Physics
Scientific paper
May 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agusm.p31a..04c&link_type=abstract
American Geophysical Union, Spring Meeting 2005, abstract #P31A-04
Physics
5410 Composition, 5460 Physical Properties Of Materials, 5464 Remote Sensing, 5480 Volcanism (8450), 5494 Instruments And Techniques
Scientific paper
The miniature Thermal Emission Spectrometer (Mini-TES) has provided remote measurements of the mineralogy and thermophysical properties of outcrops, rocks, spherules, and soils surrounding the Spirit and Opportunity Rovers [1, 2]. The composition of surface materials provides insight into the origin and evolution of the martian crust and the nature of igneous and sedimentary processes. At Gusev, undisturbed soil spectra closely match MGS TES bright-regions dust spectra, with features interpreted to be due to minor carbonates and bound water. Dark-toned soils observed on rover-disturbed surfaces are likely derived from rocks and have a derived mineralogy, with uncertainties of 5-10 vol.%, of 45% pyroxene (20% high-Ca pyroxene, 25% pigeonite), 40% sodic/intermediate plagioclase, and 15% olivine (Fo35-Fo55). Aeolian drift material has a unique spectral character with higher oxide abundances than disturbed soil. Along the rover's traverse from the lander into the Columbia Hills, at least three distinct rock types have been recognized: olivine rich basalt, a volcaniclastic rock dominated by an amorphous component (possibly basaltic glass and/or shocked plagioclase), and a second volcaniclastic rock dominated by plagioclase of intermediate composition with lesser pyroxene and olivine components. One (or possibly two) spectrally distinct coatings are observed on rocks, a possible indicator of the interaction of water, rock, and airfall dust. At Meridiani, the Mini-TES has identified coarse crystalline hematite and olivine basaltic sands as predicted from orbital TES spectroscopy [3, 4]. Basaltic materials have more plagioclase than pyroxene, contain olivine, and are similar in inferred mineral composition to basalt mapped by TES from orbit. Light-toned outcrops of aqueous origin exposed in crater walls are composed of 20 to 40% Mg and Ca sulfates, a high-silica component that is modeled as glass/feldspar/sheet silicates (~20-30%), and hematite. The Fe-bearing sulfate, jarosite, that was identified by the Mossbauer spectrometer [5], is detected in deconvolutions of several Mini-TES outcrop spectra, but never in concentrations >5%. The dominance of Mg and Ca sulfates in Mini-TES spectra is consistent with the Alpha Particle X-ray Spectrometer (APXS) results, which show that Mg and Ca are present, and that there is significantly more S and too little Fe for the sulfates to be jarosite alone [6]. Two unique surface rocks have been identified during the rover's traverse. Bounce Rock is dominated by clinopyroxene relative to basaltic sands and is closer in inferred mineral composition to the basaltic SNC meteorites. Heat-Shield Rock has a Mini-TES spectral signature that closely resembles a typical spectrum of the sky. The initial Mini-TES interpretation that Heat-Shield Rock was a metallic object with a near reflective surface, and possibly an iron bearing meteorite, was confirmed by APXS and MB observations. The occurrence of waterlain rocks covered by olivine, pyroxene, and feldspar in basaltic sands suggests a significant change from an aqueous environment at the time the rocks were deposited to one dominated by physical weathering. 1)Christensen, P.R., et al., Science, 2004. 305: p. 837-842. 2)Christensen, P.R., et al., Science, 2004. 306: p. 1733-1739. 3)Christensen, P.R., et al., J. Geophys. Res., 2000. 105: p. 9623-9642. 4)Christensen, P.R., et al., J. Geophys. Res., 2001. 106: p. 23873-23885. 5)Klingelhofer, G., et al., Science, 2004. 306: p. 1740-1745. 6)Rieder, R., et al., Science, 2004. 306: p. 1746-1749.
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