Near-surface heating on Enceladus and the south polar thermal anomaly

Abstract

Strike-slip motion is predicted to be a consequence of diurnal tidal stresses in most satellites of the outer solar system. Such motion can lead to near-surface heating through friction or viscous dissipation. Here we discuss the effect of near-surface shear heating on convection in the underlying ice shells of icy satellites. We present models of convection in spherical shells including tidal and shear heating, and show that localized near-surface heating enhances convective upwelling beneath it. The near-surface heating promotes regional melting of the ice shell, which likely results in subsidence of the surface topography. The long-wavelength geoid resulting from the subsidence, plume buoyancy and dynamic topography may lead to small ($\lesssim$4° per Ma) amounts of true polar wander, potentially contributing to the south polar location of the observed thermal anomaly. However compositional effects are likely required in addition to thermal effects to generate larger degrees of reorientation.