11 Impact Craters, Water and Microbial Life

Abstract

Because of the lack of recent plate tectonics, the surface of Mars has abundant, well-preserved impact structures. Impact structures can localize water in a number of ways including: 1) circulation of water into hydrothermal systems, 2) ponding of water in the hydrologic depression of the crater. This ponding can occur because of excavation below the water table, filling of the crater by rivers that breach the crater rim, penetration of deep, confined aquifers or by collection of precipitation in the form of rain and snow, 3) entrapment of water in the fractures of shocked rocks and 4) melting of existing frozen water sources by the heat of impact. The local enhancement of water availability provides a potential mechanism for the local enhancement of microbial communities compared to regions outside of craters, provided that an energy source and other nutrient requirements for life are present. We discuss some examples of microbial communities in terrestrial impact structures that are associated with some of these mechanisms of water enhancement and we discuss the importance of impact structures as places suitable for microbial life on other rocky planets, specifically Mars.