HR: 14:25h
AN: P23B-04    [Abstracts]
TI: Mineralogic Variations from the Plains of Gusev to the Columbia Hills: Results from Mini-TES
AU: * Ruff, S W
EM: steve.ruff@asu.edu
AF: Arizona State University, Department of Geological Sciences, Mars Space Flight Facility, Moeur Building Room 131, Tempe, AZ 85387-6305 United States
AU: Christensen, P R
EM: phil.christensen@asu.edu
AF: Arizona State University, Department of Geological Sciences, Mars Space Flight Facility, Moeur Building Room 131, Tempe, AZ 85387-6305 United States
AB: The Miniature Thermal Emission Spectrometer (Mini-TES) onboard the Spirit rover in Gusev Crater has documented significant thermal-infrared (TIR) spectral differences between the rocks on the plains surrounding the lander and those of the hills to the east informally known as the "Columbia Hills". These spectral variations are related to differences in the bulk mineralogy of the rocks. The darkest, least dusty rocks on the plains are notably similar in their spectral characteristics. A strong emissivity peak at ~440 cm-1 is attributable to olivine of intermediate composition. Surprisingly, plagioclase and pyroxene components are not apparent from the deconvolution of these spectra. However, the combination of very cold temperatures of the rocks relative to the warmer, dusty atmosphere early in the mission suggests that atmospheric downwelling radiance may have contributed spurious spectral features that have obscured some of the mineral features. The low wavenumber range of Mini-TES spectra is least affected by atmospheric contributions due to the relatively low opacity in this range. Dark-toned rocks in the location known as the west spur of the Columbia Hills were measured under much less dusty atmospheric conditions, a fact that may partially explain some of the spectral differences. The strong olivine feature that is so obvious in the plains rocks is absent in the west spur rocks suggesting that olivine is either absent or only a very minor component. Spectral deconvolution reveals evidence for plagioclase and more notably, a significant basaltic glass component. The apparent difference in olivine content between the west spur and plains rocks may imply a difference in the composition of the primary source material. Alternatively, it may represent a weathering or alteration process that involves water. Refinement of the spectral deconvolution results along with the incorporation of additional datasets likely will resolve this question.
DE: 5410 Composition
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
DE: 5494 Instruments and techniques
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting