A search for minerals associated with serpentinization across Mars using CRISM spectral data

Abstract

Sites associated with serpentinization processes, both on Earth and throughout the Solar System, are becoming increasingly compelling for the study of habitability and astrobiology. The co-occurrence of serpentine, Mg-carbonate, and talc/saponite on Mars is most like terrestrial sites where this mineral suite is produced in low-temperature serpentinizing environments, and where on Earth these reactions support biological activity. This study aims to understand the global distribution of minerals associated with serpentinization. We performed a comprehensive analysis of the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectral dataset using factor analysis and target transformation methods to efficiently parse through the large quantity of data. These methods allow for the rapid analysis of thousands of images and provide a quantitative means to determine the significant spectral constituents of an image. These methods were used to produce a global distribution map of CRISM images with a significant likelihood of containing the spectral types of interest. Previous detections of serpentine using traditional CRISM analysis techniques were typically corroborated and additional detections were identified in isolated locations across the martian southern highlands. Most serpentine across Mars is associated with another Fe/Mg-phyllosilicate phase like talc and/or saponite. Except for in the Nili Fossae region, serpentine shows no clear relationship with ultramafic bedrock or with the other mineral phases investigated (Mg-carbonate and talc/saponite). Most serpentine detections were found in isolated exposures, associated with crater ejecta, knobby terrain, or as part of discontinuous layers in crater or valley walls. Nili Fossae shows more pervasive and extensive detections of a serpentine + phyllosilicate endmember than previously recognized, particularly in the eastern portion of Nili Fossae where the highest concentration of olivine-rich basalts is located. These findings imply that large, regional-scale near surface serpentinizing systems were likely rare on Mars. However, low-concentration serpentine detections across the southern highlands do suggest more pervasive serpentinization early in Mars history, when the planet was more geologically active.