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Project Progress

Understanding the geologic history of Mars is critical to interpreting the past and present habitability of the planet and for planning future astrobiological exploration. Dr. Tom McCollom, together with collaborator Dr. Brian Hynek, has been using geochemical modeling and remote sensing data to evaluate the geologic history of bedrocks exposed on Meridiani Planum that have been observed by the Mars Exploration Rover (MER) Opportunity. The MER science team has interpreted the bedrocks to be volcanic sediments deposited in a standing body of briny water that later evaporated to leave behind sulfate salts, implying prolonged clement conditions and a relatively benign environment that might be conducive to life. However, this interpretation appears to be incompatible with the chemistry and geologic setting of the rocks, and Drs. McCollom and Hynek have instead inferred that the bedrocks are volcanoclastic airfall deposits subsequently altered by sulfur-rich volcanic gases in a solfatara-like environment. This interpretation implies an environment much less conducive to life than the interpretation favored by the MER science team. A manuscript describing these results is currently under review. In addition, Dr. McCollom has completed a review article of Mars’ habitability entitled “Is (or Was) Mars Habitable for Life? A Review of the Current Evidence” to appear in the book Solar System Update.