Regolith-atmosphere exchange of water and carbon dioxide on Mars: Effects on atmospheric history and climate change |
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| Authors: | Fraser P Fanale Bruce M Jakosky |
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| Institution: | Planetary Geosciences, Hawaii Institute of Geophysics, University of Hawaii, Honolulu, HI 96822, U.S.A.;Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, U.S.A. |
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| Abstract: | Exchange of CO2 and H2O between the Mars regolith and the atmosphere-cap system plays an important role in governing the evolution of the martian atmosphere and the martian climate. Most of the exchangeable CO2 (perhaps one or two orders of magnitude more than the atmospheric inventory) is currently adsorbed on the deep regolith, and can be “cryopumped” to a large quasipermanent CO2 cap (not now present) during lowest Mars obliquity (θ). During the obliquity driven regolith-cap CO2 exchange cycle, the atmospheric pressure varies harmonically between ~0.1 mb (lowest Θ) and ? 20 mb (highest Θ). The regolith buffer plays only a small or negligible role in the seasonal CO2 pressure variations caused by atmosphere-cap exchange because adsorption greatly inhibits diffusion of the seasonal “pressure wave” into the regolith. In contrast, thermally driven H2O seasonal exchange between the atmosphere and regolith appears to be in large part responsible for observed seasonal variations in the small atmospheric H2O inventory. Long term exchange of H2O may be dominated by transfer between the polar caps and ice in the regolith. Available and potential tests of regolith-atmospheric-cap volatile exchange models using ground-based and spacecraft-based techniques are discussed. |
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