Constraining the Interior Structure of Europa with Gravity Measurements

The NASA mission Europa Clipper is designed to conduct multi-disciplinary investigations of the interior, composition, and habitability of the Galilean moon Europa. The measurement of Europa’s gravity field, tides, orientation, and moment of inertia (MoI) will enable an accurate characterization of the moon’s interior by constraining internal structure models through the inversion of geophysical measurements. The refined knowledge of Europa’s interior will provide a better understanding of its thermal evolution and of the processes that formed and maintained the liquid water ocean underneath the moon’s outer icy shell. The accurate estimation of the tidal Love number k₂ is expected to provide geodetic evidence of the existence of the ocean, and its combination with the Love number h₂ will enable the estimation of the icy shell mean global thickness.

The determination of the MoI, obtained either through measurements of the degree-2 gravity field with the hydrostatic equilibrium assumption or by also measuring Europa’s orientation and obliquity, will provide information on the deep interior of the moon, possibly constraining the size and the composition of the solid interior. Numerical simulations are performed to assess the expected accuracy of the key geophysical quantities from the analysis of Europa Clipper radiometric data. These measurements are used in a Bayesian Inversion (e.g., Monte Carlo Markov chain) to explore the properties of Europa’s hydrosphere and deep interior.