Heterogeneity of the Noachian crust of Mars using CRISM Multispectral Mapping Data

We used CRISM multispectral mapping data to assess heterogeneity of primary and secondary mineral compositions of Noachian-aged regions of Martian crust. Multispectral data corroborate interpretations from CRISM targeted observations and OMEGA global mapping of large horizontal differences in vertical crustal structures, and degree and grade of alteration to secondary minerals. CRISM multispectral data analysis conducted at a combination of high spatial resolution and coverage not available in other datasets also reveals previously unrecognized exposures. At one extreme, basaltic crustal material is minimally altered, mostly to smectite clay; at the other, Al-enriched alteration products are present, alteration is widespread, and superposed surface materials rich in salts and precipitates suggesting multiple episodes of alteration. The revealed vertical structure of primary mineralogy is consistent with that inferred in previous studies. Controls on extent and metamorphic grade of secondary mineral assemblages are proximity to heat sources including large impact basins and inferred magmatic bodies.