Ocean tides heat Enceladus

Abstract

With a young, highly reflective surface and vigorous geological activity, Saturn's tiny moon Enceladus has been one of the most mysterious planetary bodies in the solar system. Recent observations from the Cassini spacecraft show vast plumes of vapor erupting from geysers near the south pole, and inferred heat fluxes of about 100 mW/m 2 for the same region have helped consolidate the essential enigma of Enceladus: there must be a relatively large and unidentified source of heat in the tiny moon. Here we present a case for heating from dissipation by tidal flow in an ice-covered ocean. We show that if the spin axis of Enceladus is tilted with respect to its orbital plane by at least 0.05 degree then strong tidal flow will be generated with enough dissipative heating to explain the observed heat flux. In an alternative case of a shallow (10 km or less) ocean, comparable flow velocities and heating may be obtained by eccentricity tidal forces. Copyright 2009 by the American Geophysical Union.