New Insights into the Nature of Mineralogic Alteration on Mars from Orbiter, Rover, and Laboratory Data

Introduction: Over the past ten years of Mars exploration, a wealth of information has been gathered from various sources that allows us to more fully address questions about the nature of mineralogic alteration of the Martian surface. The role of water now has been clearly identified by the presence of numerous aqueously-derived mineral phases observed from orbit and the surface. Here we present new observations that further elucidate the nature of this alteration and in some cases create new enigmas about the styles of Martian alteration. Thermal infrared (TIR) spectra from the Mars Global Surveyor Thermal Emission Spectrometer (TES) and Mars Exploration Rover Miniature Thermal Emission Spectrometer (Mini-TES) are emphasized herein and supported by laboratory spectra. Orbital Observations: Visible/near-infrared spectra from the Mars Express OMEGA and Mars Reconnaissance Orbiter CRISM instruments have provided definitive evidence for phyllosilicate alteration phases including clay minerals [e.g., 1, 2]. Such phases had been suggested based on TES data [e.g., 3], but their identification was ambiguous. We now recognize in TES spectra from Mawrth Vallis and other phyllosilicate-bearing locations identified by OMEGA/CRISM, features that are strikingly similar to those of phyllosilicate-altered terrestrial basalts (Fig 1).