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Numerical modelling of the transport of trace gases including methane in the subsurface of Mars

Stevens, Adam H.; Patel, Manish R. and Lewis, Stephen R. (2015). Numerical modelling of the transport of trace gases including methane in the subsurface of Mars. Icarus, 250 pp. 587–594.

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We model the transport of gas through the martian subsurface in order to quantify the timescales of release of a trace gas with a source at depth using a Fickian model of diffusion through a putative martian regolith column. The model is then applied to the case of methane previously observed in the martian atmosphere.

We investigate which parameters in the model have the greatest effect on transport timescales and find that transport is very sensitive to the pressure profile of the subsurface, but relatively insensitive to the temperature profile. Uncertainties in the composition, structure and physical conditions of the martian subsurface also introduce uncertainties in the timescales calculated.

It was found that methane may take several hundred thousand Mars-years to diffuse from a source at depth. Purely diffusive transport cannot explain transient release that varies on timescales of less than one martian year from sources such as serpentinization or methanogenic organisms at depths of more than 2 km. However, diffusion of gas released by the destabilisation of methane clathrate hydrates close to the surface, for example caused by transient mass wasting events or erosion, could produce a rapidly varying flux of methane into the atmosphere of more than 10-3 kg m-2 s-1 over a duration of less than half a martian year, consistent with observations of martian methane variability. Seismic events, magmatic intrusions or impacts could also potentially produce similar patterns of release, but are far more complex to simulate.

Item Type: Journal Item
Copyright Holders: 2015 The Authors
ISSN: 0019-1035
Keywords: Mars interior; martian atmosphere; Mars; atmospheric composition
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: Space
Item ID: 38492
Depositing User: Adam Stevens
Date Deposited: 30 Jan 2015 12:46
Last Modified: 09 Dec 2018 06:42
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