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Title: Life on Mars.
Authors: Michael Tennesen
Source: DISCOVER MAGAZINE, Vol.10 Number 7, p82, 7p, 7c, July 1989
Database: D Drive
LIFE ON MARS by Michael Tennesen
(The Viking probes failed to find living organizms on Mars, but new studies
suggest that the Red Planet may not have always been dead.)
A planet upon which extraterrestrial life might form, would have to be highly
specialized. It would have to be a prescribed distance from a moderately
intense star, be able to rotate, and have an atmosphere that contained the
chemical elements carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.
Science yet knows of only two places where those conditions exist: earth and
the Red Planet Mars. But in 1976 when NASA put two Viking Landers on Mars, a
search for biology turned up empty handed. According to one researcher, the
lights were on but no one was home. Mars was a cold desert. It had a climate
ranging from a high of 32 degrees Fahrenheit (at noon on a hot day at the
equator) down to 225 degrees below zero. It lacked the "sine qua non" of active
biology -- "liquid water." Mars was frozen stiff.
Still there was evidence water once ran on the planet's surface -- Viking
Orbiter images revealed vast flood plains and extensive drainage channels.
Now there is the first non geological evidence of an earlier, wetter Mars,
one that may have been able to able to support life 3 to 4 billion years ago.
Reporting in a recent issue of "Science," Dr. Tobias Owen of the State
University of New York, Stony Brook; Dr. Barry Lutz, Lowell Observatory,
Flagstaff, Arizona; and a team of French collaborators, Jean Pierre Maillard
and Catherine de Bergh, using recently developed and highly sensitive
spectrographic instruments, took measurements of the atmosphere of Mars from
atop the 14,000 foot Mauna Kea observatory in Hawaii. What those observations
revealed was an atmosphere on Mars with a high residue of deuterium or "heavy
hydrogen," a signature of photochemical distillation. It says what may have
happened to ancient Martian water -- the sun simply burned it off.
And as the sun's UV radiation broke up the water molecules, the lighter
hydrogen isotopes, protium, escaped into space while the heavier hydrogen
isotopes, deuterium, with twice the mass of protium had a little more trouble
getting off the ground. Knowing the amount of deuterium residue and
calculating todays rate of escape, Owens et al estimate that Mars has lost
well over 90% of its water. But to lose as much water as the geological
evidence would indicate, this escape would have in the past been a lot faster,
the atmosphere a lot warmer.
"And under the conditions of a warm wet atmosphere," says Dr. Owen. "The
prospects for the origin and evolution of life have to be taken seriously."
An earlier, warmer, wetter Mars could have been a very live one.
The United States is scheduled to launch the Mars Observer in 1992 which will
map out the surface and attempt to determine its elemental composition. NASA
is also planning a Mars Rover Sample Return mission which will include a dune
buggy-like vehicle with television eyes and artificial intelligence which will
seek out rock samples and return them to earth.
NASA scientists are currently engaged in a number of research projects
designed to put that rover on a likely target with the ability to recognize
signs of past life. Recognition is the first obstacle -- what are we looking
for? Are we hunting the tombs of Martian men in flowing metallic robes and
women in brass bikinis?
Researchers are focusing their attention on more primitive forms of life
since the window for life on Mars corresponds to a much earlier period of
evolution. To answer questions about that evolution, researchers are growing
things in Martian air. They're also looking at earthly microorganisms that
live in places that are Mars-like: life huddled inside polar desert sandstone
rocks, in the dry deserts of Nevada, buried 2,000 meters below the earth,
and lying at the bottom of frozen Antarctic lakes.
What are these organisms like, what kind of fossil evidence to they leave,
where do we look on Mars, what experiments do we perform, and what instruments
do we need? "We are going to be competing with geologists and atmospheric
scientists for the selection of the landing site," says Dr. Robert Wharton,
with the University of Nevada, working with the NASA life science team. "The
biologists have to have their act together."
***
It was Percival Lowell, a wealthy heir, businessman, and astronomer who first
got us excited about Mars. Reacting to Italian Astronomer Giovanni
Schiaparelli's reports in 1877 of several dozen "canali" on Mars, Lowell built
the famous Lowell Observatory in Flagstaff, Arizona. With it's hand polished
24 inch Clark refractor, he then began charting 585 canals that he believed
brought liquid water from the polar ice caps to a dying Martian civilization.
It is said, Lowell's delusions inspired H.G. Wells to write WAR OF THE WORLDS,
the story of an invasion of earth by octopus-like Martians. A radio adaptation
of that story in 1938 by Orson Wells panicked much of the nation who believed
the Martians had finally arrived.
But then a single infrared spectrogram of Mars taken at the Mount Wilson
Observatory in 1963 revealed an extremely low atmospheric pressure,
eventually calculated at 4.5 millimeters of mercury compared to 760
millimeters on earth. At 4.5 millimeters of pressure, water acts like dry
ice (C02) on earth -- at its melting point it goes directly from a solid
to a gaseous state. It made the canals impossible. Water couldn't run on Mars.
Mariners 4,6, and 7 completed the picture when they brought back photos of a
dry planet whose atmosphere was largely carbon dioxide and only 1% as dense
as ours.
In 1971, Mariner 9 took another spin around the Red Planet and found evidence
of ancient stream beds -- though not the ones Lowell charted on his numerous
globes at his Observatory. The U.S. then prepared to land two Viking probes
on Mars.
Dr. Harold P. Klein was the Director of Life Sciences at NASA Ames Research
Center in Moffett Field, California. Attempting to select the biological
experiments they would perform on the mission, NASA asked Klein's opinion.
"I was a pessimist for embarking on a search for life on Mars without
knowledge of its surface," Klein offers, then laughs. "So they made me chief
of the Viking Biology Experiment."
Klein didn't let his pessimism interfere with his new duty of helping select
3 experiments which eventually tested two different sites on the the Red
Planet for actively metabolizing Martians.
The Gas Exchange Experiment (GEX) would douse Martian soil with what the
scientists called "chicken soup," a nutrient rich solution, and then a gas
chromatograph would test to see if anything started breathing.
The Label Release Experiment (LR), was a more natural approach than the GEX
experiment. It took some soil, and gave it nothing but pure simulated Martian
sunlight and a few organics -- like you'd find on a passing comet -- labeled
the stuff with Carbon 14 and waited to see if anybody respired something
radioactive.
The Pyrolytic Release (PR) experiment took take some soil, boiled it,
separated it, and then identified it, especially organic substances, like
those used by carbon- based biology to survive.
On July 20, 1976 at 5:12 P.D.T. Viking 1 set down on the Plains of Chryse.
Later an arm extended out of the landing craft and scooped up soil while
earth based biologists held their breath. In the GEX experiment, the soil
took one whiff of that chicken soup and coughed loudly. "As soon as the water
vapor and soil got together," says Dr. Klein, "there was a violent eruption
of oxygen gas from the soil."
The trouble was, when they heated the soil sample up, past the point of
sterilization, which should have stopped the reaction, they got the same
result. Even worse was the outcome of the PR experiment which found absolutely
no evidence of organic matter. This came despite the fact that Mars' orbit was
right next to the asteroid belt, which is loaded with organic matter. The LR
experiment was considered inconclusive.
Despite initial optimism, the final interpretation, held by the majority of
the investigative team, was that neither Viking 1 or 2 found evidence of life
on Mars. Their theory instead was that the surface of Mars was covered with
"super oxides" or peroxides formed by the intense UV radiation that bombards
the surface of the dry planet. It explains what happened in the GEX experiment,
the peroxides reacted with the water and gave off oxygen. It also explains
what happened with the organic material. "It's the same as what happens when
you pour hydrogen peroxide on a cut," says Dr. Christopher McKay, a Research
Scientist at NASA Ames, and Coordinator for the Planetary Society's Mars
Institute, "it fizzles and eats up all the organics present."
There were detractors (we'll get into those later). Still the experiments dealt
only with carbon-based existing biology. They did not rule out past life. Was
it possible that Mars may have once been more hospitable? What about the
drainage channels?
The surface of Mars did indeed display some amazing geological features. Much
of the southern hemisphere was covered with impact craters; dating back 4
billion years. Olympus Mons, a volcano just north of the equator, stood
incredibly high. Compared with with Mauna Loa, the largest volcano on Earth,
which rises 6 miles above the ocean floor, Olympus Mons stood 16 miles above
the surrounding plain.
The Valles Marineris, just south of the Martian equator was an enormously
deep rift. Compared to the Grand Canyon, which is 280 miles long, Valles
Marineris extended for 2500 miles, 1/5 the circumference of the planet.
There were two significant types of water evidence. On the younger northern
terrain there appeared a number of large flood plains. Dr. Michael Carr,
leader of the Viking Orbiter Imaging Team, with the U.S. Geological Survey,
presently believes that the flood plains may have been the result of meteor
impacts or volcanic eruptions which released massive artesian systems below
the frozen surface.
On the oldest terrain lay the best evidence for an earlier wetter planet.
Here were numerous examples of runoff channels. Like earthen channels, they
start small, increase in size downstream, and show definite signs of
tributaries.
The surface of Mars was different from earth in one important geological
characteristic. Mars does not have enormous active sections drifting and
banging into one another creating mountains and quakes like earth. Mars
was born with 1/10th the mass of earth, cooled quicker, has a thicker crust,
and thus lacks plate tectonics. Its surface is static. It's why Mars' Mount
Olympus is so much higher than Mauna Loa. Mauna Loa is only the latest volcano
to stand over the Hawaiian volcanic vent. The other volcanos, known
collectively as the Hawaiian Islands, are strung out in a line over the mid
Pacific. "But on Mars," says Carr, "Olympus Mons just sits there and grows
and grows."
But a lack of plate tectonics is also why Mars lacks atmosphere. To get the
picture you must go back 4.5 billion years ago to the formation of the planets.
As the planets grew from accumulated interplanetary matter, they formed
atmospheres of carbon dioxide and nitrogen gas.
Earth was able to recycle that atmosphere. This recycling begins when carbon
dioxide dissolves in rain water to form a mild carbonic acid which weathers
rocks. Carbonate minerals, formed by this weathering process, run down stream,
eventually collecting at the bottom of the ocean as carbonate sediments.
But plate tectonics pushes these sediments under the continental plates,
super heats them, and then releases new CO2 back into the atmosphere through
volcanoes or earthquake faults. (Oxygen did not dominate the earth's atmosphere
until about a billion years ago, the by-product of photosynsthesis. We
essentially breathe the accumulated stale breath of cynobacteria, algae, and
other photosynthetic microorganisms.)
On Mars, C02 cycled into the ground from whence it never returned. For a while
meteor impact or hot lava rock may have extended the life of an early denser
Martian atmosphere by burying and then decomposing carbonate sediments. But
according to NASA Aims Planetary Astronomer Dr. James Pollack, "As you get
past the 1st billion or so years of Martian history, the impact rate dropped
dramatically and the generation of heat in the interior of the planet kept
on decreasing making it difficult to bring out enough lava to bury the
carbonate rock." The carbonate cycle on Mars ground to a halt.
But there is the matter of an initial billion years, a period when Martian C02
may have been plentiful, Martian climate a lot like earth, and a period when
life evolved on earth to a fair degree of sophistication. Given the differences
in environments, how would the Martians have evolved?
At the Nasa Aims Research Center, Dr. Rocco Mancinelli, a microbial ecologist,
tends a series of sealed bottles in his laboratory. Each bottle is attached to
different gas canisters, which feed them early Martian air which these days one
can get from Matheson Gas Co. and what Mancinelli calls, "Mars in a Jar."
What Mancinelli is trying to determine is the ability of microorganisms to fix
nitrogen from early Martian air, which scientists believe was nitrogen poor.
According to Mancinelli, nitrogen is one of the limiting factors of
carbon-based biology. "Every body needs nitrogen. It's an important biomolecule;
it's in DNA, RNA and in protein. But most of the nitrogen exists as Nitrogen
Gas -- completely useless to most organisms in that form. Only a few
microorganisms have the ability of taking nitrogen gas and reducing it to
ammonia, where it can go directly into the food chain."
So far Mancinelli's aerobic nitrogen fixers have been able to survive on 30%
of what early Mars had to offer. The anaerobic half are now taking their turns
in the bottles and the results are pending.
Mancinelli has also joined a number of NASA researchers looking for models of
early Mars right here on earth. As Mars lost its early CO2 atmosphere, it lost
the blessing of that atmosphere's greenhouse effect. If life evolved, its most
advanced forms would have had to adapt as the planet became a cold desert.
To simulate that adaptation, NASA scientist have been going to the dry valleys
of Antarctica, the coldest and driest of all places on earth. In the 60's,
Antarctica was declared a lifeless habitat. But scientists have been
discovering life there in some amazing places.
Bob Wharton, a rugged researcher who studied karate under under Chuck Norris,
has discovered life in Antarctica at the bottom of frozen lakes and is now
studying them for their Martian application. From McMurdo Station, Wharton
and several NASA scientists catch a helicopter for a ride to Taylor Valley, a
dry mountainous Martian landscape about 800 miles from the South Pole.
At Lake Hoare, in Taylor Valley, they spend a day and a half melting a hole
in the 20 foot thick crust of ice before descending into dark cavern to explore
the lake bottom. What they find below are bazaar microbial mats -- tissue like
structures that are pigmented green, red, and purple to catch the limited light
that seeps through the cold ice. "It's a fairly advanced form of life," says
Wharton, "you`ve got a cell wall, and you've got DNA inside the cell that is
able to reproduce and pass on information to it's offspring. It's not elephants,
but it's a big step in the evolution of biology."
Scientists have identified what might have been lakes 3.5 billion years ago
in the Valles Marineris. Says Christopher McKay, who is working with Wharton
at Taylor Valley, "A lake is a good place to live, because there is water, and
a good place to die, your body gets preserved." Researchers have discovered
that despite a mean temperature of -28 degrees F above the ice, underneath
everything's toasty and above freezing. The ice cover provides what the
scientists call "thermal buffering."
The ice also prevents gases escaping; thus the water in these Antarctic lakes
contains dissolved atmospheric gases that greatly exceeds those outside. Life
could have held out in this warmer and chemically enriched environment long
beyond the point where the planet as a whole had ceased to be hospitable.
"Life's last stand on Mars," says Wharton, "may have been a swim in a frozen lake."
Their remains may also be the most advanced as well as the closest to the
Martian surface. Lake Hoare's microbial mats are the same organisms that
form stromatolites -- honeycombed layers of microfossils in sedentary rock.
Our oldest fossils are stromatolites, formed on earth some 3.5 billion years
ago. Antarctic researchers will this year be taking core samples of the
sedentary material below the algal mats to understand what type of fossil
evidence Lake Hoare's lake bottom communities leave.
Another potential analog of early Martian environments has been discovered
in the Victoria Land Region of Antarctica by Dr.'s E.I. and Roseli Friedmann
of Florida State and Florida A & M Universities called cryptoendolithic
("hidden inside rocks") environments. Lichen communities survive in
temperatures that are - 20 to -35 degrees F. at about 1/2 to 1 centimeter
inside mostly sandstone rocks which channel heat and moisture into the
interior. "They are not only alive," says Roseli Friedmann, "but happy."
Not all Mars studies have been in Antarctica. Scientists have also spent
considerable effort looking at the Nevada Deserts, especially the Carson Sink
near Reno. Geologists tell us this area used to contain numerous lakes, but
dried up as the rising Sierra Nevada shielded it from Pacific storms.
This is a Martian analogue in that it is a system which though geological time
has gradually dried out. Christopher McKay, working here with Wharton,
Mancinelli, and others is especially interested in the contribution of dew
to desert biological systems. "We saw frost on Mars," says McKay. "If it had
been a little bit warmer, that frost could have been dew."
Bob Wharton also climbed the 14,162 foot volcanic summit of Mt. Shasta to
visit simple microorganisms growing in acid hot springs. "The water would
have burnt holes in in my clothes," says Wharton, "but they were thriving."
The litany of these environments reads like a list of secret hiding places.
In fact they are. One of the things NASA biologists have learned from looking
in these obscure corners is how hard it is to play hide-and-go-seek with
living matter. Says McKay, "Life can be in places and do things you can't
imagine."
Still McKay claims in all these environments, there is a dependence on water
above 32 degrees F. "That's the absolute, non negotiable, you have to have
liquid water." According to Dr. Andrew Ingersoll, a Caltech planetary
scientist, "It's the axiom of the frozen food industry, there is no life below
liquid freezing."
There can, however, be fossils below freezing. But here presents another
Martian dilemma. What would fossils look like. On earth bacteria are spiral,
spherical, or rod shaped. "But it is not clear this is universal," says McKay.
"On Mars bacteria could be pentagonal, figure 8, or even square."
Another characteristic which has questionably universal application is the
carbon isotope shift measurement. On earth when a living system takes in carbon
it has choice of taking in carbon 13 or the heavier isotope carbon 14. As a
rule it will take in more of the carbon 13. Life prefers the lighter elements,
whether it is carbon, sulfur, or nitrogen. On earth the average terrestrial
abundance of carbon 12 to carbon 13 is 90 to 1. But if you were to analyze a
plant, say in your living room right now, its ratio would be 92 to 1, the
signature of biological systems. If you find fossilized tar and want to know
whether it ever breathed, you measure this ratio. "If it has this
characteristic," says McKay, "Then you can say, this was alive once. But if
you go to Mars and make that same measurement, can you make that same
conclusion." McKay hopes to address these issues before the final countdown.
Despite the difficulties, NASA researchers feel Mars is worth it, not only
for what we may learn about the Red Planet, but for what we may learn about
earth. Two thirds of the surface of Mars is 3.8 billion years or older. The
surface of the earth is young by comparison. Our earliest fossils,
stromatolites, are 3.5 billion years old. Prior to that everything has been
cooked by plate tectonics. Scientists have recovered tars from Greenland
dated at 3.8 years ago, which by their carbon isotope shift may have been
alive, "but we don't have the body," says McKay. If life, however, evolved
on Mars, maybe it has the "body."
Earth's fossil record adds little to the scenario of our earliest organisms.
Our first fossil is of an already mature biological system. The self
replication of organic compounds, the appearance of cells, photosynthesis,
and the assembly of DNA are unrecorded in the fossil record. "It's hard to
imagine how these things could have happened," said NASA Biologist Gerald
Soffen, with the Goddard Space Flight Center in Maryland, at a recent
conference. "Once you reach the point of a single-cell organism with genes,
I am comfortable evolution takes command. But the early leaps, they're very
mysterious."
And what of non carbon-based life. All the Viking experiments, and thus far
all the Martian models have been predicated on a biochemistry that was
carbon-based. Carbon has a subatomic quirk that allows it to form
astonishingly complicated molecules such as those found in the genetic
system in the helical strands of DNA.
Graham Cairns-Smith, a Scottish Chemist, has proposed that life may have
begun on a template formed by the small flat crystals found in clay. Could
these silicon crystals have kept evolving on another planet? NASA scientists
argue that silica based life is outside earthbound experience, and we would
have no way of dealing with the hypothesis.
"Believe you me," says NASA planetary scientist Dr. Carol Stoker, "If Viking
had gone to Mars, and seen rocks walking around, we'd have a man on Mars
today."
Though NASA biologists are generally pessimistic about the possibility of
active biology on Mars, the Russians haven't ruled it out. Mikhail Ivanov,
director of the Institute of Microbiology in Moscow and a member of the Soviet
Academy, has met with a number of Viking biologists soliciting their expertise
for a future Soviet mission which would sink probes below the Martian surface.
Until the early 1980's it was thought that life did not exist under the
surface of the earth much lower than plants grew. But Dr. Carl Fliermans at
Savanna River Laboratory in Georgia has found life in the soil more than 1,700
feet deep. "These microorganisms do not decrease in number or diversity with
depth," says Fliermans. "Because that is true here, could that also be true in
a Martian environment." Could life have invaded the subsurface as conditions
topside became intolerable.
Life has been discovered at deep ocean vents getting their energy from sulfur
rather than sunlight. Though the infrared thermal mapper on the Viking Orbiters
picked up no evidence of geothermal activity, Dr. Leonard Martin, a research
scientist at the Lowell Observatory has a series of photos taken from Viking
which clearly look like a geyser going off at the surface.
Then there's Dr. Gilbert Levin. Levin thinks he saw a Martian. Levin was the
experimenter for the Vikings Label Release LR experiment (Remember, we said
we'd discuss that later). He claims his results were positive for life on Mars.
When fed simple radioactive organic compounds the soil sample burped radioactive
CO2. Levin thinks there might be some sort of lichen on the surface of Mars.
At a conference held in Washington D.C. in 1986 celebrating the 10th anniversary
of the Viking mission, Levin got up and disturbed the guests by reading a paper
he'd spent 10 years in the making. "As a result of objective evaluation of our
data," said Levin, now president of Biospherics Inc., "it is is more probable
than not there is life on Mars."
To back his claim he presented a head to head comparison of the GCMS experiment
(the one that found no organic matter on Mars) and his LR experiment on an
Antarctic soil sample. The GCMS experiment again found no organics whereas the
LR and a follow-up wet chemistry analysis showed "significant organic matter."
Levin says the explanation offered by other scientists of a highly oxidized
Martian surface is speculative, especially since Mariner 9 measured peroxides
on the surface "and found none."
Dr. Carol Stoker represents the norm of the scientific community, when she
expresses continued reservations of existing life on Mars, despite Levin's
claims. "Nevertheless," says Stoker, a member of the Theoretical Studies Branch
at NASA Ames, "maybe there's no life on Mars now, and maybe there never was,
but there will be."
Stoker, who's wanted to go to Mars ever since a recurring series of dreams
took her there when she was 8 years old, envisions a permanent research base
of closed environments on Mars, as the next most logical place to live outside
our planet. Still she claims a child grown up the Martian planet with 1/3 the
gravity of earth would never have the physical or skeletal structure again to
walk on earth. In time evolution would change this new man to adapt to its
new environment. "And those things won't look anything like us," she warns,
"they'll truly be Martians."
"The first step of men and women from our planet to Mars," says Cornell
University Astronomer Carl Sagan, "is a key step in transforming us into
a multi planet species."
Christopher McKay envisions a day when we could actually terraform Mars, turn
it into another earth. Since Mars may have once been earth-like the whole
thing could be viewed as a restoration project. The first step would be to
turn Mars' carbonate rock back to C02, and to introduce microorganisms to
start working on the oxygen. Then to warm the planet up further, we could
add orbiting giant mirrors, spread black soot over the polar caps, or introduce
a "cocktail" of green house gases like chloroflourocarbons. "Using deodorant,"
says McKay, "might become your patriotic duty."
The whole process could take over 100,000 years, but that's just a tick on
the geological scale. Self sufficiency would be imperative to any group
inhabiting Mars. Says McKay, "To them the benefits of terraforming would
be quite tangible -- the survival of their civilization."
-- End --