HR: 12:05h
AN: P22B-08    [Abstracts]
TI: The Size-Frequency Distribution of Martian Dust-Devils
AU: * Geissler, P E
EM: pgeissler@usgs.gov
AF: U.S. Geological Survey, 2255 N. Gemini Drive, Flagstaff, AZ 86001 United States
AB: Martian dust-devils appear in a wide variety of sizes ranging from a few hundred meters in height up to mountain-sized monsters with the dimensions of terrestrial tornadoes. At one end of this spectrum, the modest dust-devils that are frequently imaged by the MER rover Spirit are little larger than the dust-devils commonly seen on Earth. At the other extreme, enormous examples that tower more than 8 km high have been spotted from orbital imagery (Biener et al., LPSC 2002). How common are these giant dust-devils in comparison to their smaller cousins? Does the size-frequency distribution vary with season or time of day? Are dust entrainment and erosion dominated by the larger but rarer giants, or by more numerous but smaller dust-devils? To begin to address these questions, we are documenting the occurrence of active dust plumes in the Gusev Crater area, the target of intensive orbital imaging observations since before Spirit's landing. More than 180 MOC Wide Angle Camera images have been released so far with footprints that fall within a 5x5 degree rectangle centered on the Spirit landing site. Dust-devils larger than ~1 km in height can be detected in the wide angle images by simply blinking between pairs of pictures with the same surface coverage. These sightings will be used to determine the frequency of giant dust-devils in the Gusev region per unit surface area as a function of time. Intermediate sized (hundreds of meters high) dust devils can be monitored in the same way, in areas where redundant Narrow Angle Camera image coverage exists. Information about the smallest dust-devils, below the resolution of orbital imagery, is presently pouring in from the surface of Mars via the MER Spirit cameras. Initial results of this survey, concerning the frequency of giant dust devils in the Gusev Crater area, will be presented at this meeting.
DE: 0343 Planetary atmospheres (5210, 5405, 5704)
DE: 3346 Planetary meteorology (5445, 5739)
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: Fall Meeting 2005