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AGU: Journal of Geophysical Research, Planets

Keywords

• CO2 Condensates
• Laser Ranging
• Mars Atmosphere
• Mars Seasonal Polar Caps

Index Terms

• 5210 - Planetary atmospheres, clouds, and hazes
• 5405 - Atmospheres
• 5462 - Polar regions
• 6225 - Mars
• 6952 - Radar atmospheric physics

Paper in Press

JOURNAL OF GEOPHYSICAL RESEARCH, doi:10.1029/2012JE004087

Mars atmospheric CO2 condensation above the north and south poles as revealed by radio occultation, climate sounder, and laser ranging observations

Key Points
• We provide causal evidence that MOLA non-ground returns are CO2 condensates
• We reveal intense seasonal variation of atmospheric saturation on Mars with MCS
• We estimate the total mass of atmospheric condensation per Mars winter

Authors:

We study the condensation of CO$_2$ in Mars' atmosphere using temperature profiles retrieved from radio occultation measurements from Mars Global Surveyor as well as the climate sounding instrument onboard the Mars Reconnaissance Orbiter, and detection of reflective clouds by the MGS Mars Orbiter Laser Altimeter. We find 11 events in 1999 where MGS temperature profiles indicate CO$_2$ condensation and MOLA simultaneously detects reflective clouds. We thus provide causal evidence that MOLA non-ground returns are associated with CO$_2$ condensation, which strongly indicates their nature being CO$_2$ clouds. The MGS and MRO temperature profiles together reveal the seasonal expansion and shrinking of the spatial area and thickness where saturation occurs in the atmosphere. The occurrence rate of atmospheric saturation is maximized at high latitudes in the middle of winter. The atmospheric saturation in the northern polar region exhibits more intense seasonal variation than in the southern polar region. Furthermore, we integrate the condensation area and the condensation occurrence rate to estimate cumulative masses of CO$_2$ condensates deposited onto the northern and southern seasonal polar caps. The precipitation flux is approximated by the particle settling flux which is estimated using the impulse responses of MOLA filter channels. By comparison with the seasonal polar cap masses inferred from the time-varying gravity of Mars, our estimates indicate that the average condensate particle radius is 8 - 22 $\mu$m in the northern hemisphere and 4 - 13 $\mu$m in the southern hemisphere. Our multi-instrument data analysis provides new constraints on modeling the global climate of Mars.

Received 26 March 2012; accepted 25 May 2012.

Citation: Hu, R., K. Cahoy, and M. T. Zuber (2012), Mars atmospheric CO2 condensation above the north and south poles as revealed by radio occultation, climate sounder, and laser ranging observations, J. Geophys. Res., doi:10.1029/2012JE004087, in press.