Partial differentiation of Europa and implications for the origin of materials in the Jupiter system

Abstract

The Galileo mission measured the gravity field around Europa. The results indicated that the moon’s interior is mostly made of rock (~90 wt%). However, the level of differentiation of the deep interior is still poorly understood. We constrain the interior of Europa using Galileo gravity data and a combination of geophysical and geochemical models that connects the origin of the materials accreted in the Jupiter system with the observed gravity field. The results indicate that Europa is partially differentiated and that it probably formed primarily from CV chondrite material. We investigate this finding by coupling thermal evolution models with a detailed treatment of Fe–FeS melting. The metal–silicate differentiation temperatures (>1,600 K) are not attained if Europa formed about 4 Myr after the production of calcium aluminium inclusions. The leaching of potassium during thermal metamorphism further limits differentiation. Our results imply a cold evolution for Europa and suggest that part of water inventory of Europa was supplied by external sources, possibly by comets. These implications can be tested with the gravity data that will be acquired by Europa Clipper and JUICE.