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H. Wang, A. P. Ingersoll (CALTECH)
Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has been taking global map swaths of Mars using its red and blue wide angle cameras every two hours since March 1999. We have processed the global map swaths taken from June to August 1999 which correspond to the end of the northern summer (150 < Ls < 185), and made them into daily global maps and animations with 2-hour and 1-day time steps for the polar regions. The south polar seasonal cap recession, the north polar dust and condensate cloud activity, and the condensate clouds over the Tharsis volcanos and Valles Marineris are clearly displayed. We will continue processing data as they become available.
The north polar region stays relatively calm before Ls ~160. Active dust storms and condensate clouds show up afterwards. Cloud tracked winds are typically about 15m/s in the north polar region during this season, and there are winds blowing onto and even across the cap. North of 65N, condensate clouds change shape quickly, suggesting transient waves in the atmosphere. Dust storms about 500km and larger usually have well developed cyclonic structure and have lifetime of several days. Dust storms often blow across the residual cap, especially in late summer (Ls~180). There are sometimes condensate clouds that seem to be associated with the dust storms. Dust storms usually show up at longitudes 0 +/- 90 around the north polar cap in this season, suggesting an asymmetric circulation.