Magazine article Science News

Old Martian Questions May Have New Answer

Magazine article Science News

Old Martian Questions May Have New Answer

Article excerpt

A mystery surrounding the 1976 Viking mission to Mars has lingered for a quarter-century, but a recent experiment may have revealed the solution. The new results may guide future Mars missions, particularly those in search of life.

The Viking mission appeared to find that Martian soil can destroy organic molecules. Twenty-five years of trying to identify chemicals that might cause this breakdown hadn't found a convincing explanation, says Albert S. Yen of NASA's Jet Propulsion Laboratory in Pasadena, Calif. So, he and his colleagues simulated the Martian surface in their laboratory. They theorized that a chemical agent, superoxide radical ions, could arise and destroy organics on Mars.

In test-tube experiments, the researchers exposed mineral grains resembling those in Martian soil to a simulated Martian atmosphere and then irradiated the samples with ultraviolet (UV) light like that reaching Mars.

Using spectroscopy, Yen and his team. observed that superoxide radicals form on the mineral surfaces under these conditions, they report in the Sept. 15 SCIENCE. Such radicals would survive at Martian temperatures, they add.

The researchers report that the superoxide radicals are reactive enough to decompose organic molecules at the Martian surface. These radicals could also migrate through the Martian soil, the team claims. That is consistent with the Viking findings of soil capable of destroying organic matter both at the surface and 10 centimeters below, where superoxide-forming UV light wouldn't penetrate. …

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