Tidal Deformation of an Icy Moon with a Subsurface Ocean

Abstract

Enceladus is one of the icy moons in the outer solar system. The Cassini mis- sion has found out direct evidence on existing subsurface ocean. These evidences showed that the water contains organic molecules and nutrient, such that it could create suitable environment for emergence of life. However, the mechanism how the ocean is maintained in a liquid state, is still unknown. We studied the effect of the tidal force on maintaining the ocean in a liquid state, where the effect of the elastic ice shell is modelled through boundary condition. We modelled the ocean with the three dimensional linearised incompressible Navier-Stokes equa- tions in the time domain. Then, we solved the equations numerically with spectral method. The numerical methods are written in to Fortran 90 program. We tested the various properties of the numerical methods. We, then, investigate the tidal dissipation for various ocean thicknesses and viscosities. We conclude that the tidal dissipation heavily depends on the thickness and the viscosity. These results show us that the tidal force could have significant contribution to the total heat budget of Enceladus for given viscosities of the ocean. 1