Can rapid loss and high variability of Martian methane be explained by surface H2O2?

Details Can rapid loss and high variability of Martian methane be explained by surface H2O2? Can rapid loss and high variability of Martian methane be explained by surface H2O2?

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p52a..03g&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #P52A-03

Physics

[5405] Planetary Sciences: Solid Surface Planets / Atmospheres, [5470] Planetary Sciences: Solid Surface Planets / Surface Materials And Properties, [6225] Planetary Sciences: Solar System Objects / Mars

Scientific paper

It has been reported by several groups that methane in the Martian atmosphere is both spatially and temporally variable. Here, we consider the possibility of chemical destruction of methane (and compensating sources) operating on seasonal time scales. The lifetime of Martian methane due to known chemical loss processes is long (on the order of hundreds of years). However, observations constrain the lifetime to be 4 years or less, and general circulation models suggest methane destruction must occur even faster (< 1 year) to cause the reported variability and rapid disappearance. The Martian surface is known to be highly oxidizing based on the Viking Labeled Release experiments in which organic compounds were quickly oxidized by samples of the regolith. Here we experimentally test if simulated Martian soil is also oxidizing towards methane to determine if this is a relevant loss pathway for Martian methane. We find that although two of the analog surfaces studied, TiO2-H2O2 and JSC-Mars-1 with H2O2, were able to oxidize the complex organic compounds (sugars and amino acids) used in the Viking Labeled Release experiments, these analogs were unable to oxidize methane to carbon dioxide within a 72 hour experiment. Further, sodium and magnesium perchlorate, salts that were recently discovered at the Phoenix landing site and are potential oxidants, were not observed to directly oxidize either the complex organic mixture or methane. The upper limit reaction coefficient, α, was found to be < 4 × 10-17 for methane loss on TiO2-H2O2 and < 2 × 10-17 for methane loss on JSC-Mars-1 with H2O2. Unless the depth of soil on Mars that contains H2O2 is very deep (thicker than 500 m), the lifetime of methane with respect to heterogeneous oxidation by surface-bound H2O2 is probably greater than 4 years. Therefore, reaction of methane with H2O2 on Martian soils does not appear to be a significant methane sink, and would not destroy methane rapidly enough to cause the reported atmospheric methane variability.

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