Probing Europa's hidden ocean from tidal effects on orbital dynamics



Recent observations of Europa suggest that the Jovian satellite may have a liquid ocean underneath its icy surface. Geophysical models indicate that the tidal Love number k2 has a strong dependence on the presence or absence of an ocean. The k2 dependence on the ice shell thickness is also significant. Measurements of the static and tidal gravity fields through their dynamic effects on the trajectory of a low Europan orbiter can be essential in the detection of an ocean and inference of other internal structures. Covariance analyses have been carried out to assess accuracies using simulated Doppler tracking data. With 15 days of tracking from 2 Earth stations, the uncertainties for k2, mantle libration amplitude and the epoch radial position of the spacecraft are expected to be 0.0004, 2.8 arcsec and 5.7 m, respectively. These tight constraints will strongly contribute to ocean detection and ice thickness determination when combined with altimeter measurements.