Evidence That the Reactivity of the Martian Soil Is Due to Superoxide Ions

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Science  15 Sep 2000:
Vol. 289, Issue 5486, pp. 1909-1912
DOI: 10.1126/science.289.5486.1909

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The Viking Landers were unable to detect evidence of life on Mars but, instead, found a chemically reactive soil capable of decomposing organic molecules. This reactivity was attributed to the presence of one or more as-yet-unidentified inorganic superoxides or peroxides in the martian soil. Using electron paramagnetic resonance spectroscopy, we show that superoxide radical ions (O2 ) form directly on Mars-analog mineral surfaces exposed to ultraviolet radiation under a simulated martian atmosphere. These oxygen radicals can explain the reactive nature of the soil and the apparent absence of organic material at the martian surface.

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