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Chemical Composition by the APXS along the Downhill Traverse of the Mars Exploration Rover Spirit at Gusev CraterThe Alpha Particle X-ray Spectrometer (APXS) onboard the Mars Exploration Rover Spirit continues to determine the elemental composition of samples at Gusev Crater. Starting around sol 600 the rover descended Husband Hill, which is part of the Columbia Hills, visited the inner basin with a large dune field, called 'El Dorado', and parked at Low Ridge to conserve energy during the martian winter. Many unique samples were discovered by the instruments onboard Spirit during her downhill traverse. Here, we report only on the chemical data obtained by the APXS. The compositions of some of the soil samples are comparable to the mean soil determined along the earlier traverse. However, a light-toned subsurface sample (disturbed by the rover wheels), called Dead Sea Samra , showed the highest sulfur content of all soil samples, the lowest Na, Mg, Al, Cl, K, Ca, Ti, Mn, and Zn, among the lowest Si and P, and among the highest Cr, Fe and Ni. Assuming ferric sulfate as a major mineral, large amounts of a pure silica phase must be present. Color and quantity of Dead Sea Samra resemble somewhat an earlier soil called Paso Robles , though the latter is a mixture of sulfates with phosphate-rich soil. Manganese in Dead Sea Samra is so low that the Fe/Mn ratio exceeds 300, a value that has never been found previously on Mars (Fe/Mn ratio of 46 for Gusev basalts), indicating that only Fe(3+) occurs. The dune field El Dorado contained granulated material that exhibited the highest Mg and Ni concentrations and the lowest S and Cl compared to all other soils implying an enrichment of olivine-rich sands. Two outcrops, called Algonquin and Comanche , revealed compositions that differ significantly from those of earlier outcrops as they have the highest concentrations of Mg, Fe, and Ni (except for Ni in Independence) and the lowest of Al, K (detection limit), Ca, and Ti of all brushed and almost all abraded rocks. Normative estimates assign them the highest olivine contents ever found for martian rocks and a very mafic nature based on their high Mg/(Mg+Fe) and low Al, Ca and Na. Their significantly high Ni contents point to a different source than the Gusev plains basalts. The elemental compositions of samples encountered during the downhill traverse revealed a larger chemical diversity of the Columbia Hills than the uphill trek already published.
Document ID
20060056236
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Bruckner, J.
(Max-Planck-Inst. fuer Chemie Mainz, Germany)
Dreibus, G.
(Max-Planck-Inst. fuer Chemie Mainz, Germany)
Gellert, R.
(Guelph Univ. Ontario, Canada)
Clark, B.C.
(Lockheed Martin Corp. Littleton, CO, United States)
Cohen, B.
(New Mexico Univ. Albuquerque, NM, United States)
McCoy, T.
(Smithsonian Institution Washington, DC, United States)
Ming, D.W.
(NASA Johnson Space Center Houston, TX, United States)
Mittlefehldt, D.W.
(NASA Johnson Space Center Houston, TX, United States)
Yen, A.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Athena Science Team
(NASA Headquarters Washington, DC United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2006
Subject Category
Lunar And Planetary Science And Exploration
Meeting Information
Meeting: AGU Fall Meeting
Location: San Francisco, CA
Country: United States
Start Date: December 11, 2006
End Date: December 15, 2006
Distribution Limits
Public
Copyright
Other

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