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Project Progress

Understanding the origin and formation of clays on Mars is central to this debate. Clays may have played a critical role in the emergence of life on Earth, and can form in a wide range of conditions. We have explored formation conditions with a focus on linking specific types of phyllosilicate assemblages observed by MSL and Curiosity to early Mars climate (Bishop, lead). Major results include the identification of three groups of clays defined by different climate regimes: 1) surface smectites formed temperatures above 0-10°C, suggesting short-term warm and wet environments during a generally cold early Mars; 2) Bursts of short-lived weathering events caused by impacts or geothermal sources at 25-50°C for thousands to hundreds-of-thousands of years could have supported the formation of other clays, including the 200 m thick surface smectite deposits at Mawrth Vallis and across Arabia Terra. Studies of fluvio-lacustrine systems in other regions, such as the Hellas Basin, suggest that clay formation through hydrothermal processes was widespread over long periods on Mars. Using MRO CTX and HiRISE images, analysis of Navua Valles, a series of disconnected drainages ranging in ages from Noachian to Amazonian, show hydrological activity included several episodes of surface ponding, runoff, infiltration, subsurface flow and subsequent outflow (Gulick, lead). The formation of the older lakes is consistent with Hadriaca Patera formation and associated hydrothermal activity; 3) Poorly crystalline or nanophase aluminosilicates at Gale Crater, Mawrth Vallis, and elsewhere formed from volcanic tephra in cold or low water/rock environments as observed in terrestrial glacial environments. All three clay groups may have been able to support life, although Group 2 is associated with moderate climates that are most consistent with microbial life on Earth.