Solar Cycle and Seasonal Variations of the Mars Thermosphere-Ionosphere and Associated Impacts upon Atmospheric Escape (Invited)

Details Solar Cycle and Seasonal Variations of the Mars Thermosphere-Ionosphere and Associated Impacts upon Atmospheric Escape (Invited) Solar Cycle and Seasonal Variations of the Mars Thermosphere-Ionosphere and Associated Impacts upon Atmospheric Escape (Invited)

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p53a..01b&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #P53A-01

Physics

[0328] Atmospheric Composition And Structure / Exosphere, [5405] Planetary Sciences: Solid Surface Planets / Atmospheres, [5435] Planetary Sciences: Solid Surface Planets / Ionospheres, [6225] Planetary Sciences: Solar System Objects / Mars

Scientific paper

A major component of the current NASA Mars Exploration Program plans is the determination of the Mars climate, and hence the atmosphere’s history. A growing body of evidence supports an ancient Mars having a milder, wetter climate, suggesting that its atmosphere was once more substantial than it is today. The fate of the lost atmosphere and water is a major unanswered question. Is the “lost” water sequestered in the crust at all latitudes, or did much of it escape to space? While available measurements and theoretical studies suggest that a number of atmospheric escape processes are at work today, little is known about their efficacy, including temporal variations and dependencies on factors such as solar activity and Mars seasons. Any extrapolation of these escape processes into the past must be based on a more complete understanding of current escape processes and their rates. A brief review will be presented of the current understanding of the Mars thermosphere-ionosphere structure and its estimated variations over the solar cycle and Mars seasons. The underlying physical processes giving rise to these variations will also be described making use of recent 3-D simulations from an upper atmosphere Mars Thermosphere General Circulation Model (MTGCM). A summary of the key escape processes relevant to the current epoch will be given, with an emphasis upon their dependence on the solar cycle and seasonal variations in the underlying thermosphere-ionosphere structure. Finally, selected 3-D kinetic model (DSMC) simulations will be presented that illustrate the coupling between the thermosphere-ionosphere system and the exosphere leading to predictions of the hot oxygen escape. This mechanism is thought to be a major component of atmospheric loss for present day Mars. A NASA Mars Scout mission to study the Mars upper atmosphere and plasma environment, and to address these key atmospheric escape processes, was recently selected (MAVEN). Coupled model simulations, such as those presented in this paper, are essential to maximum the science return from this exciting mission.

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