The Geological History of Water on an Earth-like Planet

Delivered by Professor Baker, University of Arizona

Recent advances in astronomy hold the prospect for discovery of a great many Earth-like planets, rich in both water and possible habitats for life, thereby greatly expanding from the current sample of one. Nevertheless, until it proves possible to do geology for these numerous potential exo-Earths, we can greatly advance the geological science of Earth-like planets by study of Mars. The early geological histories of both Mars and Earth are closely tied to the role of water, extending from the nature of planetary accretion to the origin of a physically coupled atmosphere and ocean, the prospects for initiating plate tectonics, and historical records of punctuated greenhouse-to-icehouse climatic transitions. Recent discoveries from Mars missions reveal the extensive role of water in generating sedimentary rocks, active and relict glacial and periglacial features, aqueous weathering products (clay minerals and sulfates), alluvial fans and deltas, the extensive development of paleolakes, and even a probable, though transient ocean.