Convective-conductive transitions and sensitivity of a convecting ice shell to perturbations in heat flux and tidal-heating rate: Implications for Europa
- G Mitri, A P Showman
Heat transport across Europa's ice shell controls the thermal evolution of its interior and provides a source of energy to drive resurfacing. Recent improvements in knowledge of ice rheology, the behavior of convection, and the interaction between convection and lithospheric deformation have led to more realistic and complex models of the geodynamics of Europa's icy shell. The possibility of convection complicates efforts to determine the shell thickness because a thin conductive shell can carry the same heat flux as a thick convective shell. Whether convection occurs depends on ice viscosity, which in turn depends on grain size. The grain size may be controlled by internal deformation, or by impurities, depending on shell composition. Creating the observed surface features with steady-state thermal convection is challenging , even with tidal heating, because the near-surface ice is cold and stiff. Convection models that include surface weakening and compositional buoyancy show promise in explaining some chaos terrains, pits, and uplifts, but new spacecraft and laboratory data and geophysical techniques are needed to match theory to observation.