Mars Surface Mineralogic Diversity and Mineral Mixtures Mapping Using CRISM Data and the Tetracorder Spectral Mapping System

Abstract:

The search for minerals and other materials from the wealth of imaging spectroscopy data being returned from Mars poses a formidable task. Most recent mapping has required human intensive massaging/filtering of image cubes and mapping by parameters. The new CRISM Map-projected Targeted Reduced Data Record (MTRDR) image cubes enable a new level of sophistication in detection and mapping of materials. We use a new version of Tetracorder that has a more sophisticated expert system for the identification and mapping of materials in CRISM data, including curved continuum removal that permits more robust detection of weak spectral features embedded in larger features. The use of spectral feature fitting algorithms and curved continua enable subtle changes in mineralogy to be detected, including weak hydroxyl and carbonate features in the presence of strong >2 micron pyroxene absorptions, and organics and carbonates in the presence of the strong curvature from the 3-micron water band so prevalent on Mars. In mapping numerous CRISM scenes to date we find interesting mineralogic diversity expressed in the position and shape of the 1.9-micron water absorption, ranging from ~1.91 microns in many clays to ~1.93 microns in sulfates and may be an indicator of these minerals when the OH features are too weak to observe. All scenes mapped so far show the presence of the 1.9-micron water in various band positions. Another mineral found to be extensive is prehnite and mixtures of prehnite with chlorite and/or serpentine. Prehnite, Ca2Al(AlSi3O10)(OH)2, is a secondary or hydrothermal mineral in veins and cavities in mafic volcanic rocks and a product of low-grade metamorphism. Other minerals mapped include the clino-orthopyroxene series, clay minerals, sulfates, olivine, magnetite, hematite and goethite grain sizes, other Fe2+ and Fe3+ minerals, and H2O and CO2 ice. These diverse mineralogies could guide present and future landing missions to geologically interesting areas.