— Deep below
the surface of the Beverhead Mountains of Idaho, a research
team led by Derek Lovley, head of the microbiology
department at the University of Massachusetts, and Francis
H. Chappelle of the U.S. Geological Survey (USGS), has found
an unusual community of microoganisms that may hold the key
to understanding how life could survive on Mars. Their
findings are spelled out in the Jan. 17 issue of the journal
Nature (vol. 415).
"The
microbial community we found in Idaho is unlike any
previously described on Earth," said Lovley. "This
is as close as we have come to finding life on Earth under
geological conditions most like those expected below the
surface of Mars.
"Life requires water and an energy source. The primary
energy source for life on earth is sunlight. Plants convert
sunlight energy to organic matter that other organisms then
use for fuel. On Mars and other planets or moons in our
solar system on which life might exist, liquid water is only
available below the surface where there is no sunlight. So,
if there is life, it must sustain itself with alternative
energy sources. This study demonstrates, for the first time,
that certain microorganisms can thrive in the absence of
sunlight by using hydrogen gas released from deep in the
Earth’s surface as their energy source."
Lovley added: "The microbial community found at the
Idaho site is remarkably similar to what geochemists have
postulated might be found below the surface of Mars, based
on what they know of Martian subsurface chemistry. Now that
such a community has been discovered, we can use it to test
hypotheses about hydrogen-based subsurface life, and use
these findings to develop strategies for searching for
similar microbial communities on other planets."
According to
Lovley, geologists and microbiologists have searched for at
least a decade for a community of microorganisms on Earth
that could survive on hydrogen, somewhere underground, away
from sunlight. Chappelle, of USGS, explained that he
specifically chose the Idaho site for the study because it
provided geological conditions most like those expected on
Mars.
"The
water deep within these volcanic rocks has been isolated
from the surface for thousands of years. It is devoid of
measurable organic matter, but contains significant amounts
of hydrogen," said Chappelle.
Lovley added: "In prior studies, when we looked in
underground areas we considered promising, the DNA
signatures of the bacteria present indicated they were
living on organic matter carried in the groundwater or that
had been deposited along with the subsurface of rocks. Those
environments are not likely to represent conditions on Mars
because, on Mars, such organic matter would not be
available.
"At the Idaho site we saw something completely
different," Lovley continued. "Over 90 percent of
the microorganisms were Archaea, which are microorganisms
considered to be most closely related to ancient life on
Earth. In this case, the Archaea were methane-producing
microorganisms that live by combining hydrogen with carbon
dioxide to make methane gas. They do not require organic
carbon in order to grow. This is exactly the scenario that
geochemists have predicted for life on Mars," explained
Lovley.
The
study was funded by the U.S. Geological Survey and a grant
from the Life in Extreme Environments program of the
National Science Foundation. In addition to Lovley and
Chappelle, the team included post-doctoral researchers Stacy
A. Clufo, Barbara A. Methé and Kathleen O’Neill of UMass;
Paul M. Bradley of USGS, Columbia, S.C.; and LeRoy L. Knobel,
USGS, Idaho Falls, Idaho.
-30-
From
University of Massachusetts
Wednesday, January 16, 2002
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