Gravitational Flexing and the Potential for Life on the Outer Icy Satellites

Though water is abundant on many satellites of the solar system, the potential sources of energy for dynamic geophysical activity and possible biological processes are less well known. Gravitational flexing and the presence of a liquid medium could have provided biologically favorable conditions early in the history of the solar system when many of the satellites most likely held a water vapor atmosphere. Gravitational attraction between numerous satellites and their parent planets exceeds that between the Earth and the Moon (Gearth x moon). They include (for Gearth x moon = 1) Io (x321), Ganymede (x86), Europa (x68), Callisto (x19), Titan (x17), and Triton (x6). Perhaps more relevant is the flexing to which a satellite is exposed between maximum and minimum gravitational interactions among its sibling moons. Flexing is greatest by far on Io (13.7%), but appreciable on Oberon (0.071%), Europa (0.058%), Callisto (0.054%), Titania (0.046%), Ganymede (0.042%), Rhea (0.018%), Dione (0.010%), Tethys (0.007%), and Enceladus (0.005%). Tidal flats on Earth typically have high biological productivity, and may have provided an environment for the origin of life. Similar conditions followed by subsequent cooling in the outer solar system could have replaced the atmosphere of distant satellites with an ice shield, leaving liquid water with living organisms beneath the frozen crust. Such ecosystems conceivably could still be supported by kinetic energy due to tidal flexing within the liquid subsurface. >http://www.geo.utep.edu/pub/dirksm/geobiowater/geobiowater.html</ a>