Geology, Life and Habitability

The examination of contemporary systems and the rock record has demonstrated that the biosphere and geosphere are intimately linked, presumably since life's origin. The geosphere provides trace and essential nutrients for life, sources of reduced compounds and electron acceptors, that is, the energy for life to occur, and habitats ranging from 'simple' surfaces to grow on, to unique endolithic environments formed at least in part by the microorganisms themselves. The hydrosphere is perhaps more important than the lithosphere, because it provides the solvent necessary for biogeochemical reactions and life to occur. The major question about how life originated cannot be readily answered; however, the question of habitability is relatively easy. Using Earth as our role model, there are several candidate extrasolar bodies within our solar system, for example, Mars and Europa, that could support life