Thermal and near-infrared analyses of central peaks of Martian impact craters: Evidence for a heterogeneous Martian crust

Central peaks of impact craters contain materials exhumed from depth, and therefore, investigation of these materials provides clues to subsurface geology and mineralogy. A global spectral survey of central peaks of Martian impact craters between 10 and 200 km diameter was completed using Mars Odyssey Thermal Emission Imaging System (THEMIS) data. Twenty-six central peaks with distinctive spectral signatures from surrounding plains were identified and characterized with thermal infrared and visible/near-infrared data. The distribution of spectrally distinct central peaks (SDCPs) shows some degree of regional clustering, with most craters found in western Noachis Terra, Tyrrhena Terra, within the northern rim of Hellas Basin, and fewer in the northern lowlands. With the exception of four craters in western Noachis Terra, SDCPs contain only one spectrally distinct unit at THEMIS resolution (100 m/pixel). The maximum number of spectrally distinct units observed was three, in Jones and Ostrov craters. The western Noachis Terra SDCPs may expose crustal stratigraphies of multiple igneous compositions or impact materials from Argyre. In the highlands, most SDCP units are consistent with enrichments in olivine or pyroxene relative to surrounding plains, suggesting olivine and pyroxene basaltic lithologies; few are olivine and pyroxene poor. No spatial trend in spectrally derived compositions of SDCPs was observed. Three SDCPs contain THEMIS signatures consistent with high abundances of phyllosilicates, which may contain the most phyllosilicate-rich lithologies found in central peak-associated materials globally.