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We examined TES spectra that overlap the low albedo deposits of Amazonis Planitia craters; data were selected to have low albedo, high signal-to-noise ratio and overall data quality. Of the 23 Amazonis Planitia craters examined, we found satisfactory TES spectra for eleven of the low albedo intracrater features (Fig. 1). TES spectra were extracted for the low albedo dunes as well as the adjacent bright (dusty) crater floor for comparison; the latter will not be discussed here. The average TES surface spectrum for each low albedo deposit and bright crater floor were derived via linear deconvolution. Our end member set is a refinement of the set used by previous workers and includes spectra of eight atmospheric end members, a surface dust end member, and mineral end members including feldspars, clinopyroxenes, orthopyroxenes, olivines, oxides, clays and glass end members. These minerals are important for determining whether these deposits were exposed to an aqueous environment and to what extent (i.e., how much and how long). Finally, we used the mineral abundances derived from linear deconvolution to calculate a bulk composition for each low albedo deposit. We then used these bulk compositions to assign the deposits to lithologic classes.
For each of the 11 intracrater low albedo deposit, we extracted 2 to 13 TES spectra from 1 to 3 orbits (Table 1). As with the findings of, our deconvolution results reflect a lithology that is rich in mafic minerals (olivine and pyroxene) and the pyroxene component is dominated by clinopyroxene (Table 1). To variable degrees, the spectra display an absorption centered at ~900 cm-1 that matches well to olivine lab spectra; this may reflect variation in the olivine abundance within the deposits. Indeed, three spectra with the strongest olivine absorptions (Fig. 2) contain among the highest olivine abundances (Table 1). The persistence of olivine and low clay content indicates limited contact with water. Furthermore, we believe that these materials have been locally-derived and in the paper we present high-resolution images that demonstrate possible local source for these materials.

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