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PLANETARY FLAGSHIP MISSIONS: 

MARS ROVER 2020 AND EUROPA CLIPPER 

HEARING 

BEFORE THE

SUBCOMMITTEE ON SPACE 

COMMITTEE ON SCIENCE, SPACE, AND 

TECHNOLOGY 

HOUSE OF REPRESENTATIVES 

ONE HUNDRED FIFTEENTH CONGRESS 

FIRST SESSION 

JULY 18, 2017 

Serial No. 115–22 

Printed for the use of the Committee on Science, Space, and Technology 

( 

Available via the World Wide Web: http://science.house.gov 
(II) 

COMMITTEE ON SCIENCE, SPACE, AND TECHNOLOGY 

HON. LAMAR S. SMITH, Texas, Chair 

FRANK D. LUCAS, Oklahoma 

DANA ROHRABACHER, California 

MO BROOKS, Alabama 

RANDY HULTGREN, Illinois 

BILL POSEY, Florida 

THOMAS MASSIE, Kentucky 

JIM BRIDENSTINE, Oklahoma 

RANDY K. WEBER, Texas 

STEPHEN KNIGHT, California 

BRIAN BABIN, Texas 

BARBARA COMSTOCK, Virginia 

BARRY LOUDERMILK, Georgia 

RALPH LEE ABRAHAM, Louisiana 

DRAIN LAHOOD, Illinois 

DANIEL WEBSTER, Florida 

JIM BANKS, Indiana 

ANDY BIGGS, Arizona 

ROGER W. MARSHALL, Kansas 

NEAL P. DUNN, Florida 

CLAY HIGGINS, Louisiana 

RALPH NORMAN, South Carolina 

EDDIE BERNICE JOHNSON, Texas 

ZOE LOFGREN, California 

DANIEL LIPINSKI, Illinois 

SUZANNE BONAMICI, Oregon 

AMI BERA, California 

ELIZABETH H. ESTY, Connecticut 

MARC A. VEASEY, Texas 

DONALD S. BEYER, JR., Virginia 

JACKY ROSEN, Nevada 

JERRY MCNERNEY, California 

ED PERLMUTTER, Colorado 

PAUL TONKO, New York 

BILL FOSTER, Illinois 

MARK TAKANO, California 

COLLEEN HANABUSA, Hawaii 

CHARLIE CRIST, Florida 

SUBCOMMITTEE ON SPACE

HON. BRIAN BABIN, Texas, Chair 

DANA ROHRABACHER, California 

FRANK D. LUCAS, Oklahoma 

MO BROOKS, Alabama 

BILL POSEY, Florida 

JIM BRIDENSTINE, Oklahoma 

STEPHEN KNIGHT, California 

BARBARA COMSTOCK, Virginia 

RALPH LEE ABRAHAM, Louisiana 

DANIEL WEBSTER, Florida 

JIM BANKS, Indiana 

ANDY BIGGS, Arizona 

NEAL P. DUNN, Florida 

CLAY HIGGINS, Louisiana 

LAMAR S. SMITH, Texas 

AMI BERA, California, Ranking Member 

ZOE LOFGREN, California 

DONALD S. BEYER, JR., Virginia 

MARC A. VEASEY, Texas 

DANIEL LIPINSKI, Illinois 

ED PERLMUTTER, Colorado 

CHARLIE CRIST, Florida 

BILL FOSTER, Illinois 

EDDIE BERNICE JOHNSON, Texas 
(III) 

C O N T E N T S 

July 18, 2017 

Page 

Witness List ............................................................................................................. 2 

Hearing Charter ...................................................................................................... 3 

Opening Statements 

Statement by Representative Brian Babin, Chairman, Subcommittee on 

Space, Committee on Science, Space, and Technology, U.S. House of Representatives ........................................................................................................... 4 

Written Statement ............................................................................................ 6 

Statement by Representative Ami Bera, Ranking Member, Subcommittee on 

Space, Committee on Science, Space, and Technology, U.S. House of Representatives ........................................................................................................... 8 

Written Statement ............................................................................................ 9 

Statement by Representative Eddie Bernice Johnson, Ranking Member, Committee on Science, Space, and Technology, U.S. House of Representatives .... 11 

Written Statement ............................................................................................ 13 

Statement by Representative Lamar S. Smith, Chairman, Committee on 

Science, Space, and Technology, U.S. House of Representatives ..................... 14 

Written Statement ............................................................................................ 15 

Witnesses: 

Dr. Jim Green, Planetary Science Division Director, Science Mission Directorate, NASA 

Oral Statement ................................................................................................. 17 

Written Statement ............................................................................................ 20 

Dr. Kenneth Farley, Mars Rover 2020 Project Scientist; Professor of Geochemistry, California Institute of Technology 

Oral Statement ................................................................................................. 25 

Written Statement ............................................................................................ 27 

Dr. Robert Pappalardo, Europa Clipper Project Scientist, Jet Propulsion Laboratory, California Institute of Technology 

Oral Statement ................................................................................................. 30 

Written Statement ............................................................................................ 32 

Dr. Linda T. Elkins-Tanton, Director and Foundation Professor, School of 

Earth and Space Exploration, Arizona State University; Principal Investigator, NASA Psyche Mission 

Oral Statement ................................................................................................. 36 

Written Statement ............................................................................................ 38 

Dr. William B. McKinnon, Co-Chair, National Academy of Sciences, Committee on Astrobiology and Planetary Science; Professor of Earth and Planetary Sciences, Washington University in St. Louis 

Oral Statement ................................................................................................. 43 

Written Statement ............................................................................................ 45 

Discussion ................................................................................................................. 58 

Appendix I: Answers to Post-Hearing Questions 

Dr. Jim Green, Planetary Science Division Director, Science Mission Directorate, NASA ........................................................................................................ 74 
Page

IV 

Dr. Kenneth Farley, Mars Rover 2020 Project Scientist; Professor of Geochemistry, California Institute of Technology ................................................... 78 

Dr. Robert Pappalardo, Europa Clipper Project Scientist, Jet Propulsion Laboratory, California Institute of Technology ........................................................ 79 

Dr. Linda T. Elkins-Tanton, Director and Foundation Professor, School of 

Earth and Space Exploration, Arizona State University; Principal Investigator, NASA Psyche Mission ............................................................................... 80 

Appendix II: Additional Material for the Record 

Responses submitted by NASA ............................................................................... 84 
(1) 

PLANETARY FLAGSHIP MISSIONS: 

MARS ROVER 2020 AND EUROPA CLIPPER 

TUESDAY, JULY 18, 2017 

HOUSE OF REPRESENTATIVES, 

SUBCOMMITTEE ON SPACE, 

COMMITTEE ON SCIENCE, SPACE, AND TECHNOLOGY, 

Washington, D.C. 

The Subcommittee met, pursuant to call, at 10:09 a.m., in Room 

2318 of the Rayburn House Office Building, Hon. Brian Babin 

[Chairman of the Subcommittee] presiding. 
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Chairman BABIN. The Subcommittee on Space will come to order. 

Without objection, the Chair is authorized to declare recesses of 

the Subcommittee at any time. 

And welcome to today’s hearing titled ‘‘Planetary Flagship Missions: Mars Rover 2020 and Europa Clipper.’’ I recognize myself for 

five minutes for an opening statement. 

NASA’s planetary science flagships are the crown jewels of our 

robotic exploration of the solar system. Viking, Voyager, Galileo, 

Cassini, Chandra, and Mars Science Laboratory are programs that 

have inspired generations of Americans. One need only visit a local 

elementary school to see the wonder in children’s eyes as they 

learn about the great discoveries of these flagship missions. Mars 

Rover 2020 and the Europa Clipper will be no less amazing. 

Upholding such a legacy is not easy. From its original recommendation by the National Academies, through formulation and 

development, and ultimately launch and mission operations, there 

is much work to be done to ensure mission success, that the taxpayers’ money is being appropriately spent, and that the national 

interest is met. 

Today’s hearing serves an important oversight purpose. Our witnesses will provide important testimony on the Mars Rover 2020 

and the Europa Clipper, from both a programmatic and science 

perspective. The hearing will also provide an opportunity for Committee members to learn about the science that these missions will 

conduct and how it will benefit our nation. 

I have full faith that NASA and its hard working men and 

women will carry out its planetary science flagship missions successfully. That said, NASA is entering the most critical stage of the 

Mars Rover 2020 development and is undertaking the development 

of the Europa Clipper, and possibly a Europa Lander, at the same 

time. 

For Mars Rover 2020, the NASA Inspector General reported concerns regarding an overly optimistic schedule for Mars Rover 2020 

based largely on technology development challenges. I look forward 

to hearing from Dr. Green about these issues and how NASA is addressing them. 

A fundamental oversight question that needs to be addressed is 

how developing and operating these flagship missions at the same 

time, including a possible lander, will affect the Planetary Science 

Division and broader Science Mission Directorate portfolio. NASA 

must remain vigilant to protect against potential cost growth or 

mission creep that could impact other activities. 

The Consolidated Appropriations Act of 2017 funded and requires 

a Europa lander mission to complement the Clipper. The Act directed NASA to launch the Clipper in 2022 and a lander in 2024. 

In the fiscal year 2018 President’s budget, his request does not 

include funding for a Europa lander. NASA says that because the 

Planetary Science division already supports two other large strategic missions, Mars Rover 2020 and Europa Clipper, it cannot accommodate a Europa lander without significant impacts to other 

programs, and while a Europa lander is not included in the fiscal 

year 2018 budget request from the Administration, it has become 

an established concept for the future. NASA’s Europa Lander 

Science Definition Team conducted a study on the topic in 2016 to 
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evaluate landing on Europa and assess the science value and engineering design of a future lander mission. More recently, NASA released a community announcement to ask scientists what instruments would befit a Europa lander and NASA continues to work 

on lander design concepts. 

I strongly support NASA and its efforts with the Mars Rover 

2020 and Europa Clipper. I also believe there is great value in exploring the possibility of a Europa lander. However, it is critical 

that as Congress and NASA moves forward, we do our due diligence to assure not only flagship mission success, but also the success of the entire Planetary Science portfolio. I’d like to highlight 

the importance of sufficient research and analysis funding so that 

scientists can actually study the data derived from these missions. 

I want to thank the witnesses for being here today and I look forward to your testimonies. 

[The prepared statement of Mr. Babin follows:] 
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Chairman BABIN. And now I recognize the Ranking Member, the 

gentleman from California, for an opening statement. Mr. Bera. 

Mr. BERA. Thank you, Mr. Chairman. And I had to look back 

there. I see my old friend, our former colleague, Congressman Matt 

Salmon, in the audience. We miss you, Matt. Thanks for being 

here. 

Chairman BABIN. I just saw him too. 

Mr. BERA. You know, thank you for holding this hearing, ‘‘Planetary Flagship Missions: Mars Rover 2020 and Europa Clipper.’’ I 

think for both of us, we’ve talked about this, and for many of us 

of a generation that grew up in the space race, just the imagination, thinking about, you know, whether it was going to the moon 

or beyond, the Apollo missions to Skylab to Apollo-Soyuz to the 

space shuttle programs captured our imagination, and to a new 

generation of our kids and grandkids, they continue to capture our 

imagination of going beyond. 

We live in a time where we’ve sent spacecraft to explore the 

moon, all eight planets, Pluto, several asteroids and comets. And 

just last week, the NASA Juno spacecraft provided us an amazing 

view of Jupiter’s mysterious Great Red Spot. So, you know, these 

missions are incredibly important because it allows us to know that 

we’re part of something bigger, and now we’ve got Voyager One 

that is traveling through interstellar space. The reach of our scientific exploration is truly inspiring. 

And to maximize the scientific return on investment for planetary exploration, NASA develops both large and small missions to 

visit a range of destinations throughout our solar system. We’re 

here to talk about large flagship missions like Mars 2020 and Europa Clipper missions because they play an important role in using 

complex instruments to help us understand the challenge of exploring hard-to-reach locations but we spend less time talking about 

the smaller missions, like the Psyche mission that’s represented on 

our panel. These are launched more frequently in response to new 

discoveries. These missions also provide opportunities for students 

to engage in mission design, development, and operation. So the 

mixture of both the large planetary missions but also the small is 

an intentional mix and it provides significant value and has 

through the history of NASA’s planetary science program. 

We also know that NASA’s planetary missions have greatly advanced our understanding of the solar system and its potential to 

harbor life beyond Earth. Now, imagine if we were to identify life 

beyond Earth. That would be disruptive for all of humanity in a 

way of answering that seminal question, are we alone? And, you 

know, life may not be in the form of human life. It may be microbiotic life, et cetera, but even that discovery would be dramatic and 

change how we viewed ourselves in the context of our universe. 

So I look forward to learning more about the role of large and 

small planetary missions and the importance of supporting this 

balanced mission size and, you know, I want to acknowledge the 

panel here. I also want to acknowledge the long-term commitments 

that we make as a body to fund this discovery, and it’s incredibly 

important to us. 

So with that, I’ll yield back 

[The prepared statement of Mr. Bera follows:] 
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Chairman BABIN. Thank you, Mr. Bera. 

I now recognize the Ranking Member of the full Committee for 

a statement. Ms. Johnson. 

Ms. JOHNSON. Thank you very much, Mr. Chairman. 

Before I get into my formal statement, I just want to take a moment to say that this Friday marks 48 years of Apollo 11 moon 

landing, and as we look forward to inspiring our younger generation, whom I know many are sitting right out there, for the exciting 

future missions to Mars, Europa and asteroids, just remember that 

just 48 years ago this Friday, we had a previous generation of 

young people. America has an impressive legacy of accomplishment 

in both robotic and human space exploration, and I hope that we 

can continue to build on it. I hope that your minds will be just as 

inspired for our future as we have seen for our past. Now for my 

formal statement. 

Let me welcome all of our witnesses. I look forward to your testimony. 

Mr. Chairman, I thank you for holding this hearing on planetary 

flagship missions. Through our investigations in NASA’s planetary 

science program, NASA has been able to explore every planet in 

the solar system, as well as Pluto; continuously operate missions 

to Mars for the past two decades; and discover an expanding realm 

of potentially habitable bodies both within and beyond the solar 

system. With each discovery, NASA is advancing knowledge, pushing technological boundaries, and inspiring future generations to 

pursue science and technology education and careers. That is why 

I have often referred to NASA’s science program as one of America’s crown jewels. 

And we will hear this morning even more exciting planetary 

science missions lie ahead. As I speak, NASA is developing two 

planetary flagship missions. The Mars 2020 Rover will assess the 

habitability of Mars and look for signs of past life. In addition, the 

Europa Clipper mission will investigate the ice shell of Jupiter’s 

moon Europa and its underlying ocean, helping scientists to assess 

whether it can support life. These, like previous flagships, are very 

challenging missions. Mars 2020 will drill, collect, and cache samples of Martian rocks and soils, and Europa Clipper must withstand the intense radiation environment of Jupiter. Fortunately, 

NASA has decades of experience with flagship missions to draw on. 

With that in mind, I hope our witnesses can discuss the lessons 

learned from previous flagships and how we are using that knowledge in developing the Mars 2020 and Europa Clipper missions. 

Mr. Chairman, a discussion of flagship missions would be incomplete without mentioning the importance of balance in mission 

sizes, a critical element of a robust portfolio for both the National 

Academies and NASA Authorization Acts have repeatedly emphasized. 

To that end, I am pleased that this morning’s discussion will also 

include smaller, Discovery-class missions, and their role in maintaining a productive and balanced planetary science program. 

Looking ahead, opportunities for new and exciting planetary 

science missions abound. Maintaining balance will take discipline 

among NASA, the scientific community, and Congress. 
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Before I close, I want to take a moment to thank the talented, 

dedicated and committed workforce of NASA and its university, industry, and international partners. Our Nation’s inspiring achievements in planetary science would not be possible without all of you. 

I thank you, Mr. Chairman, and yield back. 

[The prepared statement of Ms. Johnson follows:] 
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Chairman BABIN. Thank you, Ms. Johnson. 

I now recognize our Chairman of our full Committee, Mr. Smith 

from Texas. 

Chairman SMITH. Thank you, Mr. Chairman. 

The exploration of our solar system captures Americans’ interests, inspires us to pursue extraordinary goals, and keeps us on the 

forefront of scientific achievement. 

Planetary missions teach us about how our solar system works 

and provide clues about how it was formed. They discover the locations of minerals and potential water sources on asteroids, comets, 

moons, and planets that could be used on future human missions 

or, in the case of minerals, extracted for use here on Earth. 

Planetary science also helps address a fundamental question of 

science: Is there life elsewhere in the universe? Within our own 

solar system, scientists have found strong evidence that other planetary systems could in fact host life. 

Europa, one of Jupiter’s many moons, may have the necessary ingredients for life: water and energy. Its ocean lies beneath an icy 

surface and may be two times the volume of all Earth’s oceans. 

Tidal forces drive active geological processes within Europa’s ocean 

interior and provide energy. Scientists see similar activity in hydrothermal vents on Earth’s ocean floor. 

The Europa Clipper mission, a flagship mission recommended by 

the National Academy of Sciences, will be an important mission to 

address the scientific question of whether there is life elsewhere in 

the universe. It will advance our understanding of planetary 

science as it explores the characteristics of Europa’s oceans, ice surface, and other geological activity. 

Congress directed NASA to work on a Europa lander to complement the Europa Clipper. NASA’s Europa Lander Science Definition Team conducted a study on the topic in 2016. The study 

found that the mission could analyze the biological potential of 

Europa’s ocean by directly examining both Europa’s surface and 

sub-surface. This is a very exciting concept that warrants NASA’s 

continued efforts. 

Closer to Earth, Mars Rover 2020 will also study the habitability 

of Mars. It builds upon the discoveries from the Mars Curiosity 

rover and the two Mars Exploration rovers, Spirit and Opportunity. 

The mission not only seeks signs of habitable conditions in Mars’ 

past, but also searches for signs of past microbial life itself. It will 

also test new technology that could benefit future robotic and 

human exploration of Mars. One of its instruments, MOXIE, will 

test a method for producing oxygen from the Martian atmosphere. 

Oxygen production on Mars will be critical for future human missions. 

I appreciate NASA’s planetary science exploration efforts and the 

Trump Administration’s support of American leadership in space. 

Other than national security agencies, NASA received the most favorable budget request from the Trump Administration. As a result, we can look forward to NASA undertaking a bold and ambitious agenda. 

I thank our witnesses and look forward to their testimony, and 

I’ll yield back, Mr. Chairman. 

[The prepared statement of Mr. Smith follows:] 
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Chairman BABIN. Thank you, Mr. Chairman. 

Now let me introduce our witnesses. We have a distinguished 

panel this morning. 

Our first witness today is Dr. Jim Green, the Director of the 

Planetary Science Division of the Science Mission Directorate at 

NASA. Welcome. Dr. Green has served as the Chief of the Space 

Science Data Operations Office at Goddard Space Center as well as 

the Co-Investigator and Deputy Project Scientist on the IMAGE 

mission. He received his Ph.D. in space physics from the University 

of Iowa. Welcome. 

Our second witness today is Dr. Ken Farley, the Mars Rover 

2020 Project Scientist. He is also a Professor of Geochemistry at 

the California Institute of Technology. He received his bachelor of 

science in chemistry from Yale and a doctorate in earth science 

from the Scripps Institution of Oceanography from the University 

of California in San Diego. Welcome. 

Our third witness today is Dr. Robert Pappalardo, the Europa 

Clipper Project Scientist at JPL at the California Institute of Technology. Dr. Pappalardo received his bachelor of arts in geological 

sciences from Cornell University as well as Ph.D. in geology from 

Arizona State University. Maybe that’s why we see Representative 

Matt Salmon back there. 

Dr. Linda T. Elkins-Tanton, our fourth witness today, Director 

and Foundation Professor at the School of Earth and Space Exploration at Arizona State University. She is also the Principal Investigator for the NASA Psyche Mission. She received her bachelor’s 

of science and her master’s of science as well as her Ph.D. from 

MIT. 

Our fifth witness today is Dr. William B. McKinnon. He is CoChair of National Academy of Sciences’ Committee on Astrobiology 

and Planetary Science. He is also a Professor of Earth and Planetary Sciences at Washington University in St. Louis. He received 

his bachelor of science degree in Earth and planetary sciences from 

MIT and his Ph.D. in planetary science and geophysics from Cal 

Tech. 

I would like to now recognize Dr. Green for five minutes to 

present his testimony. 

TESTIMONY OF DR. JIM GREEN, 

PLANETARY SCIENCE DIVISION DIRECTOR, 

SCIENCE MISSION DIRECTORATE, NASA 

Dr. GREEN. Chairman Babin and the Members of the Committee, 

thank you so very much for giving us the opportunity to come and 

talk about certainly my favorite subject: planetary science. In my 

opening statement, I’d like to explain how missions like Mars 2020 

and the Europa Clipper fit into an overall planetary exploration 

portfolio. 

[Chart] 

In my first chart, as you see, this is an overview of the current 

planetary missions. They’re in a variety of formulation, implementation and currently operating missions that we have. 

This is a tremendously exciting time in planetary science. All our 

operating missions are making revolutionary discoveries and all 

are rewriting the textbooks. 
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For instance, just two years ago, we had a fabulous fly-by of the 

New Horizon spacecraft through the Pluto system. With that mission, the United States becomes the first and only Nation to reach 

every major body in the solar system from Mercury to Pluto. Dr. 

Bill McKinnon on the panel is a New Horizons Co-Investigator. 

Today, NASA has numerous missions exploring and operating 

through the solar system such as the lunar reconnaissance orbiter, 

which is bringing us back to the moon and making exciting discoveries. 

The indomitable Mars Curiosity and Opportunity rovers along 

with our orbiters at Mars continue to make almost daily new discoveries about the red planet. For example, from our Maven mission, it has revealed that solar wind interactions with the upper atmosphere of Mars over time has literally stripped away most of 

that atmosphere, transforming Mars from what we believe was 

once a planet that could have supported life in its distant past to 

now a frigid, arid world. 

Adding to our Mars missions, Insight lander will be launched in 

May 2018 and land in November 2018. Insight is designed to study 

the interior of Mars along with understanding its present-day level 

of global seismic activity. 

In 2020, a new Mars rover will be launched carrying seven stateof-the-art instruments to conduct advanced geological research and 

search for signs of ancient Mars life. For the very first time, we 

will create high-grade rock core samples for potential return to 

Earth for further analysis. I look forward to Dr. Farley’s testimony, 

which will provide additional information on that mission. 

Between Mars and Jupiter is a major asteroid belt where NASA’s 

Dawn mission is currently studying the dwarf planet Ceres and 

finding evidence of past cryovolcanism. 

This year, NASA selected two discovery missions, Lucy and Psyche, which will respectively visit six Jupiter mysterious Trojan asteroids and study a unique metal asteroid that may actually be an 

exposed planetary core called Psyche. Dr. Linda Elkins-Tanton is 

here today to tell much more about the Psyche mission. 

NASA’s robotic rendezvous and sample return mission that visits 

the Bennu asteroid is called OSIRIS–Rex. It will get a gravity assist by Earth in September and it will reach that potentially hazardous asteroid in August of next year. Examinations of objects like 

Bennu will allow our scientists to investigate how planets formed 

and how materials like water and organics actually were delivered 

in early impacts in addition to looking at the effects of potential 

planetary defense. 

In our outer solar system, Jupiter’s mission Juno, which got into 

polar orbit our very first time in polar orbit at Jupiter last July. 

Since then Juno has been observing the cloud tops and into the interior of the planet, finding in the northern and southern polar regions that that planet is maintaining huge nearly Earth-size cyclones. 

After 13 years of orbiting Saturn, our Cassini spacecraft is making a daring dive between the planet’s atmosphere and the first 

ring, and it will lead to plunging that spacecraft into Saturn on 

September 15 as it runs out of fuel. Cassini has given us a power-
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ful insight into the planet’s internal structure, atmosphere and 

rings in addition to unbelievable views of Titan and Enceladus. 

And if I may go on and summarize, finally, NASA recognizes 

there is still much to learn. With your support, we will continue to 

tackle solar system exploration goals identified as top priorities by 

the scientific community and delineated in the National Academies’ 

Planetary Decadal. 

Again, thank you so much for the opportunity to testify today 

and I look forward to responding to your questions. 

[The prepared statement of Dr. Green follows:] 
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Chairman BABIN. Thank you, Dr. Green. 

I now recognize Dr. Farley for five minutes to present your testimony. 

TESTIMONY OF DR. KENNETH FARLEY, 

MARS ROVER 2020 PROJECT SCIENTIST; 

PROFESSOR OF GEOCHEMISTRY, 

CALIFORNIA INSTITUTE OF TECHNOLOGY 

Dr. FARLEY. Thank you for the opportunity to testify today on the 

Mars 2020 mission. 

Mars 2020 will seek evidence of past life in a fossil Earth-like environment that existed in the first billion years after the dawn of 

the solar system. This flagship mission will engage many hundreds 

of scientists and the American public in a very challenging journey 

through one of the most intriguing landscapes in the solar system 

and some of the most profound scientific questions of our time. 

Today Mars is too cold, too dry, and too exposed to harmful radiation to plausibly nurture life on its surface. However, more than 

two decades of sustained and strategic NASA-led exploration have 

shown that the red planet was once very different. Imagery from 

the Mars Odyssey and Mars Reconnaissance Orbiters reveals that 

prior to about 3.6 billion years ago, Mars had rivers, lakes, and 

possibly a vast northern ocean. Sophisticated analyses made on the 

planet’s surface, most notably by the Spirit and Curiosity rovers, 

have richly documented ancient environments with all conditions 

believed necessary to sustain life. In that same early time period, 

conditions here on Earth were broadly similar, and life had already 

originated, evolved, and spread across the surface. However, unlike 

Earth, with its active erosion and plate tectonics, the geologic 

record of ancient Mars is exquisitely preserved for study, allowing 

us to seek answers to grand questions including how early climate 

and habitability evolve on rocky planets, the nature of prebiotic environments that might ultimately spawn life, and whether life is 

unique to Earth. Seeking the signs of life in an ancient habitable 

environment is the central goal of the Mars 2020 mission. 

Thanks to a wealth of images from the Mars Reconnaissance Orbiter, the science community has narrowed the possible Mars 2020 

landing sites down to three very different settings that on Earth 

are both habitable and inhabited: an ancient river and lake system, 

a fossil hot spring similar to those at Yellowstone National Park, 

and a setting where warm water once circulated through shallow 

subsurface rocks. Once on Mars, the rover will use its on-board instruments to investigate the local geology, to characterize the habitable environments the rover traverses, and to look for evidence of 

ancient life. Using Earth as a guide, we expect that any Martian 

life existing at that time was primitive, consisting only of microbes. 

Truly definitive discovery of microbial biosignatures by instruments 

on board the rover is unlikely, and can best be undertaken using 

the full arsenal of terrestrial laboratories. For this reason the Mars 

2020 rover will prepare a complete suite of samples for possible return to Earth by a future mission. 

Mars 2020 starts with the designs of the remarkably successful 

Mars Science Laboratory (MSL) and the Curiosity rover. To this 

platform a suite of very capable new science instruments is being 
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added to explore the structure, chemistry, and mineralogy of the 

surface all the way from the regional scale down to the microscopic 

scale. In addition, the mission is developing advanced new capabilities for landing in rugged terrain, for autonomous navigation and 

science observation, and for robotic coring and caching of samples. 

These are critical steps towards unleashing the full capabilities of 

robotic solar system investigation. 

The mission will also test new technologies beneficial to future 

human Mars exploration, most notably a device to demonstrate 

conversion of carbon dioxide in the Martian atmosphere into oxygen for use as a component of rocket propellant. The mission is currently in the implementation phase (Phase C) with a substantial 

amount of hardware already completed. Launch will occur in the 

summer of 2020, with arrival on Mars on February 18, 2021. The 

rover will be landed using the spectacular sky-crane system pioneered by MSL, and will explore the Martian surface for at least 

two years. In that period the rover will core and cache at least 

twenty rock samples, each about the size and shape of a piece of 

chalkboard chalk. These will be thoroughly documented and placed 

on the surface, accessible to retrieval by a future mission or even 

by human explorers. By collecting and caching a diverse suite of 

high-science-value rock samples, Mars 2020 fulfills the highest priority objectives of the Mars and planetary science communities as 

described in the most recent Planetary Science Decadal Survey. 

Mars 2020 will investigate a planet known with detail sufficient 

to compellingly address, for the first time, well-posed and profound 

scientific questions that would forever elude answers from Earthbound study. Going well beyond observations on the Martian surface, return of the cache to terrestrial laboratories would provide 

future generations of scientists across many disciplines access to 

samples that would transform our understanding of Mars, the solar 

system, and life. There is still an enormous amount to learn about 

Mars, and the deeper we penetrate, the richer the scientific tapestry becomes. Mars 2020 makes the next big step in this decadeslong journey, and provides new focus and foundation for human exploration of Mars. It’s an honor and a privilege for me to play a 

part in such a grand and ambitious undertaking. 

I look forward to your questions. 

[The prepared statement of Dr. Farley follows:] 
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Chairman BABIN. Thank you, Dr. Farley. 

I now recognize Dr. Pappalardo for five minutes to present your 

testimony. 

TESTIMONY OF DR. ROBERT PAPPALARDO, 

EUROPA CLIPPER PROJECT SCIENTIST, 

JET PROPULSION LABORATORY, 

CALIFORNIA INSTITUTE OF TECHNOLOGY 

Dr. PAPPALARDO. Chairman Smith, Chairman Babin, Ranking 

Member Bera and other Members of the Committee, I’m delighted 

to appear before you to describe recent progress in NASA’s Europa 

Clipper mission. 

The ice-covered world Europa—moon of Jupiter similar in size to 

Earth’s moon—shows a landscape of cracks, ridges, and jumbled, 

chaotic terrains indicative of a tumultuous past. The Galileo spacecraft, which orbited Jupiter beginning in the late 1990s, provided 

images, compositional information, and gravity and magnetic data 

that point to a remarkable conclusion: Europa likely has a global 

ocean of liquid water beneath its icy carapace, maintained by tidal 

flexing and heating. From what we know of the tenacity of life, Europa could be one of the best places in the solar system to search 

for life beyond Earth. 

For these reasons, future detailed investigation of Europa is one 

of the top priorities for planetary exploration, as expressed in the 

National Research Council’s 2011 Planetary Science Decadal Survey. The Europa Clipper mission responds directly to the Decadal 

Survey in its top-level goal: explore Europa to investigate its habitability, and in its science objectives to understand Europa’s ice 

shell and ocean, composition, geology, and recent or current activity. The last of these categories includes the possibility that Europa 

may have active plumes that spew water vapor into space, and 

which could directly reveal Europa’s internal composition and suitability for life. This tantalizing evidence for plumes is provided by 

the Hubble Space Telescope, searching at the extreme of its detection limits. 

In the tradition of the 19th century trading ships for which this 

mission was recently named, the Europa Clipper will sail past the 

Jovian moon at a rapid clip as frequently as every two weeks. providing many opportunities to investigate Europa from as close as 

16 miles above the surface. During each flyby, the spacecraft will 

spend just a short time within the challenging radiation environment near Europa. The prime mission plan includes 40 to 45 flybys 

of Europa from Jupiter orbit, during which the spacecraft will interrogate the moon in unprecedented detail. This will include imaging to understand its geological history; compositional analyses including direct sampling of materials knocked off the surface; icepenetrating radar to examine the 3D structure of its icy shell; and 

gravity, magnetic, and plasma measurements to understand its 

hidden interior and interactions with the Jupiter environment. The 

mission can also lay the foundation for future exploration of Europa, providing critical global context and scouting potential landing sites for a potential future landed mission. 

As its Project Scientist, I represent the science and scientific integrity of the Europa Clipper mission, ensuring it will address the 
31 

top-level goal and objectives. I first testified before this Committee 

two years ago, just after NASA had competitively selected nine 

science instruments for the mission, and had given the green light 

to begin Phase A, known as mission formulation. In February of 

this year, NASA completed its second major milestone review, so 

today we’re in Phase B, refining details of how the instruments will 

achieve the mission’s science, and developing preliminary yet detailed design plans for the spacecraft and its subsystems, including 

the science instruments. 

Progress on the instrument suite has been outstanding. Instrument concepts have been reviewed; designs have matured; subsystem vendors are being selected; prototype parts are being built; 

detectors are being tested; and additional tests are being conducted 

to ensure robustness against the harsh radiation environment in 

Europa’s vicinity. 

Beginning this fall and into next spring, each spacecraft subsystem and each instrument will undergo a preliminary design review to assure that the defined science can be achieved by the instruments and spacecraft in combination. These Phase B reviews 

are in preparation for the mission to proceed to Phase C around 

October 2018. It’s also at this key decision point that NASA would 

make a final commitment as to a launch readiness date and baseline mission cost. Then during Phase C, flight hardware would be 

built. 

The members of the mission’s science team are working cooperatively together to define the synergistic science which I see as this 

mission’s hallmark. No one instrument can definitively affirm the 

ocean’s existence or tell us convincingly of Europa’s composition. 

Instead, each instrument technique provides a piece of the puzzle, 

and from the combined science data, Europa scientists will mature 

a complete picture of how Europa works as a complex system from 

its submerged rocky core to its ocean to the capping ice shell and 

surface, to its thin atmosphere, and the surrounding environment 

of Jovian space. 

The clipper ships of the late 19th century were an expression of 

speed and grace in the golden age of sail. We’re now in a golden 

age of solar system discovery, and the Europa Clipper mission will 

return to us untold scientific riches. 

Thank you, and I look forward to your questions. 

[The prepared statement of Dr. Pappalardo follows:] 
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Chairman BABIN. Thank you, Dr. Pappalardo. 

I now recognize Dr. Elkins-Tanton for five minutes to present her 

testimony. 

TESTIMONY OF DR. LINDA T. ELKINS–TANTON, 

DIRECTOR AND FOUNDATION PROFESSOR, 

SCHOOL OF EARTH AND SPACE EXPLORATION, 

ARIZONA STATE UNIVERSITY; 

PRINCIPAL INVESTIGATOR, NASA PSYCHE MISSION 

Dr. ELKINS-TANTON. Chairman Babin, Chairman Smith, Ranking 

Member Bera, and the Members of the Committee, thank you so 

much for the opportunity to speak today. Today I’ll be testifying in 

my personal capacity. 

Any discussion of NASA’s planetary science program would be incomplete without also talking about the balance between flagships 

and smaller planetary missions, and so today I’m going to talk 

about three things. I’m going to talk about the newly selected Psyche mission, I’m going to talk about portfolio balance, and I’m going 

to talk about our inevitable space future. 

I am the Principal Investigator of the Psyche mission, which in 

January was selected as the 14th in the NASA’s Discovery program. The spacecraft is scheduled to launch in August of 2022 to 

rendezvous with the asteroid Psyche in January of 2026, and to 

orbit Psyche for 22 months. Psyche is a metal world with a diameter about the same as the width of Massachusetts and with a surface area larger than the area of Texas. Humankind has explored 

rocky worlds and we have explored icy worlds and we have explored worlds covered with gas but we have never before explored 

a metal world. This is a first. 

We think that Psyche is the core of a small early-formed planet 

that was bombarded in the early solar system and had its rocky exterior knocked off so that only its metal core remains showing 

today. Computer models of planetary formation indicate that this 

is rare, and indeed, Psyche is the only large, round metal object in 

our solar system, so it’s not just unique, it’s improbable. 

The science we hope to achieve in the mission is first to determine whether indeed Psyche is a core, or if it is some previously 

undiscovered kind of material. We’ll be comparing what we learn 

at Psyche to models of the Earth’s core to better understand that 

unreachable part of our own planet. And for the first time, we’ll be 

investigating the morphology of a metal body. What do craters into 

metal look like? Could Psyche have glittering cliffs of metal and 

green pyroxene crystals? We don’t know yet. No one knows yet. At 

Psyche, we will also take the first steps toward our space resource 

future because we’re pretty confident that Psyche almost entirely 

consists of iron, nickel, copper, and a variety of trace metals. 

Now, I strongly support the Planetary Decadal Survey’s conclusion about the necessity for having a balanced mission portfolio 

combining small and mid-sized missions on a regular tempo with 

flagships. Tempo is critical. Tempo maintains our workforce and it 

also saves our institutional memory, but each size of mission comes 

with its own challenges and its own its own advantages. For smaller missions like Psyche, usually keeping costs down and keeping 
37 

risk down means that we’re going to use trusted high-heritage components whereas flagship missions give us the opportunity for innovation and new technology development, and we need both of those 

things. We need our trusted technology today and we need new 

technology for the future. 

Flagship missions can also engage a broader swath of the community through competed calls for instruments. These calls can 

bring new groups onto missions that would otherwise not be involved but then the project scientist has the challenge of organizing 

and uniting otherwise disconnected sub-teams. It’s an interesting 

challenge. In fact, all lead scientists have to build, inspire and lead 

large interdisciplinary teams, and normally engineers and scientists are not taught these skills, so we are trying to change that 

at ASU now. 

Exploration is a human imperative. It is stamped on our DNA, 

and space is the future of exploration for humankind. Every time 

we do this most extreme of technological miracles and we send a 

rocket off of our Earth to make discoveries in space, we encourage 

people all around the world to make a bolder step in their own 

lives and in their own communities. So space exploration is therefore an opportunity for us to create a better educated, more united 

society. 

At ASU I’m also co-chair with President Michael Crow of our 

new Interplanetary Initiative. In this initiative, we’re bringing together not just the technological but the educational and the social 

aspects that we need for our space future, and indeed, education 

is the single most critical thing for humanity’s future. Both at ASU 

and at our startup, Beagle Learning, we are working on next-generation learning. We need to produce a critical mass of people who 

are attracted to the unknown, who are learning how to ask better 

questions, who are willing to pursue answers through partial solutions, and who know how to build teams and to lead. All this ideation is initiated by the vision and the process of NASA, and in fact, 

space exploration will bring us to a better future here on Earth as 

well as eventually on the moon and Mars and beyond. 

Thank you very much. 

[The prepared statement of Dr. Elkins-Tanton follows:] 
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Chairman BABIN. Thank you, Dr. Elkins-Tanton. 

Now I’d like to recognize Dr. McKinnon for five minutes for your 

testimony. 

TESTIMONY OF DR. WILLIAM B. MCKINNON, 

CO-CHAIR, NATIONAL ACADEMY OF SCIENCES, 

COMMITTEE ON ASTROBIOLOGY AND PLANETARY SCIENCE; 

PROFESSOR OF EARTH AND PLANETARY SCIENCES, 

WASHINGTON UNIVERSITY IN ST. LOUIS 

Dr. MCKINNON. Good morning, Mr. Chairman, Members of the 

Committee. 

So I’m here today because I’m a Co-Chair of the Committee on 

Astrobiology and Planetary Sciences, or CAPS, for the National 

Academies, but I wish to say that my testimony today is my own 

and is not an official report from CAPS or the Academies. Nevertheless, I hope you find my remarks useful. 

So I’d like to focus on the Planetary Science Decadal Survey and 

its relation to flagship and other planetary missions. Obviously 

decadal surveys are carried out about every ten years for various 

space science disciplines and the Committees and the panels that 

carry out the decadal are drawn from the broad community associated with the discipline in question. Decadal survey recommendations to the government play a critical role in defining our country’s agenda in a given science area for ten years or even longer. 

Now, the Planetary Science Decadal Survey was tasked in particular, among many things, to create a prioritized list of flight investigations because missions lie at the heart of planetary exploration. Such a prioritization is based first and foremost on science, 

especially science per dollar, but also on programmatic balance 

among mission targets and balance among mission types—small, 

medium and large. Indeed, a balanced mix of discovery, new frontiers and flagship missions enable both a steady stream of new discoveries and the capability to address larger challenges such as 

sample return missions or outer solar system exploration. 

Prioritization also considers technological readiness, the availability of trajectory opportunities, understanding of cost and technological risk, and the fiscal climate. Anyway, these prioritizations 

take in the sense that decadal surveys succeed because the consensus they represent is compelling. 

Now, in terms of science, increasingly central to NASA’s exploration of the solar system is the emerging science of astrobiology, 

prominent examples being the scientific program of the Curiosity 

Mars Rover, the Mars 2020 rover, the development of the Europa 

Clipper mission, and the planning for the potential future landing 

on the surface of Europa and the inclusion of ocean worlds in the 

recent new frontiers call. 

Indeed, in the most recent Planetary Decadal Survey, 

astrobiology was a driving scientific rationale for the two top mission recommendations now being implemented as Mars 2020 and 

Europa Clipper. Now, my personal assessment, and as the CAPS 

leadership has previously reported to the Space Studies Board, is 

that NASA’s Planetary Science Division is doing well and the 

Decadal Survey’s priorities and recommendations are being pur-
44 

sued. Mars 2020 and Europa Clipper in particular are, I believe, 

responsive to the Decadal Survey in science and cost. 

Now, regarding NASA’s plans to explore Europa, CAPS, as well 

as the ongoing Academies’ planetary mid-term review will continue 

to consider the aspects of—consider the impacts of the evolution of 

this program. Presently, NASA has been directed to add a lander 

to the Europa exploration program. The development of any large 

mission like that is of course a programmatic challenge and can 

have unwelcome or worse effects on a broad cost-contained program. But this challenge must be balanced against the scientific 

opportunity afforded by the promise of addressing one of the greatest of scientific questions: is there extant life beyond Earth? 

As I said, these are all issues I expect CAPS will continue to consider and will also be surely considered by the next decadal as well. 

So to finish up, Mr. Chairman, as a second grader I watched the 

liftoff of John Glenn and Friendship 7 in our auditorium, and as 

a teenager at home I watched Neil Armstrong walk on the moon. 

Over the past 60 years, I have seen NASA’s exploration of the solar 

system from Mercury out to Pluto and beyond, revolutionize our 

conception of ourselves and our planet, but I believe given our ongoing discoveries and characterization of planets around other 

stars, thousands of them we know about now, and the very real 

possibility of detecting extant life in our solar system that we are 

approaching an even greater revolution, a true paradigm shift in 

our understanding of our place and our destiny in the universe. 

Thank you very much. 

[The prepared statement of Dr. McKinnon follows:] 
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Chairman BABIN. Thank you, Dr. McKinnon. All fascinating testimonies. I really appreciate it. The Chair now recognizes himself 

for five minutes. 

Dr. Green, in the near future, NASA’s Planetary Science Division 

may be running three flagship missions at the same time: the Mars 

rover for launch in 2020, the Europa Clipper for launch in 2022, 

and potentially a Europa lander for launch in the 2024 time frame. 

I greatly support this investment and NASA’s renewed focus on 

deep space exploration. At the same time, from an acquisition perspective, this is a great deal of work. What is NASA doing to address the risks of cost and schedule slips associated with this cadence of flagship missions? 

Dr. GREEN. Planetary Science I think has tackled a number of 

those topics and is doing quite well because we started to implement a couple very important and new procedures. Typically, strategic missions in the past based on a science rationale that’s almost 

at any cost. In Planetary Science, we begin the—we have begun the 

process in particular with Mars 2020 to have a cost-constrained environment. As was recognized on the Planetary Decadal, both the 

Mars Cacher and the Europa Clipper were unaffordable, and we 

took on a process early in this decade to begin to determine what 

science we can do at that reasonable cost. We’re leveraging on 

Mars 2020 the architecture for Curiosity. We’ve done a lot of work 

on the planning of the Europa Clipper where we’re looking at 

descope options, and so some of these processes are incredibly important for us to follow through on. 

Chairman BABIN. Okay. Thank you very much. 

And now the next question to Dr. McKinnon. To what extent do 

the Mars Rover 2020 and Europa Clipper missions align with the 

Decadal Survey recommendations? 

Dr. MCKINNON. Well, the original survey considered two flagship-class missions, Mars astrobiology Explorer-Cacher and a Europa Jupiter orbiter mission, a mission to orbit Europa itself, and 

in both cases the Decadal Survey concluded based on a very detailed cost and technical evaluation that these missions were probably too expensive to be carried out in the decade in question. And 

so basically they said these were our priority missions but they 

needed to be descoped. They needed to be reduced in cost and perhaps reduced—and certainly reduced in risk. And in both cases, I 

think they’ve done that. As an example, the Europa mission doesn’t 

orbit Europa anymore but it orbits Jupiter but repeatedly passes 

by Europa dozens of times and basically recovers all of the science, 

and in fact, in my own view actually does an even better job because it avoids so much of the radiation that’s near Jupiter and it 

allows in its long looping orbits around Jupiter that Dr. Pappalardo 

can tell you about, it can radio back all the data that it collects 

every time, and it does it within a very reasonable cost cap. 

Chairman BABIN. Thank you very much. 

Now, I also would like to ask Dr. Farley and Dr. Pappalardo, the 

exploration of Mars and Europa are inspiring and truly amazing. 

As Project Scientists for Mars Rover 2020 and the Europa Clipper, 

can you share with us what excites you about these exploration efforts, and what are the greatest scientific discoveries that you’re 

hoping to achieve? 
59 

Dr. FARLEY. Well, I think the most exciting thing about Mars is 

that, as I mentioned in my testimony, the surface of Mars is—carries a rock record from a time period which is completely obliterated on Earth. There is no substantial rock record that is older 

than about 3.6 billion years on Earth. Those rocks are present on 

the surface of Mars, and they will tell us a lot both about the way 

rocky planets evolve and also about things like habitable environments, and for me, linking this to the life question, I think the 

really exciting thing is, we will potentially be looking at an environment that was capable of having life originate, and that’s of 

course one of the great questions. It’s a great scientific question 

that is extremely difficult to treat as a science question because 

there’s no evidence, no substantial evidence to compare it against. 

By going to Mars, we may actually be able to find environments 

like that and learn something really profound about the way life 

works. 

Chairman BABIN. Thank you very much. 

And Dr. Pappalardo? 

Dr. PAPPALARDO. For Europa, we want to understand, is this 

really a habitable environment, Europa’s ocean, lakes within the 

ice shell, and we think we know how Europa works but planetary 

scientists are always surprised when we actually go there with new 

instruments to test hypotheses. So we’re going to both test 

hypotheses and explore and expect to be surprised. What I would 

love to see is some sort of oasis, that is, a place where there’s liquid 

water near the surface, there’s evidence of heat coming out, there 

are organics at the surface somewhere where we’d want to follow 

up with future exploration. 

Chairman BABIN. Fascinating. Thank you. My time is up so I’d 

now like to recognize the gentleman from California, Dr. Bera. 

Mr. BERA. Thank you, Mr. Chairman. 

Dr. Elkins-Tanton—and I think each of you in your opening 

statements alluded to the fact that exploration is part of our DNA, 

you know, this natural curiosity, this desire for discovery, and the 

universe is, you know, unlimited in its possibilities of what we can 

learn. That brings us back down to Congress where we have to operate in the confines of limits. Each of you has talked about the 

Decadal Survey and alluded to a bit of the roadmap for some of our 

bigger missions and laying out some of the parameters for some of 

the medium-size missions. 

Dr. Elkins-Tanton, as you talked about the Psyche mission and 

alluded to the importance of, you know, some of our smaller missions, how those—you know, what we discover, you know, they’re 

able to be launched at a lower cost, et cetera. You know, there’s 

some worry in that limited environment of Congress that we potentially focus on the big missions at the expense of the smaller missions, and we’ve got to found the right balance. Maybe if you want 

to expand on your comments and the importance of some of the 

smaller missions. 

Dr. ELKINS-TANTON. Thank you very much. Indeed, I think this 

is well recognized at NASA, and I’ve heard Jim Green talk about 

a cadence, a process for deep exploration in space that you might 

fly by, you might orbit, you might land, and then you might rove, 

and indeed, you wouldn’t spend all the money that you would have 
60 

to spend to do a flagship mission on a body that we know little 

about, and so the smaller missions form a framework and they set 

the stage for the kinds of bigger expeditions that we want to do, 

and as my colleagues here have mentioned, every time we do something in space, it surprises us, and so we must try these smaller 

missions to find out where the biggest surprises are and then put 

our money on making the big, big discoveries. 

Mr. BERA. Dr. Green, do you want to expand on the importance 

of the smaller missions? 

Dr. GREEN. Indeed, the smaller missions are really our pioneers. 

They do go out and do some initial exploration. You know, smaller 

missions in the discovery framework is really the heart of that exploration process. You know, I mentioned several of them in my 

testimony like Dawn. Others that have come and gone while I’ve 

been at NASA headquarters include Messenger, another wonderful 

mission. Grail went to the moon, Messenger went to Mercury, and 

Grail studied the moon in new and unique ways. 

And so indeed, the discovery line is really quite important for us, 

and then the next line is new frontiers. This is where we can now 

concentrate on the next level of detail. So important for us to make 

decisions on what our next flagships will be. 

Mr. BERA. Great. Switching now to Mars and, you know, our 

telecommunications infrastructure and Mars, my understanding 

right now is that the Mars Reconnaissance Orbiter handles the majority of our telecommunications relay for Curiosity Rover, but the 

MRO was launched 12 years ago. As we look at Mars Rover 2020, 

you know, I guess, Dr. Green or Dr. Farley, would you like to kind 

of comment on, you know, will we still be relying on the MRO to 

relay that information back or are we thinking about, you know, 

what next steps for telecommunications? 

Dr. GREEN. Well, telecommunications for any surface assets indeed go through our orbiters, and right now we have a wonderful 

network including MRO is Mars Odyssey, and also with partnership from ESA, other missions that are also orbiting Mars have 

that telecommunication capability. So in addition to those two, we 

also have with ESA the Mars Express mission and now the newly 

inserted into orbit, the Trace Gas Orbiter from ESA. Now, we also 

have Maven, which is not prime telecommunication capability but 

may become more dependent on using Maven as our aging assets 

occur. So indeed, supporting telecommunications is a real critical 

element of allowing us to now when Mars 2020 gets down on the 

ground be able to relay that data back so we take careful operations of all those missions and partner with other agencies. 

Mr. BERA. Great. Dr. Farley, do you want to expand or—— 

Dr. FARLEY. I’ll just say Mars 2020 has a very large demand to 

downlink data. We have a huge number of cameras. It’s quite extraordinary. There’s more than 20 cameras on the rover. And we 

will need downlink. As you point out, MRO is an aging asset but 

as Dr. Green pointed out, there are contingency plans to get us the 

data volume we need. 

Mr. BERA. Great. Thank you. And I’ll yield back. 

Chairman BABIN. You bet. Thank you. Good questions. 

I now recognize the gentleman from California, Mr. Rohrabacher. 
61 

Mr. ROHRABACHER. Thank you very much, Mr. Chairman. It was 

noted earlier that one of the purposes of, or one of the benefits, I 

should say, of your activities is that you have these robots all over 

the universe and beyond that you are inspiring people with our capabilities. 

And Mr. Chairman, let me just note that I’ve been around for a 

while, and I think that when we were deciding about the shuttle 

and we were deciding about Space Station, a lot of times the discussion was only on the immediate scientific payback, but I believe 

those two space projects have inspired generations of Americans 

now, and who knows how much more productive our people are, 

how much more visionary they are because of these investments in 

the shuttle and the space station, which were very expensive 

projects, I might add. 

And back to expensive projects, let me just note that one thing 

that I find—one of our witnesses mentioned that the Decadal Survey was supposed to prioritize and it just seems to me standing 

back and listening to everything that we haven’t had that 

prioritization and maybe we should—there’s been—when you have 

so many projects at one time, it indicates that there hasn’t been a 

real finding out of what priorities we need, and I’m certainly not 

an expert enough to tell you what those priorities should be. 

Let me ask some specific concepts or ideas about the engineering 

that I don’t know about. What type—well, first of all, is there any 

one of these missions that plan to—we know we’ve landed the robots on Mars. Do we plan to actually bring some material from 

Mars back to Earth before we plan to send human beings there and 

bring them back? 

Dr. GREEN. Indeed, the Mars 2020 mission, which is going to core 

rock, providing a detailed look at the past Mars, the geological 

records in that rock, we are currently looking at a variety of architectures, and—— 

Mr. ROHRABACHER. Right, but we are going to bring them back? 

Dr. GREEN. Our intention would be indeed that as the importance of these samples are noted based on the analysis that we do 

in situ that indeed we would plan on bringing samples back from 

Mars. 

Mr. ROHRABACHER. Okay. The reason I ask that is, it seems to 

me that rather silly to think that if we can’t bring back rocks that 

we’re going to bring back people, and certainly if we aren’t comfortable with the idea that we can bring back rocks, we should be 

focusing on getting that done before we talk about bringing people 

back. 

The exploration, to me, that’s the most inspiring. I just have to 

tell you that when we talk about going out and visiting those 

places where nobody has been, what type of fuel are we using? 

There was a mention about one of the things when we run out of 

fuel, it’s going to land into Europa or something like that. What 

type of fuel is now being used in these various projects? We know 

you have to have a big rocket to get them going, but if they’re going 

to keep going into the universe, what fuel do they use? 

Dr. FARLEY. Yeah, Mars 2020 while it’s on the surface will use 

a short-lived plutonium isotope so it’s a nuclear power source. 

Mr. ROHRABACHER. Any other—— 
62 

Dr. ELKINS-TANTON. May I add to that? During cruise and while 

orbiting Psyche, our spacecraft will use solar electric propulsion, 

and this to me is so—it’s in our heart at space age. You see the 

little blue plumes of the ions being shot out the back and it’s all 

run by solar power, and in fact, this is another good proof of this 

technology which is eventually going to be critical for getting people to Mars. 

Mr. ROHRABACHER. Yeah, I remember the solar sail project, 

which also was very exciting. These new concepts that—and you— 

and let me just note, Mr. Chairman, the fact that we can actually 

provide a fuel for something that far away indicates that maybe we 

have some knowledge that’s going to really help us here. 

But one last thought. I would hope that—again, I think the Moon 

is close by and whatever we can actually get a benefit of going back 

there, we should before you take the next step. However, the most 

important thing was, if Mars—can I ask permission for one minute 

for this question? And that is, you have indicated that Mars was 

totally different thousands of years ago. Is it possible that there 

was a civilization on Mars thousands of years ago? 

Dr. FARLEY. So the evidence is that Mars was different billions 

of years ago, not thousands of years ago. 

Mr. ROHRABACHER. Well, yes. 

Dr. FARLEY. And there would be—there’s no evidence that I’m 

aware of that—— 

Mr. ROHRABACHER. Would you rule that out? See, there’s some 

people—well, anyway—— 

Dr. FARLEY. I would say that is extremely unlikely. 

Mr. ROHRABACHER. Okay. Well, thank you all, and thanks for the 

good job you’re doing. God bless. 

Chairman BABIN. Thank you, Mr. Rohrabacher. I’m looking forward to finding out what’s up there, that’s for sure. And just last 

month, we had a great hearing in here on in-space propulsion, 

which was super, super interesting. 

Okay. Now I recognize the gentleman from Colorado, Mr. Ed 

Perlmutter. 

Mr. PERLMUTTER. Thanks, Dr. Babin. 

And good morning, and thank you for your testimony today, and 

a truism in life is, everything’s relative, and when we’re talking 

about small, medium and flagship projects that you all are undertaking, you know, to Mrs. McGillicuty from Lakewood, Colorado, 

they’re all major undertakings, and Dr. McKinnon and Dr. ElkinsTanton, I mean, we’re here for I dipped into the future far as 

human eyes could see, saw the vision of the world and all the wonder that would be. And all of you are working on kind of the ultimate question of humanity, why are we here and what else is out 

there. And so I just appreciate your willingness to take on kind of 

the nuts and bolts for us to start knowing the unknown, and this 

Committee is so exciting to all of us here and to hear the work 

you’re doing, we appreciate it. 

Now, I’d like to start with Dr. Farley. One of the things that I 

am focused on is trying to get our astronauts to Mars by—you 

guessed it—2033, all right, and so first question I have is for you. 

How will this rover, you know, 2020, our mission in 2020, how will 

that help us, inform us to get humans to Mars by 2033? 
63 

Dr. FARLEY. Well, I think it’s important to note that Mars 2020 

has a very strong collaborative involvement from the human side 

of NASA, and that is manifested in several different ways. Most 

notably, you heard about the MOXIE demonstration of in situ resource utilization. In addition, we have a weather station, which 

will characterize the environment, will also characterize dust, and 

dust on Mars is a big concern for human explorers, and in addition, 

during entry, descent and landing, we’ll have a very sophisticated 

observation package. Understanding what goes on during EDL is 

absolutely critical and almost impossible to simulate either on a 

computer or in an analog experiment on Earth, so this is very important data, and as Dr. Green mentioned in answer to the question of, you know, bringing rocks back before people back, it’s a 

very sensible thing to do. Obviously there’s no commitment to do 

that but there will be a tempting target to learn from when those 

samples come back. 

Mr. PERLMUTTER. Dr. Elkins-Tanton, where the heck is Psyche, 

I mean other than up here or wherever it might be? 

Dr. ELKINS-TANTON. Psyche is in the outer main asteroid belt between Mars and Jupiter. It’s about three times farther from the 

sun than the Earth is. 

Mr. PERLMUTTER. Okay. Dr. Pappalardo, my question to you, you 

know, often I talk about Star Trek or Star Wars or Men in Black 

but what you’re doing reminds me of 2001: A Space Odyssey and, 

you know, our mission at that point to get to Jupiter. So explain 

to me in this investigation, study of Europa, what are the—I mean, 

what do you really—what do you see already and what do you expect to see from this mission? 

Dr. PAPPALARDO. Let me preface by saying I’m a big Trekkie. 

And our Europa science team of about 130 people we have as our 

mascot, our totem, a giant monolith that we tote around our meetings. 

So we have tantalizing hints from the Galileo mission about 

what Europa is like. At high resolution we have precious little 

data. We have one six-meter-per-pixel image. We have ten-meterper-pixel images that you can count on your hands and toes to get 

an idea of what Europa is like, and so this creates this picture of 

what we think it’s like, an ice shell probably about 20 kilometers 

thick above a saltwater ocean and then the rocky mantle below. 

But, you know, right now it’s kind of a uniform picture whereas 

any world you explore in more detail and then you find out how 

it varies from place to place. We’ve seen this happen with our understanding of Mars where we first thought it was a cratered ball 

because we saw the cratered part of it and then we started understanding more and more, and now it’s at the outcrop scale we see 

differences. So we’re going to understand how Europa works as a 

world. We’re kind of in our level of understanding that we were before plate tectonics on Earth where we don’t really get how all the 

little pieces we see at the global scale fit together and we’re going 

to find more little pieces as we explore with Europa Clipper. 

Mr. PERLMUTTER. Thank you—— 

Dr. MCKINNON. If I could—— 

Mr. PERLMUTTER. —Mr. Chair, and I yield back. 

Dr. MCKINNON. I’ll just pipe in just for a second. 
64 

Mr. PERLMUTTER. Oh, I’m sorry. 

Dr. MCKINNON. We’re—you know, we have tantalizing evidence 

from the Hubble space telescope that Europa’s venting material 

into space, and we hope when we get there we’ll be able to confirm 

that and literally fly through it and sample it and analyze it. 

Mr. PERLMUTTER. Thank you, Doctor. 

Chairman BABIN. Thank you. Good questions and great answers. 

I now recognize the gentleman from Oklahoma, Mr. Lucas. 

Mr. LUCAS. Thank you, Mr. Chairman, and I share my colleagues’ enthusiasm up here and clearly the enthusiasm of the 

panel. 

Let’s visit mechanically for a moment, Dr. Farley, about the nature of the rover programs. A lot of citizens back home are very 

sensitive about how we spend their money. Could you take me 

through a discussion about Mars Rover 2020, the advances and the 

technology and the science gathering used in that compared, say, 

to Curiosity as I explain to my constituents back home why it’s important we do this? 

Dr. FARLEY. Okay. Well, in reference to Curiosity, the reason this 

mission can be done in a cost-constrained way is to take advantage 

of the platform that the Mars Science Laboratory developed. It 

should not be underestimated how difficult any new undertaking in 

space is. So we start off with that, and this allows us to actually 

focus on the stuff that is new, and there are new science instruments that will make new kinds of observations, and I think 

those—they will be directed towards characterizing samples that 

will form the basis of a discussion as to whether those samples 

should be brought back, and if those samples are brought back, I 

think they will revolutionize our understanding of many different 

things. 

If you look at the history of our understanding of many aspects 

of the solar system, it was completely changed by the return of the 

lunar samples, and that of course is an abiological world. My expectation is, if samples come back from Mars, this will be a revolution 

that goes way beyond sort of planetary science and geology. It will 

actually extend into asking and looking at samples for the first 

time to address questions about what life not as we know might 

look like, and I’ll just put it out there as a profound question for 

which we don’t have an answer, how does one look for life as we 

don’t know it? And we may have samples in our collection in 20- 

some years where we will need to answer that question. I think the 

public will be fascinated by that question. 

Mr. LUCAS. Dr. Pappalardo, discussing the plumes just a moment 

ago, tell us mechanically about what it will be involved in being 

able to use the Clipper in a way to verify their existence, whether 

it’s navigating the flybys or the sensors on board. Expand for just 

a moment on that if you would. 

Dr. PAPPALARDO. Well, first, there’re continuing observation with 

the Hubble Space Telescope so we hope, expect to have new data 

before we arrive so we can understand if they’re real, if they’re 

periodic in some way. But say we don’t or say they’re sporadic and 

we need to understand them better. We would use the time—we 

have a big looping first orbit. We would use that time to monitor 

and try to understand whether there is evidence of plumes, both 
65 

from imaging and from ultraviolet observations where we could see 

the glow from such plumes. And then during the mission, we’re 

planning on monitoring the whole time when we’re a little farther 

from Europa to look for plumes. And then if there are plumes, then 

we will certainly want to target them. Whether it be in the primary 

mission or the extended mission, we’ll figure that out, but we’ll 

want to fly through as low as possible, meaning about 25 kilometers, 16 miles off the deck if we can, depending on the location, 

depending on whether we can or not, and for that matter, how 

much particulates because you can damage—you can risk the 

spacecraft, and by flying through, we’d be able to sample that stuff 

directly and get a direct sampling of what’s in the interior of Europa. We don’t know for sure. Assuming the plumes are real, we 

don’t know for sure if they’re coming from the ocean or from lakes 

within the ice shell, and we would analyze the gas and the dust 

that’s coming off to say a lot about what the interior composition 

of Europa is like. 

This is analogous to what Cassini has done at Enceladus at Saturn, which does have plumes that spew into space. 

Mr. LUCAS. So an incredible amount of prep, an incredible 

amount of skill in maneuvering the mission, and just a little bit of 

luck would be a good thing too. 

Dr. PAPPALARDO. And we have a group of scientists. We’re thinking that through as we meet and discuss the possibilities and working with the engineers to do so. 

Mr. LUCAS. Absolutely. Thank you, Doctor. 

Yield back, Mr. Chairman. 

Chairman BABIN. Thank you. 

I now recognize the gentleman from Virginia, Mr. Beyer. 

Mr. BEYER. Dr. Babin, thank you very much, and thanks to all 

of you for being here. 

Dr. Farley, a relative softball question, but in your testimony, 

you say that past life Mars 2020 seek evidence of past life in a fossil-like Earth-like environment that existed in the first billion 

years after the dawn of the solar system—some of the most profound scientific questions of our time. Why are they profound? 

Dr. FARLEY. Well, the two questions that I was alluding to there 

are the, is there life beyond Earth, and I will just make the general 

observation from my interaction in the science community, the discovery of thousands of extrasolar planets has converted this question from something where most scientists that I knew would say 

it doesn’t seem that likely to wow, it seems really unlikely that we 

are alone. The only way I think you could really put some scientific 

evidence to that is, if you look in a habitable place, is it inhabited? 

There may be lots and lots of habitable places out there, and that 

goes to the question of the spark that makes life happen, and so 

that I think is a really profound question that we will go after. Is 

life out there? Was it out there? And what is necessary—what are 

the environments like where life might evolve, and those are really 

profound questions. 

Mr. BEYER. Thank you very much. 

Moving from life to metal, Dr. Elkins-Tanton, a couple of quick 

questions. How do we know that it’s metal? Is it a spectrometer or 

whatever? How do you know it’s the only one in the solar system? 
66 

Why did you name it Psyche? And do you really think it used to 

be a planet and the rock and the like was stripped off of it, that 

it was like Earth or Mars or Venus? 

Dr. ELKINS-TANTON. Right. Okay. Let’s see if I can remember 

this and get it all in your time. So the first question is how do we 

know it’s metal. We’ve never seen Psyche visually as more than a 

dot of light but we get radar returns from Arecibo, which seems to 

me to be also just a technological miracle. We can actually send 

radar from Arecibo, get the returns, see that the radar has 

interacted with the material of Psyche in a way that it only interacts with metal, so that’s a really key one. We can also see its reflected spectra consistent with metal and its density consistent 

with metal but the radar returns are the key. So we’re pretty certain it’s metal. There are other smaller metal asteroids like Cleopatra, which is shaped like a dog bone. If you haven’t seen it, you 

should google it. It’s a great one. But they’re all much smaller. 

They seem to be the shrapnel of leftover from planetary collisions. 

All the really heavy, rocky, metallic material is either in the inner 

solar system or in the asteroid belt or hidden inside ices and gases 

in the outer solar system. So we’re pretty sure that what we see 

in the asteroid belt is it for metal and Psyche’s the only big round 

one. 

Now, Psyche was discovered in, I believe, 1852 maybe—I might 

have the date wrong—by an astronomer in Naples, and he named 

it Psyche. It was the 16th body found in the asteroid belt by a 

group of astronomers called the Celestial Police who were trying to 

set right to the solar system and find the planet that was there, 

and they didn’t, and they were naming them all after gods and goddesses, and so Psyche’s number came and there it is, Psyche. 

There was one more question. What was it? 

Mr. BEYER. Did it used to be a planet? 

Dr. ELKINS-TANTON. Oh, we’re pretty sure it was but, you know, 

true to my scientific training, everywhere I’ve been in the world 

and given talks on Psyche, I’ve asked scientists what else could it 

possibly be. If it’s not the core of a planet, how do we make this? 

And our best other guess is that it could be material that had all 

the oxygen stripped off it by heat very close to the young sun. 

Theoretically, people think that kind of material could exist but 

we’ve never found an example of it, and so if it’s not a core, that 

would actually be more exciting. It would be something we’ve never 

seen before. 

Mr. BEYER. Exciting either way. 

Dr. ELKINS-TANTON. Thank you. I think so. 

Mr. BEYER. And I want to point out that Jules Verne did think 

we could do a journey to the center of that Earth. 

Dr. ELKINS-TANTON. I visited that Icelandic volcano. It didn’t 

work for me. 

Mr. BEYER. Dr. Green, you talked about looking for evidence of 

organic materials on Ceres and that Bennu—I hope I pronounced 

it right—is believed to contain water and organic compounds such 

as amino acids. Have we gone beyond amino acids to proteins to 

nucleic acids? Are we going to leap to DNA and RNA? 

Dr. GREEN. Well, of course, we would call that an ever-increasing 

knowledge about potentially the right stuff that life either is made 
67 

of or produces as a byproduct. That’s all part of what would be a 

ladder of life but the only way we can definitively determine what’s 

really at Bennu is to bring samples back, and that indeed is 

planned. When we get into orbit around Bennu, as we start getting 

August of next year, we’ll be studying it for about 500 or so days 

picking the right location, going down, sucking up material, perhaps as much as a kilogram, and then bringing that material back, 

and that’s when we’ll do the detailed look at what’s in it. It’d be 

great to find more complex amino acids and other organics. 

Chairman BABIN. Thank you, Mr. Beyer. 

I now recognize the gentleman from Florida, Dr. Dunn. 

Mr. DUNN. Thank you very much, Mr. Chairman. I think the 

Space Subcommittee always seems to be most inherently optimistic 

committee of the House, and you know, the can-do attitude of our 

panelists is absolutely infectious. I can only hope that you’ll expose 

yourselves to the Senate sometime soon. 

I want to frame my questions to the panel with this thought. The 

proof of life that is truly extraterrestrial life is an event that is on 

the level with the first Moon landing, so long after posterity’s forgotten all of the proceedings of this Committee and relegated the 

history of our planetary explorations to the dusty bookshelves, everyone will remember the event that proved extraterrestrial life. 

So with that thought, Dr. Farley, let’s say everything works out 

perfectly on the Mars 2020 lander. You obtain appropriate terrestrial samples. What would you consider to be the elements of a biosignature, you know, a biotic chemistry, if you will? 

Dr. FARLEY. So I’ll give two different answers to that. One is, 

what can we detect with the rover and what could we defect if we 

bring samples back, and with the rover, we have the capability to 

make a map at the scale of about a postage stamp of the distribution of organic matter. That’s one of our key observational capabilities, to take a rock and make a map of organic matter, and on that 

same postage stamp-size piece of material, we can also map the 

elemental composition. And when one looks at ancient terrestrial 

rocks, this co-registration of organic matter and elemental composition is the key to identifying on a planet where you already know 

there’s life to identify the most ancient life on Earth. So we will 

make those kinds of observations, but just like with the terrestrial 

case, those kinds of observation are seldom definitive. They’re the 

kind of thing people argue about for decades, and if we bring samples back, they’re a far greater diversity of observations we can 

make. Dr. Green was talking about different—making observations 

of the ladder of life, looking for more and more complex organic 

molecules whose composition is only reasonably associated with life 

as opposed to abiological processes. 

Mr. DUNN. I guess I kind of thought the problem with bringing 

it back is everybody always wonders about contamination, you 

know, did you sterilize the ship so thoroughly on the way out and 

the way back that you can be certain that this came from Mars. 

So if you do a test as they did on the Viking, they are in in situ 

on Mars, and if you could design a better test, a better chemical 

test, what would that be and would it involve, as you and I spoke 

before the meeting, stereoisomers and—— 
68 

Dr. FARLEY. So one of the complications of looking for ancient life 

is that there will be degradation of organic molecules. 

Mr. DUNN. You’re looking for ancient life. I’m looking for life 

today. 

Dr. FARLEY. Right. We have no capability on the rover to look for 

extant life at the microbial scale. We can’t tell the difference between live and dead, but if those samples came back, as I mentioned before, I think there will be a lot of interest in actually developing technologies, and they would include things like 

stereochemistry and that sort of thing. 

Mr. DUNN. So would you elaborate? Because I’m not sure everybody on the Committee is thinking about stereochemistry. What’s 

the significance of discovering an ongoing biochemical or chemical 

process, a biotic process that has, you know, solely left- or righthanded metabolite? 

Dr. FARLEY. Sure. So one of the key ways that one identifies molecules that are involved in life is that all life has a preference for 

a particular handedness of one of the organic molecules. There’s 

two different confirmations that these organic molecules could be 

in and most abiological processes produce them in equal abundance 

whereas life because it has a machinery involved, very specific machinery, tends to produce a specific chirality, a specific confirmation 

of these organic molecules. So this is really a critical observation 

for establishing that life is involved. There are very, very few abiological processes that would produce stereochemically specific molecules. 

Mr. DUNN. So production of a stereospecific metabolite would be 

a pretty strong presumptive proof of life, extant life, on Mars if you 

ran it the way the Vikings rover ran that? What the Viking rover 

did is run that test without stereoisomers. 

Dr. FARLEY. Right. 

Mr. DUNN. So if you ran the same test and checked for 

stereoisomers by having left- or right-handed substrates—— 

Dr. FARLEY. Yes, that would be a very important test, and I’m 

aware that there are instruments under development for actually 

making those kind of measurements in space. 

Mr. DUNN. I agree there are. I’m out of time. I would say that 

that’s about a 2-kilogram package. I look forward to talking to you 

outside of the Committee structure, and I yield back. 

Chairman BABIN. Thank you. You remember a lot from your 

training, Dr. Dunn. 

Let’s see. Another gentleman from Florida, Mr. Posey. 

Mr. POSEY. Thank you, Mr. Chairman. 

Dr. Green, traditionally, planetary exploration was a public sector endeavor that taxpayers took care of. Today the U.S. private 

sector companies are beginning to invest and develop planetary exploration programs. What is NASA doing to facilitate and encourage private sector investment and participation in planetary exploration? 

Dr. GREEN. I believe there’s a whole range of things that we’ve 

been involved in. If you take an example of the concept of going to 

asteroids and being able to extract certain metals and other compounds of interest, the first thing that they’re going to need to 

know is, where are they, what is their characteristics, how to get 
69 

to them, and indeed, we are doing an extensive finding project 

where we’ll find our small bodies, we’ll catalog and characterize 

them, and all that information will be critical, and we’ve discussed 

that openly in many different meetings working with that sector. 

Another sector is a series of commercial opportunities going to 

the moon. Now, this could be a really important element for scientists to be able to work with the commercial entities and be able 

to obtain rides to be able to bring back material or examine certain 

regions on the moon that are extremely important. The moon is 

still quite valuable in terms of being able to provide us an enormous amount of science that be done. It’s been a witness plate of 

over 4 billion years of impacts and can tell us a lot about what’s 

happened to our environment and what’s happened to the Earth. 

So those partnerships are beginning. There are some that are done 

through a Space Act agreement and others are done through collaborations and discussions at a variety of venues. 

Mr. POSEY. Thank you very much. That’s a good answer. 

Given the important role of robotic planetary missions in advancing human exploration capabilities, how can the current and future 

planetary missions be integrated into the human exploration roadmap, which we’ve asked NASA to produce? 

Dr. GREEN. Well, of course, from my perspective, planetary scientists are really the guides. You know, they’re really the ones that 

go out first. Human exploration is not Star Trek. It’s not ‘‘go where 

no human has gone before.’’ In our program, and NASA is really 

all about sending humans to locations beyond low-Earth orbit out 

into the solar system, be able to live, work, but also return, and 

all those require not only where you’re going but the characteristics 

so how to get there, what are the kind of science and other activities one can do on station, and then of course the challenges of 

entry, descent and landing for any of the bodies they choose to go 

to. 

We pioneer a lot of that, you know, in terms of being able to look 

at those environments, collect that information, but also pioneer 

some of the initial technologies that allow us to get our rovers and 

other machinery at various locations, whether it’s the moon or 

Mars. 

Mr. POSEY. Can you describe the infrastructure that missions 

will be putting in place around Mars and Europa to support future 

missions? For example, will NASA be able to use the Europa Clipper to support future Europa missions, namely the lander? 

Dr. GREEN. Yeah, actually as Lindy mentioned earlier, in planetary science, we really have a very important paradigm that we 

follow. It’s flyby, orbit, land, rove, but also return those samples. 

And indeed, the Europa Clipper gives us that opportunity to do a 

detailed examination of Europa that provides high-resolution imaging that gets us right to where we want to go that makes the next 

mission, which would be notionally a lander, to be able to land 

safely and perform the science that we wanted to do. So indeed, 

each of these missions are very much related and depend on the 

success of the previous mission. 

Mr. POSEY. Thank you very much. I yield back, Mr. Chairman. 

Chairman BABIN. Yes, sir. Thank you, Mr. Posey. 

And another gentleman from Florida, Mr. Webster. 
70 

Mr. WEBSTER. Thank you, Mr. Chairman. 

Dr. Green, is there any interest in going to the outer planets to 

do the same level of investigation and so forth, or is that just too 

expensive and too far? 

Dr. GREEN. Well, indeed, when one looks at the science that’s 

been delineated by the community and the National Academies’ 

Planetary Decadal, we have an extensive desire to be able to go out 

to the outer reaches of our solar system where our planets like 

Neptune and Uranus reside. Neptune and Uranus, although they 

are big what look like giant planets like Saturn and Jupiter, they 

actually are very different in many ways. They have a whole series 

of different compositions associated with them. We call them the 

ice giants. You know, they’re not completely hydrogen and helium. 

They have ammonias and a whole series of other elements that 

they have obtained in that accretion process that we know very little about and so being able to go out to Uranus and Neptune are 

extremely important. 

We just completed a major study and have worked with the scientific community to determine what are the characteristics of the 

measurements we want to make in those regions but also how do 

we be able—how are we able to get out there perhaps in the second 

half of the next decade and really get into orbit and analyze that 

environment. 

Mr. WEBSTER. Is that desire which you spoke of funded? 

Dr. GREEN. Right now that’s only at the study level. The Planetary Decadal is quite clear that the top things that we should be 

doing we are doing but, you know, you have to prepare, you have 

to spend some time on your future or you don’t have that future, 

and so while we do this planning, while we do this mission concepts and studies, those are indeed laying the groundwork for our 

future work. 

Mr. WEBSTER. Is Voyager still broadcasting? 

Dr. GREEN. Yes. Both Voyagers are still broadcasting. Now, 

they’re very far away. They’re more than 120 astronomical units 

away where one astronomical unit is the distance between the Sun 

and the Earth, so they’re very far out there, and therefore—and 

they have little power left although it’s a radioisotope power. It’s 

a long-lasting power system. They’re sending back a handful of bits 

whenever we can turn our big telescopes and bring that data back 

but they’re doing a marvelous job, really exploring that outer 

reaches of the heliosphere we call it. 

Mr. WEBSTER. What’s their wattage? 

Dr. GREEN. I would only guess but I would believe it’s on the 

order of tens of watts. That’s all that’s left. 

Mr. WEBSTER. And then what would be the final date that it 

won’t be able to broadcast anymore? You’re saying it’s diminishing 

now, right? Is that what you said? 

Dr. GREEN. Yeah, it uses—utilizes radioisotope, plutonium 238, 

which decays over time, and how that works is, you bring a mass 

of plutonium together, it’s radioactive. You shield that and that radioactive capability where the nucleus of the atom blows apart 

heats and that heats a sleeve that’s around this material and then 

that heat through a thermal couple is used to charge a battery and 

then you run your experiments off of it. And so over time as the 
71 

radioisotope decays, then there’s little heat involved, and now you 

have major power management activities that you have to do, 

which they’re doing to really keep the spacecraft going because not 

only is it providing power but it’s also providing warmth for the instruments and the spacecraft subsystems. 

I can’t give you, although I’ll take for the record and get back to 

you on exactly what our prediction is when it will really have not 

enough power to sustain itself or it’ll be at a distance far enough 

away that we will not be able to track it. 

Mr. WEBSTER. Thank you very much. Yield back. 

Dr. MCKINNON. If I could add just one thing to do that, that the 

New Horizons spacecraft, which passed by Pluto and is on its way 

to another body in about a year and a half, will also leave the solar 

system and it’s also powered by a similar radioisotope heating system and we anticipate that we’ll be able to contact and operate the 

spacecraft into the 2030s. 

Chairman BABIN. Thank you for those fascinating questions. 

I want to ask one more question. Why do we think that Mars lost 

its atmosphere billions of years ago? And Mars is farther away 

from the sun than Earth, and I’m just going to—Dr. Farley, would 

you take a stab at that? 

Dr. FARLEY. There may be others here that know more than I do 

about this but this is one of the central purposes of the Maven mission, to try to understand why the atmosphere was apparently lost, 

and one of the leading candidates is that the planet uses hydrogen, 

and—to space, and that causes—that hydrogen is produced by the 

breakdown of water, and so you break up the water molecule and 

the hydrogen escapes. You cannot re-form the water molecule so 

that’s a way to desiccate it by interaction with the solar wind, and 

one of the jet reasons for that is that Mars apparently lost its magnetic field very early in its history whereas Earth did not so the 

magnetic field protects the Earth from the radiation from the sun 

that causes this to happen. 

Chairman BABIN. Thank you. Anybody else? 

Dr. ELKINS-TANTON. Yeah, I’d like to add to that. I’ve worked on 

that directly. And so this is part of our interest in Psyche as a core 

is to understand the magnetic field, but to add to what Ken has 

said, it’s also possible—another hypothesis is that when Mars was 

very young and still hot, its atmosphere would have been inflated 

through heat to be further away and less well bound to the body 

itself, and the more active young sun could actually have stripped 

it at that time. And so we don’t know exactly when it was stripped 

or the processes, and that’s another thing we’d like to learn to find 

out how applicable it is to the Earth. 

Chairman BABIN. Great. Those are fascinating answers. Thank 

you so much. I think I’m the only member left here. 

But I want to say how much I appreciate all of you fascinating 

and well-educated scientists for being here, and we appreciable 

your valuable testimony. And also, the record will remain open for 

two weeks for additional comments if any Members would like to 

submit those. 

So with that, this hearing is adjourned. Thank you. 

[Whereupon, at 11:44 a.m., the Subcommittee was adjourned.] 

(73) 

Appendix I 

ANSWERS TO POST-HEARING QUESTIONS
74 

ANSWERS TO POST-HEARING QUESTIONS

Responses by Dr. Jim Green 
75 
76 
77 
78 

Responses by Dr. Kenneth Farley 
79 

Responses by Dr. Robert Pappalardo 
80 

Responses by Dr. Linda T. Elkins-Tanton 
81 
82 
(83) 

Appendix II 

ADDITIONAL MATERIAL FOR THE RECORD
84 

NASA’S SUBMITTED RESPONSES TO QUESTIONS ASKED DURING THE HEARING

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