HR: 0800h
AN: P31B-0986    [Abstracts]
TI: Wind Eroded Rocks in Gusev Crater, Mars, seen from the {\it Mars Exploration Rover}, Spirit
AU: * Thompson, S
EM: shane.d.thompson@asu.edu
AF: Arizona State University, Departement of Geological Sciences, Box 871404, Tempe, AZ 85287-1404 United States
AU: Greeley, R
EM: greeley@asu.edu
AF: Arizona State University, Departement of Geological Sciences, Box 871404, Tempe, AZ 85287-1404 United States
AU: Whelley, P
EM: pwhelley@asu.edu
AF: Arizona State University, Departement of Geological Sciences, Box 871404, Tempe, AZ 85287-1404 United States
AU: Squyres, S
EM: squyres@astro.cornell.edu
AF: Cornell University, 428 Space Sciences Building, Department of Astronomy, Ithaca, NY 14853 United States
AU: Landis, G A
EM: geoffrey.a.landis@nasa.gov
AF: NASA Glenn Research Center, MS 302 - 1, Cleveland, OH 44135 United States
AU: The Athena Science Team, .
EM: squyres@astro.cornell.edu
AF: Cornell University, 428 Space Sciences Building, Department of Astronomy, Ithaca, NY 14853 United States
AB: Ventifacts (wind abraded rocks) are common along the 3.2 km traverse of the rover, {\it Spirit}, from the landing at Columbia Memorial Station to the Columbia Hills (CH), and include flat faces on rocks ("facets"), flutes, and grooves. Facets range in size from 2 to 50 cm across and commonly occur on the north side of rocks from about 2 cm above the soil horizon up to the topmost peak of the rock. The upper third of these rock facet faces tend to be highly polished and relatively dust free and typically also is the zone of groove etching. Although facets occur on about 20-30% of rocks seen along the traverse, they are less than 10% on the southwest side of the West Spur in the CH and up to 75% occurrence on top of West Spur near Clovis. Flutes are U-shaped features on a rock that are closed on the upwind side and open on the downwind side in map view creating an "arrowhead" shape and grooves are longer and more linear than flutes, both resulting from aeolian scouring. Grooves range in size from 2 cm long and 0.25 cm wide to 9 cm long and 1 cm wide, while flutes range in size from 1 cm long and 0.5 cm wide to 8 cm long and 5 cm wide. Flutes and grooves are commonly on the northwest sides of rocks, typically on a facet face, and are oriented northwest-southeast along the long axes. Flat, light surfaces in the CH, such as Clovis, are thought to be outcrops of "bedrock," many of which have grooves as long as 10 cm and oriented 20 degrees east of north. Together, the ventifacts observed via {\it Spirit} suggest formative winds from the northwest, consistent with indicators, such as wind streaks, indicative of current wind directions in the region. The relative lack of ventifacts in the area immediately south of West Spur suggest this area is shielded from winds from the north-northwest as the wind is topographically guided more southward along the west flank of the CH complex. The grooves on Clovis are oriented in response to the wind flow over local topography.
DE: 5409 Atmospheres--structure and dynamics
DE: 5415 Erosion and weathering
DE: 6225 Mars
DE: 3322 Land/atmosphere interactions
DE: 3319 General circulation
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting