Hydrated minerals on Endeavour Crater's rim and interior, and surrounding plains: New insights from CRISM data

We have conducted a spectroscopic analysis of the rim and interior of Endeavour Crater using CRISM data in order to further constrain the mineralogical variability in the area and to identify targets of interest for in‐situanalysis by Opportunity. Our analysis reveals that the spectral character of both the sulfates and the phyllosilicates in the area is more diverse than has been reported to date, with phyllosilicates present on the rim and interior of Endeavour crater as well as on the surrounding plains. Spectra of the sulfates adjacent to the rim and in the crater's interior mound exhibit features that are consistent with a component of Ca‐sulfates. The spectral character of the phyllosilicates is consistent with that of Fe/Mg smectites, but there are clear spectral differences between the rim and interior phyllosilicates. Specifically, the phyllosilicates found inside the crater exhibit shallower, more rounded Fe/Mg‐OH bands, a subtle 1.9μm hydration band, and a strong 1–2 μm spectral slope relative to the phyllosilicates on the rim, suggesting that they have experienced modification relative to the rim phyllosilicates. This modification may be attributed either to alteration via acidic leaching or to dehydration. Stratigraphically, we find that these altered phyllosilicates unconformably overlie the sulfate‐bearing mound material, suggesting that they were emplaced by the reworking of rim phyllosilicates after the interior mound had reached its present day form. Key Points Mineralogical diversity at Endeavour Crater is greater than previously realized A Ca‐sulfate component is identified near the rim of the crater Phyllosilicates are identified on the rim, interior and surrounding plains