A simplified model for the forced libration of icy moons with subsurface oceans: Application to Enceladus and Mimas

Abstract

We investigate a simple two-layered viscoelastic rheological model capable of replicating the forced librations of an icy moon with a subsurface ocean. We show that the model, composed only of a prestressed icy crust lying over an effective fluid core (a fixed mantle cavity), can effectively describe the librational behavior of icy moons, thus holding the potential to predict the presence of a subsurface ocean through the analysis of longitudinal librations. The proposed model is applied to the longitudinal librations of Enceladus and Mimas, two small icy moons of Saturn for which relevant data are available from the Cassini mission.