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Life on Mars?

It's hard enough to identify fossilized microbes on Earth. How would we ever recognize them on Mars?

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Steele is also working on a device called MASSE (Modular Assays for Solar System Exploration), which is tentatively slated to fly on a 2011 European Space Agency expedition to Mars. He envisions the rover crushing rocks into powder, which can be placed into MASSE, which will analyze the molecules with a microarray, searching for biological molecules.

Sooner, in 2009, NASA will launch the Mars Science Laboratory Rover. It’s designed to inspect the surface of rocks for peculiar textures left by biofilms. The Mars lab may also look for amino acids, the building blocks of proteins, or other organic compounds. Finding such compounds wouldn’t prove the existence of life on Mars, but it would bolster the case for it and spur NASA scientists to look more closely.

Difficult as the Mars analyses will be, they’re made even more complex by the threat of contamination. Mars has been visited by nine spacecraft, from Mars 2, a Soviet probe that crashed into the planet in 1971, to NASA’s Opportunity and Spirit. Any one of them might have carried hitchhiking Earth microbes. “It might be that they crash-landed and liked it there, and then the wind could blow them all over the place,” says Jan Toporski, a geologist at the University of Kiel, in Germany. And the same interplanetary game of bumper cars that hurtled a piece of Mars to Earth might have showered pieces of Earth on Mars. If one of those terrestrial rocks was contaminated with microbes, the organisms might have survived on Mars—for a time, at least—and left traces in the geology there. Still, scientists are confident they can develop tools to distinguish between imported Earth microbes and Martian ones.

Finding signs of life on Mars is by no means the only goal. “If you find a habitable environment and don’t find it inhabited, then that tells you something,” says Steele. “If there is no life, then why is there no life? The answer leads to more questions.” The first would be what makes life-abounding Earth so special. In the end, the effort being poured into detecting primitive life on Mars may prove its greatest worth right here at home.

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