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L.A. McFadden, T.P. Cline (U. Maryland)
Reflectance spectra of minerals and meteorites are the basis for interpretation of remotely sensed spectra of inner planets and asteroids. The range of absorption band parameters: band center, depth and width derived from modified Gaussian model (MGM) fits is presented. They are validated against mineral chemistry and structure. Eight martian meteorites are studied. The spectrum of Shergotty and Zagami can be fit with two pyroxene bands and no bands attributed to maskelynite, the shock induced plagioclase polymorph making up ~12% by weight of the meteorite. The spectrum of ALHA 77005, containing olivine and two pyroxenes, can be fit with pyroxene bands only and no olivine. All fitted bands are validated against the known mineral chemistry of the meteorites. The resulting band parameters can be used to test for the presence of similar assemblages on the surface of Mars.
MGM analysis of spectra of Eros are used to test interpretations derived from band position vs. band area ratio. Variations in spectral band parameters for Eros measured at different locations are not indicative of a change in mineral chemistry. We use band fitting to assess reflectance differences vs. location and separate those due to mineral variation (band position) and grain size that would alter band depth.
Spectral reflectance measurements of a range of basaltic achondrites have been measured. Examination of their spectral band parameters derived from fitting modified Gaussian absorptions will be useful for analysis of spectra acquired by the spectrometer carried on the Dawn spacecraft to Vesta. We will discuss whether MGM analysis is appropriate for assemblages anticipated on 1 Ceres.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.