Enceladus’s Tidal Heating: A Simple Approach

Abstract Saturn’s moon Enceladus has a global ocean that is covered by an ice shell. The moon’s eccentric orbit forces the shell to librate, which distorts the shell and thereby generates heat. The resulting tidal heating prevents the ocean from freezing, and likely drives the moon into a limit cycle, as shown in the companion paper Goldreich et al. Here we derive the tidal heating rate needed for that study. We adopt a novel approach based on energy minimization. Our derivation is thus considerably simpler than previous ones, as is the final expression for the heating rate. We also account for what happens near libration resonance. Although we focus on Enceladus, our approach may be extended to other bodies that have a similar three-layer structure, such as Europa and Titan.