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J.B. Dalton (SETI Institute / NASA Ames Research Center), J.M. Moore (NASA Ames Research Center)
The highly degraded ancient crater, Eberswalde, and the large alluvial or fluvial fan deposit along its western interior, have been studied using MGS-TES spectra. The fan deposit appears to have been emplaced during a series of wet periods during the late Noachian or early Hesperian. Emissivity spectra from MGS-TES have been compiled over the region from selected orbits having minimal atmospheric dust and clouds. Spectra were modeled using a linear deconvolution approach, first using a set of canonical endmembers (Bandfield, 2000; Bandfield and Smith, 2003) representing atmospheric dust, water ice clouds, surface dust, surface types I and II, and a blackbody component. Spectra were next modeled using a suite of minerals. This suite, selected from the ASU Thermal Emission Library, included feldspars, pyroxenes, olivines, sulfates, carbonates, and clays/sheet silicates.
Though an adjacent area outside Eberswalde showed significant surface dust, the deposit itself appears to be relatively dust-free in the orbits that were selected for analysis. All areas studied were significantly better modeled using the ASU mineral database than with only the canonical endmembers. Spectral fits for regions within the crater all exhibit similar abundances of feldspars, pyroxenes, sulfates and carbonates. However, the fluvial deposit required at least twice as much of the clay and sheet silicate minerals (indicative of hydrated minerals) to produce a reasonable spectral match. This suggests that the water, which transported them to this location, may have chemically altered the minerals deposited in the fan.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.