1

National Aeronautics and Space Administration

www.nasa.gov

Produced by the NASA 

Astrobiology Program to 

commemorate 50 years of 

Exobiology and Astrobiology 

at NASA.

#2

Issue

3rd EDITION
Astrobiology

A History of Exobiology and Astrobiology at NASA

This is the story of life in the Universe—or at least the story as we know it so far. As 

scientists, we strive to understand the environment in which we live and how life relates to this environment. As astrobiologists, we study an environment that includes 

not just the Earth, but the entire Universe in which we live.

The year 2010 marked 50 years of Exobiology and Astrobiology research at the 

National Aeronautics and Space Administration (NASA). To celebrate, the Astrobiology Program commissioned this graphic history. It tells the story of some of the 

most important people and events that have shaped the science of Exobiology and 

Astrobiology. At only 50 years old, this feld is relatively young. However, as you will 

see, the questions that astrobiologists are trying to answer are as old as humankind.

Concept & Story

Mary Voytek

Linda Billings

Aaron L. Gronstal

Artwork

Aaron L. Gronstal

Script

Aaron L. Gronstal and Leslie Mullen

Editor

Linda Billings

Layout

Jenny Mottar

Special thanks to Daniella Scalice and Michael Meyer

Copyright 2015, NASA Astrobiology Program

First edition printed in 2011
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Issue #2—Missions to Mars

The year 2010 marked the 50th anniversary of NASA’s Exobiology Program, established in 1960 and expanded into a broader Astrobiology Program in the 1990s. To 

commemorate the past half century of research, we are telling the story of how this 

feld developed and how the search for life elsewhere became a key component 

of NASA’s science strategy for exploring space. This issue is the second in what 

we intend to be a series of graphic history books. Though not comprehensive, the 

series has been conceived to highlight key moments and key people in the feld as 

it explains how Astrobiology came to be.

-Linda Billings, Editor
Astrobiology, the study of life’s origin, evolution, distribution, and 

future in the Universe, has always been a key part of NASA’s research. 

When the frst missions into Earth orbit and beyond were launched, 

Astrobiology was ready for the ride!

Issue 2—Missions to Mars.

NASA has explored many places in the Solar System, 

but one destination is particularly important to 

Exobiology and Astrobiology—Mars.

When the space age began, Mars was a complete mystery. 

Now we know the planet may have been more Earth-like in its 

past. Astrobiologists wonder, what was ancient Mars like? Did 

it have liquid water on its surface? Long ago, could Mars have 

supported life as we know it?

The history of missions to Mars is full of struggle and 

triumph. Mars is a dangerous and diffcult planet to visit. 

The extreme environment of the planet includes frigid 

temperatures, damaging dust storms, low gravity, and a thin 

atmosphere. Many missions to Mars have ended in failure, 

but the missions that were successful have provided 

fascinating evidence of Mars’ potential habitability.

The year 2010 marked half a century of Exobiology 

and Astrobiology research at NASA. In 2011, a new 

era of Astrobiology research in Mars exploration 

began with the launch of NASA’s most ambitious 

Mars mission to date—the Mars Science Laboratory. 

But frst... let’s take a closer look at Mars’ role in 

the early history of Exobiology and Astrobiology.

Background Image: 

Globular Cluster (1)

2 
NASA’s new Exobiology 

program (see Issue 1) 

attracted a host of 

talented scientists.

NASA forged 

ahead with the 

lunar program and 

built facilities for 

analyzing space 

material such as 

lunar samples and 

meteorites...

...but exobiologists also 

had their sights set on our 

closest planetary neighbors—

Venus and Mars.

NASA’s Mariner program had 

its frst success with Mariner 

2 in 1962. Mariner 2 provided 

our frst close-up view of Venus, 

a planet that some scientists 

believed could support life. (9) On July 14, 1965, Mariner 4 

became the frst spacecraft 

to get a close look at Mars, 

identifying geological signs 

that water may have fowed on 

the planet’s surface long ago.

(11)

(12)

Harold “Chuck” Klein (2) (First 

head of the Exobiology Division, 

NASA Ames Research Center)

Vance Oyama (6), NASA 

Ames biologist

Ranger 9 (1965)

Cyril Ponnamperuma (Arrived at NASA 

Ames in the frst class of postdoctoral 

fellows (summer 1961) (7) (8)

*NASA administrator, James Webb, 

speaking on the success of Mariner 2.”

L.P. “Pete” Zill 

(3) (third head 

of Exobiology 

at NASA Ames) 

Richard “Dick” Young (5) 

(second head of Exobiology 

at NASA Ames; frst head 

of the Exobiology Program at 

NASA Headquarters)

“When I got [to NASA Ames]... 

there were only two people in the 

Life Sciences, Dick Young and Vance 

Oyama. My intention was to stay for 

one year and then hopefully get back 

to Berkeley. But on the second day, 

Dick Young said...” (4)

“Why don’t you stay and set 

up a lab for the study of 

the origin of life?” (2)

“And that’s what we 

did immediately” (2)

“More may be added to 

man’s knowledge of the 

planet Venus than has been 

gained in all the thousands 

of years of recorded 

history.”* (10)

3
Mariner 5 (1967) turned back to Venus. Observations of 

its harsh environment by Mariners 2 and 5 helped solidify 

the idea that Mars was a better place to hunt for life.

The program’s fnal mission, Mariner 10 (1973), didn’t visit Mars, but 

it demonstrated techniques that would be used in many space missions 

to follow. Mariner 10 was the frst spacecraft to visit multiple planets, 

and the frst to use the gravitational assist of one planet (Venus) to 

build up enough speed to visit a second (Mercury).

Our vision of Mars began to evolve with Mariners 6 and 7 (1969). 

These two spacecraft mapped 20% of the martian surface and 

provided detailed images of many of the planet’s unique features.

Mariner 9 (1971) was the frst spacecraft to enter orbit around 

another planet. The mission truly unveiled Mars, mapping 80% of the 

surface. Mariner 9 returned the frst images of landmarks such as 

Valles Marineris, the vast canyon named in the spacecraft’s honor.

The Soviet Union also set its sights on Mars with the Mars 

2 (1971), Mars 3 (1971), and Mars 5 (1973) missions. Each 

suffered diffculties, but collected data about the planet’s 

surface and atmospheric conditions. (20)

(15)

(14)

(16)

(18)

(19)

(13)

(17)

4 
As early as 1959, NASA was developing instruments 

for detecting life. Mars quickly topped the list of 

places where NASA could put this technology to use.

This early focus on Mars led to a 

major milestone in the history of 

Exobiology and Astrobiology. In 

1975, NASA launched an ambitious 

planetary exploration endeavor—

the twin Viking missions. 

The Viking 1 and Viking 2 missions 

each had a lander and an orbiter 

that were sent to Mars. 

Each lander carried 14 experiments, including 

a set of investigations specifcally designed 

to search for evidence of martian life.

In 1961, NASA offcials invited British scientist James Lovelock, 

an expert in life detection technology, to work with the U.S. 

space program. He had many ideas for life detection experiments and worked on early designs for a Mars probe in 1965.

Lovelock had interesting ideas about searching for life 

based on biological reactions that cells perform, rather 

than identifying physical structures such as DNA in cells.

But Lovelock’s groundbreaking theories are a 

story for another time...

He viewed the planet Earth as a 

complete living system, and began 

to discuss these ideas with Carl 

Sagan, Dian Hitchcock and Normon 

Horowitz, then head of the Biology 

Division at NASA’s Jet Propulsion 

Laboratories (JPL). (4)

“As one whose childhood was illuminated 

by the writings of Jules Verne and Olaf 

Stapledon, I was delighted to have the 

chance of discussing at frst hand the 

plans for investigating Mars.” (4)

“We must concentrate 

on concepts that are not 

‘Earthcentric.’ We ought to 

look for entropy-reduction 

phenomena.” (8)

I think I know some 

people you should meet... 

5
Lovelock’s work with NASA helped defne Viking’s life detection experiments. 

These experiments were designed to cultivate microorganisms (should there be 

any) in martian soil samples by introducing water and measuring signs of growth. 

Horowitz’s new understanding of Mars led him 

and his colleagues to search for life and test 

Viking’s equipment in similarly inhospitable 

environments on Earth, such as the Dry Valleys 

of Antarctica and Chile’s Atacama Desert. 

Scientists such as Gil Levin and Wolf Vishniac 

began to test their Viking life detection 

experiments on soils from the Antarctic Dry 

Valleys. Vishniac detected microbial life in 

soils that Horowitz and his colleagues thought 

were sterile, making the questions about life’s 

potential on Mars even more complicated.

So before Viking even launched, 

the mission spurred research 

about life on Earth. Scientists 

worked hard to develop a basic 

defnition of “life” so that they 

knew what to look for on Mars. (4)

“CO2 was [the major] component [in Mars’ atmosphere], 

with only a trace of water vapor. That discovery gave me 

and my collaborators, George Hobby and Jerry Hubbard, 

the impetus to design an instrument that would search 

for life on a dry planet. That instrument was the 

pyrolytic release experiment.” (4)

6 
In December 1969, NASA selected 

experiments. They included Horowitz’s 

pyrolytic release experiment, Levin’s 

labeled release experiment, Vishniac’s 

‘Wolf Trap’ (later removed) and Oyama’s 

gas exchange experiment.

The life detection experiments were ftted into a single package 

for the landers, which also carried miniaturized GC/MSs* to 

separate and identify organic compounds by molecular weight.

Even if the biology experiments 

showed negative results, the GC/

MS could fnd organic molecules that 

proved cells might be in the samples.

...It is certainly true that no 

terrestrial species could survive under 

average martian conditions as we know 

them, except in a dormant state, but if 

we admit the possibility that Mars once 

had a more favorable climate which was 

gradually transformed to the severe 

one we fnd there today...

“The fact is that nothing we have learned 

about Mars—in contrast to Venus—

excludes it as a possible abode of life...

“I consider [the GC/MS] the most 

important instrument on Viking.” (4)

...and if we accept the possibility that life arose 

on the planet during this earlier epoch, then we 

cannot exclude the possibility that martian life 

succeeded in adapting itself to the changing 

conditions and survives there still.” (21)

“It is not optimism about the 

outcome that gives impetus to 

the search for extraterrestrial 

life. Rather, it is the immense 

importance that a positive 

result would have.” (21)

Furthermore, we hoped 

that the details of their 

structures would indicate 

which of many possible biotic 

and abiotic syntheses are 

occurring on Mars.” (4)

“[Identifying organic compounds] seemed 

important...” because we hoped that the nature 

of Martian organic molecules would provide a 

sensitive indicator of the chemical and physical 

environment in which they formed.

*Gas Chromatograph/ 

 Mass Spectrometers

7
Cameras on the lander revealed a surface far 

different—and far more familiar—than that of 

the Moon. On July 28, the lander’s mechanical 

arm scooped samples into the instruments.

To prevent contamination of Mars, the Viking 

Landers were assembled in a special clean room, 

baked in dry heat to kill any microorganisms, 

and kept in isolation until landing on Mars.

The world watched as results began to 

pour in from the Viking experiments.

Thomas Mutch, head 

of the Viking surface 

photography team. Gerald Soffen, Viking 

Project Manager

All of the biology experiments showed evidence of activity in the 

samples after the very frst test. The pyrolytic release experiment 

gave one reading consistent with photosynthesis occurring, but the 

initial result couldn’t be repeated. The gas release experiment showed 

oxygen released from the Mars soil—but many scientists thought the 

results looked more like a chemical reaction than a biological reaction.

On September 3rd, Viking 2 landed halfway 

around the planet on the plain of Utopia.

On July 20, 1976—seven 

years after the Apollo 11 

lunar landing—the Viking 

1 lander touched down on 

the fat, martian plain of 

Chryse Planitia.

“A new reality was created. Mars became a place. It went from a word, an 

abstract thought, to a real place.” (4)

“This is just an 

incredible scene...” (22) 

(23)

8 
The labeled release experiment showed the strongest 

results, detecting CO2 that might have been released by 

the metabolism of microorganisms. The GC/MS experiment, 

however, indicated that no organics were present on Mars.

The scientists had to work quickly. The world was watching the scientifc 

process in action, and the press and public were hungry for information. The 

researchers found themselves working under constant pressure and scrutiny.

The results were unexpected... 

and confusing.

More scientists began to examine the results, 

and with each new test more questions were 

raised. Some results could be interpreted as 

“chemical”... and some as “biological.” 

Some scientists argued that chemistry could explain 

the results of the Viking experiments, while others 

believed there was a chance for life on Mars. 

By 1979, many scientists concluded that a chemical explanation for the results was the most likely. (24) The debate 

would continue, however, as new missions returned more 

detailed information about the environment of Mars.

“That’s the ball game. No organics 

on Mars, no life on Mars.” (4)

“Having to work in a fshbowl like 

this is an experience that none of 

us is used to.” (4)

“Some people thought life was more 

likely than other people thought, but I 

think what bound us together was the 

importance of the question, including the 

importance of negative answers.” (4)

(25)

9
“[Exobiology] was tied 

to the planetary missions. 

It hung on the Viking 

program.” (4)

After all the time and effort spent on Viking, 

and with many questions left unanswered, 

where was Astrobiology headed?

 However, Phobos 2 

fell silent...

...just before sending 

landers toward the moon.

Viking didn’t fnd unambiguous signs 

of life on Mars, but it made people 

wonder if we had devised the right 

tests. Astrobiologists today are still 

trying to answer this question...

In 1988, the Soviet Union (and 

international partners) launched 

Phobos 1 and 2. Only Phobos 2 

made it, and gathered data 

about Mars’ moon Phobos. 

By the mid-1990s, political changes saw 

the dissolution of the Soviet Union, 

but Russia forged ahead with the Mars 

96 orbiter and lander mission.

Unfortunately, the launch 

was unsuccessful and Mars 

96 burned up on re-entry 

into the Earth’s atmosphere.

In 1992, NASA launched the Mars Observer, 

but the spacecraft lost contact with Earth 

before entering Mars orbit.

After Phobos 2, Mars seemd 

to shroud itself in mystery.

Both the Soviet Union and 

the United States struggled 

with their missions. 

10 
On November 7, 1996, NASA 

launched the Mars Global Surveyor 

(MGS). Some of the instruments that 

MGS carried were originally designed 

for the failed Mars Observer.

MGS was a success! 

The mission returned data that covered the entire 

martian surface and helped astrobiologists learn 

more about the role of water and dust on Mars

The MGS camera recorded weather patterns 

and discovered gullies and debris fows, 

suggesting that liquid water sources were 

once present at or near the surface of Mars.

For instance, MGS images from 2004 and 2005 were 

used to identify the formation of new gully deposits in 

the Centauri Montes region. These deposits look like 

they could have been made by running water... meaning 

liquid water might still fow on Mars today. (27)

Viking proved that we didn’t yet 

know enough about life on Earth 

to search for signs of life on 

another planet. Instead, scientists 

decided to study the environment 

of Mars, both past and present, to 

determine if the planet was ever 

habitable for life as we know it.

A key requirement for life on 

Earth is liquid water—so the 

search for life in the Solar System 

focused on searching for environments where liquid water is 

(or was) present. 

(26)

In 1997, NASA 

launched Pathfnder. 

Unlike Viking, this 

mission did not 

carry instruments 

to search for life.

Pathfnder did, however, demonstrate that a low-cost 

mission to Mars was possible. Pathfnder tested important 

technologies for future visits to the red planet, including...

11
The mission focused on geology, 

but many of the lessons learned 

were valuable to astrobiologists

Matthew Golombek, Pathfnder project 

scientist: “The Pathfnder science results 

hinted at a warmer and wetter past for 

Mars.” (28)

This fnding was evidence that Mars was 

once warm enough for liquid water to 

exist—maybe even for long periods of time. 

Even if Mars has no life today, maybe the 

planet could have supported life in its past...

Among other things, the Pathfnder rover discovered 

round pebbles that looked as if they had been shaped 

by running water on the surface long ago. 

...airbag-assisted 

landing.

The Nozomi spacecraft was designed to capture images of Mars’ 

surface and to study the martian atmosphere and its interaction 

with the solar wind. Nozomi failed to enter orbit around Mars, 

but kept orbiting the Sun so that it could try again in 2003.

However, when Nozomi approached the Earth for 

a gravity assist in April of 2002, the spacecraft 

was damaged by powerful solar fares. In December 2003, the mission was abandoned, and Nozomi 

changed course to avoid a collision with Mars.

On July 3, 1998, Japan 

became the next country 

to attempt a visit to Mars. 

Golombek: “In cases like Pathfnder, 

taking a little risk can result in an 

enormous payoff.” (28)

12 
NASA’s next visits to Mars also faced diffculties after launch. First was the Mars Climate 

Orbiter, which was designed to search for 

evidence of past climate change on Mars. 

When the spacecraft reached Mars, it 

entered an orbit too close to the planet 

and atmospheric stresses tore it apart.

A success fnally came on October 24, 2001, 

with NASA’s 2001 Mars Odyssey mission. 

It’s now the longest-lived mission to study 

a planet other than Earth from orbit. 

Odyssey’s maps of hydrogen in particular helped 

scientists discover vast amounts of water ice 

just beneath the surface at Mars’ poles.

Odyssey has mapped the 

chemical elements and 

minerals that make up the 

martian surface, providing 

essential information about 

the martian environment and 

the potential for past or 

present life on the planet. 

Odyssey has also recorded 

radiation levels on Mars in order 

to determine the potential risks 

to future human explorers.

Today, Odyssey is still mapping martian minerals 

and is now part of a communications relay that 

allows scientists to ‘talk’ with other Mars 

missions. Odyssey is sure to play an important 

role in the future exploration of Mars.

Next, the Mars Polar Lander tried to 

land in the southern Planum Australe

region, near the carbon dioxide ice 

cap at the martian south pole. 

The lander was going to 

analyze polar deposits 

and soil samples for the 

presence of water ice.

NASA lost contact with the spacecraft as it 

began its treacherous descent toward Mars.

(29)

(30)

(31)

13
On June 2, 2003, the European 

Space Agency (ESA) launched the 

Mars Express mission, adding to 

the international community of 

robotic explorers at Mars.

Mars Express was a huge success and continues to return 

valuable data. (34) The orbiter has captured images of 

craters, volcanoes and other features in high resolution.

Mars Express has also identifed mysterious 

evidence of methane gas in the atmosphere 

of Mars. Some scientists believe that this 

methane may be produced by living organisms 

beneath the martian surface.

Unfortunately, the Beagle 2 lander was 

lost during its descent toward Mars. Mission scientists 

scoured images taken 

by orbiters for any 

sign of Beagle 2...

...but eventually Beagle 2 was declared lost.

Rudi Schmidt, Mars Express Project 

Manager: “Mars Express is the frst 

fully European mission to any planet. 

It is an exciting challenge for 

European technology.” (32)

Colin Pillinger, Beagle 2 

Chief Scientist. 

Mark Sims, Beagle 2 

Mission Manager 

Mars Express was designed to 

re-launch some instruments that 

were lost on the Russian Mars 96 

mission. (33) One of its primary 

goals was to determine what 

happened to the water that once 

fowed on the planet’s surface.

The mission also carried the 

Beagle 2 lander, which was the 

frst mission since Viking designed 

specifcally to look for evidence of 

past or present life.

“The Beagle 2 project was based 

on martian meteorite studies. I 

think the real thing that is driving us back to wanting to look at 

whether there is life on Mars...

... is something that Viking did 

that nobody anticipated, nobody 

planned. It was that they were 

able to show that we have martian meteorites on Earth.” (33)

(35)

(36)

14 
In 2003, NASA launched another tremendously 

successful mission to Mars—the twin Mars Exploration 

Rovers. Since landing on Mars in January of 2004, the 

Mars Exploration Rovers Spirit and Opportunity have 

had many adventures...

Spirit landed three weeks before 

Opportunity on a broad plain in Mars’ 

Gusev crater. Spirit discovered that 

most of Gusev’s geology is volcanic in 

origin, although the rover did eventually 

fnd some evidence of past liquid water. 

Opportunity’s frst image from 

Mars was of the crater’s 

wall, a cross-section punched 

through the martian surface 

eons ago by a meteorite. This 

outcropping allowed the rover 

to see many years of geologic 

history in one glance.

On the other side of the 

planet, Opportunity had a 

“hole in one” landing, bouncing 

across the fat Meridiani Plains 

directly into tiny Eagle crater. 

Some rocks in Eagle crater had 

odd, round balls that scientists 

nicknamed “blueberries.” Opportunity traveled many 

kilometers beyond its landing site inside Eagle crater.

It viewed wispy martian clouds, 

providing scientists with images of 

martian weather from the ground.

The rover discovered that they 

were spheres of hematite. Geologists say the hematite most likely 

formed long ago as a result of 

water-saturated soil. 

(37)

15
Both rovers became mired in fne, loose soil at different 

times. To avoid digging themselves deeper into a sand 

trap, scientists had to direct the rovers to move only 

centimeters at a time over several weeks.

Dust devils can’t lift a rover, but they did 

sweep dust from the solar panels. This helped 

keep the rovers powered and operating well 

beyond their mission lifetime of 3 months.

The MER rovers also 

encountered dust 

devils, mini tornadoes 

that sweep across 

the martian surface.

Opportunity continued to clock 

astonishing distances across 

the surface of Mars, turning up 

many unexpected discoveries...

Opportunity even dared to venture down 

the steep walls of Endeavor crater.

It was a dangerous trip, 

and many people thought 

there would be no return.

But inside the crater was a massive wall 

of exposed rock that could provide many 

clues about the ancient history of Mars’ 

climate. The mission team decided the 

risk was worth it.

Opportunity did make it safely out 

of Endeavor and now continues to 

roam. Spirit fell silent in the spring 

of 2009, but hopes are high that 

Opportunity will continue to carry 

out its extended mission.

...like fallen meteorites 

resting on the vast 

Meridiani Planum. 

The MER rovers made good use of their rock abrasion tools, or RATs, allowing scientists to see what 

lay hidden beneath Mars’ hard, exposed surfaces.

But sometimes the hazardous 

soil provided welcome surprises. 

Spirit’s wheels churned up salts 

when driving through one such 

area—the same kind of salts 

that form on Earth when hot 

springs mix with volcanic rock. 

16 
Glenn Cunningham, MGS 

manager through development and launch. 

On August 12, 2005, NASA added the Mars Reconnaissance 

Orbiter (MRO) to the network of martian missions.

Other missions found evidence 

of fowing water on ancient 

Mars, but MRO’s goal is to 

fgure out if it was around long 

enough for life to evolve. (38)

MRO was loaded with powerful instruments, 

including a shallow radar to ‘look’ under the 

surface of Mars. 

MRO’s images helped scientists choose 

routes for the MER rovers to drive, and to 

select landing sites for future missions.

Never before had so many 

robotic missions worked together 

to unlocking Mars’ mysteries

In November of 2006, NASA received the fnal signal from the Mars Global 

Surveyor—after the spacecraft’s decade of hard work (Page 11). (39)

After the fnal bow of MGS, NASA began a new mission 

based around the failed Mars Polar Lander (see page 13).

On August 4, 2007, the Phoenix 

Mars Lander launched toward the 

red planet. ESA’s Mars Express 

later helped track the mission as it 

made the dangerous journey down 

to the surface of Mars. With a successful touchdown on May 25, 

2008, Phoenix became the frst lander 

to explore Mars’ northern polar region. 

Phoenix searched for evidence of 

past or present water, as well as 

other chemical elements that may 

be necessary for life.

Phoenix set out to answer questions 

like: “Can the martian arctic support 

life?” and “What is the history of water at the Phoenix landing site?” (43)

“When we watched the launch 

10 years ago, we wondered if 

we would make the specifed 

mission length. We certainly 

were not thinking of a 10-year 

operating life.” (40)

Tom Thorpe, project 

manager for Mars Global 

Surveyor at JPL. 

“It is an extraordinary machine that has done 

things the designers never envisioned despite a 

broken wing, a failed gyro and a worn-out reaction 

wheel. The builders and operating staff can be 

proud of their legacy of scientifc discoveries and 

key support for subsequent missions.” (39)

(41)

(42)

(44)

17
Smooth, bright patches seen beneath 

the lander were thought to be ice that 

was uncovered when thruster exhaust 

blew off loose soil.

Phoenix became the frst mission to touch 

water ice layers underneath the surface 

when it started digging with its robotic arm.

Clumps of bright material that were 

spotted in the trenches disappeared 

over 4 days, implying they were water 

ice rather than carbon dioxide ice 

(which would have vaporized faster).

Phoenix also used its arm to scoop soil into its instruments. 

During the initial heating cycle of one sample, Phoenix’s 

Thermal and Evolved-Gas Analyzer (TEGA) detected 

water vapor. Phoenix also found calcium carbonate, which 

suggests the occasional presence of thawed water.

When capturing pictures of one of Phoenix’s legs, 

scientists spotted what appeared to be water 

droplets that grew over time... liquid water droplets.

This was completely unexpected. Scientists 

have theorized that liquid water cannot 

exist on the surface because of Mars’ thin 

atmosphere and frigid temperatures.

Some scientists think that the temperature of Phoenix’s leg and 

the presence of salts may have caused water vapor to condense 

from the air. (46) The question remains unanswered...

Salts could have other implications 

for water on Mars. For instance, 

in soil above ice, perchlorate salts 

could act as a sponge and might 

support habitats for life. (49)

Phoenix ceased communications in November 2008 as the martian 

winter set in. (50) No contact was made after the spring thaw. 

Orbiting spacecraft showed that Phoenix was crushed by frost 

accumulation, leaving Opportunity alone on Mars.

(45)

(48)

(47)

18 
Opportunity wasn’t alone for long. NASA was 

already preparing a new Astrobiology mission.

The Mars Science Laboratory (MSL) was the 

frst roving analytical laboratory sent to Mars.

MSL Entry, Descent, and 

Landing Instrument (MEDLI): 

suite collected engineering data 

during MSL’s high-speed entry 

into the martian atmosphere, 

providing invaluable data for 

engineers designing future 

Mars missions. MEDLI was 

mounted inside the heatshield 

that protected MSL during 

atmospheric entry.

MSL greatly outweighs 

its rover cousins 

Pathfnder, Spirit, and 

Opportunity.

Its suite of instruments is the biggest and most 

advanced scientifc package ever sent to the 

martian surface.

Sample Analysis at Mars 

(SAM): a spectrometer, 

gas chromatograph and 

tunable laser spectrometer. SAM is searching for 

a range of compounds of 

carbon, such as methane, 

that could be associated 

with life.

Mars Hand Lens Imager 

(MAHLI): takes close-up 

views of minerals, textures 

and structures in rocks, 

debris and dust.

Alpha Particle X-Ray 

Spectrometer (APXS): 

measures the chemical elements 

in rocks and soils and is funded 

by the Canadian Space Agency.

Mars Descent Imager (MARDI): took 

color video during MSL’s descent to the 

martian surface, providing an ‘astronaut’s’ 

view of the terrain for scientists deciding 

where the rover will drive and explore.

Chemistry and Mineralogy instrument (ChemMin): identifes minerals 

in rocks and soil. Minerals form under 

certain conditions and can thereby 

help scientists determine past environments on Mars.

Dynamic Albedo of 

Neutrons (DAN): a pulsing 

neutron generator that 

detects water content 

in ice and minerals, and 

searches for layers of 

water and ice up to 2 

meters below the surface 

[funded by the Russian 

Federal Space Agency].

Rover Environmental Monitoring 

Station (REMS): is a weather 

monitoring station from the 

Centro de Astrobiologia (CAB) 

and contributed by the Spanish 

government.

Chemistry & Camera (ChemCam): fres a 

laser to vaporize materials from small areas 

less than 1 millimeter. ChemCam can vaporize 

the dust from the surface and analyze the 

underlying rock. ChemCam can even analyze 

rocks from a distance.

Mast Camera (MastCam): 

takes color images and video 

of the martian surface. Radiation Assessment 

Detector (RAD): is helping 

to prepare for future human 

exploration of Mars by measuring high-energy radiation 

on the martian surface.

19
20 

In 2011, mission

components for MSL

were processed for

planetary protection

and installed on the

Curiosity rover.

With everything packed away

for launch, MSL successfully

began its journey on November 

26, 2011. (51-53).

The MSL rover 

received its 

name from a 

sixth-grade 

student in 

Kansas, named 

Clara Ma. Clara 

dubbed her, 

“Curiosity.” 

(54)

The MSL spacecraft safely 

entered its cruise phase, and 

Curiosity traveled inside for the 

eight and a half month journey.

En route, Curiosity used its RAD 

instrument to study space radiation 

between the Earth and Mars.

There were massive solar

storms in early 2012...

...and Curiosity 

measured how 

much radiation 

future explorers, both robotic 

and human... ...might endure on 

a trip to Mars.

20

Don Hassler, RAD

Principal Investigator

“RAD was designed to characterize 

radiation levels on the surface of Mars, 

but an important secondary objective 

is measuring the radiation during the 

almost nine-month journey...” (56)

“Curiosity is the 

passion that drives us 

through our everyday lives. 

We have become explorers and scientists with our 

need to ask questions and 

to wonder.” (55)”

“Curiosity is an

everlasting fame that

burns in everyone’s

mind.” (55)
21

The radiation was no real hurdle 

for Curiosity. The real challenge 

came during its arrival at Mars

With its heat shield as protection, the 

craft plowed through the atmosphere!

The rover then drifted 

down toward its target—

the enormous Gale Crater.

At an altitude of about 

1.8 km, Curiosity separated from its shell.

After 345 seconds, the rover dropped 

from the shell and a powered descent 

stage brought it closer to the surface.

At roughly 240 seconds, a 

parachute was released!

The descent stage 

took Curiosity 

into the martian 

atmosphere.

... seven minutes of terror before 

touching down on the surface!

(57)

(57)

21
22 

When Curiosity was just 20 meters above 

the ground, the ‘skycrane’ system gently 

lowered the rover to a soft landing. By pointing the skycrane’s jets 

outward, the landing site was 

protected from any contamination 

from their exhaust.

As Curiosity carefully works its way up the 

mound, layer by layer, it will collect data 

about what Mars’ environment was like in 

the past, how it changed with time...

All of Curiosity’s 

instruments play 

a role in fnding 

targets for research 

and collecting data.

First, 

Curiosity’s 

camera ‘eyes’

(MastCam)...

...are on the 

lookout for 

interesting 

features on 

the surface.

MastCam helps 

astrobiologists on 

Earth spot science 

targets on Mars.

..up to 7

meters

away!

... and whether or not the red 

planet could have supported life.

Finally, the powered descent 

module few away, leaving 

Curiosity on a pristine site 

inside Gale Crater

Gale Crater was chosen as a 

landing site because it has a 

huge mound in the center of 

layered materials deposited 

over time. At the bottom of 

the layers are clay minerals. On top of the clay are 

layers containing sulfate 

minerals that are known to 

form in water.

“Interesting...”

22

Curiosity can then use its 

other remote instrument, 

ChemCam, to fre 

laser pulses at rock 

and soil samples... 
23

The energized atoms and ions blasted off the rock are 

then analyzed in order to determine the elements, such 

as oxygen and silicon, that are present in the sample.

SAM is actually a suite of 

three different instruments, a 

Quadrupole Mass Spectrometer 

(QMS), a Gas Chromatograph 

(GC), and a Tunable Laser 

Spectrometer (TLS).

Each of these advanced scientifc 

instruments has a turn analyzing 

the sample.

Together, they allow SAM to 

study chemistry and search 

for organic compounds.

Curiosity drives close 

and uses the MAHLI to 

take close-up pictures.

When the samples are 

processed and delivered 

to SAM, they are deposited and sealed in one of 

74 sampling cups that 

rest inside a special oven.

The rock, dust and other 

materials are deposited in 

a special chamber and are 

moved inside the rover’s 

body to be analyzed.

APXS then determines the sample’s 

elemental chemistry, from major 

elements down to trace elements.

If the target still 

seems interesting to 

astrobiologists, then 

it’s time for Curiosity 

to use its drill and 

collect a sample!

Curiosity’s arm then transports 

the material to the rover’s onboard 

analytical laboratory, SAM and CheMin.

SAM then cooks the 

samples and analyzes the 

gases that are released.

Next up are the

contact instruments.

23
24 

Samples are

also delivered

to CheMin.

This mineralogy instrument

determines what the rocks are.

Together, SAM and CheMin are unlocking hidden secrets 

in the tiny particles of martian sand and dust.

CheMin studies how water may have

affected the formation, deposition,

or alteration of the minerals.

It didn’t take long for

Curiosity to astonish

astrobiologists.

The rover found rounded 

pebbles that were evidence 

of an ancient stream bed.

One region, known as Yellowknife Bay, 

had all the trademarks of an environment 

that would have once been habitable for 

life as we know it.

John Grotzinger (CalTech)

Rebecca Williams (The

Planetary Science Institute)

24

“At a minimum, 

the stream was fowing 

at a speed equivalent to 

a walking pace—and it 

was ankle-deep to 

hip-deep.” (59)

“Our mission is

turning a corner.”

“We are beginning to 

map a way forward, a way 

to explore deliberately for 

organic matter.” (60)
25

On November 18, 2013, NASA launched 

the Mars Atmosphere and Volatile 

EvolutioN mission, or MAVEN.

Scientists think Mars had 

a thick atmosphere and 

water at the surface.

Early Mars could have 

been as habitable as 

the early Earth.

“Where did the water go?!”

But then something

happened...

...leaving Mars as the 

cold, desert world we 

know today.

When the inner planets frst

formed, Mars wasn’t much

different than Earth.

MAVEN is using its instruments

to investigate a planetary mystery.

25
26 

A likely culprit for this 

transformation is the Sun.

Solar wind and radiation gradually blasted 

much of the martian 

atmosphere away.

Curiosity is also

helping MAVEN...

MAVEN is the frst dedicated mission to study 

how atmospheres escape into space, and the 

data from Mars could also help astrobiologists 

undertsand Earth’s atmosphere and habitability.

...by providing data from

the surface of Mars. The rover found heavy 

isotopes of gasses in the 

atmosphere, indicating 

that the lighter ones 

have indeed escaped to 

space over time.

This cooperation between MAVEN and 

Curiosity is just the beginning of the 

next phase in Mars exploration.

Unlike Earth, Mars no longer 

has a powerful magnetic feld 

to protect its atmosphere.

26
27

In September of 2014, 

the Indian Space Research 

Organization’s (ISRO) Mars 

Orbiter Mission (MOM) 

joined the team at Mars.

MAVEN and MOM are members 

of a team of active robotic 

explorers at Mars.

In the years to come, this team

of adventurers will continue to

grow as scientists develop new

technologies for Mars missions.

MOM collects thermal 

emissions from the surface 

during both day and night.
28 

Studying the martian interior will 

help astrobiologists understand the 

processes that shape rocky planets.

Future missions

could also include

robots that hunt

for biosignatures

on Mars.

Others could

help collect

samples from

the martian

surface...

... and return them to Earth

where human scientists can

study them up close.

No one knows what the 

future of Mars exploration 

will bring...

...but the planet is sure

to continue to fascinate

astrobiologists.

New landers could help

scientists study the

deep interior of Mars,

Whether or not Mars

is still geologically

active beneath the

surface is still a big

question.

28

InSight concept

ExoMars Rover

concept (ESA)

ExoMars Orbiter 

concept (ESA)
29

With the arrival of Curiosity and

MAVEN, Mars continues to be a major

target for astrobiology research.

29

Michael Meyer, lead scientist for 

NASA’s Mars Exploration Program.

“We now believe 

that Mars preserves 

a record of habitable 

environments, some of 

which may be active today. 

Our next step will be to 

determine whether or 

not life ever started

 on Mars.” (53)

“Considering how long the Spirit and 

Opportunity rovers have lasted beyond 

their design lifetimes, it almost boggles 

the mind to think how long MSL could last. 

It may be there to greet the astronauts 

when they arrive on Mars.” (52)

“With its sophisticated 

instruments, MSL is the frst 

astrobiology mission since 

Viking.” (61) (53)
Astrobiology

A History of Exobiology and Astrobiology at NASA

Further Resources and References cited in this issue:

1. The background on this page is an image of M72: A globular cluster of stars 

captured by the Hubble Space Telescope. M72 is about 50,000 light years away 

and can be seen with a small telescope pointed in the direction of the constellation Water Bearer (Aquarius). This image shows about 100,000 of M72’s stars 

and spans about 50 light years. Credit: NASA, ESA 

2. Harold “Chuck” Klein (First head of the Exobiology Division, NASA Ames 

Research Center)

3. L.P. “Pete” Zill (third head of Exobiology at NASA Ames)

4. Dick, S.J., and Strick, J.E. (2005) The Living Universe: NASA and the 

development of Astrobiology. Rutgers University Press, New Brunswick, 

New Jersey, and London. 

5. Richard “Dick” Young (second head of Exobiology at NASA Ames; frst head of 

the Exobiology Program at NASA Headquarters)

6. Vance Oyama, NASA Ames biologist.

7. Cyril Ponnamperuma (Arrived at NASA Ames in the frst class of postdoctoral 

fellows (summer 1961) (8)

8. Bugos, Glenn E. 1999. Atmosphere of Freedom—Sixty Years At The NASA 

Ames Research Center. NASA SP-4314. p77-80.3. 

9. Armagnac, A.P. (1962) Will Mariner solve these mysteries of Venus? Popular 

Science, Vol. 181, No. 6, 204p. 

10. BBC News. 1962. ‘Music of spheres’ hails Venus fy-by. BBC News. Archive 

available at: http://news.bbc.co.uk/onthisday/hi/dates/stories/ 

december/14/ newsid_4061000/4061955.stm

11. Mariner 4 image, the frst close-up image ever taken of Mars. The image is 

centered at 37oN, 187oW and is roughly 330 kilometers (km) by 1200 km. 

The resolution is roughly 5 km and north is up. Available from the NASA image 

archive at: http://nssdc.gsfc.nasa.gov/imgcat/html/object_page/m04_01d.html 

12. Mariner 4 image, the frst image to clearly show unambiguous craters on the 

surface of Mars. The area is roughly 262 km by 310 km and shows the region 

south of Amzazonis Planitia at 14oS, 174oW. North is at roughly 11:00 in this 

image. Credit: NASA 

13. This image of Venus was actually acquired by Mariner 10 during its fyby of 

the planet. Mariner 5 was built as a backup to the successful Mariner 4 

mission, and its TV camera was removed when the craft was adapted for 

travel to Venus. Instead of photographing Venus, Mariner 5 probed the 

planet’s atmosphere with its suite of instruments. Credit: NASA/JPL 

14. The cratered surface of Mars taken by Mariner 6. Image Credit: NASA/JPL

15. Mariner 7 had its closest approach to Mars at a distance of 3,524 km on 

July 31, 1969; after Mariner 6’s fyby. Image Credit: NASA/JPL 

16. Mariner 9 view of the “labyrinth” at the western end of Vallis Marineris on 

Mars. Linear graben, grooves, and crater chains dominate this region, along 

with a number of fat-topped mesas. The image is roughly 400 km across, 

centered at 6oS, 105oW, at the edge of the Tharsis bulge. North is up. 

(Mariner 9, MTVS 4187-45). Credit: NASA/JPL 

17. Mariner 9 image of the north polar cap of Mars. The image was taken on 
October 12, 1972, about one-half martian month after summer solstice. At 

this time, the cap had reached its minimal extent. The cap is about 1000 km 

across. The interior dark markings are frost-free, sun-facing slopes. A smoothlayered sedimentary deposit underlies the cap. The image is centered at 89oN, 

200oW. (Mariner 9, MTVS 4297-47). Credit: NASA/JPL 

18. Mariner 10 oblique view of Wren crater and surroundings on Mercury. Wren 

crater is barely visible at the lower center of the image, containing a number 

of craters within its 215 km diameter foor. Running along the right side of the 

image is Antoniadi Dorsum. North is at 1:00. (Mariner 10, Atlas of Mercury, 

Fig. 2-10) (edge of planet). Credit: NASA

19. Mariner 10 image of Brahms Crater, Mercury. This image of the 75 km 

diameter crater was taken on the frst fyby. Note the central peak. North 

is up. (Mariner 10, Atlas of Mercury, Fig. 3-2). Credit: NASA 

20. Other missions in the Soviet Mars series were unsuccessful, including 

the lander attempt of Mars 7. 

21. Horowitz, N.H. 1966. The Search for Extraterrestrial Life. 

Science 151(3712), 789-792. 

22. Dr. Thomas Mutch speaking to BBC News. Available at: http://news.bbc.

co.uk/onthisday/hi/dates/stories/july/20/newsid_2515000/2515447.stm 

23. The frst image transmitted by the Viking 1 Lander from the surface of Mars 

on July 20, 1976. Credit: NASA Viking Image Archive 

24. Post-Viking Biological Investigations of Mars. 1977. Committee on Planetary 

Biology and Chemical Evolution, Space Science Board, Assembly of Mathematical and Physical Sciences, National Research Council. 

25. Viking 1 Camera 1 Mosaic of Chryse Planitia. 

Credit: NASA Viking Image Archive 

26. Light Deposits Indicate Water Flowing on Mars. This fgure shows MGS 

images of the southeast wall of the unnamed crater in the Centauri Montes 

region, as it appeared in August 1999, and later in September 2005. No 

light-toned deposit was present in August 1999, but appeared by February 

2004. Credit: NASA/JPL/Malin Space Science Systems 

27. Astrobiology Magazine (www.astrobio.net), “Astrobiology Top 10: Water Flows 

on Mars.” Available at: http://www.astrobio.net/index.php?option=com_ 

retrospection&task=detail&id=2200

28. Astrobiology Magazine (www.astrobio.net), “Five Year Retrospective: Mars 

Pathfnder, Interview with Pathfnder Project Scientist, Matt Golombek.” 

Available at: http://www.astrobio.net/interview/282/fve-year-retrospectivemars-pathfnder 

29. A false-color mosaic focuses on one junction in Noctis Labyrinthus where 

canyons meet to form a depression 4,000 meters (13,000 feet) deep. Dust 

(blue tints) lies on the upper surfaces and rockier material (warmer colors) lies 

below. The pictures used to create this mosaic image were taken from April 

2003 to September 2005 by the Thermal Emission Imaging System instrument 

on NASA’s Mars Odyssey orbiter. Credit: NASA/JPL-Caltech/ASU 

30. Fans and ribbons of dark sand dunes creep across the foor of Bunge Crater 

in response to winds blowing from the direction at the top of the picture. This 

image was taken in January 2006 by the Thermal Emission Imaging System 

(THEMIS) instrument on NASA’s Mars Odyssey orbiter. The pictured location 

on Mars is 33.8 degrees south latitude, 311.4 degrees east longitude. 

Credit: NASA/JPL-Caltech/ASU 

31. This three-frame image shows a region in the southern highlands of Mars 

where Mars Odyssey found evidence of chloride salt deposits. These depos- 
its could point to places where water was once abundant, then evaporated, 

leaving the minerals behind. These images of the region were actually taken 

on March 30, 2007, by the High Resolution Imaging Science Experiment 

(HiRISE) camera on NASA’s Mars Reconnaissance Orbiter. Credit: NASA/JPLCaltech/ University of Arizona/Arizona State University/University of Hawaii 

32. European Space Agency. “Europe reclaims a stake in Mars exploration.” Available at: http://www.esa.int/SPECIALS/Mars_Express/SEMKR55V9ED_0.html

33. Matsos, Helen. 2004. “Interview with Beagle 2 Scientist Colin Pilinger.” Available at: http://www.astrobio.net/interview/interview-with-beagle-2-scientist

34. Astrobiology Magazine [www.astrobio.net]. “Sounding Out Mars: an interview with Jeffrey Plaut.” Available at: http://www.astrobio.net/interview/1464/

sounding-out-mars 

35. Image taken by the Mars Express High Resolution Stereo Camera (HRSC) 

showing water ice on the foor of a crater near the Martian north pole. 

Credit: ESA/DLR/FU Berlin (G. Neukum) 

36. Beagle 2 Landing site in Isidis Planitia. MOC2-835a: Beagle 2 December 25, 

2003, landing ellipse. Credit: Mars Global Surveyor Mars Orbital Camera Image.

37. This photo, taken by NASA’s Opportunity rover, shows Mars’ thin, diffuse 

clouds. Credit: NASA/JPL-Caltech 

38. Mars Reconnaissance Orbiter Mission Pages: Science Goals. Available at: 

http://www.nasa.gov/mission_pages/MRO/mission/science-goals.html

39. Astrobiology Magazine. 2006. “Astrobiology Top 10: MGS Bows Out.” 

Avail- able at: http://www.astrobio.net/index.php?option=com_

retrospection&task= detail&id=2191 

40. Astrobiology Magazine (www.astrobio.net), “MGS Over and Out.” 

Available at: http://www.astrobio.net/pressrelease/2152/mgs-over-and-out

41. Details in a fan-shaped deposit discovered by NASA’s Mars Global Surveyor. 

Credit: NASA/JPL/Malin Space Science Systems 

42. This is a shaded relief image derived from Mars Orbiter Laser Altimeter data, 

which few onboard the Mars Global Surveyor. The image shows Olympus 

Mons and the three Tharsis Montes volcanoes: Arsia Mons, Pavonis Mons, 

and Ascraeus Mons from southwest to northeast. Credit: NASA 

43. University of Arizona. Phoenix Mars Mission. Available at: http://phoenix.lpl.

arizona.edu/mission.php 

44. This image, one of the frst captured by NASA’s Phoenix Mars Lander, shows 

the vast plains of the northern polar region of Mars. The fat landscape is 

strewn with tiny pebbles and shows polygonal cracking, a pattern seen widely 

in Martian high latitudes and also observed in permafrost terrains on Earth. 

Credit: NASA/JPL-Caltech/University of Arizona 

45. Images from the Surface Stereo Imager camera on NASA’s Phoenix Mars 

Lander shows several trenches dug by Phoenix. Credit: NASA/JPL-Caltech/ 

University of Arizona/Texas A&M University 

46. Astrobiology Magazine. 2009. “Astrobiology Top 10: Too Salty to Freeze.” 

Available at: http://www.astrobio.net/topic/solar-system/mars/astrobiologytop-10-too-salty-to-freeze 

47. This HiRISE image shows the Phoenix lander after one year on Mars. The 

image is a close match to the season and illumination and viewing angles of 

some of the frst HiRISE images acquired after the successful landing on May 

25, 2008. The shadow that is cast by the lander is different than the previous year, indicating that Phoenix has suffered structural damage. Image Title: 

“Phoenix Lander after One Mars Year (ESP_017716_2485).” 

Credit: NASA/JPL/ University of Arizona 
48. This image taken by the HiRISE instrument onboard the Mars Reconnaissance Orbiter shows the Phoenix lander in 2008 after landing and deployment 

of the solar panels. Image Title: “Phoenix Lander Hardware: EDL +22 

(PSP_008591_2485).” Credit: NASA/JPL/University of Arizona 

49. Astrobiology Magazine. 2010. “Astrobiology Top 10: Viking Results Revisited.” 

Available at: http://www.astrobio.net/topic/solar-system/mars/astrobiologytop-10-viking-results-revisited 

50. Astrobiology Magazine. 2010. “Phoenix Crushed by Frost.” Available at: 

http://www.astrobio.net/topic/solar-system/mars/phoenix-crushed-by-frost 

51. NASA JPL. Mars Science Laboratory. Available at: http://marsprogram.jpl.

nasa.gov/msl 

52. Astrobiology Magazine. 2006. “Managing Mars Missions.” Available at: 

http://www.astrobio.net/topic/solar-system/mars/managing-mars-missions 

53. Meyer, Michael. 2009. “The MSL Science Story.” Special Planetary Science Subcommittee Meeting, Mars Exploration Program Analysis Group, 

January 9, 2009, at NASA HQ. 

54. NASA. 2009. NASA Selects Student’s Entry as New Mars Rover Name. 

NASA Jet Propulsion Laboratory. Available at: http://mars.jpl.nasa.gov/msl/

news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=99 

55. Ma, Clara. 2009. “Curiosity.” Essay written by Clara Ma, winner of the 

Mars Science Laboratory naming contest. Twelve-year-old Ma submitted the 

winning entry, “Curiosity.” NASA Jet Propulsion Laboratory. Available at: 

http://www.nasa.gov/mission_pages/msl/essay-20090527.html 

56. Schmid, D. Southwest Research Institute. 2012. Radiation En Route to Mars. 

Astrobiology Magazine. Available at: http://www.astrobio.net/topic/exploration/

moon-to-mars/radiation-en-route-to-mars

57. NASA. 2012. Daybreak at Gale Crater. NASA Multimedia Gallery. This computer-generated view depicts part of Mars at the boundary between darkness 

and daylight, with an area including Gale Crater beginning to catch morning 

light. Northward is to the left. Gale is the crater with a mound inside it near the 

center of the image. Credit: NASA/JPL-Caltech. Available at: http://www.nasa.

gov/mission_pages/msl/multimedia/gallery/pia14293.html 

58. NASA. 2012. Destination for Mars Rover Curiosity. NASA Multimedia Gallery. 

This image shows the target landing area for Curiosity, the rover of NASA’s 

Mars Science Laboratory mission. The target is near the foot of a mountain 

inside Gale Crater. Techniques for improved landing precision give Curiosity 

about a 99 percent probability of landing within the ellipse outlined in black in 

this image. The ellipse is 12.4 miles (20 kilometers) by 15.5 miles (25 kilometers). The blue line shows one possible route the rover could take onto the 

lower fank of the mountain. Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/ 

MSSS. Available at: http://www.nasa.gov/mission_pages/msl/multimedia/

pia15293.html 

59. NASA JPL (2013) Pebbly Rocks Testify to Old Streambed on Mars. 

Available at: http://www.nasa.gov/mission_pages/msl/news/msl20130530f.

html#.U0wiEcfc3Cn

60. Kerr, R.A. 2014. “New Results Send Mars Rover on a Quest for Ancient Life.” 

ScienceNow. AAAs. Available at: http://news.sciencemag.org 

chemistry/2013/12/new-results-send-mars-rover-quest-ancient-life

61. NASA. “MAVEN: Answers About Mars Climate History.” Available at: 

http://www.nasa.gov/mission_pages/maven/overview/index.html
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