Insights into Mars mud volcanism using visible and near-infrared spectroscopy

Mud volcanism (MV) has been a proposed formation mechanism for positive-relief landforms in the lowland, equatorial, and highland regions of Mars. While visible and near-infrared (VNIR) spectroscopy has been used in a few cases to argue for the presence of MV on the surface of Mars, data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) remain underutilized. We conducted a global examination of proposed Mars MV features using CRISM VNIR data. We observe variable hydration states and place constraints on the composition of these features from orbit. We do not confidently identify phyllosilicates, carbonates, or sulfates associated with suggested Martian mud volcanoes. However, specific structures in Valles Marineris exhibit VNIR signatures consistent with unaltered hydrated glass of a volcanic origin and high-Ca pyroxene. CRISM visible data from MV features reveal consistent nanophase ferric oxide signatures on a global scale, although these signatures are not unique to Mars MV materials. Limitations in specific mineral detection are likely due to the fine grain size and/or textural characteristics of putative MV features. While we do not argue in favor of a specific proposed MV site in the context of future robotic or human missions, the insights of this study could be used as a guide for Mars surface exploration.