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.

#5

Issue
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 just over 50 years old, this field 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

Editor

Linda Billings

Layout

Aaron L. Gronstal

Copyright 2015, NASA Astrobiology Program

First edition printed in 2015
Issue #5—Astrobiology and the Earth

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 field developed and how the search for life elsewhere became a key component of NASA’s science strategy for exploring space. This issue is the fifth 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 field as 

it explains how Astrobiology came to be.

-Linda Billings, Editor

1
We’ve seen how robots have 

carried astrobiology to the far 

corners of the Solar System*...

If you compare Earth to a place like Mars, it’s 

easy to see that life as we know it would have a 

tough time on the surface of any other planet.

2

...but, so far, we only know one 

planet capable of supporting life.

Earth is our key to understanding 

life’s potential in the Universe.

However, in our solar 

system, Earth is unique.

*Issue 1-4

Life simply might not be capable 

of surviving on Mars today.
Life needs liquid water. 

And if Mars ice melts, it 

can immediately sublimate

into gas due to the low 

atmospheric pressure.

Mars' thin atmosphere also doesn't provide 

as much protection as the Earth's does.

3

On Mars, water at the surface 

instantly freezes because the 

temps are as low as -153°C. 

Even inside cells, 

water can freeze.

 Radiation from space is constantly 

streaming through to the surface. 

LOTS of radiation.
Even the sand and rocks on Mars 

could be harmful for potential life.

*See Issue 2 for more on perchlorates

4

The perchlorate salts in the 

soil of Mars could be used by 

microbes for energy, but these 

salts can also cause serious 

damage to living cells.* (1, 2)

Other areas have 

‘oxidizing’ compounds.

Mars looks red because iron at 

the surface reacts with Oxygen.

The oxygen comes from 

things like carbon dioxide 

broken down by sunlight.

This process forms iron 

oxide (the stuff that 

gives rust its color).

Much like an acid, it 

is highly reactive...

... and can strip electrons away 

from molecules like DNA.
The challenges don’t 

stop there.

5

That’s true. Any microbes 

on Mars may not have had 

that kind of time.

Max Coleman, NASA Jet 

Propulsion Laboratory (JPL) James Holden, University 

of Massachusetts Amherst

Our trusty robots have visited 

many locations on Mars.

Any microbes on Mars 

might simply starve.

They’ve found a surface rich in 

metals, but poor in the nutrients 

microbes on Earth need.

Na2O 3%

Al2O3 10.1%

FeO+ 1.8%

Na2O 2.1%

Al2O3 9.1%

FeO+ 2.2%

Na2O 2.1%

Al2O3 9.5%

FeO+ 2.1%

*Rough estimates of 

elemental composition (3)

Some microbes 

on Earth have adapted to 

survive in challenging 

environments... 

...for instance, 

there are microbes out there 

that can use perchlorate for 

energy.

But life on 

Earth has had billions

of years to adapt.
Our robots have discovered so much, but to find 

life on Mars we may have to go there ourselves.

And it could be a long 

time before humans set 

foot on the red planet.

To get their hands on ‘Mars,’ 

scientists must traverse a 

different planet altogether...

...a planet even more 

important for astrobiology.

Issue 5...

Analogs on Earth!

Searching for 

life on Mars starts 

with searching for 

habitats. The trick is 

to find places on Earth 

that share some of Mars’ 

life-threatening 

characteristics!

We call these 

places analog environments. 

(4-6) Peter Doran, Louisiana 

State University

6
The Viking mission* really spurred the 

search for Mars analogs on Earth. We need somewhere to test the 

instruments!

*See Issue 2

Cyril Ponnamperuma*, 

formerly of the NASA 

Ames Research Center

Norman Horowitz*, former 

head of the Biology Division 

of NASA’s Jet Propulsion 

Laboratory (JPL)

But even in the 60's, 

scientists knew such 

comparisons had 

their limits. (7)

Truthfully, “the 

Antarctic desert is far 

more hospitable to 

terrestrial life than is 

Mars, particularly in 

regard to the abundance 

of water.”

However... “the 

Antarctic has provided us 

with a natural environment 

as much like Mars as we 

are likely to find 

on Earth.” (9)

7

How about the 

deserts of Antarctica? They look a 

lot like the images that Mariner 4* 

sent us.

Hmm... In the 

Antarctic, life as we know 

it is definitely pushed to 

the limit. (7,8)
It was physical 

appearance that 

first drew us to 

Antarctica.

The surface here 

is shaped by the 

cycling of ice.

Comparing this 

place to images from Mars 

helps us understand how 

similar features could have 

been made in the red planet’s 

past, and if water might have 

been involved.

But if you travel deep 

into Antarctica, you find 

rarer types of analog 

environments.

8

In fact, there are tons 

of sites on Earth, from North 

Africa to the California deserts, 

that are useful for this type of 

work. 
The best analogs we can hope 

for are places that get very little rain, 

and the Antarctic Dry Valleys are as 

cold and dry as it gets on Earth.

These valleys are remote, 

but, like anywhere on our planet, 

they are still part of Earth’s 

immensely productive global 

biosphere.

Just because 

Antarctica looks similar 

to Mars doesn’t always 

mean the landscapes 

were formed in the 

same way.

But always 

remember, no site on 

Earth is exactly like Mars. 

Not even close.

Yet, even here, microbial 

life thrives in soil and 

ice-covered lakes.

Dawn Sumner, Professor of Geobiology, 

Department of Earth and Planetary Sciences, 

University of California, Davis, and Member of 

the Mars Science Laboratory team.

9
Places that are geologically 

similar to Mars are great 

for testing technology. It's a chance to drive rovers through 

rocky terrain, or to test our methods for 

performing science in remote landscapes.

This includes places like 

Haughton Crater in the 

Canadian arctic, or even 

the volcanos of Hawai'i.

Features like craters and dry stream 

beds can also help us identify where 

water may have flowed on Mars.

We study Earth's geology from 

the ground, air, and space so 

that we can make comparisons 

with the images our robotic 

missions send home.

But very few places 

are good analogs for 

habitats that might 

support biology on 

other worlds.

10
You know the ozone 

layer is thinner down 

here, right?

Antarctica isn’t 

exactly like Mars, but 

it’s as close as we can 

get on this planet.

At first we thought the 

soil here was dead... ...the first naturally 

sterile habitat on 

Earth ever found.

*Wolf Vishniac testing the Wolf Trap in the 

Dry Valleys in the 1970s. (See Issue 2) 

11

Up close, the Antarctic 

Valleys do have some Marslike traits... like salty soil, and 

elevated UV* levels.

*Ultraviolet (UV) light

But then we 

started testing life 

detection instruments 

in preparation for 

Viking.*
And we began to 

wonder if there WAS

a chance for life on 

Mars. (10-12)

After Viking, more 

and more missions have 

added their data to the 

story.

We realized that 

some Antarctic soils are similar 

to the martian regolith in terms of 

their physical and chemical 

properties. (7, 13, 14)

But no matter what 

Antarctica has to throw at 

life, organisms are able to 

survive.

12

With the Wolf 

Trap, we found 

microbes.
We found 

microbes in some 

spectacular hiding 

places.

They were buried 

under layers of soil...

...and even 

inside rocks!

We call 

these microbes 

cryptoendoliths. 

(17-20)

E. Imre Friedmann (16)

Roseli OcampoFriedmann (15)

13

Even long after the completion of 

the Viking missions, Antarctica 

has remained a place of discovery 

for astrobiology and an important 

testbed for new technology.

You can see 

the green line of 

photosynthetic microbes 

just below the rock’s 

surface.

The rock provides a 

shelter for organisms 

at the micro- scale.

There’s protection 

from the elements, 

including insulation from 

the cold and radiation.

It makes you 

wonder if life could use 

similar techniques to 

survive on a place 

like Mars.
The ice-cemented 

ground is a great place 

to test drills that could 

be used at Mars’ poles. 

(21-24)

And we’ve found 

lots of other crazy 

habitats that can teach 

us about life’s 

potential.

Like isolated 

ecosystems trapped 

in ice-covered lakes... 

(25, 26)

There’s also 

water trapped 

under glaciers. High pressures 

and lots of salt keep it 

liquid - even below 

freezing!

And when the 

water is forced to 

the surface... 

(27, 28)

...just guess 

what we find.

Chris McKay, NASA 

Ames Research Center

Jill Mikucki, Assistant Professor 

Department of Biology, Middlebury College, Middlebury Vermont

14
But Antarctica 

isn’t the only analog 

we study.

Places like Death 

Valley in California and 

the Atacama desert in 

Chile are also useful.

It’s not super 

cold in the Atacama... 

but it is definitely 

dry.

Here there are 

salt basins, lava flows 

and almost concretehard ground.

The Atacama is 

a 1000-kilometer 

stretch of almost lifeless plains.

And I mean, 

almost lifeless.

Like Antarctica, 

we once thought 

these soils were 

dead.

But with careful 

study, we did find 

life. (29)

And factors like 

perchlorate salt in the 

hyper-arid soil make this 

almost alien-looking landscape great for studying 

life’s potential.

15
Even though life 

is hard to find in the 

Atacama, there are signs 

it is here. See this rock that has 

broken open? The outside 

is covered in black ‘desert 

varnish.’

It’s a layer 

of clay and iron 

oxides caused by 

microorganisms.

Low numbers of 

microbes in the soil also 

make the Atacama a good 

place to test our lifedetection skills. (30)

Today, Antarctica 

and the Atacama are 

still extremely important 

research sites.

And our work 

here has inspired 

research in many 

other deserts...

...like the Sahara, 

the Mojave, and 

the Namib desert 

in southern Africa. 

(31-33)

Nathalie Cabrol, 

The SETI Institute

16
Astrobiologists travel 

around the world, from the 

north pole to the south, 

searching for analogs.

...although, it's 

very hard to visit.

But one of the least 

explored analogs can 

be found anywhere in 

the world...

That's because 

it's basically made 

of solid rock.

...but under a 

microscope the view 

is very different.

When you dig underground, it might just look 

like dirt and rocks...

And this 

water is the key 

to life.

Drops of water can 

be found in tiny cracks 

and fissures.

Mary Voytek, Program 

Scientist for Astrobiology, 

NASA Headquarters

Drilling programs 

at the ocean floor and on 

land provided one of the 

first views into Earth’s 

deep biosphere. 

(34-36)

17
To get to the deep sub-surface, 

Astrobiologists also explore 

caves and mines.

Penny Boston, Chair of Earth and Environmental Sciences, New Mexico Tech. and Associate Director of 

the Nat'l Cave and Karst Research Institute

Tullis Onstott, 

Princeton University

Here we can 

tap into underground 

water sources and take 

samples.

In the mine, we 

drill sideways into the 

wall to collect samples 

that are free from 

contamination.

In these 

hidden pockets deep 

below ground, we find 

entire ecosystems 

thriving. (38)

It’s true that 

the surfaces of planets 

like Mars and Venus are 

vastly different than 

the Earth.

But underground, it 

could be a completely 

different story.

We ventured into 

deep mines in South Africa 

because drilling from the 

surface wasn’t enough to 

tell us how life was living 

down here. (37)

18
...could it still be 

hiding somewhere 

underground?

But if life existed on 

Mars in the past...

The surface of 

Mars might not be 

habitable today.

Questions about 

life in Mars’ past bring us 

to the slopes of Licancabur 

Volcano in the Andes, and 

another type of analog.

See those 

lakes behind 

us?

Those are 

Laguna Verde and 

Laguna Blanca. 

19
Here we find an 

analog for a Mars we 

no longer see.

Aspects like geology, 

temperature and ultraviolet 

radiation at this site might be a 

good analog for an early, wetter

Mars. (39, 40)

And there’s an 

added bonus.

In this location, 

we see climate change in 

action, and study its 

affects on habitability.

Doing so can help 

us see how a changing 

climate on early Mars 

may have affected the 

martian environment.

20
Carol Stoker, NASA 

Ames Research Center

Other 

analogs for early 

Mars also exist.

This is Spain’s 

Rio Tinto river, 

where water runs 

red.

With a pH of 2.3, 

it’s acidic enough to 

eat metal!

This river 

is nothing like 

Mars now... 

...but some aspects 

might be similar to 

a wet, acidic Mars 

in the past.

This water and the 

ground around the river 

might hold clues about 

life’s potential on ancient 

Mars. (41)

21
Even if Mars is dead now, 

maybe it used to be similar 

to places like Antarctica, the 

Atacama, or the high Andes.

A little warmer...

... a little wetter...

...with active volcanoes 

or hot springs...

...and in every corner 

of the Solar System.* 

...and a thicker atmosphere.

Our search for analogs on 

Earth continues to expand.

...but missions continue to collect data about 

the habitability of other amazing worlds... 

We focus on Mars because we know 

so much about its past and present...

*Issues 2-4

22
Damhnait Gleeson, Centro 

de Astrobiología (CAB) 

Kevin Hand,

NASA JPL

Robert Pappalardo, 

NASA JPL

*See Issue 4 for more on the icy 

moons of Jupiter and Saturn.

Arctic ice 

has already revealed 

details about Europa’s 

environment*.

We won’t 

really know what these 

oceans are like, or if they 

could support life, until 

new missions take 

us there.

Many moons 

of giant planets are 

thought to have oceans 

of water beneath 

their surfaces.

Places like the 

sulfur-rich springs on 

Canada’s Ellesmere 

Island could hold 

clues... (42, 43) 

We don’t know what 

environments might lie 

under the icy crusts of our 

solar system’s moons.

23

But analog 

habitats? That’s 

tricky.

Physically, the 

Arctic and Antarctic are 

obvious places to test 

equipment for icy moons 

like Europa or Titan.*
Pitch Lake, Trinidad 

(45, 46)

Dirk Schulze-Makuch, 

Washington State University

On Earth, things like 

hydrothermal vents and 

cold seeps provide energy 

for entire ecosystems. 

(44)**

Our best guess 

might come from environments 

on the ocean floor, or under 

the ice-covered lakes we 

saw earlier.*

**See Issue 4

Things are even 

trickier when you think 

of a place like Titan. 

But who knows? 

Life is found on Earth 

in many places that you 

wouldn’t expect.

With its lakes 

of hydrocarbons and frigid 

temperatures, Titan is very 

different than Earth.** 

24

If there’s water 

and energy on a place 

like Europa, maybe 

there is life.

* Page 15
Astrobiologists have traveled around 

the world to find analogs for places 

like Mars, Europa, and Titan.

...an analog for potentially habitable 

worlds in other solar systems.

Next issue...

Living Beyond the 

Solar System!

25

What they’ve learned has 

turned the Earth into one 

giant analog environment...

In doing so, they’re also starting 

to understand what makes the 

Earth itself habitable for life.

Studying Earth is the 

key to finding Earth-like 

planets among the stars.
Astrobiology

A History of Exobiology and Astrobiology at NASA

Further Resources and References cited in this issue:

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Microbial Isotopic Fractionation of Perchlorate Chlorine. Applied and Environmental Microbiology, Vol. 69, No. 8, 4997-5000.

2. Coleman, M. (2009) Perchlorate on Earth and Mars, Formation Processes, Fate, 

Implications for Astrobiology and Suggestions for Future Work. The New Martian Chemistry Workshop, held July 27-28, 2009 in Medford, Massachusetts. 

Lunar Planetary Institute Contribution No. 1502, p.10

3. NASA JPL Photojournal (2012) PIA16572: Inspecting Soils Across Mars. Available at: http://photojournal.jpl.nasa.gov/catalog/PIA16572

4. Preston, L., Grady, M., Barber, S. (2012) CAFÉ: Concepts for Activities in the 

Field for Exploration: tn2: The Catalogue of Planetary Analogues. The Planetary 

and Space Sciences Research Institute, The Open University, UK. Under European Space Agency contract: 4000104716/11/NL/AF

5. Doran, P.T., Berry Lyons, W. and McKnight, D.M. (Editors) (2012) Life in Antarctic 

Deserts and other Cold Dry Environments: Astrobiological Analogs. Cambridge 

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models for extraterrestrial surface habitats. Planetary and Space Science

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15. Roseli Ocampo-Friedmann (1937 – 2005), specialist in the study of cyanobacteria and extremophiles and former scientific consultant for the SETI Institute. 

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