|Title||Gusev crater: Wind-related features and processes observed by the Mars Exploration Rover Spirit|
|Publication Type||Journal Article|
|Year of Publication||2006|
|Authors||Greeley R, Arvidson RE, Barlett PW, Blaney D, Cabrol NA, Christensen PR, Fergason R, Golombek MP, Landis GA, Lemmon MT, McLennan SM, Maki JN, Michaels T, Moersch JE, Neakrase LDV, Rafkin SCR, Richter L, Squyres SW, de Souza, Jr P A, Sullivan RJ, Thompson SD, Whelley PL|
|Journal||Journal of Geophysical Research-Planets|
Wind-related features observed by the rover Spirit in Gusev crater, Mars, include patches of soil on the surface, some of which are organized into bed forms. Windblown grains include dust ( inferred to be 2 mm in diameter). Microscopic Imager data show the sands and granules to be rounded and relatively spherical, typical of grains transported long distances by the wind. The interior of bed forms exposed by rover operations suggests the infiltration of dust among the grains, indicating that these sands are not currently experiencing saltation. Orientations of 1520 features ( such as bed forms and ventifacts) along Spirit's traverse from the landing site ( the Columbia Memorial Station) to West Spur in the Columbia Hills suggest primary formative winds from the north-northwest, which correlate with measurements of features seen in orbiter images and is consistent with afternoon winds predicted by atmospheric models. A secondary wind from the southeast is also suggested, which correlates with predictions for nighttime/early morning winds. Wind abrasion is indicated by ventifacts in the form of facets and grooves cut into rocks, the orientations of which also indicate prevailing winds from the north-northwest. Orientations of many aeolian features in the West Spur area, however, have more scatter than elsewhere along the traverse, which is attributed to the influence of local topography on the patterns of wind. Active dust devils observed on the floor of Gusev from the Columbia Hills demonstrate that dust is currently mobile. Sequential images of some dust devils show movement as rapid as 3.8 m/s, consistent with wind velocities predicted by atmospheric models for the afternoon, when most of the dust devils were observed. Sands accumulated on the rover deck in the same period suggest that some sands in the Columbia Hills experience active saltation. "Two-toned'' rocks having a light band coating at their bases are considered to represent partial burial by soils and subsequent exposure, while "perched'' rocks could represent materials lowered onto other rocks by deflation of supporting soils. Measurements of the heights of the light bands and the perched rocks range from <1 cm to 27 cm, indicating local deflation by as much as 27 cm.