Partial Differentiation of Europa from a Revised Inversion of the Interior Structure

The Galileo mission provided measurements of Europa’s gravity field that yield crucial information on the moon’s interior. We present the first Bayesian inversion that constrains the interior using the mass and moment of inertia derived from Galileo gravity data. The derived probability distributions indicate a high mantle density, which can be matched by a primordial CV chondrite composition. These models agree with an undifferentiated deep interior or a smaller metallic core than previously estimated. We introduce new thermal evolution models of Europa that preserve a partially differentiated deep interior, consistent with these new geophysical constraints. A late formation of Europa (about 4 My after the production of calcium aluminum inclusions) and a significant extraction of K from rock during a phase of thermal metamorphism altogether prevent complete metal-silicate differentiation. This result bears implications for Europa’s ocean composition and upper mantle rheological properties that can be tested by a future mission.