Elsevier

Icarus

Volume 124, Issue 1, November 1996, Pages 268-279
Icarus

Regular Article
Limits on the CO2Content of the Martian Polar Deposits

https://doi.org/10.1006/icar.1996.0203Get rights and content

Abstract

It has recently been suggested that large quantities of CO2could be sequestered within the martian polar deposits as CO2ice or CO2clathrate hydrate, stabilized against sublimation by a non-porous overburden of water ice. I investigate the phase stability of CO2-bearing polar ices and place limits on the quantity of CO2that can be sequestered. The magnitude of this limitation follows from CO2-bearing ices having thermal conductivities on the order of 5 to 6 times smaller than that of water ice, producing a higher geothermal gradient. Results indicate that only under favorable, and probably unrealistic, conditions an upper limit of 112 mbar of CO2can be sequestered as CO2clathrate or 254 mbar as CO2ice in the north polar deposit. More realistic conditions will limit CO2to no more than a few 10s of mbar. In either case, less CO2is also allowed and none is required by existing observations. The south polar deposit probably consists of a similar composition, but thinner deposits make placing limits difficult. Limited quantities of CO2in the polar regions primarily implies that large amounts of CO2are not released at high obliquity, reducing the magnitude of periodic climate change. In addition, climate-evolution models that predict large CO2-bearing caps at present should be rejected, favoring models that do not predict extensive CO2-bearing ice deposits.

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