Habitability of Europa's crust: The role of tidal-tectonic processes

Jupiter's satellite Europa has been identified as one of the most likely si tes for life in the solar system. The tidal-tectonic processes that appear to have governed Europa's geology seem to require interaction with an ocean under only a very thin crust, providing a variety of evolving environmenta l niches. The mutually dependent relationship between orbital evolution and tidal processes in turn controls Europa's rotation, heating, and stress. S urface lineaments are correlated with global stress patterns, demonstrating that they form by crustal cracking, but only if a substantial ocean is pre sent to give adequate tidal amplitude. Tidal driving of strike-slip faultin g indicates that cracks penetrate to a fluid layer, which is possible only with a very thin ice crust. The characteristic ridge sets that cover tecton ic terrain are likely built by tidal pumping of fluid and slush to the surf ace on a daily basis. Widespread tectonic dilation creates new surface as m aterial rises from below. Chaotic terrain has morphology and other characte ristics indicative of melt-through from below. Surface colorants correlate with locations, such as along large-scale ridge systems and around chaotic terrain, where ocean water reached the surface. This model implies that as a result of tides, liquid water regularly bathed crustal cracks and surface s with heat and whatever nutrients are included in the oceanic chemistry, c reating a variety of habitable environments. The processes were recent and thus most likely continue today. Longer-term evolution of environmental con ditions provided the need for adaptation and opportunity for evolution.