Geomicrobiology of Impact-Altered Rocks

Rocks shocked by asteroid or comet impact events can be made more porous by the shock volatilization of minerals, and they can be fractured by the intense heat and pressures of impact. New spaces within the rock provide access points and surfaces for the growth of microbial communities, illustrating an example of how shock metamorphism can generate new habitats for microbial colonization. We review data on the colonization of shocked gneiss from the Haughton impact structure by phototrophs and heterotrophs. Shocked rocks can preferentially trap water and protect against wind-induced desiccation. The interior of shocked rocks is often warmer than the air temperature, and protects against ultraviolet radiation. Because impact events are a ubiquitous process on solid planetary surfaces, the shocked-rock habitat may be important on other planets, and it may have been important on the early Earth when primitive microorganisms lived under a much higher impact flux than today.