A synthesis of Martian aqueous mineralogy after 1 Mars yearof observations from the Mars Reconnaissance Orbiter

摘要

Martian aqueous mineral deposits have been examined and characterized using dataacquired during Mars Reconnaissance Orbiter's (MRO) primary science phase, includingCompact Reconnaissance Imaging Spectrometer for Mars hyperspectral imagescovering the 0.4-3.9 pm wavelength range, coordinated with higher—spatial resolutionHiRISE and Context Imager images. MRO's new high-resolution measurements,combined with earlier data from Thermal Emission Spectrometer; Thermal EmissionImaging System; and Observatoire pour la Mineralogie, L'Eau, les Glaces et l'Activitiê onMars Express, indicate that aqueous minerals are both diverse and widespread on theMartian surface. The aqueous minerals occur in 9-10 classes of deposits characterized bydistinct mineral assemblages, morphologies, and geologic settings. Phyllosilicates occurin several settings: in compositionally layered blankets hundreds of meters thick,superposed on eroded Noachian terrains; in lower layers of intracrater depositional fans;in layers with potential chlorides in sediments on intercrater plains; and as thousands ofdeep exposures in craters and escarpments. Carbonate-bearing rocks form a thin unitsurrounding the Isidis basin. Hydrated silica occurs with hydrated sulfates in thinstratified deposits surrounding Valles Marineris. Hydrated sulfates also occur togetherwith crystalline ferric minerals in thick, layered deposits in Terra Meridiani and in VallesMarineris and together with kaolinite in deposits that partially infill some highlandcraters. In this paper we describe each of the classes of deposits, review hypotheses fortheir origins, identify new questions posed by existing measurements, and consider theirimplications for ancient habitable environments. On the basis of current data, two to fiveclasses of Noachian-aged deposits containing phyllosilicates and carbonates may haveformed in aqueous environments with pH and water activities suitable for life.