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

Jupiter's satellite Europa has been identified as one of the most likely sites 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 environmental niches. The mutually dependent relationship between orbital evolution and tidal processes in turn controls Europa's rotation, heating, and stress. Surface lineaments are correlated with global stress patterns, demonstrating that they form by crustal cracking, but only if a substantial ocean is present to give adequate tidal amplitude. Tidal driving of strike-slip faulting indicates that cracks penetrate to a fluid layer, which is possible only with a very thin ice crust. The characteristic ridge sets that cover tectonic terrain are likely built by tidal pumping of fluid and slush to the surface on a daily basis. Widespread tectonic dilation creates new surface as material rises from below. Chaotic terrain has morphology and other characteristics 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 surfaces with heat and whatever nutrients are included in the oceanic chemistry, creating a variety of habitable environments. The processes were recent and thus most likely continue today. Longer-term evolution of environmental conditions provided the need for adaptation and opportunity for evolution.