Mineralogy of the Martian Surface

The past fifteen years of orbital infrared spectroscopy and in situ exploration have led to a new understanding of the composition and history of Mars. Globally, Mars has a basaltic upper crust with regionally variable quantities of plagioclase, pyroxene, and olivine associated with distinctive terrains. Enrichments in olivine (>20%) are found around the largest basins and within late Noachian–early Hesperian lavas. Alkali volcanics are also locally present, pointing to regional differences in igneous processes. Many materials from ancient Mars bear the mineralogic fingerprints of interaction with water. Clay minerals, found in exposures of Noachian crust across the globe, preserve widespread evidence for early weathering, hydrothermal, and diagenetic aqueous environments. Noachian and Hesperian sediments include paleolake deposits with clays, carbonates, sulfates, and chlorides that are more localized in extent. The late Hesperian to Amazonian mineralogic record of water is sparser, though sulfates and silica in some locations indicate local availability of ground and surface waters even in the most recent geologic epoch.