NASA News Update:1976 Viking Landers Detected Organics on Mars


6a00d8341bf7f753ef00e5539e30c08833.jpg 'Contrary to 30 years of perceived wisdom, Viking did detect organic materials. It's like a 30-year-old cold case suddenly solved with new facts." Christopher McKay, of NASA's Ames Research Center in California

In 1976 the NASA Viking landers took samples of soil on Mars and tested them for signs of organic carbon. Up till now, the evidence sent back from by two Mars Viking Landers in 1976 and 1977 was inconclusive. In fact, NASA's first press release about the Viking tests announced that the results were positive. The "labeled Release" (LR) experiments had given positive results. But after lengthy discussions in which Carl Sagan participated, NASA reversed its position, mainly because another experiment detected no organics in the soil.

Till this day,  Gilbert Levin, the principal designer of the LR experiment, believed the tests pointed to life. When the same two experiments were run on soil from Antarctica, the same conflicting results were obtained (LR – positive; organics – negative.) Soil and ice from Antarctica certainly contains life. The test for organics was negative because it is far less sensitive than the LR experiment. The same problem could have caused the organics test on to give a false negative.

A reinterpretation of the results now suggests the samples did contain organic compounds, but the results were not understood because of the strong oxidation effects of perchlorate, a salt now known to be found in Martian soils.
In the Viking tests the Martian soil was heated sufficiently to vaporize organic molecules in the soil and the resultant gases and vapors were analyzed by gas chromatography-mass

Chlorohydrocarbons were found at landing site 1 and 2, but they were dismissed at the time as terrestrial contaminants, even though they were not found at the same levels in blank runs. Then, in 2008 the Phoenix lander discovered perchlorate in the Martian arctic soil. Perchlorates are well known as powerful oxidizing compounds that combust organics, but their presence in Martian soils was not suspected in the 1970s.

After the Martian soils were found to contain perchlorates, scientists from Ciudad Universitaria in Mexico City, and NASA’s Space Science Division at Moffett Field, California, decided to test the soils of the Atacama Desert in Chile, which is considered more like Mars than anywhere else on Earth.

The research, reported in the Journal of Geophysical Research, found that when soil samples containing organic carbon were mixed with magnesium perchlorate and then heated, the same kind of combusted chlorohydrocarbons were found as had been detected on Mars by the Viking lander and dismissed as contaminants.

Reinterpreting the Viking results in the light of the new findings suggests the samples from landing site 1 contained 1.5 to 6.5 ppm organic carbon, while those from landing site 2 contained 0.7 to 2.6 ppm organic carbon.

The presence of organic material does not provide evidence of life or past life on Mars but only of the presence of organic compounds. NASA is now planning a new mission for November 2011 to have another look for organics and other chemicals on Mars in an effort to better understand the chemistry of Martian soils.

Source: and

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