The First Signs of Ancient Life on Mars? | SPACE NEWS

Thursday, December 06, 2012

The First Signs of Ancient Life on Mars? | SPACE NEWS | MARS

By Richard A. Kerr
news.sciencemag.org
12-3-12

SAN FRANCISCO, CALIFORNIA—The first full analysis of martian soil by the Curiosity rover has detected simple carbon compounds that could be the first traces of past martian life ever found, NASA scientists announced here today at a press conference at the annual fall meeting of the American Geophysical Union. The catch is that Curiosity team members can't tell yet whether the organic matter was once alive, was never alive and drifted onto Mars from space, or was simply cooked up in Curiosity's analytical instrument from lifeless bits of soil. Figuring out the ultimate source of the carbon in this organic matter—biological or not—will take time. "Curiosity's middle name is Patience," cautioned Curiosity project scientist John Grotzinger of the California Institute of Technology in Pasadena.

Although Curiosity did find organic matter, the media's frenzied anticipation that preceded the press conference—and drove it into a ballroom to accommodate all the TV cameras—turned out to have been provoked by a misunderstanding. A reporter overheard Grotzinger praising the superb high-quality data being returned by the rover and assumed the remarks referred to an exciting discovery from Curiosity's first thorough soil analysis. The rover had taken in fine soil particles, heated them, and passed the gases that the heating drove off through its mass spectrometer, which can separate and identify the gases by molecular weight. The only exciting result reporters could imagine was organic matter from life, and so the frenzy of anticipation began.

What Curiosity actually detected were trace amounts of three of the simplest possible carbon-containing compounds: a carbon atom with one, two, or three chlorine atoms attached in place of hydrogen atoms. According to Paul Mahaffy of NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the principal investigator of Curiosity's Sample Analysis at Mars (SAM) instrument package, these three chloromethanes were most likely generated in SAM. The heating may have decomposed a natural component of martian soil—the strong oxidizing agent perchlorate—which in turn could have broken down some form of carbon in the soil sample and chlorinated its carbon atoms.

The question would then become what form the carbon was in. It might have been big, complex organic molecules like amino acids, the molecular remains of long-dead martian organisms. . . .

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