Thermal Evolution of Europa's Silicate Interior

Abstract

The thermal evolution of Europa's silicate mantle directly influences the chemistry and dynamics of its ocean and icy shell, and has significant implications for habitability. The current state of understanding of Europa's silicate mantle is reviewed and discussed. Models of the equilibrium thermal structure of the silicate mantle subject to tidal and radiogenic heating are presented. Europa's silicate mantle, like Io's, has two possible equilibrium states, one cold and Moon-like, and one hot (super-solidus) and Io-like. The heat flux out of the mantle in the hot state is ~10^13 W, less than one-tenth of Io, but an order of magnitude larger than the heat produced in the icy shell. The thermal evolution of Europa's mantle is coupled to its orbital evolution, and models of the coupled system are presented. The dynamics of this system is rich, and includes oscillatory states in which the heat flow varies by orders of magnitude. This behavior would clearly have significant implications for the chemistry of the ocean and the thickness of the overlying ice shell.