Tidal Dissipation in the Oceans of Icy Satellites

Abstract:

Dissipation of tidal energy is an important mechanism for the evolution of outer solar system satellites, several of which are likely to contain subsurface oceans. We extend previous theoretical treatments for ocean tidal dissipation by taking into account the effects of ocean loading, self-attraction, and deformation of the solid regions. These effects modify both the forcing potential and the ocean thicknesses for which energy dissipation is resonantly enhanced, potentially resulting in orders of magnitude changes in the dissipated energy flux.

Assuming a Cassini state obliquity, Enceladus' dissipated energy flux due to the obliquity tide is smaller than the observedvalue by many orders of magnitude. On the other hand, the dissipated energy flux due to the resonant response to the eccentricity tide can be large enough to explain Enceladus' observed heat flow.The figure shows the dissipated energy flux due to the obliquity and eccentricity tides as a function of the quality factor and ocean thickness. Narrow maxima correspond to ocean thicknesses for which the tidal flow is resonantly enhanced.