Methane Doesn't Necessarily Mean Life on Mars, Says Dartmouth Study

http://www.dartmouth.edu/~news/relea...05/06/07a.html

Methane doesn't necessarily mean life on Mars, says Dartmouth study

Dartmouth College Office of Public Affairs - Press Release
Contact Sue Knapp )
(603) 646-3661
June 7, 2005

Two Dartmouth researchers have weighed in on the debate over whether
the
presence of methane gas on Mars indicates life on the red planet. Mukul
Sharma, Assistant Professor of Earth Sciences, and Chris Oze, a
postdoctoral
fellow, argue that the Martian methane could have been produced by
inorganic processes just as easily as by bacteria.

In their paper published online in May in the American Geophysical
Union's journal, Geophysical Research Letters
http://www.agu.org/journals/gl/, Sharma and Oze describe how methane
on Mars can be made from abiotic, or non-living, sources. When water
containing dissolved carbon dioxide comes in contact with olivine, it
produces hydrogen, which then combines with carbon dioxide to produce
methane. The authors contend that olivine is abundant on Mars at
shallow
depths, and it could easily react with fluids just beneath the surface.

"Most methane on Earth is produced by bacteria, and methane has been
cited as an indicator of life on other planets," explains Sharma.
"However, we show in our paper that the mineral olivine can be altered
in the presence of water and carbon dioxide, which can produce copious
quantities of methane. It's quite easy to do, and there is nothing
bacterial about it. If there is life on Mars, I would like to see
better
evidence than methane."

The paper also provides a plausible explanation for a warmer and wetter
early Mars. Recent results from rover missions on Mars have pointed to
the presence of flowing water on the planet's surface. It is, however,
impossible to heat the planet's surface to above freezing temperatures
by greenhouse action of carbon dioxide alone. The authors estimate that
the abiotic creation of methane via the altered olivine was very
efficient due to a higher surface heat flow and more intense
hydrothermal circulation. Sharma and Oze say that methane, a very
effective greenhouse gas, would have been more abundant in the
atmosphere resulting in a climate that was warm enough to allow liquid
water to be present on the Martian surface.