UMass researchers find environment on Earth that mimics Mars geochemically and supports ancient life form
University of Massachusetts
AMHERST, Mass. - 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
"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 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.