: liquid water and ample energy. It also has organic 

chemicals, which were detected in formations near the south pole.

Over time—and Enceladus has been around 4.5 billion years, just 

like Earth and the rest of the solar system—heating a cocktail of simple organics, water, and nitrogen could form some of the most basic 

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building blocks of life. Whether that’s happened at Enceladus is not 

clear, but Enceladus, much like Jupiter’s moon Europa and the planet 

Mars, now has to be a place where we eventually search for life.77

Planetary protection concerns for Enceladus flybys are similar to 

those for Europa flybys. Appropriate actions for future flyby missions 

will likely involve measures such as trajectory biasing for preventing 

accidental impacts, as well as cleanliness requirements imposed to 

some level on the spacecraft, in order to lower the probability of contaminating the moon should an accidental collision occur.78 A mission 

planning to bring samples from Enceladus’s jets back to Earth would 

of course require additional measures to prevent back contamination, 

such as quarantining the collected material.

Titan—Organics and Very Cold Temperatures

NASA launched the Cassini spacecraft in 1997, carrying the 

Huygens probe that would be sent to Titan. Project scientists thought 

at that time, and still believe, that life is unlikely to exist on the cold 

moon, whose temperatures have been measured at –160°C (–256°F). 

Near the atmosphere’s stratosphere-troposphere boundary, in fact, temperatures drop to less than –190°C (–310°F).79 Space scientists often 

describe Titan as a window on the early Earth, demonstrating what our 

planet may have looked like before life emerged. But the “harsh chemistry 

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When Biospheres Collide

and frigid temperatures of the moon make many scientists skeptical 

about the current potential for life on Titan.”80

Saturn’s largest satellite has ample organic material in its thick 

atmosphere. Methane (CH4

) gas is its second-most abundant atmospheric constituent next to nitrogen, but it has long puzzled scientists 

how the methane is generated. On Earth, methane is produced by life 

processes, the degradation of organic material, or geologic processes. 

Cassini mission scientists concluded that if life does exist on Titan, it 

cannot be manufacturing all the methane that exists. Geologic activity in Titan’s interior rather than biological activity is the most likely 

source of the chemical.

Nevertheless, if Titan does prove to harbor life, it would most 

likely be in the interior of the satellite in the presence of liquid water. 

According to Cassini scientist Francois Raulin of the University of 

Paris, “You have there, in the interior, what you need to make good 

prebiotic chemistry.”81 Mission scientists believe that, in fact, Titan 

may become “a laboratory for studying the organic chemistry that preceded life and provided the building blocks for life on Earth,”82 even 

though life may never be found on the satellite.

Planetary protection considerations. Because of the reasons 

discussed above, the Planetary Protection Officer (PPO), in consultation with the Space Studies Board, decided that the Cassini mission had a low risk of adversely contaminating Titan. The PPO did 

not deem any spacecraft sterilization procedures necessary, although 

COSPAR rules did require the spacecraft to be assembled in a class 

100,000 cleanroom (that is, with less than 100,000 particles per unit of 

volume).83 Cassini was classified by the PPO as Category II, indicating 

that any contamination on the spacecraft had only a remote chance of 

jeopardizing future exploration that focused on chemical evolution and 

the origin of life. The planetary protection requirements included only 

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simple documentation, such as the preparation of a short planetary 

protection plan, and assurances that the spacecraft was not likely to 

accidentally impact the moon.84

Do We Need To Quarantine Samples 

From Asteroids, Meteoroids, Comets, or 

Interplanetary Particles?

The space environments surrounding asteroids, meteoroids, comets, and interplanetary particles, which are referred to as “minor 

bodies” in this section, impose severe limitations on their abilities to 

harbor viable microbes, especially those exhibiting metabolic activity. Minor body environments differ in several important aspects 

from most planets and some of their larger satellites (such as Saturn’s 

Titan). Minor bodies cannot sustain atmospheres due to their weak 

gravitational fields. This eliminates the presence of gaseous metabolites such as water vapor; hydrogen sulfide; carbon monoxide and 

dioxide; oxides of nitrogen, ammonia, or methane; and others that are 

exploited for biotic use by Earth organisms.

The lack of an atmospheric blanket on minor bodies makes the 

existence of life on them unlikely in another way as well. Atmospheres 

moderate temperature swings and create a gaseous greenhouse effect 

to help warm cold surfaces. Liquid water, which is needed for life as we 

know it, cannot exist on the surface of a body without an atmosphere. 

The water will quickly sublimate or freeze. The ultrahigh vacuum on 

surfaces without atmospheres—less than 10–15 torr—is also challenging 

to life because it can cause severe desiccation.85 Furthermore, ionizing UV radiation can reach the surfaces of atmosphere-lacking bodies unimpeded, and this has a sterilizing effect. Above our planet, we 

have an ozone layer that efficiently absorbs UV radiation and provides 

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important protection for the life-forms below, but minor bodies do not 

have such an atmospheric filter.86

Most minor bodies have diameters less than 100 kilometers and 

thus are too little to maintain internal heat sources over geologic time 

scales. As a result, liquid water cores are not probable except within the 

extremely rare, giant asteroids and comets greater than 300 kilometers 

in diameter.87 In spite of these challenges, however, some of the solar 

system’s minor bodies may possibly harbor life, and planetary protection considerations need to be taken into account when exploring them.

Asteroids

Asteroids are typically irregularly shaped bodies composed of rock 

and metal that travel around the Sun, chiefly between the orbits of 

Mars and Jupiter (although some pass closer to the Sun than Earth 

and others much farther from the Sun than Jupiter). Many asteroids 

are devoid of organic substances and thus do not have one of the basic 

foundations that scientists believe is necessary for harboring life. 

While the largest known asteroid—Ceres—is approximately as wide as 

the state of Texas, and several dozen asteroids are a few hundred miles 

in diameter (large enough to have conceivably retained liquid water 

cores over geologic time periods), most have far humbler dimensions. 

Hundreds of thousands are only a small fraction of a mile in size, and 

millions are even tinier pieces of rock and metal.88

Because of the ionizing radiation that is pervasive in space, Clark 

et al. expected the top meter or so of asteroid surface to be sterile. 

For this reason as well as because of the effects of high vacuum and 

thermal disruption (which, among other impacts, cause outgassing of 

water vapor from regoliths), Clark et al. suggested that sample return 

missions excavating asteroidal material only to shallow depths should 

not require back contamination protection such as quarantining.89

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Grimm and McSween, however, performed calculations indicating that for asteroids 2 astronomical units (AUs)90 from the Sun 

with compacted, low-porosity material at their surfaces, water ice 

(and thus life) could have persisted for the age of the solar system 

at depths greater than 1 to 40 meters, depending on pore size. For 

asteroids at distances greater than 3 AUs, ice may exist as close as 

several tenths of a meter from the surface.91 Furthermore, the largest 

population of asteroids is of a distance from the Sun such that their 

temperatures range from –113° to –23°C (–171° to –9°F),92 an interval 

in which the rates of chemical reactions able to damage living cells 

are quite slow.

The Hayabusa Mission. The Japanese space mission Hayabusa 

(formerly named MUSES-C), which translates to “peregrine falcon,” 

was a robotic venture led by the Japan Aerospace Exploration Agency 

(JAXA) for the purpose of returning a sample of material from the 

near-Earth asteroid 25143 Itokawa. The mission plan was to fire a 

projectile from the spacecraft into the asteroid and capture some of 

the ejecta. Hayabusa launched on 9 May 2003 and reached Itokawa 

in mid-September 2005. After surveying the asteroid surface from a 

distance of about 20 kilometers, the spacecraft moved closer and then, 

like the bird it was named for, “swooped down to perch for about 30 

minutes on its surface.”93

Hayabusa performed two such touchdowns on the smooth terrain of the Muses Sea region of Itokawa, carried out on 19 and 25 

November 2005.94 The craft found Itokawa to be a mass of rubble—

loosely packed rocks held together by their tenuous gravity. This is 

quite different than many other asteroids—for instance, Eros, which 

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is solid. Itokawa’s shape suggested that two unequally sized lumps were 

squashed together in an earlier collision. Surface features gave clues 

of an early collisional breakup of a parent asteroid, followed by reagglomeration into the rubble-pile observed today.95

After mission controllers sent commands to Hayabusa to fire its 

tiny projectiles at the surface and then sample the resulting spray, the 

mission staff was initially unable to determine whether the projectiles were released. Subsequent telemetry data indicated that release 

of the projectiles was unlikely, although bits of dust or pebbles may 

still have been collected by the craft’s sample retrieval system. Earth 

return maneuvers were threatened due to problems with the spacecraft’s engines. JAXA did identify a possible recovery approach, however, that would combine functionalities of two different engines. If it 

completed its mission successfully, Hayabusa would be the first spacecraft to return an asteroid sample to Earth.96

Hayabusa planetary protection considerations. The projectiles 

that Hayabusa was programmed to fire into the surface of Itokawa 

were expected to penetrate the asteroid’s surface no more than several centimeters, according to estimates reported in Clark et al. that 

took into account expected surface strengths. Thus, because of ionizing radiation, high vacuum, and thermal disruption, these samples 

would likely have been sterile and would not have needed quarantining.95 Nevertheless, Japan requested NASA to review the acceptability 

of unrestricted Earth return for Hayabusa. NASA studied the mission 

and agreed that unrestricted Earth return was indeed appropriate. 

NASA’s findings were in turn presented and discussed at a COSPAR 

workshop, which concurred with NASA’s findings.97

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Although the above reviews were very thorough, there is a conceivable way that the Itokawa asteroid could harbor life. Orgel pointed out 

that in the past, water may have existed within some types of asteroids. Large pockets of water ice within rubblized asteroids (such as 

Itokawa) possibly exist today as well. If such pockets of ice do exist, 

they would have the potential to attenuate the natural radiation field 

and prevent it from killing any microorganisms that might be present, 

thus permitting the survival of dormant life within the ice.98

In June 2010, Hayabusa successfully delivered its payload back 

to Earth, dropping a return capsule over Australia. The controlling 

regulatory agency was Biosecurity Australia, a part of the Australian 

Department of Agriculture, Fisheries and Forestry. To deal with the 

sample return, this agency issued a Quarantine Review of the MUSES-C 

Project in July 2002. This review discussed the importing of surface 

samples, noting that even though the back contamination risk to Earth 

might be extremely low to negligible, environmental exposure could 

conceivably occur.99 Biosecurity Australia thus recommended that “it 

is prudent to consider risk management procedures for return samples 

from small solar system bodies [and] that, on re-entry, the returned 

sample and all associated equipment potentially contaminated with the 

sample be immediately placed into secure impervious containers, transported in a safe manner and exported from Australia”100 to the laboratories that will analyze the material.

According to JAXA, scanning electron microscope analyses 

of returned samples confirmed that they were definitely from the 

asteroid Itokawa.101

Possible future studies of asteroids. Important data could be generated from spacecraft studies conducted to better assess heterogeneities, including ice pockets, in rubblized meteorites such as Itokawa. 

Studies could include spectral reflectance mapping of the bodies as 

 98.

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well as x-ray and gamma-ray mapping. Determining the characteristics 

of an asteroid’s heterogeneities would enable estimates of the ranges of 

exposure to radiation to which the different parts of the body would be 

subjected to and could thus reduce current uncertainties regarding the 

need for quarantining return samples. These uncertainties will also be 

narrowed when we learn more about two key questions:

•	 To what degree do existing meteorites represent the range of 

materials in the asteroids believed to be their parent bodies?

•	 To what level of certainty can we estimate the resemblance of a 

target asteroid to typical asteroids of its type?102

Planetary Protection Protocols for Returned Asteroid Samples

The SSB’s 1998 review of the planetary protection aspects of asteroid sample return missions103 recommended an approach for handling 

returned asteroid samples that included several aspects. At that time, 

no special containment and handling was recommended for asteroid 

types that space scientists believed to have an extremely low potential 

for harboring life. Included in this group were many C-type (carbonaceous) asteroids as well as S-type undifferentiated metamorphosed 

asteroids (those with stony, silicaceous compositions). Together, these 

two types comprise over 90 percent of known asteroids. Scientists 

believed that except for “possible localized volumes of water ice in 

C-types,”104 the interiors of both asteroid types would have received 

sterilizing quantities of radiation during the last 4.5 billion years from 

the decay of naturally occurring radioactive materials.

Much less is known about P- and D-type asteroids (reddish, poorly 

reflective bodies found in the outer asteroid belt and beyond), and thus 

the SSB urged caution in handling samples returned from them. The 

SSB recommendations were to implement strict containment procedures since they could not determine the chances of living entities 

102. Orgel, Evaluating the Biological Potential, p. 49.

103. Ibid., pp. 77–79; C. C. Allen and M. M. Lindstrom, “Near-Earth Asteroid Sample Curation,” 

Near-Earth Asteroid Sample Return Workshop, Lunar and Planetary Institute (LPI), Houston, TX, 

11–12 December 2000, pp. 1–2, http://www.lpi.usra.edu/meetings/asteroid2000/pdf/8027.

pdf#search=%22meteorite%20planetary%20protection%22 (accessed 26 January 2011).

104. Orgel, Evaluating the Biological Potential, p. 77.

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Small Bodies of the Solar System

being present within the bodies. Handling these asteroids would 

require a dedicated asteroid sample curation laboratory with characteristics that include the following: 

•	 Cleanroom environment of class 1,000 or better.

•	 Subfreezing storage and processing capabilities.

•	 Dedicated processing cabinets for samples from each parent 

body, with positive-pressure nitrogen atmospheres.

•	 Continuous monitoring of inorganic, organic, and biological 

contamination.105

Meteoroids and Meteorites

Meteoroids—solid, rocky masses moving through space that are 

smaller than asteroids but at least the size of a speck of dust—get 

heated to incandescence by friction when they encounter Earth’s 

atmosphere and generate the bright trails or streaks that we call 

meteors. Some large meteoroids do not burn up in the atmosphere, 

but reach the surface of our planet as meteorites. Interest in meteoroids from a planetary protection perspective stems from findings that, according to some investigators, suggest the presence of 

microfossils within the bodies. In particular, McKay et al.106 presented arguments that the carbonate globules within the meteorite 

ALH84001 were likely formed at temperatures consistent with life 

and are related to Martian microorganisms. McKay and his colleagues 

observed elliptical, rope-like, and tubular structures in fractures in 

the carbonate mineral globules resembling living and fossilized terrestrial bacteria that grew inside volcanic rock similar to that found 

in the meteorite. ALH84001 is believed to have originated on Mars 

largely because it resembles another meteorite, EETA79001, which 

105. C. C. Allen and M. M. Lindstrom, “Near-Earth Asteroid,” p. 2.

106. D. S. McKay, E. K., Gibson, Jr., K. L. Thomas-Keprta, H. Vali, C. S. Romanek, S. J. Clemett, 

X. D. F. Chillier, C. R. Maechling, and R. N. Zare, “Search for Past Life on Mars: Possible Relic 

Biogenic Activity in Martian Meteorite ALH84001,” Science 273 (1996): 924–930; Allan H. 

Treiman, “Current State of Controversy About Traces of Ancient Martian Life in Meteorite 

ALH84001,” Mars Sample Handling Protocol Workshop—Summaries of Key Documents, 

February 2000, an attachment to John D. Rummel to Steven Dick, 9 March 2000.

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When Biospheres Collide

has a composition matching that of the current Martian atmosphere 

as measured by the Viking landers. 

An examination of meteorite ALH84001, a softball-sized igneous 

rock weighing 1.9 kilograms (4.2 pounds) and found in the Allan Hills 

region of Antarctica, revealed the following in its carbonate globules: 

•	 Hydrocarbons that were the same as broken-down products of 

dead microorganisms on Earth.

•	 Mineral phases consistent with byproducts of bacterial activity.

•	 Evidence of possible microfossils of primitive bacteria. 

Based on age-dating of the igneous component of ALH84001, a 

scenario was proposed that the original igneous rock from which it 

came solidified within Mars 4.5 billion years ago, or 100 million years 

after the formation of the planet. Between 3.6 and 4 billion years ago 

the rock was fractured, perhaps by meteorite impacts. Water then 

permeated its cracks, depositing carbonate minerals and permitting 

primitive bacteria to live in the fractures. About 3.6 billion years ago, 

the bacteria and their byproducts became fossilized in the fractures, 

and then 16 million years ago, a large meteorite struck Mars, dislodging a section of this rock and ejecting it into space. Thirteen thousand 

years ago, the meteorite crashed into Antarctica, where it was discovered in 1984.107

While the possibility of fossilized extraterrestrial life in the meteorite was, to say the least, intriguing, alternate theories arose holding 

that nonbiological processes and contamination could explain the findings. In addition, a 1996 letter to the journal Nature by Harvey and 

McSween presented evidence for why life processes could not have 

formed the carbonate globules. The most likely process of forming the 

carbonates in the meteorite, according to the researchers, relied on 

reactions involving hot carbon dioxide–rich fluids whose temperatures 

exceeded 650°C (1,200°F). If the carbonate globules in the meteorite 

were indeed this hot, it is quite improbable that their formation could 

have been due to a biotic process.108

107. Allan H. Treiman, “Fossil Life in ALH 84001?” Lunar and Planetary Institute Web site, 21 

August 1996, http://www.lpi.usra.edu/lpi/meteorites/life.html (accessed 13 July 2006).

108. Ralph P. Harvey and Harry Y. McSween, Jr., “A Possible High-Temperature Origin for 

the Carbonates in the Martian Meteorite ALH84001,” Nature 382 (4 July 1996): 49–51. 

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Small Bodies of the Solar System

One line of evidence for bacterial life in the meteorite that was 

difficult to refute focused on microscopic crystals in the meteorite of 

a mineral called magnetite. According to NASA scientists, the magnetite crystals were of a structure, size, chemical purity, and distinctive shape that only bacteria could have manufactured, rather than 

an inorganic process. In particular, researchers found that magnetite 

crystals embedded in the meteorite were ordered in long chains, which 

they believed had to have been formed by once-living organisms. 

These results were reported in the 27 February 2001 proceedings of 

the National Academy of Sciences.109 But this claim, too, was assailed, 

this time by new data and analyses of an Arizona State University 

team that included Peter Buseck, professor of geological sciences and 

biochemistry, and Martha McCartney, a scientist at the university’s 

Center for Solid State Science. They presented evidence that the match 

between the meteoritic crystals and those in bacteria was “inadequate 

to support the inference of former life on Mars.”110 In particular, tomographic and holographic methods employing a transmission electron 

microscope showed that the crystals formed by terrestrial bacteria did 

not uniquely match those in the Martian meteorite.111

While the presence of biotic traces in meteorites is still in question, some of the bodies do contain strong evidence, in the form of 

hydrated minerals, for the past presence of liquid water. “Hydrated” 

refers to minerals whose crystals are chemically bound to hydroxyl 

groups (OH) or water molecules. Such hydrated minerals were likely 

formed in the presence of aqueous fluids.

One critical question related to the existence of extraterrestrial 

life is whether these hydrated meteorites, which include most types of 

109. Space Daily, “Evidence Of Martian Life In Meteorite Dealt Critical Blow,” and “Scientists 

Find Evidence of Ancient Microbial Life on Mars,” 26 February 2001, http://www.spacedaily.

com/news/mars-life-01j.html (accessed 13 July 2006).

110. Peter Buseck, Martha McCartney, Rafal Dunin-Borkowski, Paul Midgley, Matthew 

Weyland, Bertrand Devouard, Richard Frankel, and Mihály Pósfai, “Magnetite Morphology 

and Life on Mars,” Proceedings of the National Academy of Sciences 98(24) (20 November 

2001): 13490–13495. 

111. Tomography employs computer analysis of a series of cross-sectional scans typically 

taken with x rays to examine a solid object. Holography is a method of producing a threedimensional image of an object from the interference pattern formed by two coherent 

beams of light. The transmission electron microscope is a tool that operates similarly to a 

normal light microscope but uses electron beams instead of light.

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When Biospheres Collide

carbonaceous chondrites,112 were altered in an extraterrestrial location (rather than on Earth) by the presence of water. Evidence that 

this was indeed the case includes the following:113

•	 Some of the hydrated meteorites were observed falling to Earth 

and were recovered too soon thereafter for terrestrial hydration 

reactions to occur.

•	 Radioisotope dating of the meteorites’ carbonate structures 

indicated that their formation occurred during a time when 

Earth was too hot to sustain liquid water (suggesting that the 

formation had to have occurred in another location).

•	 Oxygen isotope compositions in hydrated chondrite meteorites 

are distinct from those in terrestrial materials.114

•	 The ratios of two forms of iron, Fe2+/Fe3+, in the meteorites’ 

secondary minerals (those resulting from the decomposition 

of another mineral) are noticeably higher than in secondary 

minerals formed on Earth’s surface. Since processes that 

produce the secondary minerals involve aqueous alteration, this 

may indicate that aqueous impacts on the meteorites were of 

nonterrestrial origin.115

If direct evidence for meteoritic transfer of living organisms 

between planets is discovered, questions must be asked as to the 

ecological impacts that have accrued from this phenomenon, as 

well as whether alterations in our planetary protection policy are 

needed.116 For instance, if we establish that viable microorganisms 

from Mars have been transported to our planet by means of meteorites 

112. Carbonaceous chondrites are a type of meteorite that is rich in organic material. Virtual 

Planetary Laboratory (VPL), “Glossary,” VPL home page, Caltech Web site, http://vpl.ipac.

caltech.edu/epo/glossary.html (accessed 30 August 2006).

113. David Jewitt, Lisa Chizmadia, Robert Grimm, and Dina Prialnik, “Water in the Small Bodies of 

the Solar System,” University of Hawaii Institute for Astronomy preprint IfA-06-026, February 

2006, for publication in  Protostars & Planets V, http://www.ifa.hawaii.edu/faculty/jewitt/

papers/2006/JCGP06.pdf. 

114. Ibid.; Robert N. Clayton, Naoki Onuma, and Toshiko K. Mayeda, “A Classification of 

Meteorites Based on Oxygen Isotopes,” Earth and Planetary Science Letters 30(1) (April 

1976): 10–18. 

115. Jewitt et al., “Water in the Small Bodies”; Michael Zolensky, Ruth Barrett, and Lauren 

Browning, “Mineralogy and Composition of Matrix and Chondrule Rims in Carbonaceous 

Chondrites,” Geochimica et Cosmochimica Acta 57(13) (July 1993): 3123–3148. 

116. SSB, National Research Council, “Scientific Investigations That Could Reduce Uncertainty,” 

in Mars Sample Return: Issues and Recommendations (Washington, DC: National Academies 

Press, 1997), Chap. 5. 

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Small Bodies of the Solar System

for many years without apparent harm, how should that alter, if at all, 

our quarantine policy regarding Martian return samples? It might be 

argued that even if meteorites did regularly bring Martian organisms 

to our planet without harm to us, it certainly would not prove that all 

microbes from Mars would be benign. The best policy in such a case 

might still be to maintain “a rational program of containment and biohazard testing [that] will not only allow us to determine the safety of 

a returned Mars sample, but . . . will also allow us the best chance of 

detecting Mars life, if it exists, when a sample is brought to Earth.”117

The Relationships Between Meteorite and Asteroid Types

Understanding the relationships between meteorite types and 

asteroid types adds to the knowledge of both types of bodies, and 

it can shed light on when planetary protection measures may be 

required in investigating them. This is a currently evolving, multidisciplinary field that draws data from the following: 

•	 Ground-based and space-based remote sensing studies.

•	 Laboratory analyses of meteorite material.

•	 Laboratory simulations of space-weathering and other processes 

that make it difficult to accurately interpret reflectance spectra 

data.

•	 Theoretical modeling of collisions and other dynamic processes 

that liberate meteorites from their parent bodies.118

The better we understand the relationships between meteorite and 

asteroid, the more we can know about a parent asteroid’s structure, 

composition, and potential for harboring life by studying the meteorites generated from it that find their way to Earth.

Comets

Comets contain significant amounts of water ice that scientists 

believe never had a chance to melt on a large scale. This is because, 

117. John D. Rummel, “A Case for Caution,” Planetary Report (November/December 2000).

118. Ibid. 

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When Biospheres Collide

since their creation 4.6 billion years ago in the protoplanetary disc,119

the bulk of comets’ masses have rarely gotten warmer than about 

–170°C. Their surface layers, however, may have undergone monthslong heating during the comets’ closest approaches to the Sun to temperatures of the order of 27°C, causing some volatiles to sublimate and 

escape as vapor.120 In particular, water sublimates from a comet when 

it approaches to within about 5 to 6 astronomical units from the Sun 

(an astronomical unit, or AU, is the mean distance between Earth and 

Sun). This sublimation leads to formation of the distinctive cometary 

tail as well as the atmosphere of gas, or coma, surrounding the comet’s 

nucleus.121

Cosmic-ray exposure of comets whose orbits take them out of the 

heliosphere (the region of space through which our Sun’s solar wind 

extends) has been sufficient, according to space scientists, to “destroy 

any preexisting life in the outermost tens of meters”122 of the bodies, 

and the temperatures in that distant region are so low as to preclude 

the formation of any life. Although some cometary nuclei contain large 

quantities of organic molecules, this is explainable in terms of abiotic 

processes. Such molecules have also been observed in the interstellar 

medium, and these have definitely been generated by abiotic means.

The SSB Task Group on Sample Return from Small Solar System 

Bodies that was discussed earlier in the chapter considered it 

extremely unlikely that life could exist on or near the surfaces of comets but could not conclude that the probability was zero. Nevertheless, 

in its study on the biological potential of small solar system bodies, 

SSB did not recommend any special containment or handling procedures for comet return samples beyond what was required for the 

needs of scientific analyses.123

The Stardust Mission. NASA’s Stardust spacecraft flew within 150 

miles of the comet Wild 2 (pronounced “vilt two”) in January 2004, 

trapping particles from the comet in a matrix of low-density silica glass 

called aerogel and returning them to Earth on 15 January 2006 (see 

119. The protoplanetary disc was the rotating disk of dense gas surrounding our young, newly 

formed Sun, from which our solar system’s planets arose. 

120. Orgel, Evaluating the Biological Potential, p. 78. 

121. Jewitt et al., “Water in Small Bodies,” p. 8. 

122. Orgel, Evaluating the Biological Potential, pp. 78–79.

123. Ibid.

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Small Bodies of the Solar System

Figure 6.2 An artist’s concept of Stardust sample return capsule (SRC) parachuting down to 

Earth, bringing samples of comet particles and interstellar dust, including recently discovered 

dust streaming into the solar system from the direction of Sagittarius.

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When Biospheres Collide

Figure 6.3 The Stardust sample return capsule was transported by helicopter from its landing 

site at the U.S. Air Force Utah Test and Training Range. This image shows the SRC inside a 

protective covering.

Figure 6.4 Mission staff prepare to remove an aerogel particle collection grid from the 

Stardust SRC.

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Small Bodies of the Solar System

Figure 6.5 A closeup view of a cometary impact (center) into aerogel, observed at JSC hours 

after the Stardust SRC was delivered from the spacecraft’s landing site in Utah.

Figure 6.6 An artist’s concept of the Genesis spacecraft in its collection mode, opened up 

to catch and store samples of solar wind particles. The two rectangular solar panels provided 

electrical energy for spacecraft functions.

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When Biospheres Collide

figures 6.2 and 6.3). Stardust also collected interstellar dust grains. 

The aerogel matrices, depicted in figures 6.4 and 6.5, had the capability of slowing down the particles upon impact without destroying 

them. Most of the thousands of samples returned were smaller than 

the width of a hair, with only about two dozen larger particles visible to 

the naked eye. The aerogel matrices were scanned, mapped, dissected, 

and prepared for distribution in a dedicated class 10 cleanroom124 at 

Johnson Space Center (JSC).125

NASA deemed Stardust to be a Category V, Unrestricted Earth 

Return mission. Material brought back to Earth on Stardust did not 

have to meet any planetary protection requirements because NASA 

had already decided that it posed no biological risk. Even if the material did initially contain microbes which could back contaminate 

Earth (an extremely small possibility), Stardust’s procedure for collecting samples would almost certainly have killed those microbes. The 

particles collected were traveling at 22,000 kilometers (14,000 miles) 

per hour—roughly six times the speed of a bullet—when they hit the 

fluffy aerogel material of Stardust’s collector. As a result, the particles 

would have been heated to temperatures severe enough to biologically 

sterilize them.126

Approximately 40,000 tons of dust particles from extraterrestrial bodies impact our planet every year, and a large fraction of this 

(one billion particles per second) is cometary material. Comet particles have been bombarding Earth for more than the 3 billion years 

in which life has existed on this planet. These facts argue strongly 

for their minimal impact on terrestrial life-forms and support SSB’s 

124. Class 10 indicates that there are fewer than 10 particles per cubic foot within the cleanroom.

125. Susan Watanabe, ed., and Brian Dunbar (NASA official), “Stardust Samples Show 

Evidence of Fire, Ice,” http://www.nasa.gov/mission_pages/stardust/main/index.html

(last updated 15 May 2006, accessed 31 August 2006); Allen and Lindstrom, “NearEarth Asteroid,” p. 1; Randy Russell, “The Stardust Mission to a Comet,” Windows to the 

Universe Web site of the University Corporation for Atmospheric Research (UCAR), http://

www.windows.ucar.edu/tour/link=/space_missions/comets/stardust.html&edu=elem (last 

updated 21 March 2006, accessed 31 August 2006).

126. JPL, “Comets & the Question of Life,” 12 September 2005, http://stardust.jpl.nasa.gov/

science/life.html (accessed 31 August 2006); Glennda Chui, “Chasing Comets: Stardust 

Mission,” San Jose Mercury News, 11 January 2006, http://www.lbl.gov/today/2006/

Jan/11-Wed/01-11-2006.html (accessed 26 January 2011).

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Small Bodies of the Solar System

recommendation for no special containment requirements for sample 

return missions from comets.

Interplanetary Dust Particles

Interplanetary dust particles, or IDPs, are some of the solar system’s most primitive materials. IDPs are extremely small grains, typically 0.001 cm in diameter (about one-tenth the thickness of a human 

hair) and are a major component of the solar wind. Like meteorites, 

they fall on all parts of Earth, but their relation to meteorites is not 

completely understood. Some IDPs have compositions that match 

known meteorite classes. A 1991 study by Bradley and Brownlee, for 

instance, identified in an IDP the metallic mineral tochilinite, which 

is also found in carbonaceous chondrite meteorites. But most IDPs 

differ from meteorites in crystal chemistry and petrography and may 

be more primitive. IDP parent bodies probably include asteroids or 

comets, while some scientists have suggested that a percentage of IDPs 

come from other solar systems. Tomeoka and Buseck have found evidence that they are possible residue from protostellar clouds.127

One astrophysics theory suggests that low-energy protons in 

the solar wind could have interacted with IDPs containing the carbon compound anthracene to produce quinones. These are a type of 

molecule that exists in most living organisms. According to Lubomir 

Gabla and colleagues of Jagiellonian University in Poland, quinones 

may have been the precursors of life on Earth, carried to our planet 

by interplanetary dust. Tuleta et al. commented in this regard that the 

127. Tom Bernatowicz, “Interplanetary Dust Particles,” Laboratory for Space Sciences Web site, 

Washington University in St. Louis, http://presolar.wustl.edu/work/idp.html (accessed 31 

August 2006); P. H. Benoit, “Interplanetary Dust Particles (IDPs),” Meteoritical Society Web site, 

University of Arkansas, http://www.uark.edu/campus-resources/metsoc/idp.htm (accessed 

31 August 2006); J. P. Bradley and D. E. Brownlee, “An Interplanetary Dust Particle Linked 

Directly to Type CM Meteorites and an Asteroidal Origin,” Science 251 (1 February 1991): 

549; J. P. Bradley and D. E. Brownlee, “Cometary Particles: Thin Sectioning and Electron Beam 

Analysis,” Science 231 (28 March 1986): 1542–1544; Kazushige Tomeoka and Peter R. Buseck, 

“A Carbonate-Rich, Hydrated, Interplanetary Dust Particle: Possible Residue from Protostellar 

Clouds,” Science 231 (28 March 1986): 1544; Stanford University News Service, “Scientists 

Make First Measurements of Organic Molecules on Interplanetary Dust,” 17 March 1993, 

http://www.stanford.edu/dept/news/pr/93/930317Arc3362.html (accessed 26 January 2011).

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When Biospheres Collide

“simple prebiotic molecules [quinones] could play an essential role in 

the formation of more complex organisms.”128 Astrophysicist Chandra 

Wickramasinghe of Cardiff University in Wales, however, remained 

cautious on the connection of such molecules to life, commenting only 

that “this shows that biochemical monomers can form under solarsystem conditions. Although this process must occur, its contribution 

to the origin of life remains conjectural.”129

Models of the temperatures attained by IDPs due to frictional heating after entering Earth’s atmosphere estimate that only small particles of less than 20 μm (0.0008 inches), which constitute about 10–5

the IDP mass incident on our planet, stay cooler than 160°C.130 This 

is the temperature that the Microbiology Advisory Committee considered as the minimum necessary for biological sterilization under dry 

heat conditions.131 Nevertheless, 10–5 of the total IDP mass incident on 

Earth still constitutes a significant amount of matter—about 400,000 

grams per year (roughly half a ton) of potentially unsterilized particles.

This continuing bombardment of Earth by matter possibly containing biotic material, resulting in no observed deleterious effect on 

our planet’s life-forms, must be taken into account when developing 

planetary protection policy for the miniscule return samples of IDPs. 

The possibility cannot be ignored, however, that future IDP recovery missions might sample particles “that are not represented in the 

present-day . . . flux to Earth,”132 and thus could conceivably contain 

material harmful to our planet’s biota. A mitigating factor is that if the 

IDPs that were collected had been resident in interplanetary space for 

geological periods of time (rather than, for instance, protected by the 

atmosphere of a planet), then they would probably have received sterilizing doses of radiation. For this reason, the SSB recommended that 

no special containment should be warranted for IDP return samples 

128. M. Tuleta, L. Gabla, and J. Madej, “Bioastrophysical Aspects of Low Energy Ion 

Irradiation of Frozen Anthracene Containing Water,” Physical Review Letters 87(7) (13 

August 2001): 78103.

129. Katie Pennicott, “Did Interplanetary Dust Seed Life on Earth?” PhysicsWeb, 10 August 2001, 

http://physicsweb.org/articles/news/5/8/9 (accessed 31 August 2006).

130. Orgel, Evaluating the Biological Potential, Chap. 6, “Cosmic Dust.”

131. Microbiology Advisory Committee, Sterilisation, Disinfection and Cleaning of Medical 

Equipment, Guidance on Decontamination to the Department of Health Medical Devices 

Directorate (London: Medical Devices Directorate Publication, 1993).

132. Orgel, Evaluating the Biological Potential, p. 67. 

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Small Bodies of the Solar System

taken from interplanetary space. In addition, if the process of collecting 

IDPs results in the heating of the samples to temperatures considered 

sufficient for sterilization, as was the case with the Stardust mission, 

then this collection procedure would also eliminate the need for special 

sample containment requirements, regardless of the source of the IDPs.

The Genesis Mission: Questions Regarding Safe Transport of 

Extraterrestrial Material Back to Earth

The Sun and the bodies of our solar system originated, according 

to current theories, from a cloud of gas, dust, and ice. Examination of 

the solar wind, the particle streams emitted from the surface of the 

Sun, may tell us more about this process of solar system formation. To 

this end, NASA launched its Genesis mission in August 2001 to collect 

samples from the solar wind (see figure 6.6) and return them to Earth 

for laboratory analysis. Although hydrogen makes up most of the solar 

wind, Genesis aimed to collect many different types of matter. The 

mission had a goal of capturing samples of all naturally occurring elements in the periodic table, if possible, in order to determine in detail 

the Sun’s composition.133

After a three-year trip around the Sun, on 8 September 2004, an 

Earth entry vehicle from the Genesis spacecraft landed in the Utah 

Test and Training Range at Dugway Proving Ground. On the descent, 

an essential parachute failed to deploy; the root cause was traced to 

incorrect drawings that resulted in assemblers installing critical sensors 

upside down in the vehicle.134 As a result, the entry vehicle hit Earth at 

a speed of over 300 kilometers per hour (nearly 200 miles per hour) and 

cracked open upon impact. The vehicle’s outer shell as well as its inner 

science canister were breached, and some of the collector arrays, containing pristine particles from the solar wind, were shattered. 

133. Dolores Beasley, William Jeffs, and Susan Killenberg McGinn, “NASA Sends First Genesis EarlyScience Sample to Researchers,” NASA news release 05-030, 27 January 2005, http://www.nasa.

gov/home/hqnews/2005/jan/HQ_05030_genesis_sample.html (accessed 7 February 2005). 

134. Richard A. Kerr, “Flipped Switch Sealed the Fate of Genesis Spacecraft,” Science 306 

(22 October 2004): 587.

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When Biospheres Collide

The crash produced major fragmentation of the arrays and loss of 

collector materials, but much of the material recovered still had utility. Mission planners had expected to receive 275 hexagonal collector 

parts; instead, they now had greater than 15,000 small but potentially 

usable pieces (NASA estimated that the smallest usable fragment of 

collector needed to be at least 3 millimeters in size). The hardest task 

in recovering science data from the broken collectors was to mitigate 

surface contamination that included particles, mud, water drop residues, and inorganic aerosols.135

Space policy analyst John Logsdon of the George Washington 

University in Washington, DC, noted that Genesis was designed during 

the “height of the ‘faster, cheaper, better’ era”136 of NASA missions when 

spacecraft plans were drafted, and vehicles constructed and operated, by 

fewer personnel in less time than had been the case earlier. Genesis was 

thus vulnerable to the same kinds of failures as the Mars Polar Lander 

and Climate Orbiter probes that had run into mission-ending problems. In 

spite of Genesis’s crash landing, however, intensive cleaning and other mitigation efforts by NASA personnel on the spacecraft’s collector pieces has 

resulted in slow but steady recovery of some mission science data. A major 

cause for optimism in recovery efforts is that the contamination needing to 

be removed is on the surfaces of collector fragments, while the solar wind 

particles are buried below those surfaces. Curatorial and research staff are 

hopeful that the major impact of the crash will prove to be only be a delay 

in extracting the science data, rather than a loss of those data.137

While the contamination of solar wind samples with Earth matter has caused challenging problems in extracting science data from 

the mission, most space scientists do not believe that the solar wind 

samples contain any biological material or pose a risk of biologically 

contaminating our terrestrial environment.138 NASA classified the mis135. D. S. Burnett and the Genesis Science Team, “Genesis Mission: Overview and Status,” Lunar 

and Planetary Science Conference XXXVII, March 2006, http://www.lpi.usra.edu/meetings/

lpsc2006/pdf/1848.pdf (accessed 1 September 2006).

136. Kerr, “Flipped Switch Sealed the Fate of Genesis Spacecraft.”

137. Mishap Investigation Board, Genesis Mishap Investigation Board Report, Volume I, NASA, 

2005, http://www.nasa.gov/pdf/149414main_Genesis_MIB.pdf (accessed 26 January 2011); 

Burnett et al., “Genesis Mission”; Race comments to author, 2007.

138. John Rummel, “Genesis,” Planetary Protection Web site, http://planetaryprotection.nasa.

gov/pp/missions/past/genesis.htm (last updated 14 July 2006, accessed 31 August 2006); 

Amir Alexander, “NASA Assessing Damage to Genesis Capsule from Crash,” Planetary 

352
Small Bodies of the Solar System

sion as Category V, a grouping that pertains to all missions for which a 

spacecraft or one of its components returns to Earth. Category V has 

two subcategories, one of which is termed “unrestricted Earth return” 

and applies to the exploration of “solar system bodies deemed by scientific opinion to have no indigenous life-forms.”139 This was the subcategory into which Genesis’s sample return actions were placed (for 

a discussion of the evolution of NASA’s mission categorization scheme, 

see Chapter 7 on the return to Mars). 

Implications of the Genesis mishap for planetary protection. The 

Genesis crash did not endanger Earth’s biosphere, but it did raise serious questions about how to safely transport matter containing potential biotic material from space to Earth. Furthermore, we need to 

be able to assess the contamination risks incurred if return sample 

operations go wrong, as they did for Genesis,140 and develop dependable methodologies for minimizing these risks. 

The Genesis crash engendered somber concerns about Mars sample return missions, which could conceivably carry extraterrestrial 

life-forms. Plans for such a mission at the time of the Genesis mishap called for using a passive Earth entry vehicle that did not need 

a parachute. It would instead employ atmospheric friction to slow 

its descent before impacting somewhere in the Utah desert. While 

such an entry vehicle would not have to rely on the proper opening 

and functioning of a parachute assembly, it would have to be robust 

enough for the sample canister to remain unbreached even during a 

hard landing. Heavily cushioning the sample canister within the entry 

vehicle would help to attain this goal by minimizing landing impact to 

the sample canister.141

Pete Worden, USAF Brigadier General (retired) and the NASA 

Ames Research Center Director, supported another approach to Mars 

sample return that would avoid the problem Genesis ran into. The 

Society Web site, http://www.planetary.org/news/2004/0908_NASA_Assessing_Damage_

to_Genesis.html (last updated 8 September 2004, accessed 31 August 2006).

139. John Rummel, “Categories,” Planetary Protection Web site, http://planetaryprotection.nasa.

gov/pp/about/categories.htm#5 (last updated 14 July 2006, accessed 31 August 2006).

140. Alexander, “NASA Assessing Damage.”

141. Leonard David, “Biological Mishap Renews Debate About Mars Sample Return,” Space 

News Business Report, 20 September 2004, http://www.space.com/spacenews/archive04/

genesisarch_092004.html (accessed 31 August 2006).

353
When Biospheres Collide

Moon would be employed as a quarantine zone for material brought 

back from Mars, avoiding a direct return of Martian samples to 

Earth.142 Worden commented that “building a Mars habitat and receiving laboratory on the Moon for Mars samples could allow us to determine its safety—and perhaps compatibility with Earth life.”143

The space science community has not given lunar quarantine the 

support that Worden did. For instance, in a 1990 workshop held at 

NASA Ames Research Center, organized by Donald DeVincenzi, the 

participants favored an Earth-based facility as opposed to one on 

the Moon.144 In a later meeting, John Rummel expressed the thought 

“that a lunar quarantine would . . . result in a net decrement to 

safety—especially if one wishes to include the safety of the people 

setting up and doing the analyses . . . .”145 He was concerned as well 

with the effectiveness of such an operation, pointing out that scientists would still have a desire to study the extraterrestrial materials 

in the most capable laboratories possible, and it would probably not 

be feasible to build such facilities on the Moon. The samples would 

most likely have to be transported to Earth to receive the most reliable, in-depth examination.146

142. Jeff Foust, “Exploiting the Moon and Saving the Earth,” Space Review Web site, 7 November 

2005, http://www.thespacereview.com/article/490/1 (accessed 26 January 2011).

143. Simon P. Worden (speech given at the International Space Development Conference, 

Los Angeles, 7 May 2006, and transcribed and published by SpaceRef.com, 9 May 2006), 

http://www.spaceref.com/news/viewnews.html?id=1119 (accessed 26 January 2011).

144. D. L. DeVincenzi, H. P. Klein, and J. R. Bagby, eds., Planetary Protection Issues and Future 

Mars Missions, proceedings of the workshop, “Planetary Protection Issues and Human 

Exploration of Mars,” held at ARC, Moffett Field, CA, 7–9 March 1990, NASA Conference 

Publication 10086, 1991, p. 3.

145. John D. Rummel presentation, “Planetary Protection, NASA, the Science Mission 

Directorate, and Everything,” NASA Advisory Committee (NAC) Science Subcommittee 

Meetings, NASA Headquarters, Washington, DC, 6 July 2006, http://science.hq.nasa.gov/

strategy/NAC_sci_subcom/planetary_protection/PPS_Jul06_Rummel.pdf.

146. Leonard David, “Biological Mishap Renews Debate About Mars Sample Return,” Space 

News Business Report, 20 September 2004, http://www.space.com/spacenews/archive04/

genesisarch_092004.html (accessed 31 August 2006).

354
Small Bodies of the Solar System

Summary of NASA Planetary Protection 

Requirements for Missions to Small 

Solar System Bodies

This chapter has discussed various types of past or planned 

missions to explore a variety of small solar system bodies and has 

referred several times to planetary protection requirements for such 

missions. These requirements range from no actions needed for the 

exploration of bodies not of interest to studies of life or chemical 

evolution to rather restrictive constraints on mission operations 

returning samples from bodies that could potentially harbor life. 

As stipulated by COSPAR planetary protection policy, NASA’s document, Planetary Protection Provisions for Robotic Extraterrestrial 

Missions,147 is formulated around five different categories, with subcategories, to aid in determining appropriate forward and back contamination prevention approaches for various types of space projects. 

Typically, three of these categories, I, II, and V, apply to small body 

missions. Constraints on the mission depend on its characteristics 

and that of the target body or bodies. Summarized below are the constraints of NASA’s different planetary protection categories as applied 

to various types of missions to small bodies.148

For further discussion of these planetary protection categories, 

refer to Chapter 7, “Return to Mars.” In particular, table 7.1 provides a 

summary of the characteristics of all five target body and mission type 

categories. Also refer to Appendix A of this book, or Appendix A of 

NASA Procedural Requirement (NPR) 8020.12C, for more information 

on these categories.149

147. NASA Science Mission Directorate, Planetary Protection Provisions for Robotic 

Extraterrestrial Missions, NPR 8020.12C, 27 April 2005.

148. John Rummel, “Categories,” Planetary Protection Web site, http://planetaryprotection.nasa.

gov/pp/about/categories.htm#5 (last updated 14 July 2006, accessed 31 August 2006); 

Orgel, Evaluating the Biological Potential, Appendix D, “Planetary Protection Policy—NASA 

and COSPAR”; D. L. DeVincenzi, P. Stabekis, and J. Barengoltz, “Refinement of Planetary 

Protection Policy for Mars Missions,” Advances in Space Research 18(1/2) (1996): 311–316. 

149. NASA Science Mission Directorate, “Detailed Planetary Protection Requirements,” in 

Planetary Protection Provisions for Robotic Extraterrestrial Missions, NPR 8020.12C, 27 April 

2005, Appendix A.

355
When Biospheres Collide

Forward Contamination Prevention for Small Bodies:

Outbound Issues

Forward contamination prevention requirements are generally not 

warranted or are fairly limited for missions to the many small bodies 

of the solar system, except on a case-by-case basis, such as for missions to icy satellites like Europa that could conceivably harbor life. 

Most small body missions are covered by NPR 8020.12C’s Category I 

or II requirements,150 whose defining characteristics are summarized 

as follows:151

Category I: Missions that are not of direct interest for understanding the processes of chemical evolution or origin of life. 

No planetary protection requirements are imposed on these missions. Category I applies to outbound missions (or the outbound 

part of sample return missions) to the Sun, Mercury, and our Moon 

because biological contamination of these bodies is not considered 

a risk, given their extreme environmental conditions. Evidence that 

strongly supports this position for the Moon is given by Apollo mission results. None of the more than 2,000 samples of lunar material 

returned to Earth by six Apollo missions yielded any evidence of 

past or present lunar biological activity. Consequently, missions to 

and from the Moon are not required to have formal planetary protection plans in place.

Category II: Missions that have significant interest for understanding chemical evolution and origin of life processes, but only a 

remote chance that contamination carried by spacecraft could jeopardize future exploration. Category II missions must provide documentation of mission preparations and operations to the Planetary 

Protection Officer and must implement procedures to minimize the 

likelihood of accidental impact with their target planets or satellites, 

as the Galileo orbiter did by plunging into Jupiter at the end of its 

life. Both the Galileo orbiter mission to Jupiter and the Cassini orbiter 

mission to Saturn were considered Category II endeavors. So was the 

comet exploratory phase of the European Space Agency’s Rosetta 

150. NASA Science Mission Directorate, Planetary Protection Provisions.

151. Rummel, “Categories.”

356
Small Bodies of the Solar System

mission.152 The probes and landers of a Category II mission, however, 

such as the Huygens probe to Saturn’s moon Titan, may require a 

higher level of planetary protection, such as contamination control 

measures, that their mother ships do not.

Back Contamination Prevention: Inbound Issues

Category V: All missions for which the spacecraft, or a spacecraft component, returns to Earth. The concern for these missions 

is the protection of Earth from back contamination resulting from the 

return of extraterrestrial samples (usually soils, dusts, and rocks). A 

subcategory called Unrestricted Earth Return is defined for missions 

to bodies that the scientific community deems to have no indigenous 

life-forms. The Genesis spacecraft, which sampled solar wind particles, and Stardust, which sampled particles in the Wild 2 comet’s tail 

as well as interstellar dust sweeping through the solar system, were 

both classified as Category V—Unrestricted Earth Return. Missions 

in the unrestricted return subcategory may have planetary protection 

requirements imposed, but only on their outbound (Earth to target 

body) phase. The appropriate classification for the outbound phase to 

many, if not most, small bodies is either Category I (no requirements 

imposed) or Category II (requirements for documenting mission activities and avoiding accidental impact with the target).

The second subcategory of Category V missions is Restricted Earth 

Return. For this classification, which applies to spacecraft that have targeted bodies with biological potential, the highest degree of back contamination prevention concern is expressed by requiring the following: 

•	 Containment throughout the return phase of all unsterilized 

material from the target body and returning hardware which 

directly contacted the target body.

•	 No destructive impact of the spacecraft with Earth that could 

release unsterilized material from the target body.

152. G. Schwehm, J. Ellwood, H. Scheuerle, S. Ulamec, D. Moura, and A. Debus, “Planetary 

Protection Implementation for the Rosetta Mission” (presented at the 34th COSPAR 

Scientific Assembly, Second World Space Congress, 10–19 October 2002, Houston, TX, 

2002); NASA NPR 8020.12C.

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When Biospheres Collide

•	 Timely postmission analyses of the returned unsterilized 

samples, under strict containment, and using the most sensitive 

techniques.

•	 Continued containment of the return sample, if any evidence of 

a nonterrestrial replicating organism is detected, until a reliable 

sterilization procedure is applied.

A mission returning samples from the Jovian moon Europa would 

fit into this category because of the possibility of life being present 

within those samples.153

For a summary of planetary protection methodologies used on 

missions to small solar system bodies as well as other missions, see 

Appendix F.

153. NASA Science Mission Directorate, “Detailed Planetary Protection Requirements.”

358
7 RETURN TO MARS

We may discover resources on . . . Mars that will 

boggle the imagination, that will test our limits to 

dream. And the fascination generated by further 

exploration will inspire our young people to study 

math and science and engineering and create a new 

generation of innovators and pioneers.

—President George W. Bush, 

speech at NASA Headquarters, 14 January 20041

Although the Viking mission greatly expanded our knowledge of 

Mars, it was seriously limited in its search for organic chemicals and 

the existence of life by the two landing sites that NASA chose “more 

for spacecraft safety than for scientific interest.”2 Viking found no 

evidence of life in the vicinity of the landing sites or of any organic 

substances in the soil.3

 But the mission’s data could not be reliably 

extrapolated to the whole planet and thus could not answer many 

questions about possible Martian prebiotic chemistries or the past or 

present existence of life.

 1. Office of the Press Secretary, “President Bush Announces New Vision for Space Exploration 

359
When Biospheres Collide

Biological studies since Viking have highlighted the durability of 

extremophile life-forms on Earth—those that thrive in harsh environments previously thought incapable of supporting an ecology. Some 

of these microorganisms abound in very cold biospheres such as in 

polar ice caps, glaciers, and permafrost,4 and even within rocks in the 

dry, frigid valleys of the Antarctic.5 Other terrestrial microbes, the 

anhydrobiotes, have adapted to states of extreme dehydration, allowing them to live in very dry environments.6

 These findings raise the 

question of whether similar extremophiles might also exist in the cold, 

desiccated Martian environment.

The Martian surface environment may once have been far less 

challenging to life than it is now. The planet’s average temperature was 

probably at one time considerably warmer and, according to geological 

evidence, liquid water may have flowed on the surface in past eras. It is 

possible that life arose in the planet’s distant past, about the time that 

this was happening on Earth, and may still exist in localized niches.7

Since Viking, the technology for detecting microorganisms has 

advanced remarkably, and this has understandably elicited scientific 

interest in reexamining the Martian surface. The many new methods 

of bioassessment include epifluorescent microscopic techniques8 that 

 4. NASA, “Search for Life on Mars Will Start in Siberia: NASA Funds Permafrost Study to 

360
Return to Mars

directly count viable cells, as well as the polymerase chain reaction 

that enzymatically amplifies biomarkers of even a single cell to levels 

that can be detected.9

The above considerations have led to plans for new Mars missions 

that will visit different locations than Viking investigated and employ 

far more sensitive technologies than that project had access to. The 

renewed possibility of finding extant or past life on Mars, as well as 

on other celestial bodies, underlines the need for continuing to incorporate strict planetary protection concerns into all phases of such 

exploration. The following section outlines alterations to the planetary 

protection approach that have been made since Viking in order to better meet the evolving needs of missions to Mars and other solar system 

bodies while reliably guarding against forward and backward contamination dangers.

Changes in the Planetary Protection Approach 

Since Viking: Categorizing by Target Body and Type of Mission

The planetary protection procedures for the Viking mission’s two 

spacecraft were governed by the quantitative criterion that the probability of contaminating a planet of biological interest must not exceed 

one in 1,000 (1 × 10–3) during the period of biological interest. This 

was the period when space scientists would be searching for evidence 

of chemical evolution and the origin of life.10

Approximately 7,000 surface assays of Viking Lander Capsules, 

Orbiters, and shrouds taken during assembly and testing indicated that 

these components had initially carried significant bioloads. To meet 

the probability-of-contamination suballocation for each of the landers 

of roughly 10–4, reliable bioload reduction measures had to be incorporated during Viking fabrication processes. Experimental testing of 

various techniques led NASA to choose dry-heat sterilization of the 

 9. Task Group, 

361
When Biospheres Collide

landers as the major method for effectively reducing microbial counts. 

Because Viking landers contained sensitive metabolic assay technologies, the Viking biology team imposed additional heat treatment in 

order to greatly lower the possibility of terrestrial organisms contaminating their instrument.11 These approaches to bioload reduction were 

discussed in detail in Chapter 5.

Post-Viking planetary missions had a different, evolving set of planetary protection criteria than the Viking mission. An influential postViking SSB study was published in 1978 that identified the need for 

such new criteria, entitled Recommendations on Quarantine Policy 

for Mars, Jupiter, Saturn, Uranus, Neptune, and Titan. As it pertained to Mars, this study concluded that the probability of terrestrial 

organism growth on that planet was so low that landers conducting 

initial exploratory visits to a subpolar region did not require terminal 

heat sterilization.12

While the 1978 SSB study made clear the need for alterations to 

planetary protection policy, the guidelines that had governed Viking 

flights did not begin to change until the 1980s. This occurred when 

the quantitative modeling basis for the policy was reexamined in light 

of data obtained from a decade of planetary exploration, as well as 

changes to, or uncertainties in, some of the parameters employed in 

the existing policy. This quantitative modeling approach had inherent weaknesses in its application to Martian exploration (as well as 

to other target bodies). For instance, there were gross uncertainties 

in probability estimates of terrestrial microbe growth at different 

Martian surface locations. NASA also did not know how many future 

landings would be made on Mars, but both of these data needed to be 

input into the quantitative model, and thus its capability to accurately 

 11.

362
Return to Mars

predict the probability of contaminating Mars or other target bodies 

was severely strained.

In light of these issues, NASA’s planetary protection policy was 

reevaluated during the early 1980s, and a new approach was proposed,13

whose key features were the following:

•	 The quantitative, probabilistic methods employed for Viking 

would be deemphasized.

•	 Most planetary protection requirements for the majority of 

space missions would be eliminated. This recommendation 

was supported by “the wealth of data obtained by planetary 

exploration during the past decade [that was] consistently 

negative on the existence of indigenous life-forms on other 

planets.”14

•	 The missions requiring planetary protection measures, as well 

as the particular protection measures that were warranted, 

would be identified by the characteristics of the target body 

and of the mission itself—for instance, whether exploration was 

to take place using a flyby, orbiter, probe, or lander.

This approach better reflected the space science community’s 

degree of concern for protecting a specific target body, which was 

dependent on the characteristics of the body as well as on the type of 

mission. The scientists proposing the new method considered it to be 

superior to one depending on highly uncertain probabilistic calculations. Five categories corresponding to the various target planet and 

mission type combinations, as well as each category’s suggested planetary protection requirements, were proposed:

Category I included any mission to a target body not of direct 

interest for understanding the process of chemical evolution. No protection of such planets was warranted and thus no planetary protection requirements were recommended.

Category II missions comprised those to target bodies where there 

was significant interest in chemical evolution processes, but where 

there was only a remote chance that contamination carried by a 

 13.

363
When Biospheres Collide

spacecraft could jeopardize future exploration goals. Recommended 

requirements were for simple documentation, such as a short planetary protection plan outlining intended or potential impact targets, 

brief pre- and postlaunch analyses giving details of impact avoidance 

strategies, and postencounter and end-of-mission reports providing 

the impact location if such an event occurred.

Category III covered “no direct contact” missions—flybys and 

orbiters—to bodies of exobiological interest for which contamination 

would likely jeopardize future biological exploration. Requirements 

consisted of more involved documentation than Category II and the 

implementation of some procedures that included the following:

•	 Trajectory biasing. The probabilities of accidental impact could 

not exceed 10–5 for launch vehicles and 10–3 for flybys.

•	 Use of cleanrooms during spacecraft assembly and testing. In 

particular, all orbiter and flyby vehicles were to be assembled 

in cleanrooms of class 100,000 or better.

•	 Bioburden reduction.

Category IV embraced “direct contact” missions—probes and landers—to target bodies of chemical-evolution and origin-of-life interest for 

which there was a significant chance of contamination that could jeopardize future biological experiments. Recommended requirements to be 

imposed entailed detailed documentation more severe than Category III, 

including a bioassay to quantify the bioburden, a probability-of-contamination analysis for non-nominal events such as a crash or equipment 

failure, and a bulk constituent organics inventory. The implementation 

of an increased number of planetary protection procedures was recommended as well, such as trajectory biasing, the use of cleanrooms, 

bioload reduction, the possible partial sterilization of direct-contact 

hardware, and the installation of a bioshield for that hardware. The 

requirements were similar to those for Viking, with the probable exception of complete lander and probe sterilization.

Category V comprised all Earth return missions and was concerned with back contamination prevention of the terrestrial system—

Earth and the Moon. By protecting both bodies, travel between them 

would not require planetary protection procedures.15

 15.

364
Return to Mars

For the set of target bodies that the space science community 

did not believe had indigenous life-forms, a special subcategory of 

Category V, safe for Earth return, was to be designated. Missions in 

this subcategory were to have planetary protection requirements on 

their outbound phase only, corresponding to the appropriate category 

for that phase—typically Category I (as for the Genesis mission that 

brought back samples from the solar wind) or Category II (as for the 

Stardust mission to a comet).

The very highest degree of contamination concern was to be given 

to other Category V missions to targets that scientists believed could 

harbor life. These missions were termed restricted Earth return

and required the sterilization of returned spacecraft hardware that 

directly contacted the target planet as well as the quarantining of any 

unsterilized samples. Category V recommendations included a range 

of requirements that encompassed those of Category IV plus the monitoring of project activities and conducting of preproject studies such as 

those for remote sterilization and containment techniques. 

Table 7.1 summarizes the characteristics of each of the above target body and mission type characteristics. Also refer to Appendix A of 

NASA Procedural Requirement (NPR) 8020.12C,16 which can be found 

in the appendices of this book.

The major provisions of the recommended policy were reviewed 

by NASA, the SSB, and members of the U.S. and international space 

science communities, and they were also presented at the July 1984 

COSPAR meeting in Graz, Austria. Following minor changes, COSPAR 

unanimously accepted a resolution approving the revised planetary 

protection policy as a replacement for existing COSPAR guidelines.17

Still, the question of whether to include terminal sterilization in the 

planetary protection protocol was not yet answered. Meanwhile, the aerospace industry was changing and making it more difficult to employ a 

terminal sterilization regime without damaging spacecraft components. 

Don Larson, a planetary protection lead at Lockheed Martin, gave some 

 16.

365
When Biospheres Collide

Table 7.1 Summary of target body/mission type categories.

Category I Category II Category III Category IVa

Type of 

mission

Flyby, orbiter, and 

lander.

Flyby, orbiter, and 

lander.

No direct contact 

(flybys and 

orbiters).

Direct contact 

(landers and 

probes).

Subcategory IVa: Spacecraft 

not carrying 

instruments for the 

investigation of 

extant Martian life.

Target 

examples

The Moon; 

Mercury; 

undifferentiated, 

metamorphosed 

asteroids. 

Venus, Jupiter 

(exclusive of its icy 

moons), Saturn, 

Titan, Uranus, 

Neptune, Triton, 

Pluto/Charon, 

Kuiper belt 

objects, comets, 

carbonaceous 

chondrite 

asteroids.

Mars, Europa, 

Ganymede, 

Callisto.

Same as Category 

III.

Defining 

characteristic 

of mission

Not of direct 

interest for 

understanding 

process of 

chemical evolution 

or origin of life.

Significant interest 

in process of 

chemical evolution 

and origin of 

life, but only a 

remote chance 

that contamination 

carried by 

spacecraft could 

jeopardize future 

exploration. 

A target body of 

chemical-evolution 

or origin-of-life 

interest that if 

contaminated, 

could jeopardize 

future biological 

exploration. 

A target body of 

chemical-evolution 

or origin-of-life 

interest that if 

contaminated, 

could jeopardize 

future biological 

exploration; 

surface microbial 

burden level limits 

are based on 

average Viking 

lander burden 

levels before 

sterilization.

366
Return to Mars

Category IVb Category IVc

Category V

Unrestricted

Category V

Restricted

Same. Same. Earth return 

(missions making 

contact with 

another body and 

returning to Earth).

Same. Type of 

mission

IVb: Spacecraft 

carrying 

instruments 

designed to 

investigate extant 

Martian life.

IVc: Investigation 

of Martian special 

regions—those 

within which 

terrestrial 

organisms are likely 

to propagate, or 

regions which have 

high potential for 

existence of extant 

Martian life-forms.

Unrestricted Earth 

return of samples.

Restricted Earth 

return of samples.

Subcategory

Same. Same. The Moon 

(Apollo); 

undifferentiated, 

metamorphosed 

asteroids; comets 

(Stardust); solar 

wind (Genesis).

Mars, Europa. Target 

examples

Same. Same. No concern 

about back 

contamination 

resulting 

from return of 

extraterrestrial 

samples (usually 

soil and rock).

Concern about 

back contamination 

of the terrestrial 

system (Earth and 

the Moon) resulting 

from return of 

extraterrestrial 

samples (usually soil 

and rock).

Defining 

characteristic 

of mission

367
When Biospheres Collide

Category I Category II Category III Category IVa

Degree of 

planetary 

protection 

concern

None. Documentation of 

procedures and 

activities.

Passive bioload 

control. 

Active bioload 

control: Total 

surface microbial 

burden no greater 

than Viking lander 

preterminal

sterilization levels.

Detailed 

documentation 

surpassing that 

for Category III, 

microbial assay 

and reduction 

plans, organics 

inventory.

Representative 

planetary 

protection 

procedures

None. Impact avoidance 

strategies.

Documentation 

more detailed 

than Category 

II, contamination 

control, organics 

inventory as 

necessary, 

microbial burden 

limits or impact 

or orbital lifetime 

requirements.

368
Return to Mars

Category IVb Category IVc

Category V

Unrestricted

Category V

Restricted

Possible need 

for sterilization 

to Viking lander 

postterminal

sterilization levels.

Possible need 

for sterilization 

to Viking lander 

postterminal

sterilization levels.

No procedures 

needed for back 

contamination 

prevention.

Prevention of back 

contamination is 

necessary.

Degree of 

planetary 

protection 

concern

Either entire 

landed system 

must be sterilized 

to especially 

stringent 

microbial 

burden levels 

or subsystems 

involved in 

acquisition, 

delivery, and 

analysis of 

samples used 

for life detection 

must be sterilized 

and a method 

of preventing 

recontamination 

implemented.

Landing site within 

special region: 

sterilize entire 

landed system. 

Special region 

accessed through 

horizontal or 

vertical mobility—

either sterilize 

entire landed 

system or sterilize 

subsystems 

directly contacting 

special region 

and prevent their 

recontamination. 

If off-nominal 

condition such 

as a hard landing 

would cause high 

probability of 

special region 

biocontamination, 

entire landed 

system must be 

sterilized to Viking 

poststerilization 

microbial burden 

levels. 

Outbound leg: 

depends on 

category of 

target object 

(Category I, II, 

etc.). Inbound leg: 

No contamination 

control 

procedures 

needed for back 

contamination 

prevention.

Outbound leg: 

Category IVb 

requirements 

unless specifically 

exempted. Inbound 

leg: breaking 

chain of contact 

with target planet; 

postreturn sample 

containment 

(quarantine) and 

biohazard testing in 

receiving laboratory.

Representative 

planetary 

protection 

procedures

Source: NASA Science Mission Directorate, “Detailed Planetary Protection Requirements,” 

in Planetary Protection Provisions for Robotic Extraterrestrial Missions, NASA Procedural 

Requirement (NPR) 8020.12C, 27 April 2005, Chapter 2 and Appendix A.

369
When Biospheres Collide

details of this changing situation. In the late 1960s and early 1970s, 

aerospace-specific parts were generally manufactured with the government as client. When the space industry shifted to more commercial 

ventures, such as the launches of numerous telecommunications satellites, vendors and manufacturers had to become increasingly focused on 

cost-efficient solutions rather than catering their operations to government space projects with deeper pockets. This evolution of the aerospace 

industry was accompanied by a major increase in the use of microcircuitry, which contained electrical conductors that were extremely close 

together and delicate and could more easily be damaged than many of 

the old printed circuit boards. The result of these factors was that many 

post-Viking parts used in spacecraft could no longer withstand the terminal sterilization environment.18

Human Mars Missions: 

The 1990 NASA Ames Policy 

Development Workshop

Policies for exploring Mars continued to develop, including those 

related to human exploration. A March 1990 Ames Research Center 

workshop that focused on planetary protection issues for both robotic 

and human exploration of Mars19 drew scientists from the United 

States and the international community with expertise in astrophysics, 

atmospheric chemistry, biology and microbiology, ecology, environmental science, instrument design, legal issues, and other fields. Their 

object was to analyze the unique circumstances that arise during 

human Mars exploration and to understand how planetary contamination resulting from such missions might be prevented. The conference 

proposed guidelines that included the following elements:

 18.

370
Return to Mars

•	 Planetary protection questions needed to be thoroughly investigated during the precursor robotic mission phase of exploration, 

before any human contact took place with the planet.

•	 To prevent forward contamination of Mars from orbiting vehicles,

•	 all orbiters needed to be assembled in cleanrooms to 

minimize their initial bioloads,

•	 their trajectories needed to be biased to avoid unplanned 

impacts with and releases of microbes on Mars, and

•	 minimum orbital lifetime requirements needed to be met 

to ensure that no impacts occurred during the period of 

biological exploration.

•	 To prevent forward contamination from landers (including 

roving vehicles, surface penetrators, and surface stations), they 

needed to be

•	 assembled in cleanrooms,

•	 subjected to procedures for minimizing bioloads to 

prescribed levels, and

•	 enclosed in bioshields to prevent recontamination.

•	 To prevent back contamination of Earth,

•	 samples returned from Mars needed to be enclosed in 

hermetically sealed containers,

•	 the contact chain between the Martian surface and the 

return vehicle needed to be broken to prevent transfer of 

unwanted substances to Earth, and

•	 the samples needed to be subjected to a thorough 

quarantine protocol on Earth to investigate the possible 

presence of harmful species or other constituents.

The return of Martian samples to either a lunar or orbital quarantine facility was not advised by the workshop because the scientific community thought that such facilities could not provide both the required 

containment conditions and the thorough capabilities for assaying 

the samples.20 Proper containment of potentially dangerous life-forms 

required a level of sophistication, including remote handling technology, 

airflow control and filtering, and high-integrity seals, that only existed 

on Earth in facilities designed for handling highly infectious and virulent 

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microbes. Replicating such facilities, and the experience necessary to 

operate them, was unlikely to be achieved either on the Moon or in orbit.

These interim planetary protection recommendations, suggested 

by the international science community but not yet vetted and 

approved for implementation, were developed to help mission designers and planners.21 The vetting process for updating both human and 

robotic exploration policy was formally begun in July 1990 with a 

request from NASA Planetary Protection Officer John Rummel to the 

National Research Council’s Space Studies Board (SSB), which had 

served as NASA’s primary adviser on planetary quarantine matters for 

many years. Rummel asked SSB to give its advice on planetary protection policy and its application to upcoming Mars missions. Rummel 

also mentioned that if an initial SSB report on Mars planetary protection issues could be given to NASA prior to the 1992 COSPAR meeting, 

it would enable “a robust U.S. position”22 in the analysis of Russia’s 

envisioned planetary protection measures for its Mars-94 mission.

The 1992 SSB Study and the Policy Refinements That Followed

As requested by PPO John Rummel, SSB reviewed current planetary 

protection policy and published its findings in a 1992 study, Biological 

Contamination of Mars: Issues and Recommendations. The SSB study 

concluded that the contamination of Mars by the propagation of terrestrial microbes was an extremely unlikely event, largely due to “the 

high levels of ultraviolet radiation, the thin atmosphere, the extremely 

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low maximum temperatures, and the absence of liquid water on the 

surface.”23 However, terrestrial contaminants did present a significant 

risk to the integrity of experiments designed to search for extant or 

fossil Martian microbes. These experiments used extremely sensitive 

technologies, and small amounts of biotic contamination from Earth 

could cause false-positive results. Therefore, SSB recommended that 

minimization of bioloads still needed to be carried out on all lander 

missions to Mars but that the level of contamination control should be 

determined by specific mission objectives as follows:

1. Landers carrying instrumentation for in situ investigation of 

extant Martian life should be subject to at least Viking-level 

sterilization procedures. Specific sterilization methods were 

to be driven by the nature and sensitivity of the particular 

experiments, although terminal dry-heat sterilization, as had 

been implemented for Viking, was a likely candidate. The 

objective of this requirement was the reduction, to the greatest 

feasible extent, of contamination by terrestrial organic matter 

and/or microorganisms at the landing site.24

2. Space vehicles (including orbiters) without biological experiments should be subject to at least Viking-level presterilization

procedures for bioload reduction, such as cleanroom assembly 

and cleaning of all components, but such vehicles need not be 

sterilized.

By requiring stricter control of bioburden for landers carrying 

search-for-life instrumentation, SSB appeared to “shift the emphasis 

of planetary protection away from concerns about contaminating the 

planet to protection of exobiological science.”25 This change raised 

concerns that to avoid the extra restrictions and expenses, future missions might be biased away from experiments and target sites of exobiological interest.

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DeVincenzi, Stabekis, and Barengoltz26 examined the 1984 planetary protection guidelines in light of SSB’s 1992 recommendations 

and proposed several refinements to the policy. The first was to 

split Category IV into Categories IVa and IVb in order to make the 

important distinction between missions without and with specific 

life-detection objectives. Category IVa applied to landers without 

life-detection instruments. Such landers would not require terminal 

sterilization, but would require procedures for reducing bioburdens 

to levels no greater than those found on Viking landers just prior to 

terminal sterilization. 

The average presterilization spore burden on the Viking landers 

of ≤300 spores per square meter of surface and total spore burden 

level of 3 × 105 had been determined using data from over 2,000 

bioassays performed during Viking assembly and processing operations. DeVincenzi et al. thus proposed that the surface burden for 

each future Mars lander without life-detection experiments be set at 

an average of ≤300 spores per square meter of surface, and the total 

lander burden at ≤ 3 × 105 at the time of launch, using the same measurement protocol as for Viking. SSB, however, recommended that 

Viking protocols for bioload assessment be upgraded to include stateof-the-art technologies. Using more modern instrumentation had the 

potential for requiring changes to surface burden specifications. 

Category IVb related to spacecraft carrying search-for-life 

experiments. The driver for defining Category IVb, according to former Planetary Protection Officer John Rummel, was “to avoid false 

positives in looking for signs of life on Mars, not to protect Mars 

from contamination.”27 This meant that the search-for-life instruments had to be exceptionally clean, as had been the case on Viking. 

Category IVb thus required spacecraft to receive at least Viking-level 

sterilization procedures. DeVincenzi et al. interpreted this to mean 

that such vehicles should have bioburden levels no greater than was 

present on the Viking landers following terminal sterilization. The 

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two Viking Lander Capsules (VLCs), remember, were each subjected 

to a terminal dry-heat sterilization cycle. These cycles were such 

that each lander was exposed to a temperature of 111.7°C for 30 

hours, after the coldest contaminated point reached that temperature. Thus, some parts of the lander experienced slightly higher temperatures. It was Viking project management that chose the target 

temperature (111.7°C), with the concurrence of NASA’s Planetary 

Quarantine Office.28

Category III missions were those without direct contact of the 

space vehicle with the target object (Mars), and they included orbiters and flybys. Category III orbiters had to meet either one of two 

requirements: a cleanliness requirement specifying a maximum total 

spore burden of 5 × 105 (including surface, mated, and encapsulated

locations) or an orbital lifetime requirement specifying that the probability the craft would remain in orbit around Mars for 20 years must 

be at least 10–2, and for 50 years, at least 5 × 10–2. Thus, if an orbiter 

could attain a reliably stable orbit, it did not have to meet a cleanliness 

requirement.

Category III flybys had a much simpler requirement—to have 

a probability of impact with Mars that did not exceed 10–3. Launch 

vehicles in Category III missions also had a requirement imposed on 

them—a probability of impact with Mars that did not exceed 10–5.

29

An important caveat to the cleanliness requirement for Category 

III orbiters was that it be placed on the vehicle as a whole, not just 

on its surface (as was the case for Category IVa landers). This was 

because if an orbiter’s or flyby’s microbes did contaminate Mars, it 

would likely be through an accidental impact in which the vehicle 

broke open and microbes from inside got loose.30

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Piloted vs. Unpiloted Missions

Although the presence of astronauts may help in the detection 

of extant or past life, such as through the wide-ranging collection of 

samples, a human presence on the Martian surface will cause unavoidable contamination. SSB thus recognized the need for identifying local 

Martian environments, such as hydrothermal areas, in which life could 

exist, and to explore such areas with robotic vehicles before allowing 

humans onto these sites.31 NASA eventually developed explicit planetary protection policies and categories for such “special” areas; these 

will be discussed later in the chapter.

Applying the New Policies 

During Missions of the 1990s

The Mars projects of the 1990s that were conducted by NASA as well 

as by the space agencies of other countries provided a range of examples 

of how planetary protection measures were woven into mission operations and how scientific findings could impact policies for future missions.

NASA’s Mars Observer

The robotic orbiter Mars Observer, whose goal was to examine and 

map the planet’s atmosphere, surface, interior, and magnetic field for 

one Martian year,32 was the first mission to the planet to comply with 

the refined 1984 planetary protection guidelines discussed above. NASA 

designated the Mars Observer as Category III (no direct contact of the 

space vehicle with the target object).33 The mission carried out planetary 

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Table 7.2 Planetary protection activities during different Mars Observer mission phases. 

Mission 

Phase

Time Period Pollution Prevention 

Implementations

Launch Liftoff until spacecraft separation. Design components so as to 

prevent contaminating spacecraft 

with hot gases from, or collision 

with, upper stage during its 

separation procedures. Bias upper 

stage trajectory to avoid impact 

with Mars. 

Cruise Spacecraft separation until start of 

Mars orbit insertion (11 months).

Set spacecraft aimpoint so as to 

avoid accidental impact with Mars. 

Implement increased tracking 

90 days before orbit insertion to 

ensure accurate targeting at Mars.

Orbit 

insertion

Mars orbit insertion until mapping Design orbital insertion maneuver 

to minimize probability of accidental 

spacecraft impact, either during 

engine firing, on first periapsis 

after firing, or during intermediate 

orbits between orbital insertion and 

achievement of mapping orbit.

Design mapping and quarantine 

orbits to have adequate lifetimes. 

Design quarantine raise maneuver 

to reliably raise spacecraft to 

desired orbit. 

orbit achieved (8–9/93 until 12/93).

Mapping and 

quarantine 

orbits

Mapping orbit: Insertion until 

raising of spacecraft to quarantine 

orbit (12/93 to 2/96).

protection activities during each of its phases: launch, cruise, orbit insertion, mapping orbit, and quarantine orbit. These activities are described 

below and summarized in table 7.2, and they are indicative of the care 

that has to be taken to prevent forward contamination of a planet, even 

from spacecraft never meant to come in contact with the body. 

Launch phase. During the launch phase, the trajectory of the 

launch vehicle’s upper stage was carefully biased so as to prevent its 

eventual impact with Mars, which would have resulted in contamination of the planet. As indicated in table 7.3, NASA required that the 

probability the launch vehicle would impact Mars had to be less than 

1 × 10–5 (one chance in 100,000). The particular trajectory modification that was needed to attain this probability varied depending on the 

date that the mission launched. 

The upper stage eventually separated from the spacecraft using a 

maneuver designed to minimize the probability that the spacecraft 

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Table 7.3 Mars Observer impact probability estimates and requirements. 

Mission Phase Estimated Probability of NASA’s Maximum Allowable 

Impact with Mars Probability of Impact

Launch vehicle < 1 × 10–5 < 1 × 10–5

Spacecraft

Injection and cruise 1.2 × 10–5

Orbit insertion 1.2 × 10–5

Mapping orbit and 2 × 10–5 (until 2009)

quarantine raise 8.3 × 10–3 (until 2039)

Spacecraft total 4.4 × 10–5 (until 2009) 1 × 10–2 (until 2009)

8.3 × 10–3 (until 2039) 5 × 10–2 (until 2039)

would get contaminated, either through a collision with the upper 

stage or through materials given off by it. This maneuver had the secondary purpose of further biasing the upper stage away from a Mars 

impact trajectory. It was critical that the mission took these measures 

before the upper stage used all its fuel, since the upper stage would not 

be capable after that point of trajectory modifications. The spacecraft, 

on the other hand, had engines and fuel aboard that allowed it to make 

later trajectory corrections if needed.34

Cruise phase. The aimpoint of the spacecraft’s trajectory during 

its cruise phase was biased so as to be suitable for orbit insertion but 

not lead to an impact with Mars if mission control lost control of the 

craft. Approximately 90 days before orbit insertion at Mars, NASA conducted increased tracking efforts in order to reduce navigation delivery 

errors and ensure as accurate targeting of the spacecraft as possible.35

Orbit insertion. During the first part of Mars orbit insertion, the 

spacecraft entered a three-day capture orbit. This maneuver needed 

to be performed with care because at two points during it, the spacecraft engine firing and the first periapsis36 after the burn, there was 

a small probability of impact with and subsequent contamination of 

the Martian surface. All intermediate orbits between the insertion 

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maneuver and the eventual mapping orbit that the craft attained 

needed to be rigorously analyzed to make sure that their lifetimes 

were of sufficient length for the maneuver to be completed. The principal factor that decayed these orbits and shortened their lifetimes 

was atmospheric drag. Another important factor was the nonsphericity of the Martian gravitational field. Contributions to uncertainties in 

the prediction of orbital lifetimes included variances in Mars’s atmospheric density and solar activity.37

Mapping and quarantine orbit phases. Planetary protection procedures implemented during the mapping phase of the mission included 

designing the mapping orbit to have an adequate lifetime for the phase 

to be completed. They also included designing a quarantine raise procedure that would be as trustworthy as possible in maneuvering the 

spacecraft into a higher terminal orbit, circular in shape and 405 kilometers (252 miles) above the planetary surface. To meet NASA planetary protection requirements, this “quarantine orbit”38 needed to be 

stable enough such that the probability of spacecraft impact with Mars 

would not exceed 1 × 10–2 by the year 2009 and 5 × 10–2 by the year 

2039.39 Table 7.3 includes estimates of the actual probabilities of impact 

at different phases of the mission as well the maximum allowable impact 

probabilities. Note that estimated probabilities never exceed NASA’s 

required limits.

NASA’s Mars Surveyor Program

After NASA launched the Mars Observer, it continued plans to 

explore Mars in fiscal year 1995, but with some changes to its operational strategy. The program was conducted within a fairly constrained 

cost ceiling of approximately $100 million per year.40 The Mars 

Surveyor program called for the development of a small orbiter to be 

launched in November 1996 to conduct surface studies of Mars. The 

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orbiter, which was small enough to be launched on a Delta expendable launch vehicle and carried only half the science payload of the 

Mars Observer, aimed to “lay the foundation for a series of missions 

to Mars in a decade-long program of Mars exploration.”41 The orbiter—

the Mars Global Surveyor (MGS)—was the first in a series of low-cost, 

lightweight spacecraft bound for Mars. It was built by Martin Marietta 

Technologies of Denver, in part because of the company’s success in 

developing the Magellan Venus radar mapping mission and the Viking 

Mars landers.42

The Mars Surveyor missions took advantage of launch opportunities that occurred approximately every two years as Mars came into 

alignment with Earth. The orbiter designed for the 1998 launch was 

even smaller than the initial MGS and carried the remainder of the 

Mars Observer science instruments. It was meant to act as a communications relay satellite for a companion lander, launched the same year, 

and other landers in the future, such as the Russian Mars-96 lander.

A major challenge of the Mars Surveyor program, with its emphasis on fast development and low cost, was to build in effective planetary protection measures without driving up the budget or delaying 

the aggressive schedule of launches every two years. As with other 

programs, trajectory course maneuvers (TCMs) were employed during the voyage to Mars43 to better aim the craft toward its destination 

as well as to minimize the chances of an accidental impact with, and 

contamination of, the planet (this strategy for MGS is described in 

more detail in the next section). The MGS spacecraft (consisting of 

its payload of science instruments and its bus, which contained its 

propulsion system, flight hardware, and other subsystems) was also 

required to have the capability of achieving a near-circular quarantine 

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orbit with an average altitude of 405 kilometers (252 miles) above 

Mars if necessary.44

The MGS spacecraft, which was an orbiter, was not sterilized. The 

requirement on its outside was only that “The spacecraft external surfaces shall be visibly clean at payload encapsulation. Visibly clean is 

defined as the absence of all particulate and nonparticulate matter 

visible to the normal unaided . . . eye . . . .”45

NASA’s Mars Global Surveyor—Discoverer of Potential Special 

Regions

The MGS spacecraft, the first of the Mars Surveyor program, 

launched on 7 November 1996, bound for a Mars orbit that enabled it 

to gather data on surface morphology, topography, composition, gravity, atmospheric dynamics, and the magnetic field.46 MGS began its 

primary mapping mission in March 1999.47 Although its primary mission was to be two years (or approximately one Martian year), it kept 

operating for far longer, last communicating with Earth on 2 November 

2006. A review of the mission determined that the loss of the spacecraft was related to a computer error made five months before the 

craft’s apparent battery failure. If not for that error, MGS might have 

kept operating even longer.48

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Among its key science findings related to planetary protection, 

MGS imaged gullies and debris-flow features suggesting the presence 

of current sources of liquid water, similar to an aquifer, at or near 

the Martian surface. These areas could be Martian special regions, an 

important designation discussed later in the chapter.49

As with other NASA Mars missions, a major consideration in planning the maneuvers of the spacecraft was to meet all NASA planetary 

protection quarantine requirements, which it did in part by using 

the various biasing strategies that other spacecraft performed as well. 

Each TCM had to be designed to satisfy the requirements while at 

the same time minimizing the necessary change in velocity (and fuel 

usage) of the craft.

The aimpoint at the time of injection of the launch vehicle upper 

stage and spacecraft onto a Mars trajectory had to be selected to ensure 

that the probability of the upper stage and spacecraft accidentally 

impacting Mars was no more than 1 × 10–5. During the cruise phase 

of the mission, when the spacecraft journeyed to the vicinity of Mars, 

several small TCMs were implemented to remove the trajectory bias 

given for planetary protection purposes to the craft at the beginning 

of the phase. The TCMs also were performed to control the path of the 

spacecraft as it approached Mars, in part to meet planetary protection 

objectives. The navigation design had to ensure that the probability of 

accidental Martian impact did not exceed 1 × 10–2 within 20 years after 

launch and 5 × 10–2 for an additional 30 years.50

Several aspects of MGS’s orbits around Mars also related to planetary protection. The spacecraft’s mapping orbit was elliptical, with a 

minimum height of 354 kilometers (220 miles) over the southern polar 

region and 409 kilometers (254 miles) over the northern region.51 This 

orbit was carefully selected to be low enough so that the MGS instruments could make close-range observations of the Martian surface, but 

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not so low that friction from the planet’s atmosphere would slow the 

spacecraft down enough for an impact.

The MGS orbit was nearly polar, which meant that it was able to 

progressively observe all of Mars as the planet rotated below it. The 

orbit was also Sun-synchronous, in that the spacecraft passed over a 

given part of Mars at the same time each day. For instance, at about 

2 p.m. local Mars time every orbit, the spacecraft crossed the equator on the planet’s daytime side. This timing was essential for certain measurements because it allowed scientists to separate local daily 

variations from the longer term seasonal and annual trends.52

When the spacecraft completed its mapping work, its propulsion 

system was designed to raise the average altitude of the orbit in order 

to greatly reduce the frictional drag of the Martian atmosphere. This 

“quarantine orbit” practice conformed with international planetary 

protection agreements for minimizing, at least for several decades, 

the chances that the craft would crash and potentially contaminate 

Mars with terrestrial organisms. As discussed above, this strategy was 

intended to provide a contamination-free period in which to conduct 

missions examining the biotic nature of the planet.53

Russia’s Mars-94/96

The planetary protection approach taken in Russia’s Mars-94/96 

mission was somewhat different from that carried out in NASA’s missions, and it is thus interesting to examine. Mars-94/96 was an attempt 

to accomplish the first landings on Mars since the 1976 Viking craft. 

In 1990, Russia decided to split this mission into two launches—1994 

and 1996. The Mars-94 segment was to include an orbiter, two small 

autonomous stations on the surface of Mars, and two penetrators digging into the planet’s surface. Scientists from 20 countries participated 

in the effort, employing instruments built by a range of international 

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partners. The Mars-96 mission was to be configured similarly to Mars94 but was to include one or two balloons and small rovers.54

Russia claimed that its Mars missions were in accord with COSPAR 

planetary protection policy, with two main foci: protecting planetary 

environments from influence or contamination by terrestrial microorganisms and protecting experiments searching for Martian life.55 Past 

Soviet planetary protection performance had been questionable, however. While there was evidence that some precautions were taken on 

past missions, there was also reason to believe, as noted earlier in the 

book, that Soviet space exploration may have already contaminated 

Mars and possibly Venus as well by landing or crashing insufficiently 

sterilized spacecraft on the planets.56

Searches of available scientific literature and news articles indicated that by 1990, the Soviets had attempted 17 missions to Mars. 

According to DeVincenzi et al., three of the missions probably landed 

on the surface of Mars.57 The Soviet scientific community consistently 

maintained that their spacecraft complied with COSPAR guidelines 

through decontamination methods that included radiation, chemicals, 

and heat, either singly or in combination, but no literature is available on the details of how these technologies were applied to specific 

missions. However, in a report to COSPAR in 1973, Soviet scientists 

provided general information on bioburden reduction for their Mars 

series of spacecraft, stating that subcomponents were first treated by 

heat, gas, chemical, or radiation, and the final spacecraft was then 

assembled in an “ultra-clean” room.

The Soviets had the policy of building three identical spacecraft 

and disassembling one of them, pulverizing its subcomponents and 

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assaying them before launching the other two craft, in order to verify 

that the appropriate level of decontamination had been achieved. If 

these methods were indeed followed, they would have complied with 

the intent of the COSPAR guidelines. But it is known that although 

these approaches might have reduced spacecraft bioburdens sufficiently before transport to the launch site, liftoff operations were 

carried out under military authority, over which the Soviet planetary 

protection team had no jurisdiction.58

Russia’s envisioned Mars-94 launch began running into problems 

in 1993. By the end of the year, there was significant concern as to 

whether the launch schedule could be achieved. By April 1994, six 

months before the planned launch, the Russian Space Agency postponed Mars-94 until the next flight opportunity in 1996. The reason 

given by the Russian Academy of Sciences was “because of national 

economic difficulties.”59 The new flight date, however, did not have as 

favorable a launch window and required a reduction in payload. The 

original Mars-96 craft’s launch was delayed until 1998, but it was eventually canceled.

By the end of 1994, concerns arose that a complete cancellation 

of the project might be necessary.60 The spacecraft did take off on 

16 November 1996, but its fourth-stage launch vehicle ran into problems, resulting in the spacecraft crashing in the vicinity of the Chilean 

coast and the fourth stage impacting the Pacific Ocean near Easter 

Island.61 These events elicited some concerns regarding the contamination of Earth by 0.44 pounds of plutonium62 aboard the spacecraft. The 

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When Biospheres Collide

Russian Academy of Sciences announced that the spacecraft fell into 

the ocean,63 although some scientists thought it might have actually 

crashed on land. 

NASA’s Mars Pathfinder: Implementing Planetary Protection 

into a Low-Cost Lander Mission

Since the Pathfinder lander and its Sojourner rover were intended 

to make contact with the surface of Mars, this mission was classed 

as Category IVa for landers without life-detection instruments. As 

described earlier in this chapter, Category IVa requires detailed documentation, bioassays to quantify the burden on the spacecraft, a 

probability-of-contamination analysis, an inventory of bulk constituent organics, trajectory biasing, the use of class 100,000 or better 

cleanrooms during spacecraft assembly and testing, and bioload reduction to levels of the average spore burden on the Viking landers before 

they were subjected to terminal sterilization: < 300 spores per square 

meter and a total spore burden no higher than 3 × 105

.

NASA personnel achieved bioburden requirements by applying 

cleaning procedures such as those using repeated alcohol solution wiping of the spacecraft during its development and fabrication. Large surface area components such as the craft’s parachute as well as its airbags 

(which deployed around the lander and cushioned it as it hit the Martian 

surface) were heated for approximately 50 hours to a temperature of 

110°C (230°F). Bioassays were taken of spacecraft components at many 

points during their fabrication in order to determine bioburden levels.64

Mars Pathfinder, which launched in December 1996, had ambitious 

objectives. It was to be developed in only three years using largely offthe-shelf parts, for a cost to place a science payload on the surface of 

Mars of only 7 percent of the Viking price tag.65 Pathfinder, like the 

spacecraft in the Mars Surveyor program, was meant to demonstrate 

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NASA’s commitment to low-cost planetary exploration. The mission 

was also intended to showcase the mobility and usefulness of a roving 

vehicle on the Pathfinder, which needed to achieve its objectives without 

sacrificing planetary protection requirements, even though the mission 

budget was modest. The probability that any part of Pathfinder’s unsterilized launch vehicle upper stage would impact the Martian surface had 

to be less than 1 × 10–4.

66 The upper stage of the launch vehicle could 

accidentally be carried to the vicinity of Mars along with the Pathfinder 

spacecraft if, after the launch vehicle’s final burn placing the spacecraft 

on target to Mars, there was a failure in the separation process. For this 

reason, the aimpoint of the upper stage and spacecraft was biased away 

from Mars just enough to meet the upper bound of the impact probability. 

This implied that, after separation from the upper stage, the Pathfinder 

spacecraft needed to use its propulsion system to change its trajectory 

toward one that would allow it to eventually enter an orbit around Mars.

The first two trajectory correction maneuvers (TCMs 1 and 2) for 

accomplishing this changed the path of the spacecraft from the biased 

aimpoint given it when it was injected onto its cruise trajectory to a 

still slightly biased Mars arrival trajectory. The reason for maintaining 

this slight bias was to satisfy another planetary protection requirement—to make sure that the probability of the spacecraft impacting 

Mars at a speed greater than 1,000 feet per second was no more than 

1 × 10–3. This requirement was implemented to minimize the contamination of Mars from parts of the vehicle in the event of a crash 

landing.67 The trajectory after TCMs 1 and 2 was such that if control 

of the spacecraft was subsequently lost, it would enter the Martian 

atmosphere at a shallow enough entry angle for atmospheric braking 

to slow down the craft to below 1,000 feet per second at impact, even if 

the craft’s parachute did not deploy.68 Only near the end of the cruise 

to Mars, if control of the spacecraft and its systems had not been lost, 

were more correction maneuvers (TCM 3, 4, and, if necessary, 5) to 

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be executed to direct Pathfinder to precisely the desired Mars atmospheric entry conditions for an optimal landing.

Pathfinder successfully touched down on Mars on 4 July 1997 as 

planned. Only four trajectory correction maneuvers were needed to bring 

the craft in on target; TCM 5 was not required. Pathfinder landed in an 

ancient flood plain in the northern hemisphere known as Ares Vallis, 

among the rockiest parts of the planet. Mission scientists chose this plain 

because they believed it to be a relatively safe surface to land on and one 

containing a wide variety of rocks that may have been transported during 

a catastrophic flood from different geologic regions of the planet.69

Japan’s Nozomi—Fears of Contaminating Mars Through 

Accidental Impact

The Nozomi spacecraft, Japan’s first interplanetary exploration, was 

to achieve a highly elliptical Mars orbit taking it as low as 150 kilometers 

above the surface of the planet and enabling it to take valuable measurements of Mars’s upper atmosphere.70 Launched on 4 July 1998, its 

mission plan called for it to reach Mars in October 1999. But an early 

thruster problem prevented Nozomi from attaining the speed desired 

during a swing-by of Earth, which led to the scripting of an emergency 

flight plan. Then a burst of solar flares damaged the craft’s heating system and caused a loss of communication with Earth. As the craft finally 

approached Mars in 2003, it had very little fuel left and also suffered 

from a short circuit in its electrical system, possibly caused by the solar 

flares. Mission control crew sent various commands to the spacecraft in 

an attempt to bypass the short circuit. These repeated setbacks delayed 

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Nozomi’s arrival and raised fears in the space science community of a 

possible crash landing on, and contamination of, the Red Planet.71

Ichiro Nakatani, Nozomi’s spacecraft manager, explained that the 

electrical problem absolutely had to be fixed before Nozomi’s engines 

were fired for an attempt at Mars orbital insertion. Otherwise, mission 

staff would command Nozomi to fly by Mars rather than orbit it. If the 

electrical short was fixed, Nozomi’s thrusters would be fired during a 

9 December 2003 TCM whose purpose was to realign the spacecraft 

and prepare it for orbit insertion on 14 December. The 9 December 

TCM itself had a certain risk of failure, however, that could lead to 

contamination of the planet. Nakatani commented that “We have a 

probability factor for Nozomi hitting Mars at about or less than one 

percent if we fail the December 9 maneuver.”72

An impact with Mars could have had serious planetary protection 

implications because, according to Nozomi project manager Hajime 

Hayakawa, “no sterilization has been done before launch.”73 Some 

space scientists were not overly concerned about such an incident, 

arguing that even if Nozomi did impact Mars, it was not likely to present a biocontamination hazard. The spacecraft had been subjected to 

years of radiation exposure in space—several years more than planned. 

In addition, an accidental impact would occur only after the craft was 

intensely heated during its flight through the Martian atmosphere. The 

radiation and atmospheric heating would, the scientists believed, probably eradicate most microbes on the spacecraft.

Others in the science community were more conservative and 

stressed the importance of Japan’s acknowledging the possibility of 

contamination and then demonstrating why an impact was extremely 

unlikely. If it could not do this, then it should never insert Nozomi into 

Mars orbit but should make sure it flew by the planet. John Rummel, 

NASA Planetary Protection Officer at the time, stressed that the 

Japanese should insert their craft into Mars orbit only if they “put 

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extra effort into extending Nozomi’s orbital lifetime to achieve the noncontamination objectives required by international consensus.”74

On 9 December 2003, mission scientists abandoned plans for orbit 

insertion. They had failed to fix the electrical problem and thus could 

not fire the craft’s main engines.75 Mission scientists instead sent commands to the craft to fire small alternate thrusters to minimize the 

possibility of a Mars impact.

NASA’s Mars Climate Orbiter—What Was Its Fate, and Did It 

Generate Planetary Protection Concerns?

The Mars Climate Orbiter (MCO) lifted off on 11 December 1998 

atop a Delta II launch vehicle and began its Mars orbit insertion in 

September 1999. The robotic spacecraft, whose assembly is depicted 

in figure 7.1, was to orbit the planet as its first weather satellite. MCO 

was also to relay communications from the Mars Polar Lander (MPL)

when it arrived, which was scheduled for December 1999. MCO was 

lost, however, during its orbit insertion maneuver, at some point after 

it entered Mars occultation. 

NASA received the last carrier signal from the spacecraft on 23 

September 1999. The root cause for the loss of MCO was NASA’s failure to convert from English to metric units in the coding of a software file employed in trajectory models. Small errors introduced in 

trajectory estimates over the course of the 9-month journey from 

Earth to Mars became more important by the time of the Mars orbit 

insertion, when the spacecraft trajectory was approximately 170 kilometers (106 miles) lower than had been planned. As a result, MCO 

either burned up in the Martian atmosphere or left the atmosphere 

and reentered interplanetary space.76 NASA could not find the spacecraft, even though the mission team employed the 70-meter-diameter 

 74.

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Figure 7.1 Assembly of MCO.

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When Biospheres Collide

(230-foot) antennas of the Deep Space Network in an attempt to 

regain contact with it.77

From a planetary protection perspective, no contamination of the 

Martian surface apparently occurred, although under slightly different 

circumstances, this type of accident could have resulted in the orbiter’s impact with the planet, leading to serious forward contamination.

NASA’s Mars Polar Lander—Did Its Crash Contaminate the Planet?

The Mars Polar Lander launched 3 January 1999 from Cape 

Canaveral Air Station, atop a Delta II launch vehicle and carrying 

equipment to dig for traces of water beneath Mars’s surface. The 

capability to burrow into the Martian surface was provided by the 

lander’s robotic arm as well as by two basketball-sized microprobes, 

which were to be released as the lander approached Mars. The microprobes were to dive toward the planet’s surface and penetrate as 

much as 1 meter underground, where they would test 10 new technologies, including a water-ice detector. The MPL and MCO missions 

were the second phase of NASA’s long-term program of robotic exploration of Mars, which was initiated with the 1996 launches of the 

Mars Global Surveyor and the Pathfinder.78

The lander itself was to touch down on 3 December 1999 on the 

cold, windy, barren plain near the edge of Mars’s southern polar cap, 

a few weeks after the seasonal carbon dioxide frosts had disappeared. 

It was to then use its instruments to analyze surface substances, frost, 

weather patterns, and surface-atmospheric interactions. Its objectives 

included examining how the Martian climate has changed over time 

and identifying where water can be found on Mars today. Scientists 

believe that water once flowed on Mars, and they want to know where 

it went. Evidence may be found in the geologic record and, in particular, in the layered terrain of the polar regions. Their alternating 

bands of color may contain different mixtures of dust and ice and may, 

like a tree’s growth rings, help us understand climate change on Mars. 

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Scientists want to know whether it was caused by catastrophic events 

and whether the changes were episodic in nature or a gradual evolution in the planet’s environment.79

Similar to Pathfinder, MPL was to dive directly into the Martian 

atmosphere and slow its initial descent by means of an aeroshell and 

parachute. These were scaled down from Pathfinder’s design since MPL 

was considerably smaller. Unlike Pathfinder, however, MPL was not 

going to use airbags, but would instead make a soft landing by means 

of onboard guidance and retrorockets. The microprobes were to be 

released approximately 10 minutes before the lander touched down.80

MPL did not have specific life-detection experiments on board. 

Planetary protection thus required the same level of cleaning as for 

the Mars Pathfinder lander. MPL was to be cleaned to the level of the 

Viking landers before they received terminal sterilization. MPL surfaces could contain no more than 300 spores per square meter (about 

250 per square yard) and 300,000 spores total.

To meet this bioreduction goal, technicians at Lockheed Martin 

Astronautics (formally Martin Marietta) in Denver repeatedly cleaned 

MPL with alcohol wipes throughout its fabrication. Large surface areas, 

such as the thermal blankets and parachute, were baked for about 50 

hours at about 230°F (110°C). The spacecraft was bioassayed during 

processing at Lockheed Martin, and its level of cleanliness was verified 

just before encapsulation in its aeroshell. A final inspection and spore 

count was then performed at KSC before the spacecraft was integrated 

with the Delta II launch vehicle, assuring that the lander contained 

fewer than 300,000 spores total.81

Several factors in the MPL mission plan made planetary protection 

considerations especially critical. Both the lander’s robotic arm and the 

two microprobes were meant to pierce the planet’s surface and possibly 

contact water deposits. Furthermore, the microprobes were to do this 

by smashing into the Martian surface at up to 400 miles per hour (200 

meters per second), after which their aeroshells would shatter and the 

 79.

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When Biospheres Collide

probe inside would split into two parts. The microprobes’ electrical and 

mechanical systems were supposed to be tough enough to withstand 

this severe impact, but such an operation had not been tried before.82

Any terrestrial bacteria within the microprobes or the lander’s robotic 

arm might have opportunities to propagate on Mars that were not available to microbes on either the Viking or Pathfinder craft. Thus, it was 

especially important on the MPL mission that Lockheed Martin’s bioload reduction procedures were carried out effectively. 

There were certain challenges to doing this. MPL had a lack of flat 

surfaces and was thus particularly challenging to clean. Many of its 

surfaces, in fact, were not allowed to be touched, either for cleaning 

or for bioassay operations. One reason for making certain areas offlimits was that they contained extremely delicate sensors the size of 

human hairs. In addition to these areas, other locations on the spacecraft were inaccessible to cleaning. Thus, certain levels of bioburden 

had to remain in those places.83

Unfortunately, MPL did not touch down safely on Mars. As the 

lander descended, its legs were deployed in preparation for contact 

with the planet’s surface. But sensors on the legs gave erroneous signals that the spacecraft was already on Mars, and this shut down the 

engine. In fact, the lander was 132 feet (40 meters) above the ground 

at this point. It crashed into the surface at 50 miles per hour (80 kilometers per hour)—five times faster than intended. 

The premature engine shutdown was most likely caused by a 

software error related to the landing leg touchdown sensors.84 John 

Casani, former head of flight programs at JPL and head of the Mars 

Polar Lander Failure Review Board, speculated on what happened to 

the MPL when it impacted the planet, commenting that it “probably 

would have pancaked. The legs would have broken off, it might have 

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cart-wheeled or started rolling. You had two propellant tanks that were 

half full and those would have broken up, though I don’t think there 

would have been a fire or an explosion. In the end, you’d have a lot 

of pieces to pick up.”85 The question remains, what happened to any 

microbes that were on the surfaces exposed by the MPL breakup?

NASA’s Mars Exploration Rovers: 

A New, 21st Century Focus 

for Planetary Protection

NASA’s two Mars Exploration Rover (MER) spacecraft lifted off 

Earth on 10 June and 7 July 2003, with an objective to explore the 

history of water on the Red Planet. They landed on Mars on 3 January 

2004 and 24 January 2004 Pacific standard time (PST). The MER mission was part of NASA’s Mars Exploration Program, a long-term robotic 

exploration effort.86 Like the Pathfinder mission, MER was classed as 

Category IVa for landers without life-detection instruments.

The MER mission typified the evolving approach to planetary protection in that it was largely focused on protecting the integrity of the 

hardware that would make critical biologically related measurements 

as well as on contamination prevention of the planetary surface. In 

the words of Laura Newlin, JPL engineer and planetary protection lead 

for MER, “Keeping the spacecraft as clean as possible before, during 

and after launch is very important for any science instruments searching for organic compounds on the surface of other planets.”87 In other 

words, the umbrella of planetary protection now covered not only contamination prevention of the target body during the period of biological 

interest, but also of the spacecraft instruments themselves in order that 

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they could make more reliable measurements. This broad definition of 

planetary protection was beginning to develop even during the Viking 

mission, when extra bioload reduction measures were taken for the lifedetection instrument so that it would not generate false-positive indications of biotic processes.

Planetary protection measures were applied not only to the spacecraft itself, but also to the facilities in which it was handled. Before the 

MER spacecraft were shipped to KSC, for instance, the highbay facility 

and ground support equipment that would come into contact with the 

craft “were cleaned, sampled and recleaned to reduce further biological contamination when the spacecraft arrived.”88

After the two spacecraft arrived at KSC, they were disassembled 

and cleaned to remove any contaminants received during their crosscountry trip. During reassembly, JPL planetary protection team members bioassayed spacecraft surfaces to determine microbial levels. 

Mission staff cultured the bioassay samples, working in KSC life sciences labs and using equipment either from JPL or provided by KSC. 

This equipment included sonicators; water baths; incubators; microscopes; biosafety hoods; and a large, magnified colony counter.

Dry heat microbial reduction (DHMR) was performed on large 

components that could tolerate an environment of 125°C (257°F) for 

5 hours and that were difficult to adequately wipe clean. These components included thermal blankets, airbags, honeycombed parts (such 

as the core structures of the rovers), and parachutes packed in cans. 

Spacecraft propellant lines were precision-cleaned. High-efficiency particulate air (HEPA) filters89 were employed on the vents of each rover’s 

core box, which contained computers as well as other critical electronics. The aim was to keep an estimated 99.97 percent of particles 0.3 

microns or larger inside. These HEPA filters were also designed to help 

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filter out Martian dust later in the mission. The planetary protection 

team worked closely with spacecraft design engineers to set contamination reduction strategies and to determine which pieces of hardware 

needed to be cleaned and which required other approaches such as heat 

sterilization.90

Each Mars Exploration Rover had to comply with requirements 

to carry a total of no more than 300,000 bacterial spores on surfaces from which the spores could enter the Martian environment.91

An issue arose with spores detected in the acoustic foam backing 

of the fairing92 enclosing the MER-1 spacecraft. At a 2004 Planetary 

Protection Advisory Committee93 meeting after the MERs’ launches, 

possible improvements to the fairing’s foam layer manufacturing process were discussed. The Committee reached the conclusion that 

cleanliness and bioburden requirements had to be included in launch 

vehicle (as well as spacecraft) manufacturing specifications.94

As with other missions, the trajectories of various components 

had to be carefully designed to prevent unwanted impacts. In particular, when the third stage of MER’s Delta launch vehicle (which had 

not been cleaned sufficiently to allow it to impact with Mars) separated 

from the spacecraft, the two objects were on nearly identical paths. 

This shared course had been set so that both objects would miss Mars. 

Approximately 10 days later, the spacecraft performed its first trajectory correction maneuver (TCM) in order to readjust its path to arrive 

at Mars.95

 90.

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When Biospheres Collide

Reducing Bioload and Conducting Bioassays on the 

Phoenix Mars Lander and Other Mars Spacecraft

Contamination—foreign matter that does not belong on the spacecraft—can be grouped into two types: molecular and particulate. 

Molecular contamination includes the cumulative buildup of individual molecules, such as greases and oils. Particulate contamination 

refers to the deposition of visible, typically micrometer-sized conglomerations of matter, such as dust. These particulates can fall from the 

air onto exposed surfaces. Even miniscule quantities of contaminants 

can seriously degrade the performance of spacecraft hardware. So can 

outgassing, such as from various organic contaminants.96

The presence of organic contamination can be especially troublesome for Mars missions with instruments built to measure extremely 

small amounts of organic substances, in particular, biotic material. 

Mars lander equipment capable of detecting even one single spore can 

generate erroneous results if terrestrial microorganisms are also present. Thus, building clean spacecraft is absolutely critical for Mars as 

well as other missions concerned with the possible presence of life. 

Typical Bioload Reduction Procedures

The procedures used to reduce and assay bioloads on the Phoenix 

Mars Lander provide a good example of the typical post-Viking 

approach for lander spacecraft bound for Mars. These procedures were 

applied during Phoenix’s assembly and test operations beginning in 

early 2006 at Lockheed Martin Space Systems’ Denver, Colorado, facility.97 The operations were quite similar to those used earlier on MPL, 

 96.

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Figure 7.2 Phoenix spacecraft assembly, with Lockheed Martin Space Systems technicians 

working on the science deck of the Phoenix Mars Lander. Assembly operations took place in 

a class 100,000 cleanroom with NASA’s planetary protection practices being strictly followed 

to prevent organics from being transported to Mars. The lander’s robotic arm, built by JPL, is 

at the top.

MER, and Pathfinder. Assembly of the Phoenix spacecraft is depicted 

in figure 7.2.

To begin with, the Phoenix parts delivered to Lockheed Martin 

for inclusion in the spacecraft arrived already somewhat clean. The 

project’s many subcontractors and vendors were characteristically 

suppliers to the aerospace industry and understood the requirements 

of planetary protection. They generally followed precision-cleaning 

protocols and assembly of components in relatively clean areas.98

Typical precision-cleaning procedures targeted the removal of both 

particles and molecular films such as oils and greases and consisted 

of wiping gross contamination off the article, followed by an application of organic solvents and aqueous rinses with or without ultrasonic treatment. The article was then sometimes subjected to vapor 

 98.

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degreasing, followed by a final rinse typically conducted with an isopropyl or other alcohol solution.99

The Phoenix parts were usually delivered to Lockheed Martin 

containing less than 10,000 spores per square meter. The parachute, 

however, contained less than an estimated 10 spores per square 

meter because it had been subjected to dry heat microbial reduction 

involving a bakeout at temperatures above 110°C. This procedure was 

necessary because of the difficulty of adequately cleaning the large 

component. To prevent subsequent contamination, the parachute 

was double bagged before transport and packed with sample strips, 

which were then archived upon arrival at Lockheed Martin, available 

if needed to confirm parachute cleanliness. If there was a subsequent 

indication of life on Mars, it would be compared with the strips to 

hopefully prove that the life-forms had not been carried to Mars on 

the parachutes.100

After Phoenix parts other than the parachute arrived at Lockheed 

Martin, they were usually subjected to further bioload reduction. The 

basic tools for this were cloth wipes saturated with a 100 percent isopropyl alcohol (IPA) solution. The cleaning action of these wipes was 

due mainly to the IPA’s solvent properties, but a frictional action was 

applied as well in order to lift contamination off the parts’ surfaces. 

The cloth wipes were repeatedly folded to keep only clean sections 

touching the parts’ surfaces.

Biocides such as sodium hypochlorite (chlorine bleach) and hydrogen peroxide, which can also lower bioloads on a surface, were generally not approved for use on flight hardware since they are strong 

oxidants that can tarnish metals and break down coatings. Ethylene 

oxide gas was another biocide that had been considered in the past, 

but its benefits were too specific—it killed some microbes but not others—and it was also toxic to humans.101

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In past missions, Lockheed Martin subjected additional parts 

besides the parachute to DHMR bakeouts when their bioloads would 

have been difficult to reduce adequately in other ways due to such factors as their sizes, shapes, and materials. The aeroshells for the MER 

landers, for instance, which had been built by Lockheed Martin, were 

subjected to DHMR. The Phoenix aeroshell did not receive such treatment, however. It had been fabricated in the 1999 to 2000 time period 

in accordance with Pathfinder protocols. While its composite structures saw high enough temperatures during their curing processes 

to demonstrate that they could withstand the bakeout temperature 

cycle, mission staff feared that the adhesives on the fittings inside the 

aeroshell may not have been sufficiently temperature resistant to withstand the DHMR regime.102

The Bioassay Program

Bioassays of Mars spacecraft were performed typically using two 

basic sampling tools: absorbent cotton swabs mounted on wood applicator sticks and polyester wipe cloths.

Wet swab sampling. The swabs were purchased individually prepacked in test tubes for protection, then sterilized by autoclaving at a 

minimum of 121°C for at least 20 minutes. After this, they were checked 

regularly for sterility. Before sampling, the swab was removed from its 

container and moistened with sterile distilled or deionized-distilled 

water. The swab was used to sample a 2" × 2" (25 cm2

) sample area of 

the part’s surface. The swab was rubbed slowly and thoroughly over this 

surface three times, reversing direction between successive strokes and 

slowly rotating the head of the swab throughout the procedure. The head 

of the swab was then broken off and dropped back into its test tube into 

the sample recovery liquid consisting of sterile distilled or deionizeddistilled water.103

102. Ibid.; Donald C. Larson, Phoenix Flight Program Planetary Protection Lead, Lockheed Martin 

Space Systems Company, Denver, CO, telephone interview by author, 2 February 2007.

103. Lockheed Martin, “Microbiological Assay Procedure” for Phoenix Mars Lander flight 

hardware, document PHX-312-606. 

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Wet wipe sampling. The wipes were 100 percent polyester, 9" × 9" 

(23 cm × 23 cm) cleanroom cloths. These wipes were sterilized by 

autoclaving them under the same conditions as for the swabs. For 

sampling purposes, the wipes were premoistened with sterile distilled 

water. The wipes were folded in quarters and placed flat on the surface to be sampled, then rubbed over the surface using a firm, steady 

pressure. They were then refolded so that the contaminated surface 

was inside the new folded configuration. The wipe was rubbed over 

the sample area three times, rotating the direction of motion 90° after 

each complete coverage of the sample area. The wipes were rinsed in 

buffered distilled water, the assay recovery liquid that would extract 

the contaminants removed from the surface. This recovery liquid contained 0.02 percent of a surfactant (potassium dihydrogen phosphate) 

to break up the surface tension of the liquid.104

Exploring the Special Areas of Mars

By 2002, exploration data had been received from the Mars 

Global Surveyor and Mars Odyssey orbiting spacecraft that strongly 

suggested the need for a new designation for certain sections of the 

Martian surface. These were the locales that were especially interesting for extant life investigations while at the same time were potentially quite vulnerable to terrestrial biotic contamination. Recognition 

of this situation led COSPAR to introduce the term “special region” in 

2002 as part of the Mars planetary protection policy. Prior to this, forward contamination prevention requirements for spacecraft landing 

on the Martian surface fell into one of two categories distinguished by 

the mission’s purpose:

•	 Category IVa—Landers without extant life-detection investigations.

•	 Category IVb—Landers with extant life-detection investigations.

The new special regions designation differed from those above in 

that it was for Martian environments that needed a high degree of 

104. Bruce Keller, Phoenix systems test engineer, Lockheed Martin Space Systems Company, 

Denver, CO, interview by author, 15 August 2006.

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protection, regardless of the mission purpose or category.105 COSPAR 

defined a special region as “a region within which terrestrial organisms are likely to propagate, or a region which is interpreted to have 

a high potential for the existence of extant martian life-forms,”106

and designated all missions that might come into contact with such 

regions as Category IVc. This designation applied to missions without 

as well as with life-detection instrumentation. Special regions were 

thought to be those where liquid water was present or might occur,

and they included the following areas:

•	 Subsurface areas with access to a depth where the presence of 

liquid water was probable.

•	 Penetrations into polar caps.

•	 Areas with hydrothermal activity.107

Modifications of Planetary Protection Policy

NASA incorporated the Mars special regions concept into its own 

planetary protection policy in 2005 by modifying NASA Procedural 

Requirement 8020.12C—Planetary Protection Provisions for Robotic 

Extraterrestrial Missions. NASA identified some hurdles, however, 

to incorporating the policy into its present Mars exploration operations. In 2005, a National Research Council committee referred to 

as NRC PREVCOM completed the NASA-requested study, Preventing 

the Forward Contamination of Mars, and found that “there is at this 

time insufficient data to distinguish with confidence ‘special regions’ 

from regions that are not special.”108 NRC PREVCOM identified a key 

issue related to current limits on the resolution that can be obtained 

from Mars observations. The problem stems from the fact that signifi105. MEPAG Special Regions Science Analysis Group, “Findings of the Special Regions Science 

Analysis Group,” unpublished white paper, p. 66, posted April 2006 by the NASA-JPL 

MEPAG, p. 4, http://mepag.jpl.nasa.gov/reports/index.html (accessed 26 January 2011).

106. COSPAR Planetary Protection Policy, 20 October 2002 (amended 24 March 2005), approved 

by the bureau and council, World Space Congress, Houston, TX, http://www.cosparhq.org/

scistr/PPPolicy.htm.

107. Ibid.

108. Committee on Preventing the Forward Contamination of Mars, SSB, National Research 

Council, Preventing the Forward Contamination of Mars (unedited prepublication copy) 

(Washington, DC: National Academies Press, 2005).

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When Biospheres Collide

cant horizontal and spatial diversity occurs on Mars in kilometer and 

even centimeter spatial scales, but relevant observational data often 

have spatial resolutions no better than ~3 × 105 km2. NRC PREVCOM 

thus recommended an interim policy designating all of Mars a special 

region, until such time as more data could warrant more a precise 

designation.109

To discern between special and nonspecial regions, NASA made 

a request of the Mars Exploration Program Analysis Group (MEPAG), 

the space agency’s forum for providing science input to Mars projects 

over the next several decades. NASA asked MEPAG to charter a Special 

Regions Science Analysis Group (SR-SAG)110 to determine whether it 

was indeed necessary to designate all of Mars as special, or just parts 

of the planet, based on careful studies of the limits to life of known 

Earth organisms considered in light of known Martian environmental conditions. The answer to this question would strongly affect the 

conduct of future Mars missions that were already in the planning 

stage. The major issue, however, was whether even with the newest 

data, sufficient scientific information existed to construct more precise designations.111

The Period of Biological Interest

Space scientists have found from recent orbiter and rover data 

that Mars is far more diverse than indicated earlier. As a result, the 

scientific community has identified a very large number of sites for 

future exploration, and many researchers anticipate that the period 

of Martian biological interest will span the 21st century. Based 

on input from the NASA Planetary Protection Officer, the MEPAG 

SR-SAG study conducted to examine special region designations112

employed a 100-year timeframe “over which the existence of martian 

special regions would be considered and could be encountered by 

109. MEPAG, Findings, p. 5.

110. David W. Beaty, Karen L. Buxbaum, and Michael A. Meyer, “Findings of the Mars Special 

Regions Science Analysis Group,” Astrobiology 6(5) (2006): 677–678.

111. MEPAG, Findings, p. 2; Margaret Race comments, 18 September 2007.

112. Margaret Race, comments to authors regarding manuscript of this book, sent 18 September 

2007.

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any given mission.”113 The MEPAG analysis took into account past 

and present climate and included consideration of current special 

regions as well as the possibility that a locale could become a special 

region within a century after a spacecraft’s arrival, due to a natural 

event such as a volcanic eruption. Observational data backed this 

up—the southern polar cap appears to be able to change within a 

100-year time scale. Noticeable changes in the carbon dioxide ice 

cover114 have occurred from one year to another,115 and modifications 

on the scale of decades have occurred to the polar cap outline. In 

addition, observational data revealed that where carbon dioxide ice 

is disappearing, water ice is being exposed.116

How Far Below the Surface of Mars Is Planetary Protection 

Relevant?

The MEPAG SR-SAG study put an important bound on the maximum depth beneath the Martian surface to which planetary protection 

interest extended. The study used formulas estimating the expected 

crater magnitudes generated by different-sized landers accidentally 

crashing at various velocities into a range of surface materials and 

concluded that only the outermost 5 meters or so of the Martian 

crust was likely to be contaminated by such impacts. Regions of the 

planet that lie deeper were not of relevance for planetary protection 

considerations.117

113. MEPAG, Findings, p. 13. 

114. P. C. Thomas, M. C. Malin, P. B. James, B. A. Cantor, R. M. E. Williams, and P. Gierasch, 

“South Polar Residual Cap of Mars: Features, Stratigraphy, and Changes,” Icarus 174 (2005): 

535–559, as reported in MEPAG, Findings, p. 8.

115. Michael C. Malin, Michael A. Caplinger, and Scott D. Davis, “Observational Evidence for 

an Active Surface Reservoir of Solid Carbon Dioxide on Mars,” Science 294 (7 December 

2001): 2146–2148.

116. Timothy N. Titus, Hugh H. Kieffer, and Phillip R. Christensen, “Exposed Water Ice Discovered 

Near the South Pole of Mars,” Science 299 (14 February 2003): 1048–1051; S.  Douté, 

Y. Langevin, F. Schmidt, B. Schmitt, M. Vincendon, J. P. Bibring, F. Poulet, E. Deforas, and 

B. Gondet, “Monitoring and Physical Characterization of the South Seasonal Cap of Mars 

from Omega Observations” (Fourth Mars Polar Science Conference, Davos, Switzerland, 

2–6 October 2006), p. 8030, http://www.lpi.usra.edu/meetings/polar2006/pdf/download/

alpha_a-g.pdf (accessed 26 January 2011).

117. MEPAG, Findings, pp. 10–11. 

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When Biospheres Collide

The Minimum Temperature Likely To Support Propagation of Life

Microbes exist on Earth that can stay alive at temperatures well 

below the normal freezing point of water in environments such as 

within glacial ice, sea ice, and permafrost. Various mechanisms 

make this possible. Certain impurities such as mineral acids or salts 

can reduce the freezing point of water resulting in unfrozen intergranular veins that transport nutrients to and waste products from 

the microbes. Some cells can themselves resist freezing, while others synthesize stress proteins, reduce their size, enter dormant or 

spore states, adapt their components (such as making changes in 

their fatty acid and lipid composition), or alter the liquids in their 

cytoplasm. The Mars special regions designation, however, is concerned not only with cells’ abilities to survive, but also with their 

abilities to propagate. 

Many researchers have demonstrated some cellular metabolic 

activity at temperatures as low as –20°C, although at the lowest temperatures, activity was insufficient to support cell replication and 

was not sustained beyond a few weeks. According to MEPAG, no one 

has conclusively demonstrated cell replication at or below –15°C. 

Adding a safety factor of –5°C, the MEPAG SR-SAG study thus proposed that based on current data, an area needed to experience temperatures above –20°C to be designated a special region. Previously 

unknown extremophiles are always being discovered, however. If 

Earth organisms were found that were able to replicate at temperatures at or below –20°C, the MEPAG recommendation would need to 

be reevaluated.118

118. H. A. Thieringer, P. G. Jones, and M. Inouye, “Cold Shock and Adaptation,” BioEssays

20 (1998): 49–57; C. A. Bakermans, A. I. Tsapin, V. Souza-Egipsy, D. A. Gilichinsky, and 

K. H. Nealson, “Reproduction and Metabolism at –10°C of Bacteria Isolated from Siberian 

Permafrost,” Environmental Microbiology 5(4) (April 2003): 321–326; Blaire Steven, Richard 

Léveillé, Wayne H. Pollard, and Lyle G. Whyte, “Microbial Ecology and Biodiversity in 

Permafrost,” Extremophiles 10(4) (August 2006): 259–267; J. N. Breezee, N. Cady, and J. T. 

Staley, “Subfreezing Growth of the Sea Ice Bacterium Psychromonas ingrahamii,” Microbial 

Ecology 47(3) (April 2004): 300–304; MEPAG, Findings, pp. 12–14.

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The Minimum Water Activity Likely To Support Propagation of Life

While many terrestrial spores can survive extreme desiccation, 

microbes require liquid water in order to multiply and increase their 

biomass. Reasons for needing the presence of liquid water include 

making nutrients available to the cells and transporting waste products away from them. The MEPAG SR-SAG report thus proposed a 

threshold for the minimum amount of liquid water activity that needs 

to be present to classify an area as a special region. Water activity is 

a quantitative measure of the extent to which water is available in a 

region. It is defined as the actual vapor pressure of the water that is 

present divided by the vapor pressure that pure water would have at 

the same temperature. As an example, if pure water was present, it 

would have a water activity of exactly one. 

The MEPAG SR-SAG report noted that based on current data, terrestrial organisms are not known to reproduce at water activities less 

than 0.62. Adding a safety margin, a water activity threshold of at 

least 0.5 was proposed when considering special region designation 

for an area.119

Thermodynamic Disequilibrium and Martian Special Regions

MEPAG SR-SAG study results indicated that in regions of the Mars 

surface and shallow subsurface that are at or close to long-term thermodynamic equilibrium,120 conditions are not right for the propagation 

of terrestrial microbes because the temperatures and water activities 

are considerably below the thresholds required. Regions may exist on 

Mars, however, in long-term disequilibrium, “where water and temperature were in equilibrium . . . at an earlier time, but for which conditions have changed.”121 In such regions, the propagation of life may 

be more strongly supported, justifying their classification as special 

119. MEPAG, Findings, pp. 14–16.

120. When a system is in thermodynamic equilibrium, all parts of it have attained a uniform 

temperature that is the same as that of the system’s surroundings.

121. John D. Rummel, “Special Regions in Mars Exploration: Problems and Potential,” Acta 

Astronautica 64 (2009): 1293–1297.

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When Biospheres Collide

Figure 7.3 Mars Global Surveyor evidence of recent liquid water: gully landforms possibly 

caused by geologically recent seepage and runoff.

regions. Natural long-term disequilibrium conditions on the Martian 

surface would have developed as a result of geological phenomena such 

as geothermal vents or volcanoes.122

Martian Gullies: Are Some of Them Special Regions?

The genesis of gullies on the Martian surface may have involved 

liquid water (see figures 7.3 and 7.4). What’s more, the features adjacent to some of the gullies suggest that they might be so young as to 

be sites at which liquid water could occur today or in the near future, 

at least for brief periods, which would classify these sites as special 

regions. It is by no means sure, however, that it was liquid water that 

formed these features, and this contributes to the difficulty of knowing 

which Martian surface areas should be designated as special regions. 

122. MEPAG, Findings, pp. 26–27.

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Figure 7.4 Gullies eroded into the wall of a meteor impact crater. This picture taken by the 

Mars Global Surveyor’s Mars Orbiter Camera shows channels and associated aprons of debris 

that could have formed by groundwater seepage, surface runoff, and debris flow. The lack of 

small craters superimposed on the channels and apron deposits suggests that these features 

are geologically young. It is possible that these gullies are indicative of liquid water present 

within the Martian subsurface today.

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When Biospheres Collide

Alternate hypotheses consider gully-forming mechanisms such as 

flows of liquid carbon dioxide released from below-ground reservoirs 

sealed with dry-ice barriers123 or dry, granular flows not employing 

a volatile substance such as water or carbon dioxide. Dry flows have 

been modeled and appear plausible for cases when individual particle 

settling is slower than characteristic terrestrial debris flow speeds, as 

would be the situation with Mars’s reduced gravity.124

The MEPAG SR-SAG study recommended that those Martian gullies 

and gully-forming regions in which liquid water could possibly surface 

within the next 100 years be classified as special regions, but it is problematic to identify such areas. A clue can be given by the gully’s age. A 

gully formed in the recent past may be more likely to have continued 

activity than a gully that has remained static for a long period. Samplings 

of Martian gully data suggest that all of them are young relative to 

Martian geological time scales, and that liquid water sources may exist at 

shallow depths beneath some of them.125 No known geomorphic criteria 

exist, however, that can predict which of the tens of thousands of gullies 

on Mars are likely to become active in the next century, although gullies 

with the following characteristics are being examined more closely:

•	 Young ages.

•	 Channels within preexisting gully complexes.

•	 Bright material visible, possibly ice or salts.

For the purposes of planetary protection, the best strategy at present regarding gully-forming areas is probably to extend special region 

status to all of them, rather than only to specific preexisting gully features. As of yet, however, the scales of Mars’s gully-forming areas have 

not been well defined.126

123. D. S. Musselwhite, T. D. Swindle, and J. I. Lunine, “Liquid CO2 Breakout and the Formation 

of Recent Small Gullies on Mars,” Geophysical Research Letters 28(7) (2001): 1283–1285; 

N. Hoffman, “Active Polar Gullies on Mars and the Role of Carbon Dioxide,” Astrobiology

2(3) (2002): 313–323. 

124. Allan H. Treiman, “Geologic Settings of Martian Gullies: Implications for Their Origins,” 

Journal of Geophysical Research 108(E4) (8 March 2003): 8031; T. Shinbrot, N. H. Duong, 

L. Kwan, and M. M. Alvarez, “Dry Granular Flows Can Generate Surface Features Resembling 

Those Seen in Martian Gullies,” Proceedings of the National Academy of Sciences 101(23) 

(8 June 2004): 8542–8546; MEPAG, Findings, pp. 26–27.

125. Michael C. Malin and Kenneth S. Edgett, “Evidence for Recent Groundwater Seepage and 

Surface Runoff on Mars,” Science 288 (30 June 2000): 2330–2335.

126. MEPAG, Findings, pp. 29–30. 

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Midlatitude Indications of Snow and Ice

The middle Martian latitudes exhibit a range of features that 

some researchers have interpreted as evidence of ice-bearing materials. These possible special regions may have been formed during a 

period of different climatic conditions in Mars’s past, when much of 

the midlatitudes may have been mantled by ice-rich materials. Two 

remnants of these materials are particularly relevant for the discussion of special regions:

1. Midlatitude mantle covering major sections of Mars between 

30° and 60° latitude in both hemispheres.127

2. Materials called pasted-on terrain that are most commonly 

found on poleward-facing midlatitude slopes such as crater 

walls and massifs.

Midlatitude mantle is a layered deposit that scientists estimate from 

Mars data to be 1 to 10 meters thick. Mustard et al. proposed that the 

roughening observed on sections of the mantle resulted from sublimation of ice out of the mixture of ice and dust that originally produced 

the mantle.128 The midlatitude mantle varies noticeably as a function 

of latitude. Lower latitudes of ~30° to 45° characteristically have areas 

of smooth, intact mantle next to areas where the mantle has been completely stripped from the surface. Higher latitudes of ~45° to 55° typically have a knobby surface texture indicating incomplete removal of 

the mantle material.129 Latitudes higher than ~55° exhibit the least 

removal of mantle material, which suggests that deposits at these lat127. M. A. Kreslavsky and J. W. Head, “Kilometer-Scale Roughness of Mars: Results from MOLA 

Data Analysis,” Journal of Geophysical Research 105 (2000): 26695–626712, http://www.

planetary.brown.edu/planetary/documents/2447.pdf (accessed 26 January 2011); M. A. 

Kreslavsky and J. W. Head, “Fate of Outflow Channel Effluents in the Northern Lowlands of 

Mars: The Vastitas Borealis Formation as a Sublimation Residue from Frozen Ponded Bodies 

of Water,” Journal of Geophysical Research 107(E12) (2002): 5121, http://www.planetary.

brown.edu/planetary/documents/2686.pdf (accessed 26 January 2011); M. A. Kreslavsky 

and J. W. Head III, “Mars: Nature and Evolution of Young Latitude-Dependent Water-IceRich Mantle,” Geophysical Research Letters 29(15) (2002), http://www.planetary.brown.edu/

planetary/documents/2756.pdf (accessed 26 January 2011).

128. J. F. Mustard, C. D. Cooper, and M. K. Rifkin, “Evidence for Recent Climate Change on Mars 

from the Identification of Youthful Near-Surface Ground Ice,” Nature (2001): 411–414, http://

www.planetary.brown.edu/planetary/documents/2610.pdf (accessed 26 January 2011).

129. R. E. Milliken, J. F. Mustard, and D. L. Goldsby, “Viscous Flow Features on the Surface of 

Mars: Observations from High Resolution Mars Orbiter Camera (MOC) Images,” Journal of 

Geophysical Research 108(E6) (2003): 5057.

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When Biospheres Collide

itudes have experienced less erosion and thus “may still be ice-rich 

beneath a thin layer of ice-free dust.”130 Mars Odyssey data supported 

the possibility of near-surface water ice by detecting an increased 

abundance of hydrogen within the upper meter of the surface at latitudes greater than about 55°. There is, however, no evidence for melting over much of this region. The mantle material was likely emplaced 

between 2 and 0.5 million years ago, and it has been undergoing sublimation and desiccation for the last half million years. Scientists do not 

predict active layers of water flow.

Pasted-on terrain consists of apparently young mantle deposits 

that have been preferentially preserved on poleward-facing slopes in 

the midlatitudes of both Martian hemispheres. They were initially 

noted by Malin and Edgett,131 who thought they resembled accumulations of snow on colder, more frequently shadowed surfaces, even 

though the materials are not light-toned like snow. Christensen, using 

Mars Odyssey images, also noted these accumulations and speculated 

that they might be remnants of old snow accumulations.132 The deposits appear to be covered with a residue of dust that could be protecting 

snow layers from further sublimation.133

Both Christensen and Milliken et al.134 proposed that the pasted-on 

terrain might be the source of water that created the midlatitude gullies discussed above. While the temperatures at the Martian midlatitudes are so cold that the presence of liquid surface water is unlikely, 

Christensen theorized that since the surface of a snow deposit had 

mixed with dust prevalent in the Martian atmosphere, this created a 

conglomeration darker than the snow alone that readily absorbed solar 

energy. This top layer then transmitted the energy, in the form of heat, 

to the pristine layers of snow several centimeters beneath. In roughly 

5,000 years, according to his calculations, this heat melted enough of 

130. MEPAG, Findings, p. 32.

131. M. C. Malin and K. S. Edgett, “Mars Global Surveyor Mars Orbiter Camera: Interplanetary Cruise 

Through Primary Mission,” Journal of Geophysical Research 106 (October 2001): 23429–23570.

132. P. R. Christensen, “Formation of Recent Martian Gullies Through Melting of Extensive WaterRich Snow Deposits,” Nature 422 (6 March 2003): 45–48.

133. MEPAG, Findings, p. 33. 

134. Milliken et al., “Viscous Flow.” 

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the subsurface snow to erode underlying rock and carve gullies.135 Some 

of the pasted-on mantle areas thus may constitute special regions.136

Polar Caps

In COSPAR’s 2005 planetary protection policy statement regarding 

special regions,137 the polar caps were mentioned as an example of a 

special region. But the results of the MEPAG SR-SAG report suggested 

that the polar caps do not actually fit the special regions designation.138

Jakosky et al.139 (and others) have calculated that at present, maximum summer temperatures reach only about –70°C in the Martian 

polar regions, too cold for them to be naturally occurring special 

regions. Resolution of this question will have to wait until additional 

data on the polar regions are received and interpreted.

Creating a Special Region with a Spacecraft

MEPAG’s analysis revealed that it was possible for spacecraft to 

induce conditions that favored biological propagation within a localized 

region, thus transforming an area that was not a special region into one. 

For instance, spacecraft generate heat, which can enhance the conditions for the propagation of life. In regions where ice is present, thermal 

emissions from spacecraft could result in the localized elevation of temperatures and the melting of ice deposits, leading to the formation of 

135. Ron Cowen, “Martian Gullies: Carved by Melting Snow?” Science News 163(8) (22 February 

2003): 116, http://www.sciencenews.org/articles/20030222/fob3.asp.

136. MEPAG, Findings, p. 34; Rummel, “Special Regions in Mars Exploration: Problems and 

Potential,” 1296. 

137. COSPAR Planetary Protection Policy, 20 October 2002 (amended 24 March 2005), approved 

by the bureau and council, World Space Congress, Houston, TX, http://www.cosparhq.org/scistr/

PPPolicy.htm.

138. MEPAG SR-SAG, “Findings of the Mars Special Regions Science Analysis Group,” 

Astrobiology 6, no. 5 (2006): 718.

139. B. M. Jakosky, B. G. Henderson, and M. T. Mellon, “The Mars Water Cycle at Other Epochs: 

Recent History of the Polar Caps and Layered Terrain,” Icarus 102 (1993): 286–297; MEPAG, 

“Findings,” unpublished white paper, p. 47. 

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When Biospheres Collide

liquid water reservoirs. Microbes either initially present in such an area 

or transported there by the spacecraft could possibly replicate.

Many spacecraft employ radioisotope thermal generators (RTGs) to 

supply electrical energy. These devices, which are typically powered 

by the radioactive decay of plutonium, are a perennial heat source. 

Their use necessitates an in-depth analysis to determine whether they 

will create temperatures local to the RTG above the threshold needed 

for biotic propagation.140

A key factor in the impact of spacecraft-induced environmental 

changes is the duration of the new conditions and whether it is of 

sufficient length to permit microbial propagation. The highest growth 

rates documented by the MEPAG SR-SAG study at the temperatures 

of interest on Mars (–15°C to +5°C) indicated that significant replication of terrestrial microorganisms would not occur if the duration of 

a maximum surface temperature of –5°C did not exceed 22 hours, a 

maximum of 0°C did not exceed 3 hours, or a maximum of 5°C did not 

exceed 1 hour.141 Since the boiling point of water at a Martian surface 

atmospheric pressure of 8.6 millibars142 is 5°C, there was no need to 

extend this analysis to higher temperatures. 

NASA and COSPAR continue to work toward reaching a consensus within the space science community of what constitutes a Mars 

special region. One such effort toward this end was the COSPAR colloquium held in Rome, Italy, 18–20 September 2007. John Rummel, 

the former NASA PPO and (at the time of this writing) current Senior 

Scientist for Astrobiology in the Science Mission Directorate at NASA 

140. MEPAG, Findings, pp. 53–54.

141. D. A. Ratkowsky, J. Olley, T. A. McMeekin, and A. Ball, “Relationship Between Temperature 

and Growth Rate of Bacterial Cultures,” Journal of Bacteriology (1982): 1–5; D. A. Ratkowsky, 

R. K. Lowry, T. A. McMeekin, A. N. Stokes, and R. E. Chandler, “Model for Bacterial Culture 

Growth Rate Throughout the Entire Biokinetic Temperature Range,” Journal of Bacteriology

(1983): 1222–1226; R. B. Haines, “The Influence of Temperature on the Rate of Growth of 

Sporotrichum Carnis from –10 to 30°C.” Journal of Experimental Biology (1931): 379–388. 

All papers were cited in MEPAG, Findings, p. 55.

142. By means of comparison, surface atmospheric pressure on Earth is approximately 120 times 

higher.

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Figure 7.5 Scientists have speculated that the tube-like structures in these electron 

microscope images may be microscopic fossils of primitive, bacteria-like organisms that 

lived on Mars more than 3.6 billion years ago. A two-year NASA investigation found organic 

molecules, mineral features characteristic of biological activity, and possible microscopic 

fossils such as these inside an ancient Martian rock that fell to Earth as a meteorite. The 

largest of these structures are less than 1/100th the diameter of a human hair, while most are 

10 times smaller.

Headquarters, is very active in this undertaking, which seeks to define 

the appropriate use of the special regions designation within COSPAR 

and NASA planetary protection categories. The results of this work 

will impact many nations’ plans for future missions to Mars.

Mars Sample Return

The interest in bringing back sample materials from solar system 

bodies, especially Mars, increased measurably in 1996 when the analysis of a Martian meteorite found on Earth revealed possible evidence 

of life (see figure 7.5) as well as the past presence of liquid water on 

the Red Planet. This find, coupled with the discovery that even under 

extremely harsh conditions on Earth, life can be found wherever there 

is liquid water and energy, reinforced the hypothesis that life may have 

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When Biospheres Collide

Figure 7.6 An artist’s concept of the launch of a Martian sample back toward Earth.

emerged on Mars at some point in the planet’s past. Although considerable data suggest that the Martian surface is hostile to life as we 

know it, plausible scenarios have been presented for the existence of 

microbes in special locations such as possible hydrothermal oases or 

subsurface regions. 

Uncertainties regarding life on Mars may be resolved or at least 

reduced through the examination of returned Martian samples.143 Sample 

return missions are also relevant to other objectives, such as the following:

•	 Understanding the evolution of the Martian surface and interior 

via local and global studies of its chemistry, lithology, and 

morphology.

•	 Characterizing the dynamics and chemistry of the Martian 

atmosphere.

143. SSB Task Group on Issues in Sample Return, Mars Sample Return—Issues and 

Recommendations (Washington, DC: National Academies Press, 1997), pp. vii, 2–3.

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Return to Mars

•	 Determining the degree to which climatic conditions have 

evolved over time.

•	 Searching the planet not only for extinct or extant life (or 

remnants thereof), but also for evidence of prebiotic organic 

compounds and prebiotic chemical evolution.

•	 Exploring the interaction of Mars with the solar wind and the 

extent to which this interaction affects the state of the planet’s 

upper atmosphere and ionosphere.144

While NASA at one time envisioned Mars sample return missions taking place early in the 21st century, this target has been 

delayed, largely because of significant technical challenges. One 

approach for such an effort would be to use a robotic lander spacecraft that included a rocket capable of taking off from Mars to send 

samples of rocks, soils, and atmosphere back to Earth for detailed 

chemical and physical analysis. Using Earth laboratories, scientists 

could measure sample characteristics much more precisely than 

they could remotely. In addition, for decades after the samples 

were returned, they could yield new information as future emerging technologies were employed to study them.145

Figure 7.6 is an artist’s concept of a spacecraft lifting off from Mars 

to return the samples it collected back to Earth.

The Mars Science Laboratory (MSL) mission, scheduled for launch 

in 2011, actually had a sample return component under study. To practice caching Mars specimens, the mission team considered including a 

hockey-puck-sized sample cache to store Martian material until some 

future mission could bring it back to Earth. The objective of installing 

this caching capability in MSL, according to Alan Stern, NASA’s former Science Mission Directorate Associate Administrator, was to “build 

the foundation of support for future Mars sample return activities, not 

only in scientific and public circles, but also in Congress and the White 

144. SSB, “On NASA Mars Sample Return Mission Options,” National Academies Web site, 

http://www7.nationalacademies.org/ssb/msrrep.html (last updated 10 February 2000, 

accessed 3 November 2006).

145. JPL, “Missions to Mars,” NASA’s Mars Exploration Program Web site, http://marsprogram.

jpl.nasa.gov/missions/future/futureMissions.html (last updated 22 March 2006, accessed 

1 November 2006).

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When Biospheres Collide

House Office of Management and Budget.”146 The sample cache idea was 

not limited to the MSL project. The European Space Agency also considered including it in its ExoMars program.

Although the execution of Mars sample return missions is in the 

future, it is interesting to briefly examine the considerable scientific 

and engineering efforts that have already gone into conceptualizing 

and planning for such missions.

Past Efforts in the Design of Sample Return Missions

In response to NASA’s 1995 request, the National Research 

Council’s Space Studies Board (SSB) specifically convened the Task 

Group on Issues in Sample Return to examine challenges related to 

bringing back material from other solar system bodies.147 The primary driver for this action was a Mars sample return mission that, 

in the 1990s, had been envisioned for a 2005 launch, although the 

conclusions and recommendations in the Task Group’s study applied 

to return missions from “any solar system body with a comparable 

potential for harboring life.”148

Work on sample return concepts focused on issues of potential back 

contamination—i.e., how to protect Earth from contamination by exotic 

biota. This involved assessments of the potential for the following:

1. A viable biological entity to be in a return sample.

2. Large-scale impacts if that entity entered the biosphere of 

Earth.

The small sizes of any samples returned would preclude concern 

about their direct toxicity to life on Earth, due to either their chemistry or their radioactivity. These potential dangers would also be mitigated through laboratory protocols. Replicating biohazards, however, 

are serious planetary protection concerns. Even small return samples 

146. Leonard David, “Mars Sample Return Proposal Stirs Excitement, Controversy,” Space.com,

26 July 2007, http://www.space.com/4116-mars-sample-return-proposal-stirs-excitementcontroversy.html (accessed 26 January 2011).

147. Wesley T. Huntress to Claude R. Canizares, 20 October 1995, in SSB, Mars Sample Return, 

Appendix, p. 46. 

148. SSB, Mars Sample Return, p. 8. 

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Return to Mars

could conceivably harm our biosphere if they were able to propagate 

within it.149

One of the key questions pertaining to Mars that the Task Group 

examined was what scientific analyses needed to be performed to 

reduce uncertainty regarding the existence of life on the Red Planet. 

The Task Group also assessed the efficacy of existing technology for 

preventing the return of uncontained and unsterilized Martian material and made recommendations for the appropriate distribution of the 

samples.

Factors Regarding Possible Extant Life on Mars

The Task Group examined characteristics of the Martian climate, 

especially what it might have been like during the planet’s early history (prior to 3.5 billion years ago). At that time, geological evidence 

indicates that conditions were possibly warmer and friendlier to life, 

with liquid water flowing on the surface. Hydrothermal environments 

may also have been common on the early Mars. 

Studies of Earth bacteria suggest that life may first have arisen 

in hot-spring environments or that during its evolution it resided for 

some time under such conditions. Thus it was deemed plausible that 

Martian bacteria may once have existed that followed a similar evolutionary path.150

The Task Group also analyzed mechanisms by which Martian lifeforms, either of independent origin or having traveled to the planet from 

Earth by means of meteorite impacts, could have survived in localized 

niches and as spores until today. The Viking mission’s experiments 

convinced many scientists at the time that Mars was probably devoid of 

life. But the Task Group was aware of the limitations of that mission’s 

technology, which was only able to test for a few of the possible mechanisms by which Martian organisms could have obtained energy and had 

access to water. Alternatively, Viking may not have found life simply 

because it carried out its testing in the wrong locations. 

149. Ibid., pp. 8–9. 

150. C. R. Woese, “Bacterial Evolution,” Microbiology and Molecular Biology Reviews 51(2) 

(1987): 221–271; SSB, Mars Sample Return, pp. 12, 14. 

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When Biospheres Collide

Niches that Martian life could potentially occupy include the interiors of rocks in which water is present as well as in other “isolated 

oases where liquid water exists,”151 such as in recent volcanic vents that 

Viking would have missed. Including these possibilities in future missions will impact the types and locations of samples that are collected, 

as well as the technologies for examining and quarantining them. 

Protecting Against Large-Scale Impacts from Martian Biota in 

Earth’s Biosphere

A fact that the Task Group considered in its analysis is that pathogenesis, the ability to induce disease, is rare in terrestrial microbes. 

Only a tiny fraction produce adverse effects in their host organisms. 

The capacity for pathogenesis is typically generated through selective 

evolutionary pressure, and such a process of selection for pathogenesis 

to Earth organisms would have no reason to exist on Mars. What’s more, 

exotic microbes introduced into new biospheres usually do not alter 

them in any significant manner. Consider that a Martian organism able 

to survive in Earth’s environment would encounter formidable competition from terrestrial biota that have had millions of years to adapt to the 

same environmental niche. Thus, the chances are extremely low that 

a Martian organism would be able to cause widespread damage after 

it was introduced into Earth’s ecosystem. Nevertheless, because there 

is a nonzero possibility that such biota could generate environmental 

disruption on Earth, the Task Group recommended that return samples 

from Mars be kept in physical and biological isolation and treated as 

though they were hazardous until proved otherwise. 

The need for sterilization. The Task Group took the position that 

no spacecraft surfaces exposed to the Martian environment could be 

returned to our planet unless sterilized. Furthermore, if dependable 

sample containment could not be verified on the return trip to Earth, 

the sample would need to be either sterilized or not returned. The 

containment technology had to remain reliable during the spacecraft’s 

reentry through Earth’s atmosphere and landing as well as the sample’s 

151. SSB, Mars Sample Return, p. 15.

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Return to Mars

subsequent transport to its receiving facility. Finally, sample distribution can only be undertaken if rigorous examination determined that 

the extraterrestrial material was not biologically hazardous.152

Breaking the chain of contact with Mars. A key factor in protecting Earth is to design sample return missions and spacecraft so as to 

“break the chain of contact” with Mars. This means that no uncontained hardware that came into contact with the Martian environment, 

directly or indirectly, can be returned to Earth. Uncontained hardware that will be returned to Earth needs to be isolated from anything 

exposed to the Martian environment during all phases of the mission, 

including during any in-flight transfer operations.153

Research Approaches for Reducing Uncertainty Regarding the 

Existence of Martian Life

The Task Group identified several categories of research aimed at 

better understanding the possibilities for the existence of Martian life. 

These included the following:

•	 Observations conducted from Mars orbiting craft, robot landers, 

and rovers.

•	 Examinations of Martian meteorites.

•	 Studies of terrestrial extremophiles.

•	 Analyses of Mars return samples.

Several key research questions that needed to be answered based 

on data generated by the above investigations as well as past work are 

included below.

Are there present regions of Mars where life-forms could conceivably exist? The search for these niches is closely related to the search 

for evidence of water, active volcanism, and the presence of nonequilibrium gases.

152. SSB, Mars Sample Return, pp. 19–20.

153. NASA Science Mission Directorate, “Detailed Planetary Protection Requirements,” in Planetary 

Protection Provisions for Robotic Extraterrestrial Missions, NPR 8020.12C, 27  April 2005, 

Appendix A, http://nodis3.gsfc.nasa.gov/displayDir.cfm?Internal_ID=N_PR_8020_012C_&page_

name=AppendixA (accessed 26 January 2011).

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When Biospheres Collide

Are there regions that are sterile? If Mars exploration could identify regions with physical and chemical characteristics that preclude 

the existence of life, planetary protection guidelines for those locales 

could be relaxed, opening the door to a wider spectrum of analyses.

Are meteorites able to carry living organisms between planets? 

To date, 12 meteorites believed to be from Mars have been found on 

Earth, although scientists estimate that roughly five Martian meteorites fall somewhere on Earth (including into the oceans) each year. If 

some of these meteorites can be shown to have transported viable 

microbes to Earth, can any evidence be found that they propagated in 

or impacted our biosphere in any way?

Transport of terrestrial meteorites to Mars is also believed to have 

occurred, although considerably less often due to the relative strengths 

of the two planets’ gravitational fields as well as to their different orbital 

characteristics. The question then emerges whether terrestrial organisms could have survived ejection from Earth, transport through space 

and through the Martian atmosphere, and impact with the planet. If 

viable microbe transport from Earth was possible, it could conceivably 

have resulted in the microbes propagating and evolving on Mars.

The Mars Sample Handling Protocol Workshops

In response to the Task Group’s findings and recommendations, 

NASA undertook a series of workshops to prepare for the receiving, 

handling, testing, distributing, and archiving of return samples from 

Mars. The overall objective of the workshop series was to develop a 

draft protocol guiding the assessment of returned samples for biohazards and evidence of extant or extinct life while at the same time preventing sample contamination with terrestrial materials.154 Emerging 

from these workshops were important research questions that needed 

to be pursued. These questions are clearly relevant to return samples 

from other target bodies in addition to Mars. Discussions of some of 

these questions are included below.

154. Margaret S. Race, Donald L. DeVincenzi, John D. Rummel, and Sara E. Acevedo, eds., 

Workshop 4 Final Report and Proceedings—Arlington, Virginia, June 5–7, 2001, NASA/CP2002-211841, Mars Sample Handling Protocol Workshop Series, June 2002, pp. 1, 71–132.

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Return to Mars

What criteria must be satisfied to demonstrate that a Martian 

material does not present a biohazard? Answering this was to involve 

testing for adverse effects on a range of organisms, from unicellular 

organisms to animals and plants, as well as tests specifically for identifying mutagenesis and DNA damage. Testing on multi-organism populations was also identified as important in order to gauge the potential 

for ecosystem disruption.155

What are the facilities needed for making reliable assessments? 

To determine this, an important issue that needed to be resolved was 

whether all sample receiving, processing, characterization, life, and 

biohazard detection should take place at one sample receiving facility (SRF), or were these functions better addressed by distributing 

them among several labs? Also, the best equipment to perform all 

these functions needed to be identified. These were issues similar to 

those that NASA faced in developing concepts for the Apollo Lunar 

Receiving Laboratory (see Chapter 4).

What sample sizes are required? These depend on such factors as 

the relevance of the dose of a material being examined, limitations to 

the dose that the biological model system can receive, the particular 

sample preparation procedure being used, the number of tests that 

need to be conducted, and the total biohazard testing time required.

What total duration of biohazard testing is needed? To estimate 

this, NASA had to determine the durations of the slowest tests and 

add a safety margin to these times. Workshop participants estimated 

that three months would be too short a time for biohazard testing and 

considered four to six months more preferable.156

Can survival mechanisms of terrestrial extremophiles serve as 

models of how putative Martian extremophiles might exhibit resistance to sterilization?157 This is a key question when designing appropriate sterilization approaches for equipment and materials returned 

from Mars. Workshop participants made the point that since a species’s 

adaptation to stress evolved through natural selection, they expected 

155. Race et al., Workshop 4, pp. 71, 110–112.

156. Race et al., Workshop 4, pp. 112–116. 

157. Carl W. Bruch, Richard B. Setlow, and John D. Rummel, eds., Interim Report of the Workshop 

Series—Workshop 2a (Sterilization) Final Report, Arlington, Virginia, November 28–30, 2000,

NASA/CP-2001-210924, Mars Sample Handling Protocol Workshop Series, June 2001, p. iii. 

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When Biospheres Collide

a life-form able to survive on Mars to have adapted to extremely hostile conditions, including a low temperature and very dry environment 

with an atmosphere that provided no protection against UV exposure. 

Since the combination of severe conditions found on Mars does not 

exist anywhere on Earth, terrestrial microbes would not have adapted 

to it, and thus it was unlikely that Earth-microbe survival mechanisms 

could serve as ideal models for Martian ones when developing sterilizing approaches for returned samples and materials. Nevertheless, terrestrial microbes could be found that are very resistant to a subset of 

Martian conditions, and these microbes could be useful in helping to 

validate sterilization procedures

What sterilization procedures will best preserve the integrity of 

Martian soil and rock samples for future scientific analyses outside 

the proposed containment facility? The ideal method would destroy 

all replicating life-forms in Martian material but have no effect on 

its geological or chemical properties and leave no residue that might 

obfuscate further analysis. The method chosen should be supported 

by all the different scientific communities (geological, biomedical, and 

public health) and comply with all regulations. 

Methods considered included moist heat, dry heat, gamma radiation, ethylene oxide, other gas sterilization methods (hydrogen peroxide plasma or vapor, chlorine dioxide gas), and combinations of the 

above. The aim was to find the method that came as close as possible to the ideal, although all the methods presented some problems. 

Heat could alter or destroy components of the material; ethylene oxide 

could leave a residue as well as changing the chemistry by adding 

ethyl groups to certain materials; and gamma radiation could make 

physical, chemical, and biological changes in the material.158

The workshop concluded that only two methods of sterilization 

appeared to be viable, assuming that Martian life was based on similar 

chemistry to that on Earth. These methods were dry heat and gamma 

radiation (used together or separately). These were chosen because 

both would penetrate the material and could provide high assurances 

of organism destruction while causing a minimal level of alteration to 

the material.159

158. Bruch et al., Interim Report of the Workshop Series—Workshop 2a, pp. 19–20.

159. Ibid., pp. 15–16. 

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Return to Mars

When is sample material from Mars safe to be released from containment? Workshop participants identified several questions that first 

had to be answered, as well as technologies that could help to do so:

•	 Is there anything in the samples that looks like a life-form? 

Microscopy as well as high-resolution analytic probe techniques 

such as beam synchotron methods would be useful in answering 

this. Techniques were especially sought that would allow 

testing of contained, unsterilized samples outside of the Sample 

Receiving Facility.

•	 Is there a chemical signature of life? Mass spectrometry was 

suggested as an approach for analyzing contained samples to 

identify biomolecules and certain asymmetries and special 

bonding suggestive of life.

•	 Is there evidence of replication? Answering this question would 

require attempts to replicate any extant Martian microbes in 

cultures or in living organisms.

•	 Is there any adverse effect on workers or the surrounding 

environment? Medical surveillance and evaluation of living 

systems in proximity to the SRF were recommended.160

If life other than terrestrial microbes are detected in Martian 

samples, then what are the next steps? Workshop participants were 

clear that “if life is discovered in any sample material,”161 Martian 

materials could not immediately be released from maximum containment. A previously constituted scientific oversight committee needed 

to review all actions taken, and testing had to be stopped until the adequacy of the protocol and the provisions for containment were thoroughly reviewed. Some participants also recommended a “prophylactic 

sterilization”162 method that would involve applications of gamma radi160. Margaret S. Race, Donald L. DeVincenzi, John D. Rummel, and Sara E. Acevedo, eds., 

Workshop 4 Final Report and Proceedings—Arlington, Virginia, June 5–7, 2001, NASA/CP2002-211841, Mars Sample Handling Protocol Workshop Series, June 2002, pp. 77–80.

161. Margaret S. Race, Kenneth H. Nealson, John D. Rummel, and Sara E. Acevedo, eds., Interim 

Report of the Workshop Series—Workshop 3 Proceedings and Final Report—San Diego, 

California, March 19–21, 2001, NASA/CP-2001-211388, Mars Sample Handling Protocol 

Workshop Series, December 2001, pp. 9–10. 

162. Margaret S. Race, Donald L. DeVincenzi, John D. Rummel, and Sara E. Acevedo, eds., 

Workshop 4 Final Report and Proceedings—Arlington, Virginia, June 5–7, 2001, NASA/CP2002-211841, Mars Sample Handling Protocol Workshop Series, June 2002, p. 10. Material 

in this paragraph is also drawn from p. 126.

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ation and minimal heating. There were fears, however, that such a protocol could destroy some of the samples’ scientific value. It could also 

erode public trust in the methodologies that had been painstakingly 

developed for handling potentially life-bearing samples, without adding substantively to public safety.

Although a Mars sample return is still years away, material from 

the planet will eventually be collected by spacecraft and returned to 

Earth for scientific study. Because the samples may contain specimens 

of microorganisms, perhaps even in a viable state, the material needs 

to be collected and handled in a manner that will protect it as well as 

our planet. Considerable behind-the-scenes planning has been under 

way at JPL and other Centers, at NASA Headquarters, and within the 

international community to make sure that reliable planetary protection controls and safeguards are built into return missions from the 

earliest stages of planning, to ensure compliance with all international 

regulations, and to protect the integrity of scientific efforts. 

Continued Development of 

Human Mars Mission Policy

Sometime within the first several decades of the 21st century, NASA 

will likely send a human mission to Mars. The introduction of astronauts 

to the Martian environment, with all their needs and support systems, 

will greatly increase planetary protection concerns compared to those 

of robotic landers, orbiters, and flybys. To address these concerns, NASA 

sponsored or cosponsored a series of interorganizational meetings and 

studies, which included the following:

The Pingree Park Workshop

Ames Research Center sponsored a workshop in 2001, the Pingree 

Park workshop, held at Colorado State University, that focused on this 

question: Can human exploration of the Martian surface be done effectively and without harmful contamination? The many contamination dangers were placed within three general categories: 1) protecting 

Mars and Martian samples from forward contamination, 2) protecting 

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Return to Mars

astronaut health against risks from the Martian environment, and 

3) preventing the back contamination of Earth from possible Mars contaminant sources. 

The question—can nonharmful Martian exploration be performed—elicited an examination of key human and mission requirements that led to planetary protection concerns, along with strategies 

to mitigate or negate them. Human missions to Mars will by their 

nature be very complex, entailing all the planetary protection issues of 

robotic missions as well as others “arising through the direct involvement of humans and their accompanying microbial companions.”163

The Pingree Park workshop was the first specifically devoted to 

this topic since the 1990 “Planetary Protection Issues and Human 

Exploration of Mars” meeting, over a decade earlier.164 That workshop 

preceded the Mars Global Surveyor and Mars Pathfinder missions and 

thus did not have the advantage of using the data they collected to better understand human exploration issues regarding Mars. 

The Pingree Park workshop identified and discussed several key 

areas of inquiry related to human Mars missions, including these: 

•	 Spatial dispersion of dust and contaminants on Mars by wind 

and other means.

•	 Potential impacts of a human-occupied Martian base, such as 

generation and management of respiratory and food-supply wastes.

•	 The best use of robotics for helping to conduct operations on 

Mars in a manner consistent with planetary protection concerns.

•	 Spacesuit designs consistent with planetary protection needs, 

especially for human activities away from pressurized habitats 

and rovers.

•	 Technology required for life detection and potential pathogen 

detection.

163. M. E. Criswell, M. S. Race, J. D. Rummel, and A. Baker, eds., “Planetary Protection Issues in 

the Human Exploration of Mars,” NASA/CP-2005-213461, final report of a workshop held 

in June 2001 at Pingree Park Mountain Campus, Colorado State University, Fort Collins, CO, 

9 May 2005.

164. D. L. DeVincenzi, H. P. Klein, and J. R. Bagby, eds., Planetary Protection Issues and Future 

Mars Missions, proceedings of the workshop “Planetary Protection Issues and Human 

Exploration of Mars,” NASA/CP-1991-10086, final report of a workshop held at ARC, 

Moffett Field, CA, 7–9 March 1990. 

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When Biospheres Collide

•	 Site classification and biological plausibility mapping of the 

Martian surface and subsurface based on remote sensing data.

The Pingree Park workshop was an investigative meeting that 

examined vital Mars exploration issues but certainly did not have the 

time or personnel to completely work through these complex areas of 

inquiry. More meetings as well as extensive research were required. 

One of the Pingree Park workshop’s accomplishments was to identify a 

range of questions that needed to be examined by future conferences. 

These questions included the following:

•	 If Martian life is discovered, what would appropriate responses 

be? Should it be left in place and no invasive study conducted, 

should it only be analyzed in situ, or should it be carried back 

to Earth for detailed study?

•	 How do human factors such as life support, work environment, 

and psychological stresses interact with planetary protection 

issues during an extended mission of many months to a few 

years?

•	 What are the best ways to prepare the public for the possible 

detection of nonterrestrial life? How can details regarding 

mission discoveries, possible impacts to Earth, and efforts to 

control associated risks be effectively communicated?165

•	 What might the public response be to the detection of life on 

Mars? Will the public accept the very small but finite risks 

associated with discovering and analyzing extraterrestrial life?

Mars Human Precursor Studies

In June 2004, NASA’s Mars Exploration Program Analysis Group 

(MEPAG), whose function was to provide science input to Mars projects, chartered the Mars Human Precursor Science Steering Group 

165. Another study that addressed societal interest in the search for extraterrestrial life and the 

need for public outreach and education was Margaret S. Race and Richard O. Randolph, 

“The Need for Operating Guidelines and a Decision Making Framework Applicable to the 

Discovery of Non-Intelligent Extraterrestrial Life,” Advances in Space Research 30(6) (2002): 

1583–1591.

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Return to Mars

(MHP SSG)166 to identify priorities for investigations, measurements, 

and planetary protection technology demonstrations that would be 

carried out prior to the first human mission to Mars. The aim of 

the precursor missions was to mitigate, to the extent possible, the 

risks and costs of the first human mission to Mars. Recommended 

MHP SSG precursor activities with planetary protection–related 

concerns included the following:

•	 Determining if each Martian site to be visited by humans was free, 

to within acceptable risk standards, of replicating biohazards. 

The investigation would include analyses of atmosphere, dust, 

near-surface soil, deep soil, rock, and ice.

•	 Determining the possible toxic effects of Martian dust on 

humans. In particular, determining whether the dust and other 

Martian particulates that would be present in or on a returning 

spacecraft (other than deliberately collected samples, which 

could be held in sealed containers) had life-forms associated 

with them, and if so, whether that life was hazardous.

•	 Determining whether terrestrial life could survive and 

reproduce on the Martian surface.

•	 Determining processes by which terrestrial microbial life, or its 

remains, would be dispersed and/or destroyed on Mars.167

The MHP SSG study expanded on the work of two earlier 21st century analyses—a MEPAG 2004 report and the NRC’s 2002 Safe on 

Mars report.168 These studies, although important, needed to be reconsidered in light of new data from Mars robotic missions—in particular, 

data regarding the possibility of near-global, subsurface water and the 

increased biohazard that might result if liquid subsurface water was 

166. N. W. Hinners, R. D. Braun, K. B. Joosten, C. E. Kohlhase, and R. W. Powell, Report of 

the MEPAG Mars Human Precursor Science Steering Group Technology Demonstration 

and Infrastructure Emplacement (TI) Sub-Group, NASA document posted July 2005 by 

the MEPAG at http://mepag.jpl.nasa.gov/reports/MEPAG_MHP_SSG_TI_Sub-Group.pdf 

(accessed 25 January 2011).

167. D. W. Beaty, K. Snook, C. C. Allen, D. Eppler, W. M. Farrell, J. Heldmann, P. Metzger, L. Peach, 

S. A. Wagner, and C. Zeitlin, “An Analysis of the Precursor Measurements of Mars Needed to 

Reduce the Risk of the First Human Missions to Mars,” unpublished white paper posted June 

2005 by MEPAG, http://mepag.jpl.nasa.gov/reports/index.html (accessed 26 January 2011).

168. MEPAG, “Scientific Goals, Objectives, Investigations, and Priorities: 2003,” ed. G.  J. 

Taylor, http://mepag.jpl.nasa.gov/reports/index.html (posted 16 July 2004); SSB, National 

Research Council, “Safe On Mars: Precursor Measurements Necessary to Support Human 

Operations on the Martian Surface” (Washington, DC: National Academies Press, 2002).

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When Biospheres Collide

found to be present and accessible.169 The MPG SSG study was meant 

to support the planning of a continuous series of Mars robotic precursor missions prior to human exploration. One of the key goals of such 

voyages will be to certify human mission landing sites for their safety, 

low risk, and scientific potential.

The NASA/ESA Workshop

Another NASA workshop was held in 2005 in conjunction with the 

European Space Agency (ESA). Both NASA and ESA have initiated 

long-term plans for the sequencing of robotic and human missions, 

and the sharing of planetary protection needs for these missions was 

very useful. The “top-level workshop goal”170 was to map out how planetary protection requirements should be implemented during human 

missions and what contamination control standards should apply to 

human explorers. Workshop discussions considered not only the prevention of forward contamination of the Martian environment, but also 

the protection of the human habitat on Mars and of Earth’s biosphere 

upon the crew’s return. Future research and development needs were 

also identified. One of these was to investigate the impact of planetary 

protection requirements on various types of in situ resource utilization (ISRU), such as employing any existing Martian water resources 

near the landing site.

For a summary of planetary protection methodologies used on 

return-to-Mars as well as other missions, see Appendix F.

The Phoenix Lander Touches and Tastes Water Ice

In July 2008, the robot arm aboard NASA’s Phoenix Mars Lander 

excavated a soil sample from a shallow trench dug next to the spacecraft 

and delivered the soil to an instrument in the craft’s onboard laboratory 

169. Beaty et al., “An Analysis of the Precursor Measurements,” pp. 4, 73–74. 

170. Margaret S. Race, Gerhard Kminek, and John D. Rummel, “Planetary Protection and Humans 

on Mars: NASA/ESA Workshop Results,” submitted to Advances in Space Research in 2007. 

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Return to Mars

that heated samples and analyzed the vapors given off. When the results 

were examined, William Boynton of the University of Arizona and lead 

scientist for Phoenix’s Thermal and Evolved-Gas Analyzer announced, 

“We have water.”171 For years, remote observations such as from Mars 

orbiters had been picking up evidence of water ice. Phoenix too had 

collected data suggesting the presence of such ice. But this was the first 

time that “Martian water has been touched and tasted.”172

What was of vital planetary protection importance about this 

find was the possibility that the ice periodically melted, forming thin 

films of liquid water around soil particles.173 The Phoenix landing 

site could thus at times harbor a favorable environment for microbial 

life. According to Phoenix principal investigator Peter Smith, “the soil 

chemistry and minerals we observed lead us to believe this site had 

a wetter and warmer climate in the recent past—the last few million 

years—and could again in the future.”174

A key lesson from the Phoenix experience is that the future exploration of Mars must proceed very carefully, in accordance with strict planetary protection procedures, because we now know that “somewhere 

on or under Mars it is likely that conditions exist that are amenable to 

at least some Earth microbes—and perhaps to martian life.”175 Future 

lander missions intending to search for life at Mars’s highest priority 

astrobiological sites will require Viking-level sterilization at a minimum, 

and perhaps even more stringent planetary protection protocols.

171. Guy Webster, Sara Hammond, and Dwayne Brown, “NASA Spacecraft Confirms Martian 

Water, Mission Extended,” NASA news release 08-195, 31 July 2008, http://www.nasa.gov/

mission_pages/phoenix/news/phoenix-20080731.html (accessed 26 January 2011).

172. Ibid.

173. P. H. Smith, “H2O at the Phoenix Landing Site,” Science 325 (3 July 2009): 58–61.

174. Guy Webster and Johnny Cruz, “NASA Phoenix Results Point to Martian Climate Cycles,” 

NASA news release 2009-106, 2 July 2009, http://www.nasa.gov/mission_pages/phoenix/

news/phoenix-20090702.html (accessed 26 January 2011).

175. John D. Rummel, “Special Regions in Mars Exploration: Problems and Potential,” Acta 

Astronautica 64 (2009): 1293–1297.

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8 DO WE HAVE THE RIGHT TO 

CONTAMINATE?

The Ethical and Legal Aspects of Planetary Protection

It will be “a moral disaster because man will have 

presumed the right to inject his own contaminated 

material into an extraterrestrial environment where 

organic evolution may well be in progress.”

—Sir Bernard Lovell1

The ancient Greek philosophers interpreted the study of ethics to be 

a search for answers to the question, how should we live? Such a question has value today, even as it did millennia ago, because as human 

beings, we must sometimes make decisions based on our own consciences and moral judgments in addition to simply obeying the law. 

The question of how to live can be extended to the topic of this book 

by posing the question, how shall we, the people of Earth, act in space? 

And in particular, how shall we act on bodies that may contain life?2

Ethical Aspects of Planetary Protection

The problem that arises in considerations of protecting extraterrestrial biota is that there are a myriad of opinions and “correct” 

 1. A. C. B. Lovell, 

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When Biospheres Collide

actions. J. Baird Callicott, a founder of the field of environmental philosophy, explained that “there is general agreement that human life 

is a subject of moral concern but . . . there is no general agreement 

about the moral concern that should be considered for non-human 

life.”3

 Nevertheless, one of the moral benefits discussed by Callicott 

that resulted from space travel was that “humankind saw itself as a 

whole, inhabitants of a small and somewhat fragile island in space,”4

emphasizing our dependence on each other and the need for protection of our planet’s biosphere.

Callicott examined an interesting combination of Kenneth E. 

Goodpaster’s life-principle ethic,5 which held that the fact of an organism 

simply being alive was a sufficient criterion for moral considerability,6

and Albert Schweitzer’s Reverence for Life Ethic, which held that “It 

is good to maintain and to encourage life; it is bad to destroy life or to 

obstruct it.”7 Schweitzer, in particular, strongly defended his belief that 

we should revere all “wills-to-live”8 as we do our own. He thought that 

we are truly ethical only when we help all life that we are able to and 

shrink from harming anything that lives. 

What is relevant to planetary protection is that both Goodpaster 

and Schweitzer refuted sentiency as the discriminator for protecting 

life, favoring instead conativity—having the minimal characteristics of 

life—which is sufficient for the entity to be a thing of value.9 Schweitzer 

and Goodpaster were hardly the first to articulate these compelling 

sentiments. In the first chapter of Genesis, for instance, God affirmed 

repeatedly, in regard to grass, herbs, trees bearing fruit, ocean life, and 

 3. J. Baird Callicott, “Moral Considerability and Extraterrestrial Life,” in 

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Do We Have the Right To Contaminate?

every living creature that crept across Earth, “kee-tov,”10 that it was 

good, and even “tov m’od,”11 it was very good. 

The conservationist Aldo Leopold took a step beyond simply 

identifying all life-forms as good things to be preserved. In his essay, 

“The Land Ethic,” he presented reasons, both ethical and aesthetic, 

for why he believed this is so: “A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It 

is wrong when it tends otherwise.”12 In this statement he envisioned 

the connected life-skeins and interdependence necessary to maintain 

a bionetwork’s health. In other words, he argued that an organism’s 

importance to the web of community that surrounded it was a reason 

to protect it.

How Much Is Curiosity Worth?

Human beings have always longed to understand their place in the 

cosmos. This inquiry has been reexamined and reformulated through 

the centuries as our understanding of space science progressed and 

our technology for observing celestial bodies and making measurements improved. But a basic question that we are asking today—are 

we alone in the universe?—was asked ages ago. In 300 BC, the Greek 

philosopher Epicurus wrote to Herodotus regarding the infinite number of worlds that existed; he saw no reason why these bodies “could 

not contain germs of plants and animals and all the rest of what can 

be seen on Earth.”13 Epicurus was expressing his human curiosity to understand whether forms of life exist beyond the confines of 

our planet. The Roman philosopher Lucretius conveyed similar musings when he said, “Confess you must that other worlds exist in other 

regions of the sky, and different tribes of men, kinds of wild beasts.”14

 10.

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When Biospheres Collide

But does a burning curiosity to know what lies beyond the sky 

justify sending ships to, and possibly contaminating forever, those 

other worlds? One rather arrogant position that has emerged during 

discussions of planetary exploration is that “the destiny of humanity 

is to occupy space, a destiny written in our genes.”15 This is a position 

reminiscent of the political philosophy of manifest destiny, held by 

many U.S. statesmen and business leaders in the 19th century, that 

our country deserved to, in fact was destined to, conquer the heart 

of North America from the Atlantic Ocean to the Pacific Ocean,16 no 

matter the price paid by indigenous people or the environment. In 

defending the U.S. claim to new territories, the Democratic leader and 

influential editor John L. O’Sullivan insisted in 1845 on

. . . the right of our manifest destiny to over spread and 

to possess the whole of the continent which Providence 

has given us for the development of the great experiment 

of liberty and federaltive [sic] development of self 

government entrusted to us. It is right such as that of the 

tree to the space of air and the earth suitable for the full 

expansion of its principle and destiny of growth.17

O’Sullivan’s articulation of our country’s supposedly God-given right 

to expand our sphere of influence became a rallying cry in political 

discourse, newspapers, and advertisements, although the philosophy 

behind manifest destiny surfaced even earlier in U.S. history. Andrew 

Jackson, for instance, appeared to act on a similar belief in 1818 when 

he led military forces into the Floridas to punish the Seminole Indians 

for taking up arms with the Spanish. Jackson’s soldiers also destroyed 

 15.

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Do We Have the Right To Contaminate?

Spanish forces and captured several cities and forts.18 The essence of 

the manifest destiny philosophy is still alive and well, I believe, and 

reflected within our country’s program of exploring space. 

While the concept of manifest destiny was once, and still may be, 

popular among many U.S. citizens, we were never unanimous in our 

support of it, either in the past or in the present. In 1837, for instance, 

William E. Channing wrote to Henry Clay that “We are a restless people, prone to encroachment, impatient of the ordinary laws of progress 

. . . forgetting that, throughout nature, noble growths are slow. . . . It is 

full time that we should lay on ourselves serious, resolute restraint.”19

And today, there are those who believe that “the Earth can be seen as 

a spaceship driven by humanity acting as a crew, and it is the destiny 

of a crew to stay onboard the ship . . . .”20

The Implications of a Second Genesis of Life in Our Solar System

Life may have begun in only one place in the solar system and possibly spread to other locations through the assistance of, for instance, 

asteroids and comets. Or life may have originated in two or more locations. The ethical implications are huge of discovering a life-form with 

an independent genesis from organisms on Earth. The existence of a 

second genesis would be strongly indicative that such an event probably occurred elsewhere as well and that life originating independently 

of Earth is widespread throughout our galaxy. Ethically, the need to 

protect an organism, however lowly, would be stronger if it represented 

“a unique life-form with an evolutionary history and origin distinct 

from all other manifestations of life.”21

 18.

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Should We Explore Other Celestial Bodies as 

Preservers, Stewards, or Exploiters of Their 

Environments?

What do the various ethical positions say about appropriate guidelines for sending our ships and technologies to extraterrestrial worlds? 

Shall we conduct our activities on these bodies as strict environmentalists would, i.e., preserve the bodies in unchanged states; shall we 

act as stewards of these planets, seeking a path that maximizes the 

benefits to all parties concerned; or shall we exploit these bodies, 

treating them as resources that can greatly aid our species? 

The Preservation Ethic

The preservation ethic suggests that human action in nature 

should be minimized, and this translates to the imperative to leave an 

extraterrestrial body unaltered—“to neither enhance its environment 

for the indigenous biology, if any, nor to introduce life from Earth.”22

A key question that comes up when preservation is discussed is, what 

exactly has intrinsic worth on the body? Is it only biological life, or 

should all the natural attributes of the body be preserved, including 

its rocks and its dirt?

I. Almar, in a paper presented at the 34th COSPAR Scientific 

Assembly, expressed the concern that damage caused by any human 

intervention on a lifeless world would be irreversible. One possible 

reason for protecting the lifeless space environment was its scientific 

aspect—areas and objects could exist of the highest scientific priority on different celestial bodies. As an example of this, much can be 

learned about volcanism and the impacts of tidal forces by studying 

the Jovian moon Io, which is most probably lifeless.23 Almar identified 

 22.

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Do We Have the Right To Contaminate?

the need “not to prevent any commercial utilization of Solar System 

resources, but to make space exploration and exploitation of resources 

a controlled and well-planned endeavor”24 and recommended initiating 

a large-scale discussion on the possible ethical values of the lifeless 

environment.

The Dilemma of Planetary Stewardship: Protecting Our Species 

vs. Protecting Other Planets

The concept of stewardship can be understood by considering the 

mission of the nonprofit Association of Forest Service Employees for 

Environmental Ethics (AFSEEE): “to forge a socially responsible value 

system for the Forest Service based on a land ethic which ensures ecologically and economically [author’s emphasis] sustainable resource 

management.”25 The key is on resource management rather preserving 

the forest in a pristine, unaltered state. Applied to extraterrestrial bodies, stewardship “would imply that the broad scientific and economic 

advantages from having a second planetary-scale biosphere [in addition to Earth’s] would justify planetary alteration.”26

An interesting combination of the preservationist and stewardship 

approaches arises from the belief that only biotic life has intrinsic 

value, not a body’s geology. Thus, the stewardship perspective, which 

desires that we humans use nature wisely for our own benefit, would 

consider terraforming a celestial body to be ethical, even obligatory, 

if it promoted the growth of indigenous life (even as yet undiscovered 

life) on that body.27

 24.

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When Biospheres Collide

Other compelling reasons for exploring and colonizing include the 

following:28

1. Providing a long-term, unifying project on which humans, cooperating around the globe, could focus. This could prove to be 

an important step toward world peace.

2. Constructing active biospheres on other bodies that could serve 

as refuges for terrestrial life, in the event of war or some other 

global catastrophe.

Some voices in the space science community called for the colonization of other worlds in much stronger terms than the second point 

expressed above. Michael J. Rycroft of the International Space University 

argued that “the overarching goal of space exploration for the twenty-first 

century should be to send humans to Mars, with the primary objective of 

having them remain there,”29 so that our human species might have a second home in the event that a disaster on Earth rendered it uninhabitable. 

Rycroft believed that many factors could cause such a catastrophe, including overpopulation; global terrorism; nuclear or biological war or accident; 

the occurrence of a super-virus; a natural disaster (e.g., from an asteroid 

collision, flood, volcano, and so on); the depletion of vital resources such 

as oil or natural gas reserves; climate change, global warming, and sea level 

rise; and stratospheric ozone depletion. Rycroft thought that the colonization of a habitable world was thus an imperative human endeavor of this 

century and an insurance policy, and he emphasized his point by quoting 

M. Rees’s opinion that ‘‘the odds are no better than 50–50 that our present 

civilisation on Earth will survive to the end of the present century.”30

But can colonization of a world containing indigenous life be performed while at the same time following the strictures of planetary 

protection? It could be argued that if planetary protection measures 

seriously delayed colonizing another world, they would be unethical to 

perform, since they would endanger the safety and future of our own 

species. Compulsory colonization as soon as it is feasible, on the other 

hand, will likely contaminate a body with Earth organisms and may 

 28.

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Do We Have the Right To Contaminate?

well extinguish any indigenous life-forms. The human race has arguably 

done a terrible job of protecting its own planet’s environment, so can we 

even imagine that we will appropriately protect other bodies we visit?31

Deciding which course should be followed—colonization as soon 

as it is feasible or waiting until a thorough search for life has been performed—depends on the intrinsic value we give to extraterrestrial lifeforms, even nonsentient forms, and to the biotic communities of those 

organisms. Arguing for the planetary protection approach, however, is 

not always easy. It is difficult to make a convincing case for protecting 

the possible existence of some nonsentient microbes when their ecological niche may be required by the human race for its own survival.

Exploitation of Other Planets as Natural Resources

UNESCO discussions have viewed some issues in the ethics of 

outer space as similar to those in environmental ethics. The question 

of respect for the terrestrial environment also applies to respect for 

other celestial bodies. One of the ethical issues raised by the “conquest” of another planet is its possible appropriation for our own 

purposes. In establishing human-inhabited lunar stations or Mars outposts, does a nation have the right to mine and farm this extraterrestrial land?32 Or should undeveloped lands of great natural beauty or, 

as mentioned above, of great scientific interest be carefully preserved? 

Our country’s history has demonstrated the devastating speed at 

which natural resources can be exploited and destroyed, but throughout U.S. history we have also taken pride in, and placed high value on, 

the extraordinary beauty of our country.33

Lynn White’s writings connect our use of a new territory’s 

resources for our own benefit to the nature of our religious faith, which 

sought to destroy the pagan animism that believed “every tree, every 

 31.

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When Biospheres Collide

spring, every stream, every hill had its own genius loci, its guardian 

spirit.”34 According to White, our western religious tradition allowed 

us to develop an indifference to natural objects that then made it possible for us to exploit them.

Such an attitude seems to have been extended to parts of the outer 

space realm. Conquest and alteration of a celestial object certainly is 

acceptable to many people if the body does not harbor life. This attitude was apparent as far back as the Apollo mission. The waste that 

remained on the lunar surface to reduce liftoff mass was considered 

an acceptable price to pay for the science return. And the footprints, 

wheel tracks, and augur holes that were left were celebrated by some 

as indicative of “mankind’s triumph over adversity and a symbol of its 

conquest of the Moon.”35

Should We Do Away with Human Missions 

to Sensitive Targets?

One of the most reliable ways to reduce the risk of forward contamination during visits to extraterrestrial bodies is to make those 

visits only with robotic spacecraft. Sending a person to Mars would 

be, for some observers, more exciting. But in the view of much of the 

space science community, robotic missions are the way to accomplish the maximum amount of scientific inquiry since valuable fuel 

and shipboard power do not have to be expended in transporting and 

operating the equipment to keep a human crew alive and healthy. And 

very important to planetary protection goals, robotic craft can be thoroughly sterilized, while humans cannot. Such a difference can be critical in protecting sensitive targets, such as the special regions of Mars, 

from forward contamination. 

Perhaps a change in the public’s perspective as to just what today’s 

robotic missions really are would be helpful in deciding what types of 

 34.

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Do We Have the Right To Contaminate?

missions are most appropriate to implement. In the opinion of Torrence 

Johnson, who has played a major role in many of NASA’s robotic missions, including serving as the project scientist on the Galileo mission 

and the planned Europa Orbiter mission,36 the term “robotic exploration” 

misses the point. NASA is actually conducting human exploration on 

these projects. The mission crews that sit in the control room at JPL “as 

well as everyone out there who can log on to the Internet” can observe 

in near-real time what’s going on. The spacecraft instruments, in other 

words, are becoming more like collective sense organs for humankind. 

Thus, according to Johnson, when NASA conducts its so-called robotic 

missions, people all around the world are really “all standing on the 

bridge of Starship Enterprise.”37 The question must thus be asked, when, 

if ever, is it necessary for the good of humankind to send people rather 

than increasingly sophisticated robots to explore other worlds?

Legal Aspects of Planetary Protection

Who Owns a Celestial Body?

Ancient Roman law spoke of the concept of res nullius—those 

physical things that have never had an owner. Res nullius refers to 

objects that have not been reduced to property because they are not, 

or cannot, be appropriated by individuals. Light, for example, is res 

nullius. On the other hand, the property status of something in a wild, 

unappropriated state was res communis to the Romans—literally a 

thing common to all. Unlike a res nullius object, which cannot be 

owned, res communes objects can be owned by the state.38

 36.

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When Biospheres Collide

A key question in outer space ethics is, to which category should 

celestial objects belong? The res communis doctrine has been 

applied on Earth to territories that belonged to the community at 

large and therefore were considered accessible and exploitable by 

everyone. Res communis has been applied as well to outer space. 

Since the signing of the Outer Space Treaty of 1967, the predominant international view regarding the use of space has been aligned 

with res communis, but in the sense that space belongs to all 

humankind rather than to one country.39

The 1984 UN Agreement Governing the Activities of States on the 

Moon and Other Celestial Bodies (the “Moon Treaty”) appears to consider celestial bodies to be res communis as well, stating in Article 4 

that the use of the Moon shall be the “province of all mankind” and 

holding to a basic objective “to promote on the basis of equality the 

further development of co-operation among States in the exploration 

and use of the moon and other celestial bodies. . . . Bearing in mind 

the benefits which may be derived from the exploitation of the natural 

resources [author’s italics] of the moon and other celestial bodies. . . .” 

In Article 11, the treaty states its position even more clearly regarding the human right to exploit the Moon: “The moon and its natural 

resources are the common heritage of mankind.” But the treaty also 

embraces the principle of stewardship in its use of the Moon, stating in 

Article 7 that countries need to “take measures to prevent the disruption 

of the existing balance of its [the Moon’s] environment, whether by introducing adverse changes in that environment, by its harmful contamination through the introduction of extra-terrestrial matter or otherwise.”40

International Efforts To Develop a Legal Structure

In 1958, the United Nations General Assembly established an ad 

hoc Committee on the Peaceful Uses of Outer Space (UNCOPUOS) 

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Do We Have the Right To Contaminate?

with Resolution 1348 (VIII) in reaction to the launch of Sputnik and to 

the need for preventing contamination of celestial environments. The 

United Nations asked its ad hoc committee, as one of its first tasks, to 

report on the legal issues arising from human exploration of space.41

In response, UNCOPUOS identified forward and back contamination 

dangers in a July 1959 report and recommended developing international agreements to “minimize the adverse effects of possible biological, radiological, and chemical contamination.”42 The UN General 

Assembly made UNCOPUOS a permanent committee in December 

1959 with Resolution 1472 (XIV) and added new member states to it.43

USSR input and the UN Declaration of Legal Principles. The 

USSR’s Chairman Khrushchev wrote an important letter to President 

Kennedy in March 1962 that built on UNCOPUOS’s recommendation, advising that any outer space activities that could hinder other 

countries’ exploration should first be discussed and agreed upon “on 

a proper international basis.”44 This letter as well as other USSR proposals linked the issue of outer space contamination to interference 

with the rights of states to conduct their activities and were reflected 

in the international planetary protection guidelines that the United 

Nations developed. In December 1963, the United Nations issued a 

Declaration of Legal Principles Governing the Activities of States in 

the Exploration and Use of Outer Space,

45 which included various 

guidelines related to planetary protection matters:

 41.

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When Biospheres Collide

•	 Outer space exploration and use shall be carried out for the 

benefit and in the interests of all people.

•	 Outer space and celestial bodies are free for exploration by all 

states and are not subject to national appropriation or claims 

of sovereignty.

•	 All states will follow international legal principles, including 

those of the United Nations, in their use and exploration of space.

•	 States shall conduct all their outer space activities with due 

regard for the interests of other states. This declaration, which 

was reminiscent of the USSR’s position on space activities, 

required that a state planning an activity that might conflict 

with the interests of other nations first consult them.

•	 States are liable for damage to the earth or air of any other 

nations due to objects launched into space.

The Outer Space Treaty. The UN Declaration of Legal Principles

was a first step toward an international planetary protection legal 

structure but, as the UN Canadian delegation commented, the 

Declaration did not specifically ask states to consult with other states 

if an activity would harm Earth’s natural environment. Also, it “did not 

constitute positive international law,”46 and thus a more formal treaty 

document was required.

President Lyndon Johnson issued a statement on 7 May 1966 in 

which he proposed the development of such a treaty. The next month, the 

United States presented a draft treaty to UNCOPUOS, Article 10 of which 

provided that nations take steps “to avoid the harmful contamination 

of celestial bodies and adverse changes in the environment of the Earth 

resulting from the return of extraterrestrial matter.”47 It is noteworthy 

that the U.S. draft treaty extended planetary protection concerns to both 

forward and back contamination. The scope of the U.S. draft, however, 

included only celestial bodies, while the Soviet one, which was eventually 

accepted, covered the entire outer space environment.48

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Do We Have the Right To Contaminate?

447

The U.S. draft left out a powerful statement that the UN 

Declaration of Legal Principles had included: the need for international consultations for activities that may lead to interference with 

other nations’ activities. While this omission may have been indicative of the United States’ desire for autonomy in conducting its own 

exploration of outer space, the United States did agree to such international consultations when it signed the Outer Space Treaty, which 

was issued in January 1967.49

This international agreement had many similarities to another 

agreement—the Antarctic Treaty. Both sought to prevent a new type 

of colonial competition and self-seeking exploitation. In addition, the 

treaties for planetary protection of the solar system and environmental 

stewardship of the Antarctic were both implemented through “a political and legal forum in which science plays an advisory role.”50

Article I of the Outer Space Treaty provided that extraterrestrial 

exploration and use, including of the Moon and other celestial bodies, 

must be performed for the benefit and in the interests of all countries and 

“shall be the province of all mankind.”51 G. M. Goh and B. Kazeminejad 

argued that the protection and preservation of celestial bodies such as 

Mars “is properly an extension of the province of Mankind principle” and 

that their contamination “would jeopardize the rights of all countries to 

use and explore outer space,”52 although this was not explicitly stated in 

the treaty. Furthermore, while Article IX of the treaty directed nations 

to “pursue studies of outer space, including the Moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful 

contamination and also adverse changes in the environment of the Earth 

49. United Nations, Treaty on Principles Governing the Activities of States in the Exploration 

and Use of Outer Space, Including the Moon and Other Celestial Bodies (“Outer Space 

Treaty”), UN doc. 6347 (January 1967).

50. Committee on Principles of Environmental Stewardship for the Exploration and 

Study of Subglacial Environments, National Research Council, “Antarctic Governance and 

Implications for Exploration of Subglacial Aquatic Environments,” in Exploration of Antarctic 

Subglacial Aquatic Environments: Environmental and Scientific Stewardship (Washington, 

DC: National Academies Press, 2007), Chap. 5.

51. UN Outer Space Treaty, Article I.

52. Both quotes are from Gerardine Meishan Goh and Bobby Kazeminejad, “Mars Through 

the Looking Glass: An Interdisciplinary Analysis of Forward and Backward Contamination” 

IAC-03-Q.3.b.05, 54th International Astronautical Congress of the International Astronautical 

Federation, the International Academy of Astronautics, and the International Institute of 

Space Law (Bremen, Germany, 29 September–3 October 2003): 4. 
When Biospheres Collide

resulting from the introduction of extraterrestrial matter,”53 the treaty 

did not explicitly define what constituted harmful contamination or an 

adverse change to the environment, and thus left these concepts somewhat vague and open to legal interpretation.

Was harmful contamination that which hindered the rights of all 

countries to use (i.e., exploit) celestial bodies, or did the term refer 

to actions potentially harmful to any actual biota that might reside 

there? SETI Institute scientist Margaret Race commented that there 

were strong indications the early Outer Space Treaty “had greater 

interest in protecting opportunities for science and research than it 

did about protecting celestial bodies per se.”54 And as discussed in 

Chapter 1, the planetary protection field did not in its policies have 

an ethical component, or one that sought to protect planets for their 

own sake. Planetary protection policy aimed to preserve celestial bodies for the sake of biological exploration.55 This situation may now be 

changing, however. An influential 2006 document published by the 

National Research Council’s Space Studies Board, Preventing the 

Forward Contamination of Mars, recognized the need for the space 

science community to address ethical issues regarding the introduction of terrestrial biota into sensitive extraterrestrial environments, to 

appropriately modify planetary protection policy if necessary, and to 

involve the public in a dialogue on this issue. Furthermore, the document strongly urged that addressing ethical concerns be done on an 

international level and “at the earliest opportunity.”56

The Moon Treaty. A strong planetary protection statement that 

did not get included in the Outer Space Treaty was a proposed 

Japanese amendment that would have required nations to “exercise 

maximum care for the preservation and conservation of the natural 

resources and environment of celestial bodies.”57 The Japanese delegation to UNCOPUOS thought that other nations were afraid such 

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Do We Have the Right To Contaminate?

wording would restrict future activities on celestial bodies.58 While 

the proposed amendment was not put into the Outer Space Treaty, 

stricter planetary protection language was included in a treaty regarding the Moon. In June of 1971, the USSR proposed such a treaty to 

the General Assembly; it recommended “avoiding the disruption of the 

existing balance of the lunar environment.”59

UNCOPUOS’s Legal Subcommittee reached consensus on the final 

wording of the above statement and on the article in which it appeared, 

but the UN General Assembly did not approve the Moon Agreement

and open it for signature until December 1979. While the planetary 

protection language in the Moon Treaty was strong, the UN General 

Assembly felt the need to clarify just what UNCOPUOS’s intent was. It 

was eventually determined that the intent was definitely not to prohibit 

the exploitation of natural resources on celestial bodies, but rather to 

“protect the existing balance of the natural celestial environments.”60

The Moon Agreement finally entered into force in July 1984, with 

the clause in Article 7 that nations “shall take measures to prevent 

the disruption of the existing balance of its environment, whether 

by introducing adverse changes in that environment, by its harmful 

contamination through the introduction of extra-environmental 

matter or otherwise.”61

This language may have been perceived by many countries as too 

restrictive to their future operations, because the Moon Agreement

was far from universally accepted. As of 1 January 2006, only 12 

nations had ratified it and 4 had signed it.62 While it did provide a 

legal structure applicable at least to these states and possibly to other 

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When Biospheres Collide

nations collaborating with them on space missions, neither the United 

States nor Russia has ratified or signed this agreement.63

The Outer Space Treaty of 1967 had a stronger legal standing than 

the Moon Treaty. The Outer Space Treaty was ratified or acceded to 

by the majority of nations, and these included the major spacefaring 

nations. Widespread international support presently exists for its basic 

principles; as of 1 January 2006, 98 nations had ratified it and 27 had 

signed it.64

From the few treaty law documents that address planetary protection, it is clear that a very limited international legal framework 

exists that specifically deals with the protection of the extraterrestrial 

environment. As a result, outer space and celestial bodies are open to 

use and abuse by all nations. Legal standards will become increasingly 

important as outer space and celestial bodies become ever more accessible to exploration and exploitation.65

The Development of a U.S. Legal Structure 

The National Aeronautics and Space Act of 1958 granted NASA 

authority over a range of activities that have bearing on the exploration and successful use of outer space. The situation becomes 

more complex, however, as applied to sample return missions that 

bring back extraterrestrial material. Earth-based activities associated with sample return—such as land, water, and air transportation; quarantine; environmental protection; hazardous material 

handling; occupational safety; human health; emergency preparedness; and building construction—trigger not only NASA scrutiny, 

but also the interest of a range of different U.S. agencies and organizations. The Environmental Protection Agency (EPA), for instance, 

has the responsibility for reviewing proposed activities that may 

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Do We Have the Right To Contaminate?

impact Earth’s biosphere, while the Occupational Safety & Health 

Administration (OSHA) examines operations with questionable 

human safety considerations. The Department of Health and Human 

Services (HHS) and its Public Health Service (PHS) have a legal 

charter to protect our nation’s health; the Department of Agriculture 

(USDA)66 has legal jurisdiction over the importation of soils and 

organisms that could be potential pathogens to livestock and economically important crops, while the transport of samples and other 

routine activities associated with a mission may come under the 

jurisdiction of the Federal Highway Administration (FHWA) and the 

Federal Aviation Administration (FAA). Local jurisdictions may also 

have an interest in sample return activities.

The end result of this situation is that multiple agencies “from the 

federal level to local zoning and permit offices”67 become involved 

in sample return oversight, complicating operations with conflicting 

regulations and overlapping jurisdictions. A way of dealing with this 

potentially confusing situation in the future is to do as the Apollo 

program did and establish an organization akin to its Interagency 

Committee on Back Contamination (ICBC), which had the charter 

for conducting joint-agency regulatory reviews and analyzing applicable statutes.

The basic tenet of planetary protection as applied to sample return, 

in place since the early days of space travel, has been to avoid the 

harmful contamination of Earth. However, there is another complicating factor to this endeavor—the need to take action without having 

definitive answers on which solar system bodies, if any, harbor or have 

ever harbored life. 

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Specific U.S. Legal Requirements

U.S. legal strictures addressing issues related to extraterrestrial 

sample return include the following: 

Code of Federal Regulations (CFR) Title 14, Part 1211—

Extraterrestrial Exposure. This important U.S. code established 

NASA’s responsibility and authority to “guard the Earth against any 

harmful contamination or adverse changes in its environment resulting from personnel, spacecraft, or other property returning to Earth 

after landing on or coming within the atmospheric envelope of a celestial body.”68 In particular, it gave the NASA Administrator the right to 

determine the beginning and end of quarantine periods for any U.S. 

space mission and to isolate a “person, property, animal, or other form 

of life or matter whatever is extraterrestrially exposed.”69 The validity of this U.S. code was questionable,70 however, because in contrast 

to typical U.S. regulatory agencies, NASA was never granted legislative authority to promulgate or enforce quarantine regulations, even 

though it did develop regulations for Apollo sample return operations. 

Nevertheless, NASA published its lunar quarantine regulations in the 

Federal Register on the day of the Apollo 11 launch, 16 July 1969, as 

CFR Title 14 Part 121171 and avoided the public discussion activities 

that could have caused an administrative delay.

Such a unilateral decision on quarantine regulations was potential 

grounds for challenging them. In addition, NASA’s quarantine operations involved the detention not only of extraterrestrial material, but 

also of human beings, which could have raised issues about NASA’s 

authority to deprive U.S. citizens of liberty.

These regulations had been adopted largely as guidance for the 

Apollo program. After Apollo ended, they were not of use for many 

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Do We Have the Right To Contaminate?

years. NASA removed CFR Title 14 part 1211 effective 26 April 1991, 

with the explanation that it had served its purpose and was no longer in keeping with current missions and practices.72 This was certainly true, for no sample return missions requiring quarantine were 

on NASA’s near horizon. But the rescinding of the regulations left no 

legal quarantine requirements or authority under existing federal statutes for handling extraterrestrial sample returns.73 NASA did, however, 

reserve Section 1211 of the CFR for applicable extraterrestrial exposure regulations to be reinstated as appropriate if sample return or 

human exploration missions to other planets were initiated.

National Environmental Policy Act (NEPA). NEPA, the basic 

national policy instrument for protecting the human environment,74

requires that potential environmental impacts of any kind from a 

NASA project be analyzed during the project’s planning stages. In 

particular, NEPA requires that NASA provide public disclosure in 

an environmental assessment (EA) or environmental impact statement (EIS) of the full range of potential impacts, project alternatives, 

worst-case scenarios, and uncertainties for all phases of a sample 

return mission.75

These documents need to address planetary protection concerns 

if there is any question of a sample return impacting Earth’s environment. For example, the team for the sample return Stardust mission to 

the Wild 2 (pronounced “vilt two”) comet had to prepare an EA that 

analyzed and described the planned mission. It concluded in a Finding 

of No Significant Impact (FONSI) that “On the basis of the Stardust 

EA, NASA has determined that the environmental impacts associated 

with the mission would not individually or cumulatively have a significant impact on the quality of the human environment.”76

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When Biospheres Collide

Other applicable regulations and agreements. During the Apollo 

era, the ICBC compiled an important regulatory analysis, Excerpts of 

Federal Regulations Pertinent to Contamination Control for Lunar 

Sample Return Missions.77 The rules in this document were also relevant to future sample return efforts and included the following, each 

of which provides an example of an organization’s reason for involvement in planetary protection activities:

•	 Public Health Service Act (Public Law 410-78th Congress) 

gives the Surgeon General authority to prevent the introduction 

and spread of communicable disease in the United States.

•	 Department of Agriculture import regulation (CFR Title 9, 

Chapter I, Subchapter E, Part 122-4 March 1913) restricts 

organisms from being imported into the United States without 

issuance of a permit and also allows quarantine of materials 

that are not under permit or are on prohibited lists.

•	 Fish and Wildlife Act of 1956 (16 USC 742f(4) and (5)) gives the 

Secretary of the Interior the right “to take such steps as may 

be necessary for the conservation and protection of the fish and 

wildlife resource.”78

These and other rules presented in the ICBC regulatory analysis 

were likely taken from a similar summary of relevant codes prepared 

the previous year by G. Briggs Phillips of the Public Health Service’s 

Communicable Disease Center.79 As mentioned above, an organization such as the ICBC that analyzes the missions and regulations of 

various U.S. organizations might prove invaluable for future NASA 

sample return missions in identifying the legal structure that needs 

to be satisfied.

Interagency agreements. The various agencies involved in Apollo 

sample return activities found it helpful not only to identify and examine all relevant statutes and regulations, but also to implement interagency agreements that assigned responsibilities to the appropriate 

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parties. For instance, a 1967 NASA agreement with the National 

Academy of Sciences and the Departments of Agriculture; Health, 

Education, and Welfare; and the Interior confirmed the non-NASA 

member agencies that had a seat on the ICBC as well as their authorization to analyze and advise NASA on such matters as 1) proposed 

quarantine protocols, 2) Lunar Receiving Laboratory specifications 

and construction practices, 3) recovery procedures for astronauts, 

4) lunar sample protocols, 5) equipment specifications, and 6) the date 

and manner in which astronauts and samples could be released from 

quarantine.80 Such interagency agreements could be valuable as well 

for future missions returning samples from outer space. 

Under John Rummel’s leadership as Planetary Protection Officer, 

an interagency Planetary Protection Advisory Committee (now called 

the Planetary Protection Subcommittee, or PPS) was established in 

February 2001 to advise the NASA Administrator on matters such 

as interpretation of policy, implementation plans, mission strategies, 

contamination risks of future missions, and research progress in such 

areas as sterilization technologies and life-detection approaches. PPS 

will likely serve a role for future Mars sample returns that is similar to 

what ICBC did for the Apollo missions.81

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9 CONCLUSION

The planetary protection field comprises a complex, long-term 

effort by the United States and other countries to prevent forward and 

back contamination of celestial objects while still achieving numerous 

science goals. Planetary protection strategies are meant to preserve 

meaningful scientific investigation by keeping celestial objects as pristine as possible. The field is driven by the need to protect our quest for 

understanding the true nature of our universe and, in particular, the 

place of life in that universe.

Many approaches have been necessary in order to implement effective planetary protection into space exploration. One of the interesting aspects of the field has been the mix of political and technical 

efforts required to include planetary protection measures in an aggressive space exploration agenda and to do so with limited economic 

resources. NASA and its Apollo program, for instance, had to use both 

political skills and scientific and engineering know-how to develop an 

expensive quarantine facility with cutting-edge equipment for analyzing return samples, spacecraft, and astronauts. The battles for this 

facility took place in the halls of Congress and through more informal 

agreements with other agencies. But the effective design and operation 

of the facility came about through the dedicated efforts of a large community of scientists and engineers.

Implementing effective planetary protection measures into a mission necessitates the ongoing reconciliation of conflicting visions and 

values. As an example, the development of the Apollo postsplashdown 

astronaut recovery plan revealed the underlying hierarchy of ethical 

values that controlled operational decisions and illustrated how widely 

differing views needed to be considered before an operations plan 

could be finalized.

Planetary protection actions have had beneficial influences on 

other types of operations as well. After Viking, for instance, NASA 

managers determined that designing components to meet the 

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When Biospheres Collide

mission’s strict bioload limits and to withstand the rigorous terminal 

sterilization environment resulted in a more reliable spacecraft with a 

better probability of completing all mission requirements. The Viking 

mission provided an example of how a strict contamination reduction 

requirement could improve manufacturing approaches for the smallest 

to the largest of a spacecraft’s parts.

The development of planetary protection has demonstrated the 

power that a small number of influential, charismatic people with persuasive ideas can have over the actions and expenditures of a much 

larger group. If not for the influence of two men, Joshua Lederberg 

and Carl Sagan, the field would probably look very different today, and 

the effort spent to prevent forward and backward contamination of 

our solar system’s bodies might have been considerably smaller. These 

men’s influence in both the political and scientific arenas was vital in 

establishing planetary protection as an indispensable part of our space 

exploration program, even for targets where the chances of finding 

extraterrestrial life were small.

Lederberg and Sagan were not, of course, the only people with dramatic influences on the field. The list of these individuals is long and 

includes such luminaries as University of California at Berkeley chemist and Nobel Laureate Melvin Calvin, British biologist J. B. S. Haldane, 

former NASA Director of Space Flight Programs Abe Silverstein, 

former Planetary Protection Officer John Rummel, Lawrence Hall, 

Charles Phillips, Donald DeVincenzi, Perry Stabekis, Margaret Race, 

and many others. Nevertheless, Lederberg’s and Sagan’s vision helped 

set the course of the planetary protection field for the next half century of effort. These people had the ear of Congress and of many 

managers and researchers in the space science community, and their 

recommendations were enormously influential. 

Since the beginning of the Space Age, planetary protection considerations have been woven into missions to celestial bodies. Back contamination prevention played a major part in Apollo mission planning. 

Sterilization procedures for the Viking spacecraft were so rigorous that 

the mission’s landers may have had fewer terrestrial microbes aboard 

than any other craft yet launched. Missions to Jupiter, Saturn, Mars, 

and the solar system’s other bodies must minimize the chances of forward or back contamination when such occurrences might be harmful. And return sample missions to Mars, while still years in the future, 

have already received intense scrutiny for the purpose of preventing 

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Conclusion

both forward contamination of Mars and back contamination of our 

planet. No mission involved in the search for extraterrestrial life can 

escape the demands and requirements of planetary protection. 

We humans have a burning desire to increase our understanding of 

everything around us, but we are accountable to future generations of 

scientists to explore our solar system without destroying the capability 

of others to conduct their own investigations. The planetary protection 

field is thus driven by a deep regard for the importance of both present and future scientific inquiry. Careless planetary exploration in the 

present could forever obfuscate the answer to a vital question: Are we 

Earthlings alone in the universe?

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APPENDICES

Appendix A: 

Detailed Planetary Protection Requirements

(Source: Appendix A in Planetary Protection Provisions for Robotic Extraterrestrial Missions,

NASA Procedural Requirement [NPR] 8020.12C, 27 April 2005)

Contents

 A.1 Category-Specific List of Target Body/Mission Types

A.1 Category-Specific List of Target Body/Mission Types 

(advisory only)

a. Category I: Flyby, Orbiter, Lander: Earth’s Moon; Mercury; 

Undifferentiated, Metamorphosed Asteroids; others TBD pending National Research Council or other recommendations.

b. Category II: Flyby, Orbiter, Lander: Venus, Jupiter (exclusive of 

its icy moons), Saturn, Titan, Uranus, Neptune, Triton, Pluto/

Charon, Kuiper belt objects, Comets, Carbonaceous Chondrite 

Asteroids, others TBD pending National Research Council or 

other recommendations. 

c. Category III: Flyby, Orbiter: Mars, Europa, Ganymede, Callisto, 

others TBD pending National Research Council or other 

recommendations.

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d. Category IV: Lander, Probe: Mars, Europa, Ganymede, Callisto, 

others TBD pending National Research Council or other 

recommendations. 

e. Category V: Any Earth return mission. Unrestricted Earth 

return: Earth’s Moon; Undifferentiated, Metamorphosed 

Asteroids; Short-Period Comets; Solar Wind; others TBD. 

Restricted Earth return: Mars, Europa, others TBD.

A.2 Category III/IV/V Requirements for Mars

A.2.1 Category III (Mars Orbiters)

a. Orbiter spacecraft that achieve microbial burden levels 

(surface, mated, and encapsulated) defined in the specification “Maximum Total Microbial Spore Burden for Category 

III Missions to Mars” shall not be required to meet impact 

or orbital lifetime requirements. The microbial burden level 

requirement for Mars is noted in the specification sheet 

“Maximum Total Microbial Spore Burden for Category III 

Missions to Mars.” The achievement of these levels will likely 

require some form of active microbial reduction. Approved 

bioassays (see NPR 5340.1) are required to establish the 

microbial burden levels. Assembled spacecraft and all modules that have been bioassayed must be protected against 

recontamination. 

b. Orbiter spacecraft that do not meet the requirements, 

“Maximum Total Microbial Spore Burden for Category III 

Missions to Mars,” are required to meet a probability of impact 

requirement of 10–2 for a specified orbital lifetime limit, as 

noted in the specification “Orbital Lifetime Probability, Mars.” 

Mission compliance with these requirements will consist of 

probability-of-impact analysis and orbital lifetime analysis. 

Trajectory biasing may be employed to lower the probability of 

impact for mission hardware, but it is not required. 

c. For orbiters that meet orbital lifetime requirements, biological cleanliness is assumed by the use of International 

Organization for Standardization (ISO) Class 8 (or Class 

100,000 under Fed. Std. 209E) cleanrooms and the associated 

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Appendices

procedures. No additional bioload quantification is generally 

necessary.

A.2.2 Category IV (Mars Landers) 

For Mars landers, Category IV is subdivided into IVa, IVb, and IVc:

a. Category IVa missions comprise lander systems not carrying 

instruments for the investigation of extant Martian life. These 

lander systems are restricted to a total surface microbial burden no greater than Viking lander preterminal sterilization levels (see specification sheet “Maximum Surface Microbial Spore 

Burden for Category IVa Missions to Mars”). 

b. Category IVb missions comprise lander systems carrying 

instruments designed to investigate extant Martian life. For 

such missions, the following requirements apply: 

1. Either the entire landed system must be sterilized to 

the microbial burden levels defined in the specification 

sheet “Maximum Surface Microbial Spore Burden for 

Category IVb and IVc Missions to Mars” or to levels 

driven by the nature and sensitivity of the particular 

life-detection experiments, whichever are more 

stringent. 

2. Or the subsystems that are involved in the acquisition, 

delivery, and analysis of samples used for life detection 

must be sterilized to burden levels defined in the 

specification sheet “Maximum Surface Microbial Spore 

Burden for Category IVb and IVc Missions to Mars” 

and a method of preventing recontamination of the 

sterilized subsystems and the contamination of the 

material to be analyzed must be put in place. 

c. Category IVc missions comprise lander systems that investigate Martian special regions (see definition below). For such 

missions, whether or not they include life detection experiments, the following requirements apply: 

1. Case 1. If the landing site is within the special region, 

the entire landed system shall be sterilized at least to 

the burden levels defined in the specification sheet 

“Maximum Surface Microbial Spore Burden for Category 

IVb and IVc Missions to Mars.” 

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When Biospheres Collide

2. Case 2. If the special region is accessed through 

horizontal or vertical mobility, either the entire landed 

system shall be sterilized to the microbial burden 

levels defined in the specification sheet “Maximum 

Surface Microbial Spore Burden for Category IVb 

and IVc Missions to Mars,” or the subsystems that 

directly contact the special region shall be sterilized 

to these levels and a method of preventing their 

recontamination prior to accessing the special region 

shall be provided. 

 If an off-nominal condition (such as a hard landing) 

would cause a high probability of inadvertent biological 

contamination of the special region by the spacecraft, 

the entire landed system must be sterilized to the Viking 

post-terminal sterilization microbial burden levels. 

A.2.2.1 Definition of “Special Region”

A special region is defined as a region within which terrestrial 

organisms are likely to propagate or a region that is interpreted to 

have a high potential for the existence of extant Martian life-forms. 

Given the current understanding, this applies to regions where 

liquid water is present or may occur. Specific examples include but 

are not limited to the following:

a. Subsurface access in an area and to a depth where the presence of liquid water is probable. 

b. Penetrations into the polar caps or other regions with significant water ice. 

c. Areas of hydrothermal activity. 

For all subcategories (IVa, IVb, and IVc), the following apply:

1. Achieving the prescribed levels of cleanliness will require 

contamination control (minimum ISO Class 8, or Class 

100,000 under Fed. Std. 209E, assembly and attendant procedures), microbiological assays, and the maintenance of hardware cleanliness. Contamination-control effectiveness must 

be monitored and demonstrated by periodic assays. These 

assays must also be employed to determine the hardware’s 

microbial burden.

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Appendices

2. When needed to meet the burden requirement specifications, 

the project must provide the facility and the means to accomplish any required microbial reduction. The facility will be 

subject to certification and the means of microbial reduction 

subject to approval and monitoring by the PPO. 

3. Dry heat is the approved microbial reduction method. 

Alternative methods may later be certified for this purpose, but 

they will require a demonstration of effectiveness by the project and the approval of the PPO. Following the final predecontamination (or presterilization) microbiological assays and the 

microbial reduction procedure (as required), the project must 

demonstrate that the spacecraft or subsystem(s) are adequately 

protected against recontamination. This may require the use 

of a bioshield or shroud. Whatever the means of protection, the 

project must provide evidence that decontamination requirements are not compromised following the terminal treatment. 

4. An organics archive is required of the bulk (>1 kg) organic constituents of all launched hardware that is intended to directly 

contact the target planet or that might accidentally do so. Each 

flight program office will provide for the collection and storage, for at least 20 years from the launch of the spacecraft, of a 

50-g sample of each organic compound whose total amount in 

a planetary landing system exceeds 25 kg.

A.2.3 Category V (Sample Return Missions from Mars)

The Earth return mission is classified as “restricted Earth return” 

and is subject to the following requirements:

a. Unless specifically exempted, the outbound leg of the mission shall meet Category IVb requirements. This provision is 

intended to avoid false-positive indications in a life-detection 

and hazard-determination protocol or in the search for life in 

the sample after it is returned. A false-positive could prevent 

the distribution of the sample from containment and could 

lead to unnecessarily increased rigor in the requirements for 

all subsequent Mars missions.

b. Unless the sample to be returned is subjected to an accepted 

and approved sterilization process, the sample container must 

be sealed after the sample’s acquisition. A redundant, fail-safe 

465
When Biospheres Collide

containment procedure with a method for the verification of its 

operation before Earth return shall be required. For unsterilized samples, the integrity of the flight containment system 

shall be maintained until the sample is transferred to containment in an appropriate receiving facility. 

c. The mission and the spacecraft’s design must provide a method 

to break the chain of contact with Mars. No uncontained 

hardware that contacted Mars, directly or indirectly, shall be 

returned to Earth. Isolation of such hardware from the Mars 

environment shall be provided during the sample container’s 

loading into the containment system, its launch from Mars, 

and any in-flight transfer operations required by the mission. 

d. Reviews and approval of the continuation of the flight mission 

shall be required at three stages: 1) prior to launch from Earth, 

2) prior to leaving Mars for return to Earth, and 3) prior to 

commitment to Earth entry. 

e. For unsterilized samples returned to Earth, a program of lifedetection and biohazard testing or a proven sterilization process shall be undertaken as an absolute precondition for the 

controlled distribution of any portion of the sample. 

A.3 Category III/IV/V Requirements for Europa

A.3.1 Category III/IV (Europa Orbiters and Landers)

Requirements for Europa flyby, orbiter, or lander missions, 

including microbial reduction, shall be applied in order to reduce 

the probability of inadvertent contamination of a Europan ocean to 

less than 1 × 10–4 per mission. These requirements will be refined 

in future years, but the calculation of this probability should 

include a conservative estimate of poorly known parameters and 

address the following factors, at a minimum:

a. Microbial burden at launch. 

b. Cruise survival for contaminating organisms. 

c. Organism survival in the radiation environment adjacent to Europa. 

d. Probability of landing on Europa. 

e. The mechanisms of transport to the Europan subsurface. 

f. Organism survival and proliferation before, during, and after 

subsurface transfer. 

466
Appendices

Preliminary calculations of the probability of contamination 

suggest that microbial reduction will likely be necessary for 

Europa orbiters as well as for landers. This will require the 

use of cleanroom technology, the cleaning of all parts before 

assembly, and the monitoring of spacecraft assembly facilities 

to understand the bioload and its microbial diversity, including 

specific problematic species. Specific methods should be developed 

to eradicate problematic species. Methods of microbial reduction 

should reflect the types of environments found on Europa, focusing 

on Earth extremophiles most likely to survive on Europa, such as 

cold- and radiation-tolerant organisms.

A.3.2 Category V (Sample Return Missions from Europa)

The Earth return mission is classified as “restricted Earth return” 

and is subject to the following requirements:

a. Unless specifically exempted, the outbound leg of the mission shall meet Category IVb requirements. This provision is 

intended to avoid false-positive indications in a life-detection 

and hazard-determination protocol or in the search for life in 

the sample after it has been returned. A false-positive could 

prevent the distribution of the sample from containment and 

could lead to unnecessarily increased rigor in the requirements for all subsequent Europa missions. 

b. Unless the sample to be returned is subjected to an accepted 

and approved sterilization process, the sample container must 

be sealed after the sample’s acquisition. A redundant, fail-safe 

containment procedure with a method for the verification of its 

operation before Earth return shall be required. For unsterilized samples, the integrity of the flight containment system 

shall be maintained until the sample is transferred to containment in an appropriate receiving facility.

c. The mission and the spacecraft’s design must provide a method 

to break the chain of contact with Europa. No uncontained 

hardware that contacted Europa, directly or indirectly, shall 

be returned to Earth. The isolation of such hardware from the 

Europan environment shall be provided during the sample container’s loading into the containment system, its launch from 

Europa, and any in-flight transfer operations required by the 

missions. 

467
When Biospheres Collide

d. Reviews and approval of the continuation of the flight mission 

shall be required at three stages: 1) prior to launch from Earth, 

2) prior to leaving Europa for return to Earth, and 3) prior to 

commitment to Earth entry. 

e. For unsterilized samples returned to Earth, a program of lifedetection and biohazard testing or a proven sterilization process shall be undertaken as an absolute precondition for the 

controlled distribution of any portion of the sample. 

A.4 Requirements for Small Solar System Bodies

A.4.1 Outbound Categorization

The small bodies of the solar system not elsewhere discussed in 

this document represent a very large class of objects. Forward 

contamination requirements for these missions are not warranted 

except on a case-by-case basis, so most such missions should 

adhere to Category I or II requirements (see table 7.1).

A.4.2 Sample Return Missions from Small Solar System Bodies

a. The determination as to whether a mission is classified as 

“restricted Earth return” or not (Category V) shall be undertaken with respect to the best multidisciplinary scientific 

advice, using the framework presented in the 1998 report of 

the U.S. National Research Council’s Space Studies Board entitled Evaluating the Biological Potential in Samples Returned 

from Planetary Satellites and Small Solar System Bodies: 

Framework for Decision Making (SSB 1998). Specifically, 

such a determination shall address the following six questions 

for each body intended to be sampled: 

1. Does the preponderance of scientific evidence indicate 

that there was never liquid water in or on the target 

body? 

2. Does the preponderance of scientific evidence indicate 

that metabolically useful energy sources were never 

present in or on the target body? 

3. Does the preponderance of scientific evidence indicate 

that there was never sufficient organic matter (or CO2

468
Appendices

or carbonates and an appropriate source of reducing 

equivalents) in or on the target body to support life? 

4. Does the preponderance of scientific evidence indicate 

that subsequent to the disappearance of liquid water, 

the target body was subjected to extreme temperatures 

(i.e., >160°C)?

5. Does the preponderance of scientific evidence indicate 

that there is or was sufficient radiation for biological 

sterilization of terrestrial life-forms? 

6. Does the preponderance of scientific evidence indicate 

that there has been a natural influx to Earth (e.g., via 

meteorites) of material equivalent to a sample returned 

from the target body?

 For containment procedures to be necessary (“restricted Earth 

1. Unless specifically exempted, the outbound phase of the 

mission shall meet contamination-control requirements 

to avoid false-positive indications in a life-detection and 

hazard-determination protocol or in the search for life 

in the sample after it has been returned. 

2. Unless the sample to be returned is subjected to an 

accepted and approved sterilization process, the sample 

container must be sealed after the sample’s acquisition. 

A redundant, fail-safe containment procedure with a 

method for the verification of its operation before Earth 

return shall be required. For unsterilized samples, the 

integrity of the flight containment system shall be 

maintained until the sample is transferred to containment in an appropriate receiving facility. 

3. The mission and the spacecraft’s design must provide 

a method to break the chain of contact with the target 

body. No uncontained hardware that contacted the 

target body, directly or indirectly, shall be returned to 

Earth. The isolation of such hardware from the body’s 

environment shall be provided during the sample container’s loading into the containment system, its launch 

469
When Biospheres Collide

from the body, and any in-flight transfer operations 

required by the mission. 

4. Reviews and approval of the continuation of the flight 

mission shall be required at three stages: a) prior to 

launch from Earth, b) prior to leaving the body or its 

environment for return to Earth, and c) prior to commitment to Earth entry. 

5. For unsterilized samples returned to Earth, a program 

of life-detection and biohazard testing or a proven sterilization process shall be undertaken as an absolute 

precondition for the controlled distribution of any portion of the sample. 

A.5 Additional Implementation Guidelines for Category V Missions

If during the course of a Category V mission there is a change 

in the circumstances that led to its classification or there is a mission failure—e.g., new data or scientific opinions arise that would 

lead to the reclassification of a mission originally classified as “unrestricted Earth return” to “restricted Earth return” and the safe return 

of the sample cannot be assured, or the sample containment system 

of a “restricted Earth return” mission is thought to be compromised 

and the sample’s sterilization is impossible—then the sample to be 

returned shall be abandoned. If the sample has already been collected, 

the spacecraft carrying it must not be allowed to return.

470
Appendices

Appendix B: 

The Impact of “Faster, Better, Cheaper” 

on Planetary Protection Priorities

A lot of the new ways of doing things in industry are 

not the best way to go for the space business.

—NASA Advisory Council1

During the NASA Advisory Council’s June 2000 meeting, Tom 

Young, a space-industry executive formerly of Lockheed Martin, 

presented results from the Mars Program Independent Assessment 

Team (MPIAT) that he chaired.2 MPIAT investigated the failures of 

Mars Climate Orbiter (MCO), Mars Polar Lander (MPL), and Deep 

Space 2 (DS2), which put planetary protection objectives at risk and 

destroyed the eagerly awaited scientific returns from the missions. 

MPIAT examined the relationships between NASA Headquarters, 

JPL, the California Institute of Technology (Caltech), and Lockheed 

Martin and how breakdowns in those relationships were partially 

responsible for the failures. Young noted that while NASA could not 

go back to its old way of doing business, which involved billion-dollar 

missions taking 15 or more years, current industrial policies were 

not always compatible with the needs of the space program. These 

needs included protecting planetary surfaces from contamination 

that could result from a spacecraft crash. 

 1. Lori B. Garver (exec. secretary) and Bradford W. Parkinson (chair), NASA Advisory Council, 

471
When Biospheres Collide

Young talked of the requirement for a margin of safety that would 

allow for human operational errors without causing a mission failure. 

Where this margin was not implemented, either because of industry or NASA management decisions or because of insufficient mission budgets, missions sometimes failed. In particular, MPIAT found 

that the lack of an established, clear definition of the faster, better, 

cheaper (FBC) approach and its associated policies for guiding operations had resulted in both NASA and Lockheed Martin project managers having different interpretations of what were allowable risks to 

take.3 While MPIAT deemed the FBC approach to building spacecraft 

a good one if properly applied (as evidenced by the achievements of 

the Pathfinder and Mars Global Surveyor missions), it found a “willingness to cut corners and a failure to follow a disciplined approach 

successfully,” which was unacceptable in a “one strike and you’re 

out” business such as space exploration.4

The situation that put some of the FBC missions and their 

accompanying planetary protection objectives at risk was that 

NASA’s agenda for developing and launching these projects rigidly 

constrained parameters that normally had some variability in them 

and which could have been used to reduce the risk of failure. For 

instance, many of the FBC missions, which were committed to quick 

development and relatively small budgets, were characterized by 

fixed launch dates; this constrained schedules that perhaps should 

have been more flexible. Established launch vehicle weights, science 

payloads selected in large part on their competitive pricing, rigid performance standards, and fixed mission costs without adequate contingency funding also increased the risks of both mission failure and 

inadvertent contamination of the target planet. 

Space exploration projects typically have two variables—their 

margins and their risks. If margins are adequate, risks can be 

reduced. But the above constraints severely minimized project margins. The negative results of this, as determined by MPIAT, were 

analysis and testing deficiencies as well as inadequate preparations 

 3. “Testimony of Thomas Young, Chairman of the Mars Program Independent Assessment 

472
Appendices

for mission operations; all of these factors led to excessive risk and 

contributed to the failures and to the possible forward contamination 

of Mars, the target body. Being managed as a single Mars ’98 Project, 

the MCO and MPL missions were particularly constrained by significant underfunding from their inception and in meeting their inflexible performance requirements.5

 5. Young, 

473
When Biospheres Collide

Appendix C: 

Biohazard Identification: 

The Synergism Between Bioterror Prevention 

and Planetary Protection Research

The anthrax mailings of 2001 raised public and governmental concerns about bioterrorism threats, and this resulted in significantly 

increased detection and countermeasure research funding, as well 

as the implementation of the Public Health Security and Bioterrorism 

Preparedness and Response Act of 2002 and other measures.6

 The 

Department of Homeland Security (DHS) has made preparation against 

bioterrorism a priority and has developed the BioWatch program to provide early detection of mass pathogen releases. DHS has also funded 

research programs at national laboratories and universities for developing improved early-warning as well as decontamination technologies.7

The technology for a nationwide network, involving mass spectrometry 

and modeling approaches, is being developed by Oak Ridge National 

Laboratory (ORNL) and the American Tower Corporation for realtime detection, identification, and assessment of bioterror as well as 

other threats.

The planetary protection and bioterror detection fields have markedly 

different objectives. Planetary protection programs will take extremely 

stringent preventive measures to ensure that any biota in future return 

samples does not enter our biosphere. Space scientists consider the 

chances that such biota even exist to be very low, but not zero. Therefore, 

a conservative approach is warranted in the handling of return samples.

Bioterror detection, on the other hand, seeks provide awareness 

of the release of hazardous agents. This may be achieved through 

the identification of symptoms in the victims of an attack. In contrast, planetary protection programs do not expect anyone to exhibit 

 6. Jim Kulesz, “CBRN Detection and Defense—Sensor Net,” Oak Ridge National Laboratory 

474
Appendices

symptoms of an extraterrestrial infection, since mission personnel go 

to great lengths to prevent exposure.

There is a potential connection between the two fields, however, 

and it is this: the advanced technologies that have been developed 

to detect and contain potential bioterror agents can be used in the 

planetary protection field to search for extraterrestrial biota in return 

samples and, if life is detected, to reliably contain it.

Planetary protection life-detection technology may also be of use 

in bioterror detection. Both fields are concerned with distinguishing 

small quantities of microorganisms that might have large effects on 

human health. Data from planetary protection research on the identification of, for instance, extremophile microorganisms that are highly 

resistant to heat, radiation, and temperature extremes may also be 

useful in bioterrorism studies.

Some of the newer investigative methods of planetary protection, 

such as epifluorescent microscopic techniques, can detect the presence of a single microbe. The polymerase chain reaction (PCR) methodology, which enzymatically amplifies biomarkers, can also do this in 

addition to identifying the cell’s genetic characteristics (these methodologies were discussed in Chapters 6 and 7). PCR has been examined 

extensively in Homeland Security studies such as ones at the Centers 

for Disease Control and Prevention (CDC) and at Lawrence Livermore 

and Los Alamos National Laboratories, as well as other institutions. 

But extraterrestrial back contamination prevention studies have had 

a different emphasis; they have focused on the approaches for identifying as yet unknown microbes able to survive in severely harsh 

environments.8 Such planetary protection efforts may thus have applications to bioterror detection of unknown agents.

 8. E. K. Wheeler, W. J. Benett, K. D. Ness, P. L. Stratton, A. A. Chen, A. T. Christian, J. B. 

475
When Biospheres Collide

Appendix D: 

Committees, Organizations, and Facilities 

Important to the Development of Planetary 

Protection

Organization Abbreviation Parent 

Organization

Date 

Established

Importance to Planetary 

Protection

Ad Hoc 

Committee on 

the Lunar Sample

Handling Facility

Hess NAS SSB 1965 Non-NASA review of LSRL needs. 

Formed by NAS SSB chairperson 

Harry H. Hess.

Committee 

Ad Hoc 

Committee 

on the Lunar 

Sample Receiving 

Laboratory

Chao 

Committee

NASA 1964 Chaired by Edward Ching Te 

Chao, a U.S. Geological Survey 

geochemist. Investigated LSRL 

needs and established general 

facility concepts.

Advanced 

Research Projects 

Agency

ARPA 

(now DARPA)

DOD 1958 Concerned with military aspects 

of space, DARPA was established 

as a response to the Soviet 

launching of Sputnik. 

American Institute 

of Biological 

Sciences

AIBS 1947 Cosponsor of key 1958 

symposium.

Army Biological 

Warfare 

Laboratories

DOD 1943 Methods for managing 

biologically hazardous materials 

were used to help develop 

quarantine and handling 

procedures for lunar samples.

Baylor University 

College of 

Medicine

1900 Published an in-depth set of 

procedures for operating the 

Lunar Receiving Laboratory and 

quarantining lunar samples and 

astronauts.

Bionetics 

Corporation

1969 Founded specifically to perform 

planetary quarantine support for 

NASA’s Viking mission.

Bioscience 

Advisory 

Committee

Kety 

Committee

NASA 1959 Studied NASA’s capabilities and 

future roles in bioscience.

Committee on 

Contamination by 

Extraterrestrial 

Exploration

CETEX ICSU 1958 Early work on planetary 

protection policy. Superseded by 

COSPAR.

476
Appendices

Organization Abbreviation Parent 

Organization

Date 

Established

Importance to Planetary 

Protection

Committee on 

Planetary and 

Lunar Exploration

COMPLEX NAS SSB early 1970s Advisory committee to NASA.

Committee on 

Space Research

COSPAR ICSU October 

1958

Major contributor over the years 

to planetary protection policy.

Communicable 

Disease Center

CDC PHS 1946 Developed protective procedures 

for handling and quarantining 

lunar samples. Later renamed the 

Centers for Disease Control and 

Prevention.

Department of 

Agriculture

USDA 1862 Responsibility concerning the 

health of U.S. crops and animals 

of economic importance.

Department of 

Defense

DOD 1789 Military and strategic 

perspective.

Goddard Space 

Flight Center

GSFC NASA 1959 Contributor to many NASA 

missions.

Interagency 

Committee 

on Back 

Contamination

ICBC January 

1966

Advised and guided NASA on 

planetary protection matters, 

with a charter to protect public 

health, agriculture, and other 

resources.

International 

Council of 

Scientific Unions

ICSU 1931 Contributor to international 

planetary protection policy. 

In 1958, ICSU’s ad hoc 

Committee on Contamination 

by Extraterrestrial Exploration 

(CETEX) developed a code of 

behavior for space exploration.

Jet Propulsion 

Laboratory

JPL NASA early 1930s NASA Center managing robotic 

space missions.

Kennedy Space 

Center

KSC NASA 1962 Provided launch services for 

many NASA missions. Also 

conducted terminal sterilization 

of the Viking craft. Began as the 

Launch Operations Center and 

was renamed after President 

Kennedy’s death.

Langley Research 

Center

LaRC NASA 1917 Managed NASA’s Viking project 

and contributed to many other 

NASA missions.

Lewis Research 

Center

LeRC NASA 1941 Designed the Titan-Centaur 

launch vehicles for the Viking 

mission. Renamed Glenn 

Research Center in 1999. 

477
When Biospheres Collide

Organization Abbreviation Parent 

Organization

Date 

Established

Importance to Planetary 

Protection

Lunar Sample 

Receiving 

Laboratory

LSRL NASA July 1969 Quarantined and examined 

Apollo lunar samples as well as 

astronauts. Later renamed the 

Lunar Receiving Laboratory (LRL). 

The last of LRL’s certifications were 

not officially signed until less than 

24 hours before the Apollo 11 

Command Module splashed down 

in the Pacific Ocean.

Manned Spacecraft 

Center

MSC NASA 1961 Managed the Apollo program. 

Renamed the Lyndon B. Johnson 

Space Center (JSC) in 1973.

Mars Exploration 

Program Analysis 

Group

MEPAG NASA JPL ca. 2000 Considered a 100-year timeframe 

for Martian special regions in 

which they could be visited by any 

given mission. The analysis took 

into account past and present 

climate and included the study of 

current special regions as well as 

the possibility that a locale could 

become a special region within a 

century after a spacecraft’s arrival 

due to a natural event such as a 

volcanic eruption.

Mars Human 

Precursor Science 

Steering Group

MHP SSG MEPAG 2004 Identified priorities for 

investigations, measurements, and 

planetary protection technology 

demonstrations to be carried out 

prior to the first human mission to 

Mars.

Marshall Space 

Flight Center

MSFC NASA 1960 Contributor to many NASA 

missions.

Martin Marietta 

Corporation (later 

Lockheed Martin)

MMC 1961 Built the Viking spacecraft. Later 

became Lockheed Martin Space 

Systems and assembled many 

robotic spacecraft. 

Mobile 

Quarantine 

Facility

MQF NASA 1966 Housed personnel, equipment, 

and material returning from the 

Moon during their trip to the LSRL. 

The MQF was constructed by 

MelPar, a subsidiary of American 

Standard, and resembled an 

Airstream housetrailer.

National Academy 

of Sciences

NAS March 1863 Key adviser to NASA.

478
Appendices

Organization Abbreviation Parent 

Organization

Date 

Established

Importance to Planetary 

Protection

National 

Aeronautics 

and Space 

Administration

NASA October 

1958

National 

Research Council 

Committee 

on Preventing 

the Forward 

Contamination 

of Mars

NRC 

PREVCOM

NAS SSB ca. 2005 Conducted the NASA-requested 

study Preventing the Forward 

Contamination of Mars.

National Science 

Foundation

NSF 1950 Adviser to NASA. 

Pickering 

Committee

NASA MSC March 1966 A site survey board, led by 

NASA’s Col. John Pickering, 

which screened 27 existing 

facilities around the U.S. for 

possible use as a lunar sample 

receiving facility.

Planetary 

Protection Advisory 

Committee (now 

the Planetary 

Protection 

Subcommittee)

PPAC 

(now PPS)

NASA 2001 Advised NASA Administrator on 

planetary protection policy and 

technical issues.

Planetary 

Quarantine Office

PQO NASA 1963 Later renamed the Planetary 

Protection Office, this is the NASA 

entity overseeing protection of 

solar system bodies, including 

planets, moons, comets, and 

asteroids, from contamination by 

Earth life, as well as protecting 

Earth from possible life-forms that 

may be returned from other solar 

system bodies. 

Public Health 

Service

PHS Now part of 

HHS

July 1798 Had responsibility for the health 

of the United States and for 

any potential threat to that 

health from extraterrestrial 

life, particularly from back 

contamination.

Space Science 

Board

SSB NAS 1958 Major adviser to NASA on all 

interplanetary contamination 

issues. Later renamed the Space 

Studies Board.

479
When Biospheres Collide

Organization Abbreviation Parent 

Organization

Date 

Established

Importance to Planetary 

Protection

Space Science 

Steering 

Committee

NASA February 

1960

Active during the Apollo 

program. Developed 

specifications for a lunar sample 

receiving facility.

Task Group on 

Issues in Sample 

Return

TGISR NAS SSB ca. 1996 Examined issues related to 

bringing back material from solar 

system bodies.

Task Group on 

Sample Return 

from Small Solar 

System Bodies

NAS SSB ca. 1998 Assessed the potential for a living 

entity to be contained in or on 

samples returned from planetary 

satellites and other small solar 

system bodies such as asteroids 

and comets.

UN Committee on UNCOPUOS United December Concerned with contamination 

the Peaceful Uses 

of Outer Space

Nations 1958 dangers to celestial bodies. 

Dealt with the legal aspects of 

planetary protection.

West Coast 

Committee on 

Extraterrestrial 

Life 

WESTEX NAS February 

1959

Formed by Joshua Lederberg 

to address the protection and 

preservation of planetary surfaces 

during space exploration.

480
Appendices

Appendix E: 

Timeline of Important 

Planetary Protection–Related Events

481
When Biospheres Collide

482
Appendices

483
When Biospheres Collide

Appendix F: 

Planetary Protection Approaches 

Used on Various Missions

Chapter Mission Planetary Protection Approach

General Approaches Used on Many Missions

3 Payload capsule deflection maneuvers to prevent unsterilized parts of 

spacecraft, such as propulsion sections, from impacting target body.

4 Spacecraft assembly in cleanrooms.

Apollo

Planetary Protection While Apollo Was on Moon Flight

4 Apollo 11 Astronaut reentry to spacecraft after Moon walk: brushed off as much loose 

lunar material from their spacesuits as they could and left their outer shoe 

coverings and backpacks behind on the Moon.

4 Apollo 11 Before docking Lunar Module (LM) with Command Module (CM) orbiting 

the Moon, astronauts who had visited the lunar surface cleaned LM’s insides 

with vacuum brush to minimize quantity of material carried into CM. Vacuum 

did not work that well; lunar material clung tenaciously to surfaces.

4 Apollo 11 Astronauts extensively cleaned LM while it was docked with CM in order to 

minimize contamination of CM.

4 Apollo 11 LM cabin gas continuously circulated through lithium hydroxide (LiOH) filter 

beds intended to remove virtually all particulate matter.

4 Apollo 11 Atmospheric pressure in CM kept higher than in LM so that gas would flow 

out of rather than into CM and exit spacecraft through LM’s cabin relief valve.

4 Apollo 11 During the trip back to Earth, astronauts repeatedly vacuumed and wiped 

CM interior. 

4 Apollo 11 CM atmosphere constantly circulated through LiOH filters to trap particles 

as small as bacteria. 

After Splashdown

4 Apollo 11 Biological isolation garments (BIGs) were passed into CM and astronauts 

donned them before exiting and boarding raft. BIGs trapped any organisms 

astronauts exhaled. Astronauts would wear BIGs until they entered 

shipboard quarantine unit.

4 Apollo 11 Recovery crew scrubbed area around CM’s escape hatch as well as 

around postlanding vents with Betadine (an iodine solution) to kill any 

microorganisms that might have escaped the inside of the module and 

might be adhering to the vent area. The Betadine would not, of course, have 

killed any organisms that had escaped into the atmosphere or the ocean.

4 Apollo 11 Astronauts and recovery crew decontaminated each other’s protective suits 

with a sodium hypochlorite (bleach) solution.

4 Apollo 11 CM was sealed until arrival at Lunar Receiving Laboratory (LRL). 

484
Appendices

Chapter Mission Planetary Protection Approach

4 Apollo 11 Astronauts were hoisted aboard a helicopter and taken to recovery 

vessel. Helicopter crew wore oxygen masks at all times to guard against 

inhaling any germs from the astronauts. The helicopter itself was later 

decontaminated with formalin.

4 Apollo 11 Astronauts walked across the recovery ship’s deck between helicopter and 

Mobile Quarantine Facility (MQF). NASA personnel sprayed their path with 

glutaraldehyde, a sterilant typically used in hospitals to disinfect equipment. 

Mobile Quarantine Facility

4 Apollo 11 Astronauts entered MQF, which was capable of biologically isolating 

them until arrival at LRL. Quarantine conditions were maintained on MQFs 

through negative internal air pressure, filtration of effluent air, internal 

capture and storage of wastes in holding tanks, and a transfer lock 

system that could bring materials into or out of the facility without letting 

potentially infected air out. 

4 Apollo 11 The recovery ship contained a second MQF that could be used to 

quarantine any of the ship’s crew who might have been directly exposed 

to either astronauts or spacecraft. If a major biocontainment breach had 

occurred, the recovery ship would itself have become the isolation unit and 

would have had to remain at sea for the entire astronaut and lunar sample 

quarantine period.

4 Apollo 11 After the astronauts were helicoptered to recovery ship, CM was hoisted 

aboard and connected by plastic tunnel to MQF. 

4 Apollo 11 Film shot on Moon and lunar sample containers were carried through 

the tunnel into the MQF since they, too, were potential sources of back 

contamination. These items were then passed out of MQF through a 

decontamination lock and flown to LRL.

Lunar Receiving Laboratory

4 Apollo 11 Quarantine of lunar material, astronauts, spacecraft, and equipment took place 

at LRL until analyses behind biological barriers indicated no danger to Earth.

4 Apollo 11 LRL was kept at negative air pressure.

4 Apollo 11 All effluents and emissions from LRL were sterilized before release.

Apollo 11 Staff transferred materials out of isolated areas using two-door sterilization 

cabinets, in which steam and/or ethylene oxide gas was employed.

4 Apollo 11 Glove boxes were employed in the quarantine facility so that lunar 

samples could be analyzed without contaminating the user. Technicians 

did not directly touch the samples but worked from the outside boxes 

and reached into interior by putting their hands in glove ports. The 

glove boxes were enclosures designed so that a range of tools inside the 

chambers could be manipulated by staff through a pair of impermeable 

gloves attached to ports in the chamber wall. The glove boxes were 

critical for preventing contamination of LRL staff and the outside 

environment with Moon material. 

4 Apollo 11 A leak in a glove exposed two technicians to the Moon rocks, and these 

personnel had to go into quarantine.

485
When Biospheres Collide

Chapter Mission Planetary Protection Approach

4 Apollo 11 The MQF was flown to Ellington Air Force Base near Houston, then 

transferred onto a special flatbed truck designed for it and driven to the 

Crew Reception Area (CRA) of the LRL. The truck backed up to the CRA’s 

loading dock, and technicians taped a shroud tightly in place that formed 

a sort of airlock preventing outside air from being contaminated when the 

MQF was opened and the astronauts entered the CRA. 

4 Apollo 11 Medical staff watched astronauts, support personnel, and technicians put 

in quarantine after breach of biobarrier for any sign of infection and illness, 

conducting frequent examinations and blood tests. Staff conducted clinical 

observations and chemical, biological, and immunological analyses. Mission 

plans called for astronauts to remain in quarantine for at least 21 days after 

exposure to lunar material. Period of quarantine might have been extended 

if anyone had exhibited signs of infection in the vacuum laboratory. 

4 Apollo 11 CM was quarantined and decontaminated at LRL in its spacecraft storage 

room. All stowed equipment, including clothing, was also quarantined. CM’s 

water and waste management system was decontaminated by a piped-in 

formalin solution containing 40 percent formaldehyde, which remained in the 

system for 24 hours. A recovery engineer opened all compartments and wiped 

them down with disinfectant. LRL staff heated interior of CM to 110°F (43°C), 

evacuated its pressure to 8.5 psi, and filled it with formaldehyde gas for 24 

hours. Because recovery crew that performed the decontamination might have 

gotten contaminated themselves, they had to be quarantined afterward. 

Viking

General Planetary Protection Approaches for Viking Mission

5 Viking Selected or developed materials for spacecraft components that were as 

heat-resistant as possible in order to resist damage from thermal sterilization.

5 Viking Engineered manufacturing processes that minimized biological loads 

accruing on the Viking Lander Capsule (VLC).

5 Viking Applied sterilizing heat to a range of components and assemblies.

5 Viking Conducted terminal sterilization of the entire VLC, then hermetically sealed 

it in order to maintain sterility.

Viking Orbiter (VO)

5 Viking Assembly procedures generating a minimum of contamination.

5 Viking Periodic bioassays of VO surfaces.

5 Viking Designed VO trajectory to avoid impact with, and contamination of, Mars.

Viking Lander Capsule

5 Viking Testing and development program to determine which off-the-shelf 

materials and components withstood sterilization heating environments. 

Testing was conducted on electronic parts, solder, coatings, fasteners, 

gyroscopes, recorders, computers, batteries, bioshield, and other parts.

Clean Manufacturing Processes

5 Viking Maximized cleanliness of raw materials and basic parts.

5 Viking Reduced dust and contamination in work space and on personnel.

5 Viking Regular cleaning of subassemblies, including wiping down, vacuuming, and 

blowing off all accessible surfaces. 

486
Appendices

487

Chapter Mission Planetary Protection Approach

5 Viking Applying standard spacecraft cleaning procedures to all surfaces prior to mating.

5 Viking Implementing component packaging requirements that preserved their 

level of cleanliness.

Subcontractor Planetary Protection Responsibilities

5 Viking Applied flight acceptance heat cycle that verified parts’ abilities to 

withstand heat sterilization environments and reduced bioburdens, 

especially of encapsulated and mated-surface microbes. These heat cycles 

helped minimize the necessary exposure time and thermal stresses of the 

terminal sterilization cycle on the complete spacecraft.

5 Viking Biology package probability of contamination had to be kept below 1 × 10–6, 

which required additional cleaning and sterilization. Plasma cleaning of surface 

contaminants was employed as well as sterilization in 120°C (248°F) drynitrogen atmosphere environment for 54 hours. Biology package was sealed in 

biological barrier during its sterilization and transport procedures in order to 

lower the risk of recontamination.

Prime Contractor (Martin Marietta) Planetary Protection Responsibilities

5 Viking Built and heat-sterilized certain electronics assemblies, then tested them to 

ensure they were functional.

5 Viking Heat-sterilized loose, nonmetallic hardware parts.

5 Viking Periodic surface cleaning of spacecraft was carried out as it was being assembled.

5 Viking All cleaning, assembly, and test operations of VLC systems as well as of the 

capsule itself were conducted in cleanrooms with personnel working under 

strict handling constraints and procedures. This minimized the bioburden 

accumulation on the VLC.

5 Viking Conducted heat-compatibility test on spacecraft antenna.

5 Viking Conducted heat-compatibility flight acceptance test (FAT) after assembly of 

entire VLC, before sending it to KSC.

5 Viking Monitored activities of Viking subcontractors who were manufacturing key 

parts of spacecraft.

Kennedy Space Center (KSC) Terminal Sterilization of VLC

5 Viking Verification tests performed in which KSC staff disassembled, inspected, 

and functionally checked each VLC.

5 Viking Performed detailed bioassays to estimate microbe load on each VLC. Bioassays 

were key in determining appropriate durations of terminal sterilization cycles.

5 Viking Applied terminal sterilization with VLC bioshield sealed and pressurized. 

Procedure carried out in thermal test chamber using inert gas atmosphere of 

97 percent nitrogen, 2.5 percent oxygen, and 0.5 percent other gases. To bring 

interior VLC temperatures up more quickly and reduce temperature gradients 

(and thermal stresses they could cause), heated nitrogen gas mixture was 

injected directly into VLC, including into its heating and coolant lines. Residence 

times ran from 43 to 50 hours, with each VLC being exposed to 111.7°C for 30 

hours after the coldest contaminated point reached that temperature.

5 Viking Preventing recontamination of the VLC: electrical and mechanical connections 

from lander (within VLC) interfaced with bioshield, which in turn interfaced 

with VO. This prevented contamination from VO reaching inside VLC.
When Biospheres Collide

Chapter Mission Planetary Protection Approach

5 Viking Positive air pressure within the bioshield during and following terminal 

sterilization also helped prevent recontamination.

5 Viking Pressurized gas and propellant loading: Pressurized gas fill lines for VLC and 

line filters went through terminal sterilization. Pressurant gases themselves 

were sterilized by being passed through the filters. Hydrazine propellant 

was self-sterilizing, in that it was toxic to terrestrial microbes and thus did 

not need additional sterilization.

5 Viking Alcohol-formaldehyde sporicide was pumped into coolant loop for 

radioisotope thermal generators (RTGs), a source of shipboard power. 

5 Viking Hydrazine propellant was subjected to a repeated freezing and thawing 

process to remove aniline contamination. When aniline was burned, 

hydrogen cyanide was produced, a substance often involved in amino acid 

reactions that could interfere with search for life.

5 Viking Lander engine nozzles redesigned to minimize chemical contamination and 

severe disturbance of Martian surface.

All equipment and materials used for bioassays (test tubes, racks, nutrient 

materials, alcohols, and squeeze bottles) were themselves thoroughly 

sterilized to prevent recontaminating parts of the spacecraft being analyzed. 

5 Viking

Planetary Protection Procedures During Launch and Cruise Phases

5 Viking Excess pressure buildup within VLC during launch ascent, when outside 

pressure rapidly dropped, was vented through biofilter that did not allow 

microbes to reenter. This avoided danger of bioshield rupture. 

5 Viking After spacecraft separated from Centaur upper stage rocket, which was not 

sterilized, Centaur was deflected off its flight path in order to prevent an 

eventual impact with, and possible contamination of, Mars. 

5 Viking Bioshield was removed from VLC only after spacecraft exited atmosphere, 

eliminating danger of recontamination by atmospheric molecules.

Particles, chemicals, and possibly biotic material from VO, which was 

unsterilized, as well as gases emitted by its coatings, greases, and paints 

and propellants from its rocket engines were all capable of contaminating 

VLC, although NASA calculated this was very unlikely. Nevertheless, before 

Viking reached Mars, mission control turned it so that VLC faced toward the 

Sun, allowing ultraviolet solar radiation to provide a sterilant function on the 

capsule’s exposed surfaces.

5 Viking

Planetary Protection During Arrival at and Descent to Mars

5

5

Viking

Viking

After separation of lander, trajectory of unsterilized VO had to be carefully 

controlled so it didn’t impact Mars.

After touchdown, lander’s biology package, which was sensitive enough to 

detect a single microbe, confirmed no contamination within the biology package 

itself. 

Missions to Small Bodies of the Solar System

6 Galileo To prevent an accidental impact with Europa or another Jovian icy moon, Galileo 

orbiter used last of its fuel to impact and burn up in Jupiter’s atmosphere.

488
Appendices

Chapter Mission Planetary Protection Approach

6 Cassini Cassini was deemed to have low probability of contaminating Titan, and 

so PPO did not impose planetary protection requirements other than 

assembly of spacecraft in a cleanroom, limited mission documentation, 

and assurances that spacecraft was not likely to accidentally impact Titan. 

However, with the presence of water detected on Enceladus, most planetary 

protection requirements may be added.

6 Hayabusa Japanese return mission to Itokawa asteroid had landing site in Australia. 

Although back contamination risk to Earth was extremely low to negligible, 

Australian Department of Agriculture, Fisheries and Forestry recognized that 

environmental contamination could occur and required that return samples 

be immediately placed into secure, impervious containers and exported. 

6 Return 

samples 

from P- and 

D-type 

asteroids

Since little is known about them, SSB recommends analysis in dedicated 

asteroid sample curation laboratory with cleanroom, subfreezing storage 

and processing, dedicated processing cabinets for samples from each 

parent body, with positive-pressure nitrogen atmospheres, and continuous 

monitoring for inorganic, organic, and biological contamination.

6 Stardust An unrestricted Earth return mission because this mission, which sampled 

particles in the Wild 2 comet’s tail as well as interstellar dust sweeping 

through the solar system, was considered by scientific opinion to be 

carrying no extraterrestrial life-forms.

An unrestricted Earth return mission because this mission, that sampled 

solar wind particles, was considered by scientific opinion to be carrying no 

extraterrestrial life-forms. 

6 Genesis

Return to Mars

General Bioload Reduction Procedures Typical of Post-Viking Mars Missions

7 Post-Viking 

Mars 

missions

Spacecraft contamination involves both molecular and particulate types. 

Molecular contamination includes greases and oils, while particulate 

includes typically micrometer-sized conglomerations of matter such as 

dust. Subcontractors and vendors followed precision-cleaning protocols 

and assembly of components in relatively clean areas in order to reduce 

bioburdens on their parts. Typical precision-cleaning procedures targeted 

removal of both particles and molecular films and consisted of wiping 

gross contamination off part followed by application of organic solvents 

and aqueous rinses with or without ultrasonic treatment. The part was then 

sometimes subjected to vapor degreasing, followed by final rinsing typically 

conducted with isopropyl or other alcohol solutions.

7 Post-Viking 

Mars 

missions

After parts arrived at Lockheed Martin, they were usually subjected to 

further bioload reduction using cloth wipes saturated with 100 percent 

isopropyl alcohol (IPA) solution. Cleaning action of wipes was due mainly to 

IPA’s solvent properties, but a frictional action was applied as well in order 

to lift contamination off part surfaces. Cloth wipes were repeatedly folded 

to keep only the clean sections of cloth touching parts. 

Numerous bioassays were performed using two moistened, absorbent 

cotton swabs mounted on wood applicator sticks and moistened polyester 

wipe cloths. Swabs and wipes were first sterilized in autoclave.

7 Post-Viking 

Mars 

missions

489
When Biospheres Collide

Chapter Mission Planetary Protection Approach

Specific Missions

7 Mars 

Observer

Category III (no direct contact of space vehicle with target object).

7 Mars 

Observer

Launch phase: trajectory of launch vehicle’s upper stage was carefully 

biased so as to prevent its eventual impact with Mars.

7 Mars 

Observer

Upper stage separated from the spacecraft using maneuver designed 

to minimize probability that spacecraft would get contaminated, either 

through collision with the upper stage or through materials given off by 

it. This maneuver also further biased upper stage away from a Mars impact 

trajectory.

7 Mars 

Observer

Cruise phase: aimpoint of spacecraft trajectory biased so as to be suitable 

for orbit insertion but not lead to an impact with Mars if Earth lost control of 

the craft.

7 Mars 

Observer

Approximately 90 days before orbit insertion at Mars, increased tracking 

efforts implemented to reduce navigation delivery errors and ensure as 

accurate targeting of spacecraft as possible.

7 Mars 

Observer

Orbit insertion objective was for spacecraft to enter three-day capture orbit. 

Care had to be taken during spacecraft engine firing and first periapsis, 

when there was a small probability of impact with Mars. All intermediate 

orbits between insertion maneuver and eventual mapping orbit had to be 

rigorously analyzed to make sure that their lifetimes were of sufficient length 

for the maneuver to be completed. Factors that decayed these orbits and 

shortened their lifetimes included atmospheric drag and nonsphericity of 

Martian gravitational field. 

7 Mars 

Observer

Mapping orbit needed to be designed to have an adequate lifetime for the 

phase to be completed. 

7 Mars 

Observer

A quarantine orbit needed to be designed such that the craft could be 

raised into it and have a probability of impact with Mars that would not 

exceed 1 × 10–2 by the year 2009 and 5 × 10–2 by the year 2039.

7 Mars 

Surveyor 

Program

As with other programs, trajectory course maneuvers (TCMs) were 

employed to minimize chances of an accidental impact with Mars.

7 Mars 

Global 

Surveyor 

(MGS)

Not sterilized. External surfaces needed only to be visibly clean at payload 

encapsulation. 

7 MGS Orbit selected to be low enough for instruments to make close-range 

observations of Martian surface, but not so low that friction from planet’s 

atmosphere would slow spacecraft down enough for an impact. 

When spacecraft completed its mapping work, propulsion system was 

designed to raise the average altitude to a quarantine orbit that would 

greatly reduce frictional drag. Quarantine orbits were intended to provide 

a contamination-free period of decades in which to conduct missions 

examining the biotic nature of the planet.

7 MGS

490
Appendices

Chapter Mission Planetary Protection Approach

7 Mars 

Pathfinder

Category IVa: landers without life-detection instruments. Required detailed 

documentation, bioassays, probability-of-contamination analysis, an 

inventory of bulk constituent organics, trajectory biasing, use of cleanrooms 

during spacecraft assembly and testing, and bioload reduction to levels on 

Viking before terminal sterilization: 300 spores per square meter and total 

spore burden no higher than 3.0 × 105.

7 Mars 

Pathfinder

Aimpoint of the upper stage and spacecraft was biased away from Mars to 

ensure that any unsterilized part of Pathfinder would not impact Martian 

surface.

7 Mars 

Pathfinder

Trajectory after TCMs 1 and 2 was such that if control of spacecraft was 

subsequently lost, the craft would enter Martian atmosphere at a shallowenough entry angle for atmospheric braking to slow down the craft to below 

1,000 feet per second at impact, even if craft’s parachute did not deploy. 

This was to minimize contamination of Mars from parts of spacecraft in the 

event of a crash landing.

7 Nozomi Japanese spacecraft to Mars had thruster problems and damage from solar 

flares that raised danger of a crash and contamination of planet. Mission 

scientists sent commands to spacecraft to fire small alternate thrusters and 

avoid orbit insertion, minimizing possibility of a Mars impact.

7 Mars 

Climate 

Orbiter 

(MCO)

Small errors in trajectory estimates became more important by Mars orbit 

insertion. Spacecraft flew too low and burned up in Mars atmosphere 

or left atmosphere and reentered interplanetary space but did not hit or 

contaminate planet.

7 Mars Polar 

Lander 

(MPL)

MPL did not have specific life-detection experiments on board and was 

thus cleaned to level of the Viking landers before they received terminal 

sterilization (same as Pathfinder). 

7 MPL MPL did not land softly as planned. Engines shut down prematurely. It 

crashed at about 50 miles per hour and probably broke up, exposing 

surfaces to Mars that may have contained Earth microbes.

7 Mars 

Exploration 

Rover 

(MER)

New planetary protection focus: protecting integrity of equipment for 

making critical biologically related measurements as well as preventing 

contamination of planetary surface.

7 MER Category IVa mission—landers without life-detection instruments. Science 

instruments could, however, detect organic compounds that might suggest 

presence of life.

7 MER Planetary protection measures were applied not only to spacecraft but also 

to facilities in which it was handled. Before MERs were shipped to KSC, its 

highbay facility and ground support equipment were thoroughly cleaned 

and sampled to reduce biological contamination.

7 MER After MERs arrived at KSC, they were disassembled and cleaned to remove 

any contaminants received during their cross-country trip. 

Dry heat microbial reduction was performed on large components that could 

tolerate 125°C (257°F) for 5 hours and were difficult to adequately wipe clean. 

These components included thermal blankets, airbags, honeycombed parts 

(such as the core structures of the rovers), and parachutes packed in cans. 

7 MER

491
When Biospheres Collide

Chapter Mission Planetary Protection Approach

7 MER Spacecraft propellant lines were precision-cleaned. 

7 MER High-efficiency particulate air (HEPA) filters were employed on the vents of 

each rover’s core box, which contained computers as well as other critical 

electronics. The aim was to keep an estimated 99.97 percent of particles 0.3 

microns or larger inside and not contaminate the Martian surface. 

7 MER Spores detected in acoustic foam backing of fairing enclosing MER-1 

spacecraft led to additional cleanliness and bioburden requirements in 

launch vehicle and spacecraft manufacturing specifications.

7 MER As with other missions, trajectories of various components were carefully 

designed to prevent unwanted impacts. When third stage of MER’s 

unsterilized Delta launch vehicle separated from spacecraft, both objects 

were on nearly identical paths that would miss Mars. Approximately 10 

days later, spacecraft performed its first TCM in order to readjust its path to 

arrive at Mars.

7 MER Aeroshells for landers were subjected to dry heat microbial reduction 

(DHMR). Necessary for parts with bioloads difficult to reduce adequately in 

other ways due to factors such as sizes, shapes, and materials.

7 Phoenix 

Mars 

Lander

Parachute subjected to DHMR involving bakeout above 110°C. Procedure 

was necessary because of difficulty cleaning large components.

To prevent recontamination, parachute was double bagged before transport 

and packed with sample strips, which were then archived upon arrival at 

Lockheed Martin, available if needed to confirm parachute cleanliness. If 

there was a life indication on Mars, it would be compared with the sample 

strips to hopefully prove that life-forms had not been carried to Mars on 

parachutes.

7 Phoenix 

Mars 

Lander

492
ACRONYMS AND ABBREVIATIONS

AEC Atomic Energy Commission

AFCOB National Research Council-Armed Forces Committee on Bioastronautics 

AFSEEE Association of Forest Service Employees for Environmental Ethics

AgZn Silver-zinc

AIBS American Institute of Biological Sciences

ALSRC Apollo Lunar Sample Return Container

APHIS USDA Animal Plant Health Inspection Service

ARC Ames Research Center

ARPA Advanced Research Projects Agency (now DARPA)

AU Astronomical unit

BG Bacillus globigii (also known as Bacillus subtilis variety niger)

BIG Biological isolation garment

BPA Bioshield Power Assembly

Caltech California Institute of Technology

CDC PHS’s Communicable Disease Center (later renamed the Centers for 

Disease Control and Prevention)

CETEX Committee on Contamination by Extraterrestrial Exploration

CFR Code of Federal Regulations

CM Command Module

CM2 Carbonaceous chondrite type 2 (for example, the Murchison meteorite)

CO2 Carbon dioxide

COMPLEX Committee on Planetary and Lunar Exploration

COSPAR Committee on Space Research

CRA Crew Reception Area

CSIRO Commonwealth Industrial and Scientific Research Organization

DARPA Defense Advanced Research Projects Agency

DHMR Dry heat microbial reduction

DHS Department of Homeland Security

DNA Deoxyribonucleic acid, a material inside the nucleus of cells that carries 

genetic information

DOD U.S. Department of Defense

DOE U.S. Department of Energy

DOI Department of the Interior

DS2 Deep Space 2

EA Environmental Assessment

EASTEX East Coast Committee on Extraterrestrial Life

EDT Eastern daylight time

EIS Environmental Impact Statement

EOS Electro-Optical Systems, a subsidiary of Xerox Corporation

493
When Biospheres Collide

EPA U.S. Environmental Protection Agency

ESA European Space Agency

ESB Electric Storage Battery Company

EST Eastern standard time

FAA Federal Aviation Administration

FAT Flight acceptance test

FBC Faster, better, cheaper

FEP Fluorinated ethylene propylene

FHWA Federal Highway Administration

FONSI Finding of No Significant Impact 

GCMS Gas chromatograph mass spectrometer

GRC Glenn Research Center at Lewis Field

GSFC Goddard Space Flight Center

HEPA High-efficiency particulate air (a type of filter)

HHS Department of Health and Human Services

HZE High atomic number and energy

IAF International Astronautical Federation

ICBC Interagency Committee on Back Contamination

ICSU International Council of Scientific Unions

IDP Interplanetary dust particles

IGY International Geophysical Year

IPA Isopropyl alcohol

ISO International Organization for Standardization

ISRU In situ resource utilization

JAXA Japan Aerospace Exploration Agency

JPL Jet Propulsion Laboratory

JSC Johnson Space Center

KSC Kennedy Space Center

LaRC Langley Research Center

LCROSS Lunar CRater Observation and Sensing Satellite

LeRC Lewis Research Center (now GRC)

LiOH Lithium hydroxide

LM Lunar Module

LRL Lunar Receiving Laboratory

LSRL Lunar Sample Receiving Laboratory (now LRL)

MCO Mars Climate Orbiter

MEPAG Mars Exploration Program Analysis Group

MER Mars Exploration Rover

(Mg,Fe)2SiO4

 Olivine

MGS Mars Global Surveyor

MHP SSG Mars Human Precursor Science Steering Group

μm Micrometer

MMC Martin Marietta Corporation (later Lockheed Martin)

MPIAT Mars Program Independent Assessment Team

MPL Mars Polar Lander

MQF Mobile Quarantine Facility

MSC Manned Spacecraft Center

MSFC Marshall Space Flight Center

MSL Mars Science Laboratory

494
Acronyms and Abbreviations

NAI NASA Astrobiology Institute

NAS National Academy of Sciences

NASA National Aeronautics and Space Administration

NEPA National Environmental Policy Act 

NHB NASA Handbook 

NHRC NASA Historical Reference Collection

NiCd Nickel-cadmium

NIH National Institutes of Health

NIMS Near-infrared mapping spectrometer

NMI NASA Management Instruction

NPD NASA Policy Directive

NPR NASA Procedural Requirement

NRC National Research Council

NRC PREVCOM National Research Council Committee on Preventing the Forward 

Contamination of Mars

NSF National Science Foundation

NSSDC National Space Science Data Center

O2 Molecular oxygen

OMB Office of Management and Budget

ORNL Oak Ridge National Laboratory

OSHA Occupational Safety & Health Administration

OSSA NASA Office of Space Science and Applications

PCR Polymerase chain reaction

PHS U.S. Public Health Service

PI Principal investigator

PP Planetary protection

PPAC Planetary Protection Advisory Committee (now PPS)

PPO Planetary Protection Officer

PPS Planetary Protection Subcommittee

PQ Planetary Quarantine

PQO Planetary Quarantine Office

PREVCOM See “NRC PREVCOM”

PST Pacific standard time

PTC Proof test capsule

R&D Research and development

RNA Ribonucleic acid, a molecule similar to DNA but containing ribose rather 

than deoxyribose

RTG Radioisotope thermal generator

SAEB Spacecraft Assembly and Encapsulation Building

SETI Search for Extraterrestrial Intelligence

SRC Sample return capsule

SRF Sample receiving facility

SRI Stanford Research Institute

SR-SAG Special Regions Science Analysis Group

SSB Space Studies Board (previously Space Science Board)

TCM Trajectory course maneuver

TGISR Task Group on Issues in Sample Return

TRW Thompson Ramo Wooldridge Inc., from the 1958 merger of Thompson 

Products with the Ramo-Wooldridge Corporation

495
When Biospheres Collide

UCLA University of California at Los Angeles

UN United Nations

UNCOPUOS United Nations Committee on the Peaceful Uses of Outer Space

UNESCO United Nations Educational, Scientific and Cultural Organization 

USAF United States Air Force

USAMRIID U.S. Army Medical Research Institute of Infectious Diseases

USDA U.S. Department of Agriculture

USGS U.S. Geological Survey

UV Ultraviolet

VLC Viking Lander Capsule

VO Viking Orbiter

WESTEX West Coast Committee on Extraterrestrial Life

496
THE NASA HISTORY SERIES

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Press, 1971.

Hacker, Barton C., and James M. Grimwood. On the Shoulders of 

Titans: A History of Project Gemini. NASA SP-4203, 1977; rep. ed. 

2002.

Benson, Charles D., and William Barnaby Faherty. Moonport: A 

History of Apollo Launch Facilities and Operations. NASA 

SP-4204, 1978.

Brooks, Courtney G., James M. Grimwood, and Loyd S. Swenson, Jr. 

Chariots for Apollo: A History of Manned Lunar Spacecraft. NASA 

SP-4205, 1979.

Bilstein, Roger E. Stages to Saturn: A Technological History of the 

Apollo/Saturn Launch Vehicles. NASA SP-4206, 1980 and 1996.

No SP-4207.

Compton, W. David, and Charles D. Benson. Living and Working in 

Space: A History of Skylab. NASA SP-4208, 1983.

Ezell, Edward Clinton, and Linda Neuman Ezell. The Partnership: A 

History of the Apollo-Soyuz Test Project. NASA SP-4209, 1978.

Hall, R. Cargill. Lunar Impact: A History of Project Ranger. NASA 

SP-4210, 1977.

Newell, Homer E. Beyond the Atmosphere: Early Years of Space 

Science. NASA SP-4211, 1980.

502
The NASA History Series

Ezell, Edward Clinton, and Linda Neuman Ezell. On Mars: Exploration 

of the Red Planet, 1958–1978. NASA SP-4212, 1984.

Pitts, John A. The Human Factor: Biomedicine in the Manned Space 

Program to 1980. NASA SP-4213, 1985.

Compton, W. David. Where No Man Has Gone Before: A History of 

Apollo Lunar Exploration Missions. NASA SP-4214, 1989.

Naugle, John E. First Among Equals: The Selection of NASA Space 

Science Experiments. NASA SP-4215, 1991.

Wallace, Lane E. Airborne Trailblazer: Two Decades with NASA 

Langley’s 737 Flying Laboratory. NASA SP-4216, 1994.

Butrica, Andrew J., ed. Beyond the Ionosphere: Fifty Years of Satellite 

Communications. NASA SP-4217, 1997.

Butrica, Andrew J. To See the Unseen: A History of Planetary Radar 

Astronomy. NASA SP-4218, 1996.

Mack, Pamela E., ed. From Engineering Science to Big Science: The 

NACA and NASA Collier Trophy Research Project Winners. NASA 

SP-4219, 1998.

Reed, R. Dale. Wingless Flight: The Lifting Body Story. NASA SP-4220, 

1998.

Heppenheimer, T. A. The Space Shuttle Decision: NASA’s Search for a 

Reusable Space Vehicle. NASA SP-4221, 1999.

Hunley, J. D., ed. Toward Mach 2: The Douglas D-558 Program. NASA 

SP-4222, 1999.

Swanson, Glen E., ed. “Before This Decade Is Out . . .” Personal 

Reflections on the Apollo Program. NASA SP-4223, 1999.

Tomayko, James E. Computers Take Flight: A History of NASA’s 

Pioneering Digital Fly-By-Wire Project. NASA SP-4224, 2000.

503
When Biospheres Collide

Morgan, Clay. Shuttle-Mir: The United States and Russia Share 

History’s Highest Stage. NASA SP-2001-4225, 2001.

Leary, William M. “We Freeze to Please”: A History of NASA’s Icing 

Research Tunnel and the Quest for Safety. NASA SP-2002-4226, 

2002.

Mudgway, Douglas J. Uplink-Downlink: A History of the Deep Space 

Network, 1957–1997. NASA SP-2001-4227, 2001.

No SP-4228 or SP-4229.

Dawson, Virginia P., and Mark D. Bowles. Taming Liquid Hydrogen: 

The Centaur Upper Stage Rocket, 1958–2002. NASA SP-2004-

4230, 2004.

Meltzer, Michael. Mission to Jupiter: A History of the Galileo Project. 

NASA SP-2007-4231, 2007.

Heppenheimer, T. A. Facing the Heat Barrier: A History of 

Hypersonics. NASA SP-2007-4232, 2007.

Tsiao, Sunny. “Read You Loud and Clear!” The Story of NASA’s 

Spaceflight Tracking and Data Network. NASA SP-2007-4233, 

2007.

CENTER HISTORIES, NASA SP-4300:

Rosenthal, Alfred. Venture into Space: Early Years of Goddard Space 

Flight Center. NASA SP-4301, 1985.

Hartman, Edwin P. Adventures in Research: A History of Ames 

Research Center, 1940–1965. NASA SP-4302, 1970.

Hallion, Richard P. On the Frontier: Flight Research at Dryden, 1946–

1981. NASA SP-4303, 1984.

504
The NASA History Series

Muenger, Elizabeth A. Searching the Horizon: A History of Ames 

Research Center, 1940–1976. NASA SP-4304, 1985.

Hansen, James R. Engineer in Charge: A History of the Langley 

Aeronautical Laboratory, 1917–1958. NASA SP-4305, 1987.

Dawson, Virginia P. Engines and Innovation: Lewis Laboratory and 

American Propulsion Technology. NASA SP-4306, 1991.

Dethloff, Henry C. “Suddenly Tomorrow Came . . .”: A History of the 

Johnson Space Center, 1957–1990. NASA SP-4307, 1993.

Hansen, James R. Spaceflight Revolution: NASA Langley Research 

Center from Sputnik to Apollo. NASA SP-4308, 1995.

Wallace, Lane E. Flights of Discovery: An Illustrated History of the 

Dryden Flight Research Center. NASA SP-4309, 1996.

Herring, Mack R. Way Station to Space: A History of the John C. 

Stennis Space Center. NASA SP-4310, 1997.

Wallace, Harold D., Jr. Wallops Station and the Creation of an 

American Space Program. NASA SP-4311, 1997.

Wallace, Lane E. Dreams, Hopes, Realities. NASA’s Goddard Space 

Flight Center: The First Forty Years. NASA SP-4312, 1999.

Dunar, Andrew J., and Stephen P. Waring. Power to Explore: A History 

of Marshall Space Flight Center, 1960–1990. NASA SP-4313, 1999.

Bugos, Glenn E. Atmosphere of Freedom: Sixty Years at the NASA 

Ames Research Center. NASA SP-2000-4314, 2000.

No SP-4315.

Schultz, James. Crafting Flight: Aircraft Pioneers and the 

Contributions of the Men and Women of NASA Langley Research 

Center. NASA SP-2003-4316, 2003.

505
When Biospheres Collide

Bowles, Mark D. Science in Flux: NASA’s Nuclear Program at Plum 

Brook Station, 1955–2005. NASA SP-2006-4317, 2006.

Wallace, Lane E. Flights of Discovery: An Illustrated History of the 

Dryden Flight Research Center. NASA SP-2007-4318, 2007. 

Revised version of NASA SP-4309.

Arrighi, Robert S. Revolutionary Atmosphere: The Story of the 

Altitude Wind Tunnel and the Space Power Chambers. NASA 

SP-2010-4319, 2010.

GENERAL HISTORIES, NASA SP-4400:

Corliss, William R. NASA Sounding Rockets, 1958–1968: A Historical 

Summary. NASA SP-4401, 1971.

Wells, Helen T., Susan H. Whiteley, and Carrie Karegeannes. Origins 

of NASA Names. NASA SP-4402, 1976.

Anderson, Frank W., Jr. Orders of Magnitude: A History of NACA and 

NASA, 1915–1980. NASA SP-4403, 1981.

Sloop, John L. Liquid Hydrogen as a Propulsion Fuel, 1945–1959. 

NASA SP-4404, 1978.

Roland, Alex. A Spacefaring People: Perspectives on Early Spaceflight. 

NASA SP-4405, 1985.

Bilstein, Roger E. Orders of Magnitude: A History of the NACA and 

NASA, 1915–1990. NASA SP-4406, 1989.

Logsdon, John M., ed., with Linda J. Lear, Jannelle Warren Findley, 

Ray A. Williamson, and Dwayne A. Day. Exploring the Unknown: 

Selected Documents in the History of the U.S. Civil Space 

Program, Volume I: Organizing for Exploration. NASA SP-4407, 

1995.

506
The NASA History Series

Logsdon, John M., ed., with Dwayne A. Day and Roger D. Launius. 

Exploring the Unknown: Selected Documents in the History of 

the U.S. Civil Space Program, Volume II: External Relationships. 

NASA SP-4407, 1996.

Logsdon, John M., ed., with Roger D. Launius, David H. Onkst, and 

Stephen J. Garber. Exploring the Unknown: Selected Documents 

in the History of the U.S. Civil Space Program, Volume III: Using 

Space. NASA SP-4407, 1998.

Logsdon, John M., ed., with Ray A. Williamson, Roger D. Launius, 

Russell J. Acker, Stephen J. Garber, and Jonathan L. Friedman. 

Exploring the Unknown: Selected Documents in the History of 

the U.S. Civil Space Program, Volume IV: Accessing Space. NASA 

SP-4407, 1999.

Logsdon, John M., ed., with Amy Paige Snyder, Roger D. Launius, 

Stephen J. Garber, and Regan Anne Newport. Exploring the 

Unknown: Selected Documents in the History of the U.S. Civil 

Space Program, Volume V: Exploring the Cosmos. NASA SP-2001-

4407, 2001.

Logsdon, John M., ed., with Stephen J. Garber, Roger D. Launius, and 

Ray A. Williamson. Exploring the Unknown: Selected Documents 

in the History of the U.S. Civil Space Program, Volume VI: Space 

and Earth Science. NASA SP-2004-4407, 2004.

Logsdon, John M., ed., with Roger D. Launius. Exploring the 

Unknown: Selected Documents in the History of the U.S. Civil 

Space Program, Volume VII: Human Spaceflight: Projects 

Mercury, Gemini, and Apollo. NASA SP-2008-4407, 2008.

Siddiqi, Asif A., Challenge to Apollo: The Soviet Union and the Space 

Race, 1945–1974. NASA SP-2000-4408, 2000.

Hansen, James R., ed. The Wind and Beyond: Journey into the 

History of Aerodynamics in America, Volume 1: The Ascent of the 

Airplane. NASA SP-2003-4409, 2003.

507
When Biospheres Collide

Hansen, James R., ed. The Wind and Beyond: Journey into the History 

of Aerodynamics in America, Volume 2: Reinventing the Airplane. 

NASA SP-2007-4409, 2007.

Hogan, Thor. Mars Wars: The Rise and Fall of the Space Exploration 

Initiative. NASA SP-2007-4410, 2007.

MONOGRAPHS IN AEROSPACE HISTORY, NASA SP-4500:

Launius, Roger D., and Aaron K. Gillette, comps. Toward a History 

of the Space Shuttle: An Annotated Bibliography. Monographs in 

Aerospace History, No. 1, 1992.

Launius, Roger D., and J. D. Hunley, comps. An Annotated 

Bibliography of the Apollo Program. Monographs in Aerospace 

History, No. 2, 1994.

Launius, Roger D. Apollo: A Retrospective Analysis. Monographs in 

Aerospace History, No. 3, 1994.

Hansen, James R. Enchanted Rendezvous: John C. Houbolt and the 

Genesis of the Lunar-Orbit Rendezvous Concept. Monographs in 

Aerospace History, No. 4, 1995.

Gorn, Michael H. Hugh L. Dryden’s Career in Aviation and Space. 

Monographs in Aerospace History, No. 5, 1996.

Powers, Sheryll Goecke. Women in Flight Research at NASA Dryden 

Flight Research Center from 1946 to 1995. Monographs in 

Aerospace History, No. 6, 1997.

Portree, David S. F., and Robert C. Trevino. Walking to Olympus: An 

EVA Chronology. Monographs in Aerospace History, No. 7, 1997.

Logsdon, John M., moderator. Legislative Origins of the National 

Aeronautics and Space Act of 1958: Proceedings of an Oral 

History Workshop. Monographs in Aerospace History, No. 8, 1998.

508
The NASA History Series

Rumerman, Judy A., comp. U.S. Human Spaceflight: A Record of 

Achievement, 1961–1998. Monographs in Aerospace History, No. 9, 

1998.

Portree, David S. F. NASA’s Origins and the Dawn of the Space Age. 

Monographs in Aerospace History, No. 10, 1998.

Logsdon, John M. Together in Orbit: The Origins of International 

Cooperation in the Space Station. Monographs in Aerospace 

History, No. 11, 1998.

Phillips, W. Hewitt. Journey in Aeronautical Research: A Career at 

NASA Langley Research Center. Monographs in Aerospace History, 

No. 12, 1998.

Braslow, Albert L. A History of Suction-Type Laminar-Flow Control 

with Emphasis on Flight Research. Monographs in Aerospace 

History, No. 13, 1999.

Logsdon, John M., moderator. Managing the Moon Program: Lessons 

Learned from Apollo. Monographs in Aerospace History, No. 14, 

1999.

Perminov, V. G. The Difficult Road to Mars: A Brief History of Mars 

Exploration in the Soviet Union. Monographs in Aerospace 

History, No. 15, 1999.

Tucker, Tom. Touchdown: The Development of Propulsion Controlled 

Aircraft at NASA Dryden. Monographs in Aerospace History, No. 16, 

1999.

Maisel, Martin, Demo J. Giulanetti, and Daniel C. Dugan. The History 

of the XV-15 Tilt Rotor Research Aircraft: From Concept to 

Flight. Monographs in Aerospace History, No. 17, 2000. NASA 

SP-2000-4517.

Jenkins, Dennis R. Hypersonics Before the Shuttle: A Concise History 

of the X-15 Research Airplane. Monographs in Aerospace History, 

No. 18, 2000. NASA SP-2000-4518.

509
When Biospheres Collide

Chambers, Joseph R. Partners in Freedom: Contributions of 

the Langley Research Center to U.S. Military Aircraft of the 

1990s. Monographs in Aerospace History, No. 19, 2000. NASA 

SP-2000-4519.

Waltman, Gene L. Black Magic and Gremlins: Analog Flight 

Simulations at NASA’s Flight Research Center. Monographs in 

Aerospace History, No. 20, 2000. NASA SP-2000-4520.

Portree, David S. F. Humans to Mars: Fifty Years of Mission Planning, 

1950–2000. Monographs in Aerospace History, No. 21, 2001. NASA 

SP-2001-4521.

Thompson, Milton O., with J. D. Hunley. Flight Research: Problems 

Encountered and What They Should Teach Us. Monographs in 

Aerospace History, No. 22, 2001. NASA SP-2001-4522.

Tucker, Tom. The Eclipse Project. Monographs in Aerospace History, 

No. 23, 2001. NASA SP-2001-4523.

Siddiqi, Asif A. Deep Space Chronicle: A Chronology of Deep Space 

and Planetary Probes, 1958–2000. Monographs in Aerospace 

History, No. 24, 2002. NASA SP-2002-4524.

Merlin, Peter W. Mach 3+: NASA/USAF YF-12 Flight Research, 1969–

1979. Monographs in Aerospace History, No. 25, 2001. NASA 

SP-2001-4525.

Anderson, Seth B. Memoirs of an Aeronautical Engineer: Flight Tests 

at Ames Research Center: 1940–1970. Monographs in Aerospace 

History, No. 26, 2002. NASA SP-2002-4526.

Renstrom, Arthur G. Wilbur and Orville Wright: A Bibliography 

Commemorating the One-Hundredth Anniversary of the First 

Powered Flight on December 17, 1903. Monographs in Aerospace 

History, No. 27, 2002. NASA SP-2002-4527.

No monograph 28.

510
The NASA History Series

Chambers, Joseph R. Concept to Reality: Contributions of the NASA 

Langley Research Center to U.S. Civil Aircraft of the 1990s. 

Monographs in Aerospace History, No. 29, 2003. NASA SP-2003-4529.

Peebles, Curtis, ed. The Spoken Word: Recollections of Dryden History, 

The Early Years. Monographs in Aerospace History, No. 30, 2003. 

NASA SP-2003-4530.

Jenkins, Dennis R., Tony Landis, and Jay Miller. American X-Vehicles: 

An Inventory—X-1 to X-50. Monographs in Aerospace History, No. 

31, 2003. NASA SP-2003-4531.

Renstrom, Arthur G. Wilbur and Orville Wright: A Chronology 

Commemorating the One-Hundredth Anniversary of the First 

Powered Flight on December 17, 1903. Monographs in Aerospace 

History, No. 32, 2003. NASA SP-2003-4532.

Bowles, Mark D., and Robert S. Arrighi. NASA’s Nuclear Frontier: The 

Plum Brook Research Reactor. Monographs in Aerospace History, 

No. 33, 2004. NASA SP-2004-4533.

Wallace, Lane, and Christian Gelzer. Nose Up: High Angle-ofAttack and Thrust Vectoring Research at NASA Dryden, 1979–

2001. Monographs in Aerospace History, No. 34, 2009. NASA 

SP-2009-4534.

Matranga, Gene J., C. Wayne Ottinger, Calvin R. Jarvis, and D. Christian 

Gelzer. Unconventional, Contrary, and Ugly: The Lunar Landing 

Research Vehicle. Monographs in Aerospace History, No. 35, 2006. 

NASA SP-2004-4535.

McCurdy, Howard E. Low-Cost Innovation in Spaceflight: The 

History of the Near Earth Asteroid Rendezvous (NEAR) 

Mission. Monographs in Aerospace History, No. 36, 2005. NASA 

SP-2005-4536.

Seamans, Robert C., Jr. Project Apollo: The Tough Decisions. 

Monographs in Aerospace History, No. 37, 2005. NASA 

SP-2005-4537.

511
When Biospheres Collide

Lambright, W. Henry. NASA and the Environment: The Case of Ozone 

Depletion. Monographs in Aerospace History, No. 38, 2005. NASA 

SP-2005-4538.

Chambers, Joseph R. Innovation in Flight: Research of the NASA 

Langley Research Center on Revolutionary Advanced Concepts 

for Aeronautics. Monographs in Aerospace History, No. 39, 2005. 

NASA SP-2005-4539.

Phillips, W. Hewitt. Journey into Space Research: Continuation 

of a Career at NASA Langley Research Center. Monographs in 

Aerospace History, No. 40, 2005. NASA SP-2005-4540.

Rumerman, Judy A., Chris Gamble, and Gabriel Okolski, comps. 

U.S. Human Spaceflight: A Record of Achievement, 1961–

2006. Monographs in Aerospace History, No. 41, 2007. NASA 

SP-2007-4541.

Dick, Steven J., Stephen J. Garber, and Jane H. Odom. Research in 

NASA History. Monographs in Aerospace History, No. 43, 2009. 

NASA SP-2009-4543.

Merlin, Peter W. Ikhana: Unmanned Aircraft System Western States 

Fire Missions. Monographs in Aerospace History, No. 44, 2009. 

NASA SP-2009-4544.

Fisher, Steven C., and Shamim A. Rahman. Remembering the Giants: 

Apollo Rocket Propulsion Development. Monographs in Aerospace 

History, No. 45, 2009. NASA SP-2009-4545.

ELECTRONIC MEDIA, NASA SP-4600:

Remembering Apollo 11: The 30th Anniversary Data Archive

CD-ROM. NASA SP-4601, 1999.

512
The NASA History Series

Remembering Apollo 11: The 35th Anniversary Data Archive 

CD-ROM. NASA SP-2004-4601, 2004. This is an update of the 1999 

edition.

The Mission Transcript Collection: U.S. Human Spaceflight Missions 

from Mercury Redstone 3 to Apollo 17. NASA SP-2000-4602, 2001.

Shuttle-Mir: The United States and Russia Share History’s Highest 

Stage. NASA SP-2001-4603, 2002.

U.S. Centennial of Flight Commission Presents Born of Dreams—

Inspired by Freedom. NASA SP-2004-4604, 2004.

Of Ashes and Atoms: A Documentary on the NASA Plum Brook 

Reactor Facility. NASA SP-2005-4605, 2005.

Taming Liquid Hydrogen: The Centaur Upper Stage Rocket 

Interactive CD-ROM. NASA SP-2004-4606, 2004.

Fueling Space Exploration: The History of NASA’s Rocket Engine Test 

Facility DVD. NASA SP-2005-4607, 2005.

Altitude Wind Tunnel at NASA Glenn Research Center: An Interactive 

History CD-ROM. NASA SP-2008-4608, 2008.

A Tunnel Through Time: The History of NASA’s Altitude Wind Tunnel. 

NASA SP-2010-4609, 2010.

CONFERENCE PROCEEDINGS, NASA SP-4700:

Dick, Steven J., and Keith Cowing, eds. Risk and Exploration: Earth, 

Sea and the Stars. NASA SP-2005-4701, 2005.

Dick, Steven J., and Roger D. Launius. Critical Issues in the History of 

Spaceflight. NASA SP-2006-4702, 2006.

513
When Biospheres Collide

Dick, Steven J., ed. Remembering the Space Age: Proceedings of the 

50th Anniversary Conference. NASA SP-2008-4703, 2008.

Dick, Steven J., ed. NASA’s First 50 Years: Historical Perspectives. 

NASA SP-2010-4704, 2010.

SOCIETAL IMPACT, NASA SP-4800:

Dick, Steven J., and Roger D. Launius. Societal Impact of Spaceflight. 

NASA SP-2007-4801, 2007.

Dick, Steven J., and Mark L. Lupisella. Cosmos and Culture: Cultural 

Evolution in a Cosmic Context. NASA SP-2009-4802, 2009.

514
INDEX

absolute sterilization, 77–78, 82, 254

aerogel, 344, 346–347, 348

aeroshell, 248, 260, 264, 294, 393, 401, 492

Aldrin, Buzz, 206, 211–212, 228, 240

Agreement Governing the Activities 

of States on the Moon and Other 

Celestial Bodies (the “Moon Treaty” 

or “Moon Agreement”)—see “United 

Nations Agreement Governing the 

Activities of States on the Moon and 

Other Celestial Bodies of 1984”

Almar, I., 438

American Tower Corporation, 474

Ames Research Center (ARC), 12, 76, 144, 

156, 158, 353–354, 370, 426

Andromeda Strain, The, 74–75, 215

Apollo 11 planetary protection, 211–237, 

452, 484–486

Apollo 12 planetary protection, 237–242

Apollo 13 planetary protection, 243–244

Apollo 14 planetary protection, 243–245

Apollo mission, xix, 113–246, 356, 442, 458

Apollo Personnel Quarantine Facilities 

Review, 141–145

Armstrong, Neil, 206, 211–212, 215, 228, 

240

Army Biological Warfare Laboratories 

(Army BioLabs or Fort Detrick), 38, 40, 

42–44, 67–68, 120, 123, 127, 143–144, 

156–157, 186, 476

asteroid, 4, 6, 13, 301–302, 311, 315–316, 

333–339, 343, 349, 366–367, 437, 440, 

461–462, 479–480, 489

Atwood, K. C., 253

Bacillus subtilis variety niger (also known 

as Bacillus globigii, or BG), 93, 96, 

103, 309

back contamination, 113–246, 302, 315, 

327, 331, 335, 337, 355, 357, 364, 367, 

369, 371, 418, 427, 445, 446, 451, 

457–459, 475, 479, 485, 489

Bagby, John, 139, 140, 145–146, 167

Barengoltz, Jack, xix, 322, 374

Baylor University College of Medicine 

operating procedures, 175–179, 185, 

476

Bean, Alan, 240–241

Berry, Charles, 139–140, 176, 180–183, 

244–245

bioassay, 66–67, 92–93, 260, 274, 276–277, 

289–291, 364, 374, 386, 393–396, 

401–402, 462, 486–491

bioburden, 259–260, 274–276, 289–291, 

364, 373–374, 384–386, 394, 397, 487, 

489, 492

Biological Contamination of Mars: Issues 

and Recommendations, 372–376, 483

biological isolation garment (BIG), 133, 

204–205, 212–215, 240–241, 484

Bionetics Corporation (The), 248, 258, 276, 

476

biopool sample, 232–233, 238

bioprime sample, 226, 232, 238

bioshield, 248, 264–267

Blagonravov, Anatoli A., 29–30

Boeing, 260

Boorstin, Daniel, 2, 5

Boynton, William, 430–431

Bradbury, Ray, 71

Broome, G. Calvin, 281

Brower, David, 75–76

Brown, Allan, 35, 50, 139, 160

Brown, Robert, 330

Bureau of the Budget, 136

bus, 81, 86, 106–111

bus-deflection maneuver, 108–110

Buseck, Peter, 341, 349

Bush, President George W., 359

515
When Biospheres Collide

California Institute of Technology (Caltech), 

33, 328, 471

Calio, Anthony, 238

Callicott, J. Baird, 433–434

Callisto, 318–319, 323–325, 328–330, 366, 

461–462, 483

Calvin, Melvin, 12, 17, 18, 33, 53, 61, 458

Carpentier, William, 228

Casani, John, 60, 394–395

Cassini mission, 330–333, 356–357, 483, 489

Category I through V missions, 332, 348, 

352–353, 356–358, 363–369, 374–376, 

386, 395, 402–403, 461–470, 490–491

Centaur, 255, 276–277, 293, 315, 477, 488

Centers for Disease Control and Prevention—

see “Communicable Disease Center”

Chandrayaan-1, 315

Channing, William, 437

Chao, Edward Ching Te, 123–124, 476

Chao Committee, 123–126, 137, 146, 152–

153, 160, 163, 476

Christensen, P. R., 412

Clark, Ben, xix, 298

cleanroom, 39, 66, 118, 271, 275, 286, 321, 

326–327, 332, 339, 348, 364, 371, 373, 

386, 399, 402, 462, 467, 484, 487, 489, 

491

Clementine, 313–314

Code of Federal Regulations (CFR) Title 14, 

Part 1211—Extraterrestrial Exposure, 

452–453

Collins, Michael, 212, 215, 228

comet Wild 2, 344, 357, 453

comets, 6, 13, 301–302, 311, 313, 315, 333–

334, 343–349, 356–357, 365–367, 437, 

453, 461–462, 479–480, 489

Command Module (CM), 133–134, 171, 187, 

195–206, 210, 212–214, 217, 229, 231, 

239, 241, 244, 478, 484

Committee on Contamination by 

Extraterrestrial Exploration (CETEX), 

12, 19–25, 28, 33–34, 476–477

Committee on Planetary and Lunar 

Exploration (COMPLEX), 323–324, 477

Committee on Space Research (COSPAR), 

12, 13, 23–27, 29–31, 35, 81–84, 111–

112, 254–255, 315, 332, 337, 355, 365, 

372, 384–385, 402, 413–415, 476–477, 

483

Communicable Disease Center (CDC), 

later renamed the Centers for Disease 

Control and Prevention, 128–131, 136, 

139–140, 145, 156–157, 161, 167, 181, 

183, 253, 454, 475, 477

Conley, Cassie, xv–xvii, xix

Conrad, Charles “Pete,” 240–241

Craven, Charles, 85, 92–94

Crew Reception Area (CRA), 157, 184, 185, 

187, 189–190, 198, 221, 228–230

Crichton, Michael, 74, 215

D-value, 96–97

Daddario, Congressman Emilio, 153, 163

Declaration of Legal Principles Governing 

the Activities of States in the 

Exploration and Use of Outer Space—

see “United Nations Declaration 

of Legal Principles Governing the 

Activities of States in the Exploration 

and Use of Outer Space”

Deimos, 316–317

Deinococcus radiodurans, 307

Department of Agriculture (USDA), 120, 

129–132, 139, 145, 193, 337, 451, 454–

455, 477, 489

Department of Defense (DOD), 59, 60–61, 

163, 167, 476–477

Department of the Interior (DOI), 129–130, 

139, 203–204, 238, 454 (Secretary of 

the Interior), 455

descent capsule, 248, 260, 294

DeVincenzi, Donald, 354, 374–375, 384, 458

dry heat microbial reduction (DHMR), 396, 

400–401, 491–492

Dryden, Hugh, 46, 136

Earth return, 336, 348, 353, 357, 364–365, 

367, 462, 465–470, 489

East Coast Committee on Extraterrestrial 

Life (EASTEX), 33

Eggleston, John, 117–118, 125

Eisenhower, President Dwight D., 2, 24, 52

Ellington Air Force Base, 210, 219, 228, 244, 

486

Enceladus, 318, 330–331, 483, 489

Environmental Protection Agency (EPA), 

450–451

ethylene oxide, 40, 42–44, 49, 56, 65–68, 97, 

99, 100, 102, 185, 222, 230, 258, 265, 

400, 424, 485

516
Index

Europa, xvi, 318–325, 329, 358, 483, 488

European Space Agency (ESA), 430

Exotech Systems, 84

exploitation of other planets, 441–442

extraterrestrial exposure regulations, 453

extremophiles, 7, 13, 304, 326, 360, 406, 421, 

423, 467, 475

Faget, Max, 116–117, 122

Falmouth Conference, 179–180

faster, better, cheaper (FBC), 352, 471–473

Favero, Martin, xix, 253

Fischer, Craig, xix, 226–229

Fish, Bob, xix, 199, 206

Fish and Wildlife Service, 130, 203, 454

flight acceptance test (FAT), 274–275, 289, 

487

Florkin, Marcel, 20

Flory, Donald, 116, 121–122, 125

Fort Detrick—see “Army Biological Warfare 

Laboratories”

forward contamination, 36, 62, 211, 254, 

258–260, 264, 283, 288, 290, 292, 298, 

302, 312, 325, 327, 356, 371, 377, 392, 

402–403, 426, 430, 442, 448, 459, 468, 

473, 479

Foster, Willis, 122–123, 125

Frazier, Marvin, 307

Fulton, Congressman James, 151–153, 

162–166

Gabla, Lubomir, 349

Galileo mission, xv, 60, 317–325, 356, 443, 

483, 488

Ganymede, 318–319, 323–325, 328–330, 483

gas chromatograph mass spectrometer 

(GCMS), 266–270

gas sterilization, 49–50, 67, 258, 424

Gehrig, James, 167

Genesis mission, 347, 351–354, 357, 365, 367, 

483, 489

Gilruth, Robert “Bob,” 122–123, 172, 186, 

200, 237

Glenn, John, 148–149

Glenn Research Center at Lewis Field (GRC, 

formerly Lewis Research Center), 276, 

477

Glennan, T. Keith, 24, 28, 40, 46, 52–54

glove boxes, 186, 188, 222, 224–227, 238, 

241, 265, 485

Goddard, James, 130–132, 136, 139–140

Goddard Space Flight Center (GSFC), 28, 

38–40, 125, 132, 477

Goldin, Daniel S., 41

Goodpaster, Kenneth, 434

Gordon, Richard, 241

Greeley, Ron, 329

Haldane, J. B. S., 5, 18, 32, 458

Hall, Lawrence B., 3, 56, 65–66, 129–130, 

133–134, 458

Hayabusa (formerly named MUSES-C) 

mission, 335–337, 483, 489

heat sterilization (thermal sterilization), 47, 

50, 67, 88, 95–102, 105, 109, 230, 258–

283, 286–287, 291–292, 298–299, 397, 

424, 486–487

Hess, Harry H., 126–127, 476

Hess, Wilmot, 175, 187

Hess Committee, 126–128, 160, 476

Hickam Air Force Base, 210, 219, 228

Hirasaki, John, 228, 240

Hobby, George L., 47–48, 54, 58

Horowitz, Norman, 33, 36–37

House Subcommittee on Manned Space 

Flight, 145, 150–157

Hughes Aircraft, 268

human Mars missions, 370–372, 426–430

Ierusalimskii, N. D., 64

Imshenetsky, A. A., 65, 67, 79

Interagency Committee on Back 

Contamination (ICBC), 138–141, 

175–177, 181, 183–185, 190–194, 198, 

201–206, 229–230, 237, 239, 240, 243, 

313, 451, 454, 455, 477

International Council of Scientific Unions 

(ICSU), 19, 23–25, 27, 476–477

interplanetary dust particles (IDPs), 349–354

interstellar dust, 301, 344–345, 357, 489

Itokawa asteroid, 335–337, 489

Jackson, Andrew, 436–437

Jaffe, L. D., 78–81

Japan Aerospace Exploration Agency (JAXA), 

335–337

Jet Propulsion Laboratory (JPL), 28, 34, 38, 

40, 46–47, 49–50, 54, 58–59, 78, 88, 

98–99, 101–102, 248, 260, 268, 276, 

394–396, 399, 426, 443, 471, 477–478

Johnson, President Lyndon B., 9, 16, 147, 149, 

165, 446

Johnson, Torrence, 323, 443

517
When Biospheres Collide

Johnson Space Center (JSC), xix, 116, 348, 478

Johnston, Richard, 200, 204, 239

Johnston Island, 219

Joint House-Senate Committees, 168–169

Jupiter, xvi, 317–324, 328–331, 334, 356, 

362, 366, 458, 461, 488

Keldysh, M. V., 111

Kemmerer, Walter, 139, 176, 178, 181–182

Kennedy, President John F., 2, 10, 50, 78, 

113–114, 119, 147–148, 165, 203, 445, 

477

Kennedy Space Center (KSC), 211, 240, 252, 

271, 274–275, 277–280, 289, 393, 396, 

477, 487

Kety, Seymour, 52–53

Kety Committee, 52–53, 476

Khrushchev, Nikita, 10, 445

Khurana, Krishan, 320–321

King, Elbert, 116, 121–122, 125, 130–131, 

225

Kivelson, Margaret, 320–321, 329

Koons, Wayne, 198

Langley Research Center (LaRC), xix, 85, 

186, 248, 268, 276, 477

Larson, Don, xix, 365, 370

Lawrence Livermore National Laboratory, 

475

Lederberg, Joshua, xvi, 12, 15, 17, 18–19, 

23–24, 28, 31–38, 40, 42, 53, 61–65, 68, 

72–73, 80, 252, 458, 480

legal aspects of planetary protection, 443–

455

Leopold, Aldo, 435

Levinthal, Elliott, 13

Lewis Research Center (LeRC), 41, 276, 477

Lilly, William, 152–155, 163

lithium hydroxide (LiOH) filters, 196, 484

Locke, Louis, 203–204

Lockheed, 72, 115–116

Lockheed Martin, xix, 298, 365, 370, 393–

394, 398–402, 471–472, 478, 489, 492

Logsdon, John, 352

Los Alamos National Laboratory, 156, 159, 

475

Lovell, Sir Bernard, 110–111, 163, 433

Low, George, 152–155, 245

Lowell, Percival, xv, 69

lunar contamination, 48, 50, 81, 114, 193

Lunar CRater Observation and Sensing 

Satellite (LCROSS), 314–315

Lunar Module (LM), 195–196, 211–213, 240, 

244, 484

Lunar Orbiter, 98

Lunar Prospector, 314

Lunar Receiving Laboratory (LRL), xix, 13, 

153–155, 167, 169–198, 206, 208, 218–

242, 313, 423, 455, 478, 484–486

Lunar Sample Receiving Laboratory (LSRL), 

116, 121, 123–128, 130–132, 134–138, 

140, 141, 144–153, 476, 478

manifest destiny, 436–437

Manned Spacecraft Center (MSC), 116–118, 

121–125, 127–128, 130–131, 133–137, 

139, 140–141, 144–146, 150, 152–153, 

155–157, 159–162, 166, 169, 171–174, 

176, 178, 180, 182–183, 186–187, 192, 

194, 197–198, 200, 202–205, 213, 219–

221, 226, 229, 237–239, 244, 478–479

Mars Climate Orbiter (MCO), 352, 390–392, 

471, 483, 491

Mars Exploration Program Analysis Group 

(MEPAG), 404–414, 428–429, 478

Mars Exploration Rovers (MER), 395–397, 

483, 491

Mars Global Surveyor (MGS), 380–383, 402, 

408–409, 427, 472, 490

Mars Human Precursor Science Steering 

Group (MHP SSG), 428–430, 478

Mars Observer, 376–380, 490

Mars Odyssey, 402, 412

Mars Pathfinder, 386–388, 392–395, 399, 

401, 427, 472, 491

Mars Phoenix lander—see “Phoenix Mars 

Lander”

Mars polar caps, 295, 297, 403, 413, 464

Mars Polar Lander (MPL), 352, 390, 392–395, 

398, 471, 473, 483, 491

Mars Program Independent Assessment 

Team (MPIAT), 471–472

Mars sample handling protocol workshops, 

422

Mars sample return missions, 14, 353, 415–

426, 455, 458

Mars Science Laboratory (MSL) mission, 

417–418

Mars special regions, 14, 367, 369, 376, 381–

383, 402–415, 442, 463–464, 478

Mars subpolar regions, 295–298, 362

518
Index

Mars Surveyor Program, 379–381, 386, 490

Marshall Space Flight Center (MSFC), 100–

101, 103–104, 478

Martian Chronicles, 71–72

Martin, Jim, 299

Martin Marietta, 248, 251, 268, 271, 274–276, 

285–286, 289, 478

maximum biotesting fraction, 179–183

Maynard, Owen, 135

McCartney, Martha, 341

McKay, Christopher, 8, 12, 76, 339

MelPar Company, 137–138, 208–209, 478

meteorite ALH84001, 339–341

meteoroid and meteorite, xvi, 3–4, 6, 13, 76, 

87, 92, 131, 165, 234, 256, 290, 301, 303, 

310–312, 317, 319, 333, 339–343, 349, 

409, 415, 419, 421–422, 469, 483

Michener, James, 3, 5

Milliken, R. E., 412

Mitchell, Edgar, 244

Mobile Quarantine Facility (MQF)/mobile 

quarantine chamber/mobile quarantine 

unit, 134, 138, 206–219, 228, 241, 244, 

478, 485

Moon Treaty and Moon Agreement—see 

“United Nations Agreement Governing 

the Activities of States on the Moon and 

Other Celestial Bodies of 1984”

Mueller, George, 107, 134, 141, 145, 155–156, 

162–167, 173, 180, 187, 191

Muir, John, 75

Murray, Bruce, 110

NASA Handbook (NHB) 8020.12—see 

“Planetary Quarantine Provisions for 

Unmanned Planetary Missions”

NASA Policy Directive (NPD) 8020.7—see 

“Outbound Spacecraft: Basic Policy 

Relating to Lunar and Planetary 

Contamination Control”

NASA Policy Directive (NPD) 8020.10 and 

8020.10A—see “Outbound Planetary 

Biological and Organic Contamination 

Control Policy and Responsibility”

NASA Procedural Requirement (NPR) 

8020.12C—see “Planetary Protection 

Provisions for Robotic Extraterrestrial 

Missions”

NASA Unmanned Spacecraft 

Decontamination Policy (NMI-4-4-1), 

51, 81

National Academy of Sciences (NAS), 19, 

23–24, 32, 112–113, 120, 127, 139, 188, 

341, 455, 476–480

National Aeronautics and Space Act of 1958, 

24, 450

National Environmental Policy Act (NEPA), 

453

National Research Council (NRC), 60, 302, 

325, 372, 403, 418, 448, 461–462, 468, 

479

National Science Foundation (NSF), 23–24, 

479

National Space Technology Laboratories, 28

Newell, Homer, 26, 41, 58, 126–127, 180

Newlin, Laura, 395

Nixon, President Richard M., 57, 216–219

North American Rockwell Corporation, 231

Nozomi mission, 388–390, 491

NRC PREVCOM (National Research Council 

Committee on Preventing the Forward 

Contamination of Mars), 403–404, 479

Oak Ridge National Laboratory (ORNL), 123, 

156, 158, 171, 474

Odishaw, Hugh, 40, 62–64

Office of Life Science Programs, 46, 53–55

Office of Management and Budget (OMB), 

147, 417–418

Office of Space Science and Applications 

(OSSA), 117–118, 122–129, 156

orbital insertion, 377, 389

O’Sullivan, John, 436

Outbound Planetary Biological and Organic 

Contamination Control Policy and 

Responsibility (NPD 8020.10 and NPD 

8020.10A), 83

Outbound Spacecraft: Basic Policy Relating 

to Lunar and Planetary Contamination 

Control (NPD 8020.7), 82

Outer Space Treaty of 1967—see “United 

Nations Treaty on Principles Governing 

the Activities of States in the 

Exploration and Use of Outer Space of 

1967”–

Pago Pago, American Samoa, 241, 244

Paine, Thomas O., 182–183, 188, 191, 202–

203

panspermia, 21, 34

payload capsule deflection, 108–109, 484

519
When Biospheres Collide

Pearl Harbor, 210, 228

Phillips, Charles, 44–47, 458

Phillips, G. Briggs, 139, 176, 181, 192–194, 

454

Phillips, Sam, 187

Phobos, 316–317

Phoenix Mars Lander, 398–402, 430–431, 

483, 492

Pickering, Col. John E., 139, 156, 165, 172, 

182, 190, 479

Pickering Committee, 156–164, 479

Piland, Joseph, 174–175

Pingree Park workshop, 426–428

Planetary Protection Officer, xvi–xvii, 5, 7, 

323, 325, 332, 356, 372, 374, 389, 404, 

455, 458

Planetary Protection Provisions for Robotic 

Extraterrestrial Missions (NPR 

8020.12C), 327–328, 355–358, 365, 403, 

461

Planetary Quarantine (PQ) Officer, 56–57, 

58, 65, 83–84, 91, 133

Planetary Quarantine Program, 26, 55–59, 

260–261

Planetary Quarantine Provisions for 

Unmanned Planetary Missions (NHB 

8020.12), 96, 259

planetary stewardship, 14, 438–441, 444, 447

plutonium, 414, 385

Polutchko, Bob, 94–95, 284–286

polymerase chain reaction (PCR), 326, 475

Potential Hazards of Back Contamination 

conference, 120, 150–151, 160

preservation ethic, 33, 438–439, 447–448, 

480

Preventing the Forward Contamination of 

Mars, 403, 448, 479

Public Health Service (PHS), 120, 124, 127–

145, 156–157, 167, 176, 178, 192–194, 

451, 454, 477, 479

quarantine of astronauts, 120, 130–258

quarantine orbit, 377, 379, 383, 490

Quimby, Freeman, 77

quinones, 349

Race, Margaret, xix, 8, 9, 448

Randt, Clark, 46, 52, 53–55

Ranger, 46–51, 265

Raulin, Francois, 332

Recommendations on Quarantine Policy 

for Mars, Jupiter, Saturn, Uranus, 

Neptune, and Titan, 362

Red Mars, 75–76

res communis (also res communes), 443–

444

res nullius, 443

Restricted Earth Return missions, 357, 365, 

367, 462, 465, 467–470

Robinson, Kim Stanley, 75–76

Rosetta mission, 356–357

Roudebush, Richard L., 165–166

Rummel, John, xiii–xiv, xix, 5, 323, 354, 372, 

374, 389–390, 455

Rumsfeld, Congressman Donald, 151–153, 

165

Russia’s Mars-94/96 mission, 372, 383–386

Rycroft, Michael, 440

Sagan, Carl, 12, 33, 35, 65, 79–80, 114–115, 

251, 458

Saturn, 6, 308, 317–318, 330, 332, 333, 356–

357, 362, 366, 458, 461, 483

Schiaparelli, Giovanni, xv, 69

Schweitzer, Albert, 434

Seitz, Frederick, 188, 202

Senate Committee on Aeronautical and 

Space Sciences, 107, 167–168

Sencer, David, 139, 140, 176, 183, 188–192, 

203

Shepard, Alan, 244

Silverstein, Abe, 12–13, 28, 40–42, 46, 52, 

54, 77, 254, 458

Slayton, Deke, 198

Smith, Senator Margaret Chase, 115

Soviet planetary protection, 63, 65, 107, 109, 

384–385

Space Science Board (SSB), 12, 23–24, 28, 

35, 38, 91, 113–115, 120, 126, 160, 243, 

257, 291, 297–298, 313, 362, 476–477, 

479–480

Space Studies Board (SSB), 302, 317, 325, 

332, 338, 344, 348, 350, 365, 372–374, 

376, 418, 448, 468, 479–480, 489

Spacecraft Assembly and Encapsulation 

Building (SAEB), 278

Sputnik, 1, 15–16, 24, 29, 445, 476

Stabekis, Pericles “Perry,” xix, 7, 11, 374, 458

Stardust mission, 344–348, 350, 357, 453

sterilization, 13–14, 25, 28, 32, 36, 38–51, 

66–67, 77–112, 358, 361–362, 364–366, 

520
Index

368–370, 373–375, 386, 389, 393, 397, 

420, 423–425, 431, 455, 458, 463–470, 

477, 485–488, 491

Stern, Alan, 417–418

Stevenson, Dave, 328

Stewart, U.S. Surgeon General William, 

135–137, 140

Stonesifer, John, xix, 199, 206

Subcommittee on Manned Space Flight of 

the House Committee on Science and 

Astronautics, 149

Surveyor, 98, 250

Taback, Israel, 258

Target Body/Mission Types, 361, 366, 461

Task Group on the Forward Contamination of 

Europa, 325–328, 483

Task Group on Issues in Sample Return 

(TGISR), 418–422, 480

Task Group on Sample Return from Small 

Solar System Bodies, 302–303, 344, 480

Teague, Congressman Olin “Tiger,” 150

terminal sterilization, 13, 67, 103–106, 269, 

276–280, 288, 290, 298, 322, 386, 393, 

458, 463–464, 477, 486–488, 491

thermal sterilization—see “heat sterilization”

Timakov, T. V., 63

Titan launch vehicle, 276–277, 293, 322, 477

Titan (moon of Saturn), 6, 308, 318, 331–333, 

357, 362, 366, 461, 489

trajectory biasing, 86–87, 108, 331, 364, 386, 

462, 491

trajectory course maneuver (TCM), 380, 382, 

387–389, 397, 490–492

TRW, 102, 285–287

Tuleta, M., 349

United Nations Agreement Governing the 

Activities of States on the Moon and 

Other Celestial Bodies of 1984 (the 

“Moon Treaty” or “Moon Agreement”), 9, 

10, 444, 448–450

United Nations Committee on the Peaceful 

Uses of Outer Space (UNCOPUOS), 12, 

27, 29, 444–446, 448–449, 480

United Nations Declaration of Legal 

Principles Governing the Activities of 

States in the Exploration and Use of 

Outer Space, 445–446

United Nations Educational, Scientific and 

Cultural Organization (UNESCO), 11, 

441

United Nations Treaty on Principles 

Governing the Activities of States 

in the Exploration and Use of Outer 

Space of 1967, 9, 444, 446–450

unrestricted Earth return, 336, 348, 353, 

357, 367, 489

Urey, Harold, 24, 33

USDA—see “Department of Agriculture 

(USDA)”

USS Hornet, xix, 199, 206, 210, 213–219, 

228–229, 239, 241

USS New Orleans, 244

USSR, 10–11, 13, 15–16, 25–26, 29–31, 32, 

59–68, 107–112, 147–149, 317, 445–446

Venera 4, 107

Venus, 19, 22, 33, 67, 72–73, 79–81, 107, 

110–112, 366, 380, 384, 461

Viking descent capsule, 248, 260, 294

Viking lander, 247–250, 256, 259–260, 270, 

277, 282, 284, 292, 295, 321, 339, 362, 

366, 368–369, 374–375, 386, 393, 463, 

488, 491

Viking Lander Capsule (VLC), 247–249, 

255–256, 259–260, 264–265, 270–282, 

286–290, 292–293, 298, 361, 486–488

Viking mission, 247–299, 321, 359–362, 373–

375, 383, 386, 394, 396, 419–420, 431, 

457–458, 476

Viking Orbiter (VO), 248, 255, 260, 276, 279, 

289–291, 293–294, 486–488

Vishniac, Wolf, 139, 187–188, 202

Voyager mission, 321–322

War of the Worlds, 69–73

Warrior Constructors, 173–174

Webb, James, 136, 138, 149

Welles, Orson, 70

Wells, H. G., xv, 69–72

West Coast Committee on Extraterrestrial 

Life (WESTEX), 12, 31–38, 64, 68, 72, 

480

White Sands Test Facility, 284

White, Lynn, 441–442

Wickramasinghe, Chandra, 349–350

Wiesner, Jerome B., 2, 5

Wild 2—see “comet Wild 2”

WNN Contractors, 173–175

Wolfson, Robert, 92–94, 85

Worden, Pete, 353–354

521
When Biospheres Collide

Young, Tom, 247, 471

Zond 2 mission, 110–111

Zubrin, Robert, 12, 76

522