Geological implications of a physical libration on Enceladus

Given the non-spherical shape of Enceladus [Thomas et al., 2007], the satellite will experience gravitational torques that will cause it to physically librate as it orbits Saturn. Physical libration would produce a diurnal oscillation in the longitude of Enceladus’ tidal bulge, which could have a profound effect on the diurnal tidal stresses experienced by the surface of the satellite. Although Cassini ISS has placed an observational upper limit on the amplitude of Enceladus’ libration, smaller amplitudes can still have geologically significant consequences. Here we present the first detailed description of how physical libration affects tidal stresses and how those stresses might then affect geological processes including crack formation and propagation, south polar eruption activity, and tidal heating. Our goal is to provide a framework for testing the hypothesis that geologic features on Enceladus are produced by tidal stresses from diurnal librations of the satellite.