New Constraints on the size of Io's Core

Abstract

Io, a satellite of Jupiter, is known for being a highly geologically active body. The properties of this Jovian moon were extensively studied during the Galileo spacecraft mission, which orbited the Jovian system from 1995 to 2003. In particular, the mean density and moment of inertia factor were determined with high accuracy. From these measurements, simple layered models of the interior structure of Io can be constructed assuming hydrostatic equilibrium. Existing models are limited by, among other factors, the density of Fe-FeS liquids that are expected to be the main constituents of Io's core. This study builds a two layer model consisting of an olivine mantle and an Fe-FeS core, with constraints based on new high pressure and temperature compression data from literature. These new constraints yield a range of core sizes of 690-780 km or 38-43% Io's radius and a range of core densities of 6360 kg·m-3 for a eutectic composition core and 7630 kg·m-3 for a pure iron core.