Effects of asteroid and comet impacts on habitats for lithophytic organisms - A synthesis

Asteroid and cornet impacts can have a profound influence on the habitats available for lithophytic microorganisms. Using evidence from the Haughton impact structure, Nunavut, Canadian High Arctic, we describe the role of impacts in influencing, the nature of the lithophytic ecological niche. Impact-induced increases in rock porosity and fracturing can result in the formation of cryptoendolithic habitats. In some cases and depending upon the target material, an increase in rock translucence can yield new habitats for photosynthetic cryptoendoliths. Chasmoendolithic habitats are associated with cracks and cavities connected to the surface of the rock and are commonly increased in abundance as a result of impact bulking. Chasmoendolithic habitats require less specific geological conditions than are required for cryptoendolithic habitats, and their formation is likely to be common to most impact events. Impact events are unlikely to have all influence on epilithic and hypolithic habitats except in rare cases, where, for example, the formation of impact glasses might yield new hypolithic habitats. We present a synthetic understanding of the influence of asteroid and comet impacts on the availability and characteristics of rocky habitats for microorganisms.