Non‐Synchronous Rotation on Europa Driven by Ocean Currents

It has been suggested that the ice shell of Jupiter's moon Europa may drift non-synchronously due to tidal torques. Here we argue torques applied by underlying ocean are also important and can result in non-synchronous rotation. The resulting spin rate be slightly slower than synchronous angular would have kept same point facing Jupiter. We develop an rotation model, driven stress calculated using a high-resolution state-of-the-art general circulation take into account viscoelastic deformation shell. use model results together with observed limits on speed constrain parameters such as effective viscosity, which is currently uncertain at least four orders magnitude. Our suggest, best, sluggish convection. Depending relaxation time scale currents, exhibit negligible drift, constant or oscillatory superimposed random fluctuations. expected exceeds ∼30 m/yr; future spacecraft observations used test these predictions yield insight properties ocean.