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New Mars tests find possible life ingredients
Perchlorate, which consists of chlorine and oxygen, actively absorbs electrons from surrounding compounds when heated. "It could sit there in the Martian soil with organics around it for billions of years and not break them down," McKay said. "But when you heat the soil to check for organics, the perchlorate destroys them rapidly."
In addition, the researchers found evidence of the organic compound chloromethane after they heated the Atacama soil with perchlorate. That compound had been detected during the organics experiments at both Viking landing sites but had been written off as a contaminant from Earth because it is in cleaning fluids.
Navarro-Gonzalez said his team ran the experiment many times and always produced some form of chloromethane, leading to the conclusion that it was being formed by the combining of the perchlorate with some form of organic Mars material.
"The big lesson here, and the great importance of this finding, is that we have to know what we're looking for and how we can find it," Voytek said. "It shows that we could actually uncover life on Mars and not know it."
That is what some believe already happened on Mars. A life-detection experiment on both Viking landers gave a positive signal that something in the soil was metabolizing a food source introduced and a negative signal in the control experiment. The principle investigator of that experiment, Gilbert Levin, has argued for more than 30 years that Viking did, indeed, find life.
It was the no-organics conclusion of a subsequent Viking experiment that convinced scientists that Levin's test had detected a non-biological chemical reaction. Although many planetary scientists have remained convinced that Levin did not find life, the increasingly apparent problems with the no-organics experiment are leading some to reconsider.
The new paper will also be important for NASA's 2011 Mars Science Laboratory mission, which is designed specifically to find organic material on the planet. The mission's Curiosity rover has some of the same high-temperature equipment to detect organics that Viking had, although it also has a secondary experiment that involves solvents at low temperatures.
Navarro-Gonzalez is on the MSL science team and will bring his new interpretation of Martian chemistry to the effort. Confirming the presence of organic material on the Martian surface and learning about its properties, he said, would add enormous impetus to the search for possible Martian life.