Constraints on the depth and thermal vigor of melting in the Martian mantle

Abstract

Studies of rocks in Gale Crater and clasts within the Martian meteorite breccia Northwest Africa (NWA) 7034 (and paired stones) have expanded our knowledge of the diversity of igneous rocks that make up the Martian crust beyond those compositions exhibited in the meteorite collection or analyzed at any other landing site. Therefore, the magmas that gave rise to these rocks may have been generated at significantly different conditions in the Martian mantle than those derived from previously studied rocks. Here we build upon our previous models of basalt formation based on rocks analyzed in Gusev Crater and Meridiani Planum to the new models of basalt formation for compositions from Gale Crater and a clast in meteorite NWA 7034. Estimates for the mantle potential temperature, TP based on Noachian age rock analyses in Gale Crater, Gusev Crater, and Bounce Rock in Meridiani Planum, and a vitrophyre clast in NWA 7034 are within error, which suggests that the calculated average TP of 1450 ± 70°C may represent an average global mantle temperature during the Noachian. The TP estimates for the Hesperian and Amazonian, based on orbital analyses of the chemistry of the crust, are lower in temperature than our estimates for the Noachian, which is consistent with simple convective cooling of the interior of Mars. However, the TP estimates from the young meteorites are significantly higher than the estimates based on surface chemistry and are consistent with localized “hot spot” melting and not heating up of the interior.