MARS THROUGH MANY EYES: CONNECTIONS BETWEEN THE MARTIAN METEORITES AND MARS REMOTE SENSING DATA

The martian meteorites provide detailed insight into the mineralogical, chemical and isotopic nature of the martian crust. They have almost uniformly young (180 Ma – 1.3 Ga) crystallization ages and are linked by a common FeO-rich, Al₂O₃-poor parent melt that is consistent with their pyroxene-rich, plagioclase-poor mineralogies. New insight into the nature of the martian crust with global geologic context not provided by the martian meteorites is provided by remote sensing data from Mars. The Thermal Emission Spectrometer (TES) on Mars Global Surveyor identified two lithologies in martian dark regions (areas containing little or no weathering) distinct from the martian meteorites: basalt and andesite. TES basalt resembles a terrestrial tholeiite, more Al₂O₃-rich than the martian meteorites. It is almost exclusively found in the dark regions of the old, heavily cratered southern highlands. TES andesite, found in both southern and northern hemisphere dark regions, is plagioclase- and SiO₂ glass-rich, although the primary or secondary nature of the SiO₂ glass component is currently under debate. The spectra of the TES lithologies do not resemble the thermal infrared spectra of martian meteorites.

Despite their differences, the martian meteorites and the TES lithologies have chemical affinities that suggest they can be petrogenetically linked. The Al₂O₃-rich nature of the TES lithologies and, relative to the martian meteorites, the higher K and Th concentrations (determined by the Gamma-Ray Spectrometer (GRS) on Mars Odyssey) in Mars surface regions containing the TES lithologies are consistent with derivation of TES lithologies from a mantle source less depleted than the source of the martian meteorite parent melts. GRS data also indicate that martian surface materials have similar K/Th ratios to the martian meteorites. These data suggest that the martian meteorites were extracted from a mantle depleted by removal of an early crust (e.g. the TES lithologies) and are consistent with the predominance of TES lithologies in old terrains and the young crystallization ages of the martian meteorites. Overall, the martian meteorites and remote sensing datasets provide complementary data necessary for development of a complete understanding of martian differentiation and igneous evolution.