A Thermodynamical Model of the Icy Crust of Europa

Introduction. A fundamental question concerning Europa’s ice shell is whether the rigid lithosphere vis ible at the surface is underlain by a layer of warm, convecting ice. The heat produced by tidal friction in Europa’s silicate interior might be shed by simple conduction through a passive, relatively thin ice shell directly overlying a subsurface sea, or transported equally well through a much thicker ice shell consis ting of an actively convecting sublayer that efficiently delivers heat to a somewhat thinner upper conductive layer. While both of these configurations are plausible, they have very different implications for the thermal history of Europa, the formation of surface features and the prospects for future exploration.