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R.C. Quinn (SETI Institute/NASA Ames), P. Ehrenfreund (Leiden Institute of Chemistry), F.J. Grunthaner (NASA JPL), C.L. Taylor (SETI Institute), A.P. Zent (NASA Ames)
The discovery of the existence of present-day near-surface ground ice on Mars and evidence of past aqueous processes at the Mar Exploration Rover Opportunity site raises the possibility of the presence of liquid water or thin-films of water at soil/ice interfaces on the planet. These environments are potentially vastly different from the desiccated soils sampled by the Viking landers and the stability of organic compounds in these systems is unknown. We report the results of experiments which examine the degradation kinetics of aqueous organic substrates using Atacama soils as Mars analogs. We compare our results with direct information on the kinetic behavior of Mars soils in contact with organic compounds in aqueous systems obtained from Viking data. We find that the decomposition of organic compounds in our experiments is dominated by soil surface catalysis and that the overall rate of organic decomposition by some Atacama samples exceeds that of the Viking soils. However, in the Viking biology experiments, surface catalysis was one of multiple types of oxidative processes that occurred, but it was not the dominate process. In situ, organic decomposition on Mars, and in the Atacama, may be dominated by active photochemical mechanisms. Soil and water ice may serve as a sink for photochemically produced oxidizing species resulting in accelerated organic decomposition kinetics during transient wetting events.
This work was supported by the NASA Mars Fundamental Research program and the NASA Astrobiology Science and Technology for Exploring Planets program. P. Ehrenfreund acknowledges grant NWO VI 016.023.003.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.