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P. G. Ford, G. H. Pettengill (MIT)
During the past 26 months, the MOLA laser altimeter instrument aboard the Mars Global Surveyor spacecraft has flown over both poles through their respective winter and spring seasons at an altitude of 300 km. Cloud echoes from CO2-ice particles have been seen on approximately half of all winter passes, representing some 3% of all measurements made above 70o latitude at both poles.
In this study, the clouds have been classified in two ways: by their particle density gradient, as measured by the time dispersion of the received echo, and by their morphology, i.e., whether or not they show evidence for (a) traveling waves, (b) standing waves associated with surface topography, (c) near-surface layering, or (d) isolated domes. While some cloud classes are correlated with particular surface feature types, others are correlated with each other, consistent with a mean zonal flow around each pole from west to east with a mid-winter circumpolar period of ~15 days in the north and ~12 in the south.
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