September 3, 2010

New Study Revisits Viking’s Mars Soil Discovery

NASA's Phoenix Mars Lander discovered a surpise chemical in 2008, which suggests that carbon-based chemicals found in 1976 by Viking Mars landers could be from the Martian soil and not from cleaning fluids, according to a NASA statement released on Friday.

"This doesn't say anything about the question of whether or not life has existed on Mars, but it could make a big difference in how we look for evidence to answer that question," said Chris McKay of NASA's Ames Research Center, Moffett Field, Calif. McKay coauthored a study published online by the Journal of Geophysical Research.

The chloromethane and dichloromethane chemicals were discovered when the Viking landers heated samples of Martian soil, but they were thought of as likely contaminants from cleaning fluids.  However, the new study found that when perchlorate was added to desert soil from Chile, it contained organics similar to those found during the Viking tests.

"Our results suggest that not only organics, but also perchlorate, may have been present in the soil at both Viking landing sites," said the study's lead author, Rafael Navarro-González of the National Autonomous University of Mexico, Mexico City.

Meteorites that have been falling onto Mars and Earth for the past 5 billion years also contain organics.  Scientists have long speculated that Martian soil would contain organics from these meteorites.

"The lack of organics was a big surprise from the Vikings," McKay said. "But for 30 years we were looking at a jigsaw puzzle with a piece missing. Phoenix has provided the missing piece: perchlorate. The perchlorate discovery by Phoenix was one of the most important results from Mars since Viking."

When perchlorate is heated, it becomes a strong oxidant.  Perchlorate is an ion of chlorine and oxygen.

"It could sit there in the Martian soil with organics around it for billions of years and not break them down, but when you heat the soil to check for organics, the perchlorate destroys them rapidly," McKay said.

The researchers challenged how the Viking scientists perceived the Martian organic compounds.  They said that the chemicals were not present in their samples because of the limited technology during the Viking experiment. 

The scientists said that further work is needed in order to help determine whether the Viking scientists were wrong or not.

The Curiosity rover that will be sent off to Mars in 2012 along with the Sample Analysis at Mars (SAM) instrument the NASA Goddard Space Flight Center developed on board.  Curiosity can rove and analyze a wider variety of rock and samples that the Viking and Phoenix landers could not. 

SAM is able to check for organics in Martian soil and powdered rocks by baking samples to even higher temperatures than Viking could. 

If Curiosity finds organic compounds on the Martian surface, scientists could then search or life on Mars by checking for DNA.


Image 1: In this artist's concept illustration, NASA's Phoenix Mars Lander begins to shut down operations as winter sets in. Credit: NASA/JPL-Calech/University of Arizona

Image 2: This is the first photograph ever taken on the surface of the planet Mars. It was obtained by Viking 1 just minutes after the spacecraft landed successfully early today. Credit: NASA


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