HR: 17:50h
AN: P24A-10    [Abstracts]
TI: Residual South Polar Cap of Mars: MY28 MARCI Observations
AU: * James, P
EM: pjames@cableone.net
AF: Space Science Institute, 4750 Walnut St, Boulder, CO 80301, United States
AU: Calvin, W
AF: University of Nevada, Dept. Geological Sciences, Reno, NV 89557, United States
AU: Thomas, P
AF: Cornell University, Center Radiophysics and Space Res, Ithaca, NY 14853, United States
AU: Wolff, M
AF: Space Science Institute, 4750 Walnut St, Boulder, CO 80301, United States
AB: MGS observations revealed that the Residual South Polar Cap (RSPC) consists of several identifiable units that show evidence of deposition and erosion with characteristic times on the order of ~ 100 years (Thomas et al., 2005). These authors suggested that significant changes observed in the RSPC between Mariner 9 and Viking represent deposition of a new CO₂ layer following erosion of a previous layer(s) by unidentified processes. One possibility is that the a layer erodes gradually due to growth of the pits observed by MGS (Thomas et al., 2000; Malin et al., 2001). However, the changes in the small-scale structure over the four MGS years were not accompanied by changes in the albedo (James et al., in press) or surface area (Piqueux and Christensen, 2007) of the residual cap. Thus the current expansion of the pits may not result in any net sublimation of the cap as would be required to remove a layer. A possible mechanism for removal of a layer is a change in absorbed insolation caused by interannual variability in the dust content of the atmosphere near perihelion. In particular a major perihelic dust storm, such as the event observed by Mariner 9, would accelerate cap sublimation; such a storm, or a succession of such storms, could lead to the erosion of a CO₂ layer(s) (Bonev et al., in press). MRO observed a major dust event in MY28 that obscured the south polar cap in much the same way that the Mariner 9 storm obscured the cap in MY9. At the time of this meeting Mars Reconnaissance Orbiter (MRO) will have observed the RSPC for the entire summer following the storm; these observations will be compared to the four complete summers recessions observed by MGS in order to see if there are changes in the RSPC and test the dust hypothesis. This work was funded through JPL Contract 1275776. References: Bonev, B.P. et al. Planetary and Space Science (in press). James, P.B. et al. Icarus (in press). Malin, M. C. et al., Science 294, 2146-2148 (2001). Piqueux, S. and Christensen, P.R. Seventh International Mars Conference, Abstract 3068 (2007). Thomas, P.C. et al. Nature 404, 161-164 (2000). Thomas, P.C. et al.. Icarus 174, 535-559 (2005).
DE: 5462 Polar regions
DE: 5464 Remote sensing
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting