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A. Colaprete (Lab. for Atmospheric and Space Physics), O. B. Toon (Program in Atmospheric and Oceanic Science, Lab. for Atmospheric and Space Physics)
Observations from the Mars Orbiter Laser Altimeter (MOLA) has revealed an assortment of clouds existing within the polar night (1). Some of these clouds appear to be composed of carbon dioxide ice particles and are associated with surface topography. A mountain wave model of cloud formation has been developed to explain these MOLA observations. Simulations have been conducted using a time dependent microphysical cloud model. Results of these simulations agree well with both the observed structure of the clouds and their estimated back-scatter cross sections. A significant result from these simulations is a substantial precipitation rate to the surface of carbon dioxide ice. For a 1 hour ``snow" storm as much as 0.75 g cm-2 of CO2 ice falls to the surface.
A second type of cloud has been observed by MOLA in the southern hemisphere. These clouds are seen in the first MOLA channel and thus have a much higher extinction per kilometer than those clouds seen in the forth MOLA channel (2, 3). It is speculated here that these ``Type 1" clouds are convective towers composed of carbon dioxide ice particles. Numerical simulations of the formation of these convective towers are presented and compared to the observations.
This work was supported by NASA Grant NAG5-6900.
1. Pettengill, G. H. and P. G. Ford, GRL 27, 609, 2000. 2. Muhleman, D.O. and A.B. Ivanov, MGS Mars Water and Atmosphere Workshop, 2000. 3. Pettengill, G. H. and P. G. Ford, MGS Mars Water and Atmosphere Workshop, 2000.