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Degradation of Victoria Crater, MarsThe $\sim$750 m diameter and $\sim$75 m deep Victoria crater in Meridiani Planum, Mars, presents evidence for significant degradation including a low, serrated, raised rim characterized by alternating alcoves and promontories, a surrounding low relief annulus, and a floor partially covered by dunes. The amount and processes of degradation responsible for the modified appearance of Victoria crater were evaluated using images obtained in situ by the Mars Exploration Rover Opportunity in concert with a digital elevation model created using orbital HiRISE images. Opportunity traversed along the north and northwest rim and annulus, but sufficiently characterized features visible in the DEM to enable detailed measurements of rim relief, ejecta thickness, and wall slopes around the entire degraded, primary impact structure. Victoria retains a 5 m raised rim consisting of 1-2 m of uplifted rocks overlain by 3 m of ejecta at the rim crest. The rim is $\sim$120 to 220 m wide and is surrounded by a dark annulus reaching an average of 590 m beyond the raised rim. Comparison between observed morphology and that expected for pristine craters 500 to 750 m across indicate the original, pristine crater was close to 600 m in diameter. Hence, the crater has been erosionally widened by approximately 150 m and infilled by about 50 m of sediments. Eolian processes are responsible for modification at Victoria, but lesser contributions from mass wasting or other processes cannot be ruled out. Erosion by prevailing winds is most significant along the exposed rim and upper walls and accounts for $\sim$50 m widening across a WNW-ESE diameter. The volume of material eroded from the crater walls and rim is $\sim$20% less than the volume of sediments partially filling the crater, indicating eolian infilling from sources outside the crater over time. The annulus formed when $\sim$1 m deflation of the ejecta created a lag of more resistant hematite spherules that trapped darker, regional basaltic sands.
Document ID
20090014052
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Wilson, Sharon A.
(Smithsonian Institution Washington, DC, United States)
Grant, John A.
(Smithsonian Institution Washington, DC, United States)
Cohen, Barbara A.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Golombek, Mathew P.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Geissler, Paul E.
(Geological Survey Flagstaff, AZ, United States)
Sullivan, Robert J.
Kirk, Randolph L.
(Geological Survey Flagstaff, AZ, United States)
Parker, Timothy J.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 24, 2013
Publication Date
December 15, 2008
Subject Category
Geophysics
Report/Patent Number
M09-0072
Meeting Information
Meeting: American Geophysical Union 2008 Fall Meeting
Location: San Francisco, CA
Country: United States
Start Date: December 15, 2008
End Date: December 19, 2008
Distribution Limits
Public
Copyright
Other

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