MARTIAN RESEARCH ALIVE & WELL
By Sean Henahan, Access Excellence
Seattle, WA (2/17/97) Is, or was, there life on Mars? This basic
question stirred lively debate at the annual meeting of the American Academy
for the Advancement of Science.
Graphic: False-color backscatter electron (BSE) image
of fractured surface of a chip from ALH84001 meteorite showing distribution
of the carbonate globules.
At the center of the controversy is a Martian meteorite, known as Alan
Hills 84001, which was found in Antarctica about 13 years ago. It formed
on Mars 4.5 billion years ago and appears to have come in contact with
liquid water between 3.6 billion and 4 billion years ago. From the water
sprouted mineral deposits that bear a strong resemblance to fossilized
Researchers believe that about 16 million years ago, a comet or asteroid
struck the Martian surface and blasted pieces of the rock into space, where
they drifted for millions of years. The meteorite, found in Antarctica
in 1984, fell to Earth about 13,000 years ago.
However, some naysayers were quick to question the claims of Martian
life, offering various potential alternative explanations to the findings,
from contamination of the sample to natural, but non-biological possibilities.
Cornell researchers believe that not only was there life on Mars long
ago, there is a good possibility that lifeforms may still exist today on
the red planet. The researchers argue that there may be life below the
surface of Mars for the same reason it exists on Earth, noting that both
planets are made of similar stuff and provide similar conditions.
Microbes deep inside the Earth's crust get oxygen from rocks and use
it to oxidize hydrocarbons that come streaming up from below, receiving
energy by this process. It now seems probable that life evolved by such
processes from the inside out, rather than commencing at the surface, said
Thomas Gold, Cornell professor emeritus of astronomy. The same scenario
is likely to be true for Mars and several other planetary bodies, said
Gold, a member of the National Academy of Sciences
"Microbial subsurface life has existed on Earth for billions of
years and still does," Gold said. "It is very likely that we
will find a deep, hot biosphere on Mars, as we have found on Earth, and
probably on many other planetary bodies in our solar system."
He noted that the Earth contains internal chemical energy sources in
which microbes thrive, using hydrogen, methane and other liquids and gases
that percolate up through cracks from the planet's interior, together with
oxygen and other components of the local rocks. He suggested that such
microbial life probably would be found in many areas below the surface
of the Earth and will exist also on many other bodies, such as the moon,
Mars, many asteroids between Mars and Jupiter, Titan (satellite of Saturn)
and Triton (satellite of Neptune) and other satellites of the giant planets,
and Pluto, the farthest known planet, where similar fluids have come up
He suggested that the known meteorites found on the Earth and identified
as having come here from Mars should be examined for evidence of such microbial
life. He also suggested that the search for such evidence of life would
become a central issue in planetary research.
Dr. Gold considers the evidence for Martian life to be particularly
strong because the meteorite ALH84001 contains solids that are known on
the Earth to be residues of such microbial activity. The key to his theory
is that petroleum has come up from great depth, not from biological sediments
generated at or near the surface. The clearest evidence for that: helium.
The chemically inert gas, helium, is found to be strongly associated
with petroleum all over the Earth, Gold said. This is true not only for
great petroleum deposits, but also in detail in gases that are measured
in thousands of locations at shallow depths. Yet no chemical process exists
in which biological sediments would have concentrated this gas.
Helium is generated diffusely by the decay of uranium and thorium in
the rocks. Gold is first to suggest that fluids, such as petroleum, that
have washed through great distances in the rocks flush out the small quantities
of helium that have accumulated along their way, increasing the helium
concentration in such fluids.
"This is the only possible mechanism. Why else would helium be
found together with petroleum?" Gold asks. "The association of
helium with biological matter has not been accounted for in any other way."
If so, this requires that petroleum has come up from great depths, like
100 miles or more, rather than from just the upper four miles or so where
there are biological sediments.
"In that case all the biological components that petroleum contains
must have been additions it obtained later at the shallower levels from
which we extract it," Gold said. What accounts for this biology? Microbial
life, he said.
It was for this reason, Gold said, that he had to suppose that there
was a huge amount of microbial life at all these shallower levels. "At
the levels to which we drill, petroleum is a wonderful food for microbes,"
Gold said. "They thrive on that. With this combination we can understand
why there is helium in petroleum and at the same time why there are biological
molecules in it also."
And if it is true that hydrocarbons are cooked deep inside the Earth
and then are mechanically washed up by geologic forces, where microbes
then feed on them, then it's just a small step to wonder whether similar
processes would not exist on other similar bodies in the solar system,
"The Earth, then, has no particular prerogative to develop microbial
life. Its subsurface is not unique. We know there are petrochemicals under
the surfaces of many other bodies in the solar system, and in fact most
other solid bodies have shown evidence of hydrocarbons."
USGS Scientist Michael Carr, an astrogeologist with the U.S.Geological
Survey in Menlo Park, Calif. offered further support for the idea of life
"There is mounting evidence that Mars is a water-rich planet that
may have experienced warmer climates, and therefore, life, in the past.
Furthermore early terrestrial life may have evolved in hydrothermal environments
resembling those in Yellowstone Park and along mid-ocean ridges and such
environments were likely common on early Mars."
Carr said that both Earth and Mars experienced an early era of heavy
meteorite bombardment that ended 3.8 billion years ago. Evidence for life
is found in 3.8 billion year old terrestrial rocks, indicating that the
Earth recovered remarkably quickly from this era of large and presumably
sterilizing impacts. "We do not know what happened on Mars, but conditions
on the two planets at that time could have been quite similar."
Upcoming unmanned missions to Mars will certainly provide important
new data, he stressed. The Mars Global Surveyor will map various properties
of the surface from orbit, and Mars Pathfinder will land a small rover
at the mouth of a large flood channel. Other missions will follow in the
1998 and 2001.
Carr said a major goal of those missions is to return samples to Earth
later in the decade from "places that we judge will have the best
chance of revealing whether there was life on Mars in the past."
Some scientists were far too quick to condemn the martian meteorite
findings, according to Dr. Christopher Romanek, of the University of Georgia's
Savannah River Ecology Laboratory in Aiken, S.C.
"It's time to pry the lid off the coffin, as our interpretations
are still very much alive and doing well," said. "We had nine
people working on the project for three years, and just since our press
conference, researchers have had to formulate and design tests, perform
experiments and interpret and publish the results in an amazingly short
"While these works are admirable on these grounds alone, they do
not provide the information required to resolve the current contamination
and formation temperature issues we face. And yet some of the press cling
to reports that ring the `death knell' for potential Martian life. Nothing
could be further from the truth."
Two years earlier before the idea of Martian life ever crossed his mind,
Romanek (and others) determined the Martian origin for mineral deposits
or carbonate "globules" in the meteorite and determined the globules
formed at a temperature capable of sustaining life. This information is
crucial because extremely high formation temperatures rule out the possibility
"In my opinion, it is clear the globules formed at low temperatures
-- perhaps not as low as 0 to 80 degrees centigrade (as originally estimated),
but surely not at the plus-or-minus 650 degrees centigrade, as suggested
in one theory," said Romanek.
Romanek said that other papers, which focus on individual aspects of
the NASA team's Science paper, fail to take into account all features in
the carbonate globules collectively.
Romanek does not discount the possibility that future studies could
provide a convincing alternative explanation for the formations found inside
the meterorite, but for now, he believes the original conclusions of the
study still offer the best explanations.
"We are completely open to new ideas and tests that will resolve
the issues at hand, but these ideas need to be fully explored before informing
the public," said Romanek. "I think we can resolve the issues
of formation temperature and contamination soon, and we should do so with
all expediency. If it turns out that either issue precludes a biologic
origin for the features we found, we can move on to the many other exciting
opportunities that our research has provided concerning processes on the
surface of Mars."
Related information on the Internet
with Stanly Miller
on Martian Meteorite?