Surface runoff features on Mars: Testing the
carbon dioxide formation hypothesis
S. Stewart and F. Nimmo, J. Geophys. Res., in press.
(PDF file (1890K) available)
Fresh gully-like features on Mars strongly suggest that fluid flowed
on the surface in the recent past. The hypothesis that liquid water
formed these features suffers from the thermodynamic difficulties of
melting ice or maintaining water in equilibrium shallow depths or
transportation issues related to conveying water from depth while
satisfying the observed gully properties, e.g.latitude range, head
alcove depth, and slope preference. Here we consider the possibility
that CO2 vapor-supported flows formed the gullies. We find that
neither condensed CO2 nor CO2 clathrate hydrate are likely to
accumulate in significant quantities in the Martian crust. In
addition, if condensed CO2 were present under lithostatic
pressures, exposure to the atmosphere would produce explosive
features, not surface runoff. Finally, the source volume of CO2
required to support a flow excludes clustered or episodic gully
formation. Therefore, we conclude that CO2 cannot have formed the
gullies. In light of these results, liquid water flow remains the
preferred formation mechanism for the surface runoff features.
Francis' Page
Department of Earth Sciences
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nimmo@esc.cam.ac.uk
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