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But the SAM also detected some simple hydrocarbons made up of chlorine and methane. Does that mean Martian-based organics are in the bag? The team suspects not, although it is conducting a thorough analysis. Surface soils are exposed to a range of radiation and chemicals in the atmosphere that tend to dismantle organic compounds.
The researchers say they suspect that the chlorine came from perchlorates in the soil, perhaps calcium perchlorate, Dr. Mahaffy says. Perchlorates are chlorine-based salts. The Phoenix Mars lander found perchlorates in abundance at its polar landing site in 2008.
The carbon in the methane is another story, however. It could represent residual contamination from Earth, despite extensive efforts to scrub the rovers before launch. Or the carbon could have come from the soil. But carbon in soils could be organic as well as inorganic. Indeed, Mahaffy holds out the possibility that the simples forms of chloromethane SAM detected could have formed during the analysis process, with carbon dioxide freed from the soil samples as they were heated serving as the source of the carbon. If the carbon is organic, researchers still have to figure out if the carbon is indigenous to Mars, or hitched a ride to the surface on micrometeoroids.
Given the various ways organic compounds can be destroyed on the Martian surface, "it's really going to be an exciting hunt ... over the course of this mission to find early environments that might be kind of protected from this harsh surface environment and really see what we can add to the organics story," Mahaffy says.