Non-synchronous rotation on Europa driven by ocean currents by Yosef Ashkenazy et al. on Monday 21 November
It has been suggested that the ice shell of Jupiter's moon Europa may drift
non-synchronously due to tidal torques. Here we argue that torques applied by
the underlying ocean are also important and can result in retrograde
non-synchronous rotation (NSR). We develop an ice shell rotation model, driven
by ocean stress calculated using a high-resolution state-of-the-art ocean
general circulation model, and take into account the viscoelastic deformation
of the ice shell. We use the ice shell model results together with observed
limits on the ice shell drift speed to constrain ice shell parameters such as
effective viscosity, which is currently uncertain by at least four orders of
magnitude. Our results suggest, at best, sluggish ice shell convection.
Depending on the relaxation time scale of the ice shell and on the ocean
currents, the ice shell may exhibit negligible drift, constant drift, or
oscillatory drift superimposed on random fluctuations. The expected rotation
rate exceeds $\sim$30 m/yr; future spacecraft observations can be used to test
these predictions and yield insight into the properties of the ice shell and
underlying ocean.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.04961v2
