HR: 11:05h
AN: P22A-04    [Abstracts]
TI: Surface Dust Redistribution on Mars as Observed by the Viking and Mars Global Surveyor Orbiters
AU: * Szwast, M
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States
AU: Richardson, M I
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States
AU: Vasavada, A R
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Wang, H
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States
AU: Wang, H
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AB: The global redistribution of dust by the atmosphere is geologically and climatologically important. Dust deposition and removal at the surface represents ongoing sedimentary geology: a vestige of aeolian processes responsible for the concentration of vast dustsheets and potentially for ancient layered units at various locations on Mars. The varying amount of dust on the surface has also long been hypothesized as a factor in determining whether regional or global dust storms occur in a given year. Indeed, the atmosphere has a very short, sub-seasonal time-scale (or memory) and as such, any inter-annual variability in the climate system that is not simply ascribable to stochastic processes, must involve changing conditions on the surface. An excellent, multi-year dataset is provided by the combined Viking and Mars Global Surveyor (MGS) orbiter albedo and thermal observations, from the Infrared Thermal Mapper (IRTM) and Thermal Emission Spectrometer (TES), and from the MGS Mars Orbiter Camera Wide Angle imager (MOC-WA). This dataset allows investigation into the degree to which surface dust deposits on Mars really change: over decadal time scales, over the course of the annual cycle, and as a result of global and regional dust storms. The MGS mapping orbit data set extends over almost 3 Martian years at the time of writing, while the Viking data set provides a much less complete sampling of three northern summers/autumns and one southern summer/autumn. These data sets include three global dust storms (two for Viking and one for MGS) and smaller regional storms (one in the first TES mapping year and two in the third). We have examined the Viking IRTM, MGS TES, and MGS MOCWA data sets to determine what types of changes in dust coverage have occurred. Viking-to-MGS changes in albedo are highlighted by the drastic modification of a large, low albedo (low dust) feature to the east of Utopia Planitia. Year-to-year changes within the Viking and MGS records are dominanted by the effects of global dust storms. The 2001 storm observed by MGS is the best documented. We found a number of regions that changed significantly after the 2001 global dust storm. Areas with noticeable changes include the brightening of Syrtis Major, Hellas Planitia, and the region east of Hellas Planitia, and the darkening of Tharsis. Solis Planum, a region known to have participated as a secondary source for the 2001 storm became darker following the storm, while an area directly to the east of Solis became brighter. The majority of these changes are visible in both TES maps and MOC wide-angle images. These changes have been slowly relaxing back towards pre-storm conditions since the end of the storm. Similar albedo changes in these same regions were found associated with the global storms observed by the Viking IRTM. This suggests that the very limited number of dust storms observed by spacecraft have tended to produce the same kinds of changes in surface dust coverage. The origin of the long-term changes in Utopia are not understood.
DE: 5415 Erosion and weathering
DE: 5445 Meteorology (3346)
DE: 5462 Polar regions
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting