Enhanced Tidal Deformation in Icy Satellites with Subsurface Oceans

Abstract:

Tidal dissipation is a major heat source for the icy satellites of the giant planets. Several icy satellites likely possess a subsurface ocean underneath an ice shell. Previous studies of tidal dissipation on icy satellites, however, have either assumed a static ocean, or ignored the effect of the ice lid on subsurface ocean dynamics. In this study, we examine inertial effects on tidal deformation of satellites with a dynamic ocean overlain by an ice lid based on viscoelasto-gravitational theory. Although ocean dynamics is treated in a simplified fashion, we find a resonant configuration when the phase velocity of ocean gravity waves is similar to that of the tidal bulge. This condition is achieved when a subsurface ocean is thin (<1 km). The enhanced deformation (increased h₂ and k₂ Love numbers) near the resonant configuration would lead to enhanced tidal heating in the solid lid. A static ocean formulation gives an accurate result only if the ocean thickness is much larger than the resonant thickness. The resonant configuration strongly depends on the properties of the shell; a thicker shell and a more rigid shell leads to a thinner resonant thickness. This result demonstrates the importance of the presence of a shell on tidal dissipation.