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|Title:||Scientists Read Messages From Mars In Plumes Of Methane|
Plumes of methane, a gas typically produced on Earth by cow digestion and rice paddies, were reported on Mars by scientists yesterday, again raising the tantalizing possibility that life could dwell beneath the planet\'s inhospitable surface.
\'Roving Mars\' film opens at the Museum of Science. G26
On Earth, most methane is a byproduct of life, whether it is belched out by livestock or excreted by hardy microbes deep within thick sheets of ice. But methane can also be produced by geological processes, and that explanation, while less intriguing, could also account for the methane found on Mars.
"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 produced biologically, that\'s been one of the quests since Mars was first explored," he said, referring to the enduring question of whether life exists on the Red Planet.
But even if it is produced geologically - by, say, a chemical reaction in underground water sources - "that\'s of keen interest because it means we have a window into the interior of Mars just by what gases are being released," he said.
Either possibility - and if the methane does signal life on Mars, it would likely be in the form of methane-producing microbes, not little green men - helps to reshape the image of a planet long thought of as frozen and inhospitable.
Since the Viking Mission to Mars more than three decades ago, people have wondered whether the planet was habitable and could have once supported life. Evidence has accumulated. Water - essential for life - has been confirmed on Mars in frozen form. This summer, the Mars Phoenix Lander found salts that could be nutrients for life. The newest evidence means scientists can contemplate the possibility that organisms might be active.
"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 possibility - 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 reported on Mars in 2003, although some initial accounts were questioned, and scientists debated their accuracy. 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," said James Lyons, a scientist at the Institute of Geophysics and Planetary Physics at the University of California at Los Angeles, who also was not involved in the research.
The work also raises new questions about methane. The plumes appear to be seasonal, showing up during Martian summer. Mumma and colleagues used three ground-based telescopes to observe the atmosphere of Mars in several spots in 2003 and 2006. Anayzing light from the planet, they found that there appeared to be distinct methane hotspots in places called Nili Fossae, Terra Sabae, and Syrtis Major. Normally the gas would diffuse fairly rapidly, but the defined plumes suggest a continuing release. The researchers compared the largest plume to Coal Oil Point, a massive hydrocarbon seep in Santa Barbara, Calif.
Scientists agreed that the origins of the gas were more likely to be geological, some citing Occam\'s Razor, the principle that the simplest explanation is usually best.
P. Buford Price, a physics professor at the University of California at Berkeley, said that was his guess. But, he added, "I think we could argue, using my measurements in the laboratory of microbial life in ice, that if [microbes] were made early in the history of Mars, when there was a lot of water and conditions were OK for building up biomolecules, they could still be alive," Price said.
The Mars Science Laboratory, a Mars mission set to launch in 2011, will be able to add more certainty to the calculations on the methane. Mumma said one of the methane hotspots is among potential landing sites.
One way to determine whether the methane was produced by life would be to send a special instrument to Mars - perhaps on a future Rover mission - to measure the ratio of isotopes of carbon, Price said.
But for now, just the presence of the gas is exciting to scientists.
Carolyn Y. Johnson can be reached at email@example.com.