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Undercut Rocks at the MER Gusev Landing SiteOn January 3 2004, the NASA Spirit rover landed on the plains inside the Gusev Crater in the southern hemisphere of Mars, and has made observations of the landing site and nearby region in visual and infrared wavelengths, as well as making in-situ measurements of rocks and soil. A number of rocks at the Gusev site are perched, with a significant undercut above the surface; additional rocks show a feature of being eroded or etched at a height of one to three centimeters immediately above the soil line. Some rocks also show terracing, and others show a two-tone pattern of albedo, with a distinct dividing line between a lighter area near the surface and a darker color above the surface. In a small number of cases, the dividing line is correlated with a visible horizontal groove in the rock, most likely indicating an earlier location of burial of the rock. A number of explanations for this undercutting are possible. Perched rocks can be placed on the surface by deflation of the soil from underneath the rock. The surface etching may be abrasion due to reptation. Reptation, or surface creep, occurs as sand moves without leaving the surface, as small (100-200 micron particles) moved by saltation set larger particles in motion. These large particles are effective at abrading the rocks at the surface level. The structure of "ripple" features at the site is evidence to support reptation at the Gusev site. An alternate explanation is etching at the surface by chemically active grit.
Document ID
20050203987
Acquisition Source
Glenn Research Center
Document Type
Conference Paper
Authors
Landis, Geoffrey A.
(NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
September 8, 2013
Publication Date
January 1, 2004
Subject Category
Lunar And Planetary Science And Exploration
Meeting Information
Meeting: Geological Society of America Annual Conference
Location: Denver, CO
Country: United States
Start Date: November 7, 2004
End Date: November 10, 2004
Sponsors: Geological Society of America
Funding Number(s)
WBS: WBS 22-390-30-10
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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