Methane plume on Mars a sign of life?

Scientists report finding gas on planet's surface

Plumes of methane, a gas typically produced on Earth by cow digestion, flatulence and rice paddies, were reported on Mars by scientists today, raising the tantalizing possibility that life may dwell beneath the planet's inhospitable surface.

On Earth, most methane is a byproduct of life, whether it is belched out by livestock or excreted by hardy microbes that dwell deep within thick sheets of ice, but it can is also produced by geological processes.

"We don't know what's producing it on Mars, quite frankly," said Michael Mumma, director of NASA's Goddard Center for Astrobiology who led the work. "If it's geochemistry, that's of keen interest because it means we have a window into the interior of Mars just by what gases are being released; if it's produced biologically, that's been one of the quests since Mars was first explored."

Either possibility is exciting to scientists, and helps to reshape the image of a planet long thought of as a frozen, inhospitable place studded with extinct volcanoes and carved by water that flowed on its surface long ago.

"Something's going on -- it's not cold and dead and extinct," said Phil Christensen, a planetary geologist at Arizona State University, who was not involved in the research. "There's the biological possiblity -- but even if it's not biology, the geological possibilities are pretty exciting as well...either way, we're discovering Mars is more and more dynamic than we thought."

Methane was first detected on Mars in 2003, although some of the initial reports were controversial and several scientists said the new work, published online yesterday in the journal Science, provided the best evidence yet.

"For all we know, this may be the only detection -- there were lots of disagreements, lots of holes in the arguments" of previous work, said James Lyons, a scientist at the Institute of Geophysics and Planetary physics at the University of California, Los Angeles not involved in the research.