Little variability of methane on Mars induced by adsorption in the regolith

The mechanisms that can induce short term variations of methane in the Martian atmosphere, and thus explain the observations currently available, are yet to be discovered. Seasonal exchange with the regolith, caused by reversible adsorption, is expected to induce both spatial and time variabilities...

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Bibliographic Details
Published in:Planetary and space science 2011-02, Vol.59 (2), p.247-258
Main Authors: Meslin, P.-Y., Gough, R., Lefèvre, F., Forget, F.
Format: Article
Language:English
Subjects:
Adsorption
Astrophysics
Atmospherics
Earth and Planetary Astrophysics
Exchange
Global climate model
Mars
Methane
Modules
Orbitals
Physics
Regolith
Reservoirs
Sciences of the Universe
Trace gas transport model
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Summary:The mechanisms that can induce short term variations of methane in the Martian atmosphere, and thus explain the observations currently available, are yet to be discovered. Seasonal exchange with the regolith, caused by reversible adsorption, is expected to induce both spatial and time variabilities without the need for additional sources and sinks, thus avoiding difficulties raised by other scenarios. However, a comprehensive view of the role of reversible exchanges with the subsurface was still lacking. We have investigated the efficiency of such a process by implementing a coupled subsurface–atmosphere transport module in a Global Climate Model, taking into account both the thermodynamics and the kinetics of the adsorption process. It is based on recent experimental data on the adsorption of methane. We show that even with an optimistic set of parameters, and although the regolith can potentially take up a large fraction of the atmospheric reservoir, the seasonal variability induced by an exchange with the subsurface is very limited. If a local plume is detected, however, the apparent decay rate of methane in the atmosphere can be affected by the regolith uptake. This study could be extended to any trace gas reacting with the regolith, to help interpret future in situ or orbital measurements.
ISSN:0032-0633
1873-5088
DOI:10.1016/j.pss.2010.09.022