Friday, January 16, 2009

methane on Mars

In 2003, earth-based telescopes detected methane on Mars. Those discoveries raised so many questions and were so widely challenged that only now have they been published, in Science. And these astronomers are sticking to their guns.

A team of researchers reported Thursday that the bursts of methane originated from three specific regions in the planet’s northern hemisphere, where it was midsummer. The gas came out at a rate of 0.6 kilograms a second, the scientists said, and the plume contained 19,000 metric tons of methane.

“This is the first definitive detection of methane on Mars,” Michael J. Mumma of the NASA Goddard Space Flight Center in Greenbelt, Md., the leader of the research team, said. . . .

Methane — the simplest of hydrocarbon molecules, with one carbon atom and four hydrogen atoms — is fragile in air. It falls apart when hit by ultraviolet radiation in sunlight. That means any methane in the Martian air must be recent.

When the presence of methane was reported in 2004 by three teams of scientists, the findings generated surprise and skepticism because only a few explanations seemed to be plausible.

One was geothermal chemical reactions involving water and heat in volcanoes or underground hot springs. But evidence for recent volcanism on Mars is scarce. Also, volcanoes would be expected to spew other gases like sulfur dioxide, and those are not plentiful in the planet’s atmosphere.

A second possibility is biological. On Earth, a class of bacteria known as methanogens breathes out methane as a waste product.
This is intriguing data, but I remain skeptical of Martian life. Life as we know it on earth is so powerful and creative that it could not be confined to a few underground reservoirs. It would evolve ultraviolet shields and whatever else it had to do to spread across the whole planet.

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