Microorganisms Grow at Low Pressures, Implying Possible Life on Mars

FAYETTEVILLE, Ark. – Using a unique device known as the Andromeda
Chamber to simulate conditions found on Mars, University of Arkansas researchers
discovered that certain microorganisms called methanogens could grow at low
pressures. Their findings imply that life could have existed on the Red Planet
in the
past, present, or that it could do so at some point in the future. Associate
professor
of biological sciences Tim Kral presented the preliminary results at a
bioastronomy
conference in Australia in July.

“Our goal is first to get the organisms to grow well, then systematically
experiment
with conditions found on Mars,” said Kral. He and his team first grew test tube
cultures of various methanogens in a Mars soil simulant called JSC Mars-1.
Derived from altered volcanic ash, it approximates the composition, grain size,
density, and magnetic properties of Martian soil.

The researchers exposed the cultures to an atmosphere that consisted only of
hydrogen and carbon dioxide, the raw materials methanogens need to produce
energy. They incubated the cultures at each methanogen’s optimal growth
temperature. Methanogens release methane as a waste product, so the researchers
were able to measure their growth by analyzing the amount of methane produced.

After successfully growing three different methanogens on Mars soil simulant,
Kral
moved on to the next step — simulating various Martian conditions in the
Andromeda Chamber, a large stainless steel vacuum container donated to the
University of Arkansas by the Jet Propulsion Laboratory in Pasadena,
California.

The chamber, which was originally constructed for comet simulations, consists
of an
insulated compartment with heating and cooling elements. A sample container,
approximately one meter on each side, can be lowered into the chamber, which
contains various detection and monitoring instruments. The device is believed
to be
the largest such instrument dedicated to space simulation research on a North
American university campus.

The researchers grew methanogenic cultures in bottles and froze them. They
inverted the frozen cultures and placed them below the surface of the soil
simulant in
the sample container, lowering it into the chamber. After sealing and
evacuating the
chamber, they replaced the atmosphere inside with an equal mixture of hydrogen
and
carbon dioxide at 500 millibars (about half the Earth’s atmospheric pressure).
Finally, they raised the temperature of the chamber to 35 degrees Celsius to
ensure
that the cultures melted into the soil simulant. A gas chromatograph was used to
analyze samples daily.

So far, the Andromeda Chamber studies indicate low levels of methane production.
This means that the organisms are metabolizing under low pressures, a
significant
finding. Martian life would have to be able to survive at such pressures, since
Mars’
atmosphere is much less dense than Earth’s.

“The Viking Missions that landed on Mars in 1976 gave no substantial evidence
for
life on the surface today,” Kral says. “There were also no measurable organic
compounds detected. This led most researchers to believe that if life existed
there, it
was a long time ago, and is extinct today.”

But Kral’s work with methanogens got a significant boost from the discovery
earlier
this year of large quantities of frozen water below the surface of Mars. “With
the
recent successful missions to Mars (Pathfinder, Global Surveyor, Odyssey), and
especially the discovery that there is probably a vast ocean of frozen water
below
the surface, there is a greater possibility that life may exist below the
surface
today.”

Kral doesn’t want to rush to categorical conclusions about the implications of
his
research, but if methanogens can grow well under simulated Martian conditions,
it
might be possible to take the organisms to Mars if humans ever colonize the
planet.

“Of course, there are many potential ethical and environmental problems with
this,”
Kral points out. Since methane is a “greenhouse gas,” one that traps heat near a
planet’s surface, methanogens could theoretically be used to raise Mars’ surface
temperature, eventually “terraforming” the planet so that it could support life.
However, Kral thinks this might take too long to be effective-perhaps hundreds
or
thousands of years.

Martian surface conditions include low pressure, low temperature, very little
water,
and an atmosphere that contains large amounts of carbon dioxide with almost no
oxygen. Assuming that hydrogen and some water are present under the surface, the
basic requirements for methanogen growth are met on Mars. And even if hydrogen
is not present, carbon monoxide is, and some methanogens can use this instead of
hydrogen.

Subsurface life on Mars would not be able to produce energy through
photosynthesis, but would need to use chemical energy through the oxidation of
inorganic matter. Such organisms are called chemoautotrophs.

Methanogens are chemoautotrophs that consume hydrogen and carbon dioxide,
producing methane as waste. Few terrestrial organisms could survive anything
approaching harsh Martian conditions, but methanogens can flourish in some of
Earth’s most inhospitable environments, such as ocean floor vents and peat
bogs.

Kral wants to continue his research by experimenting with a range of Mars-like
conditions, thoroughly analyzing the effects of lower pressures and
temperatures on
methanogenic growth, and ultimately ascertaining the effects of radiation,
which is
much higher on Mars because of its thin atmosphere.

What is the probability of extraterrestrial life? In all likelihood, it’s quite
high. But
whether or not life actually exists on Mars — or did exist sometime in the
past —
is a question that terrestrial research can answer only partially. Kral’s work
paves
the way for future experiments with Mars-like conditions and may one day provide
a basis for studying biology in a real-life Martian laboratory.