Degree-one convection and the origin of Enceladus' dichotomy

Abstract: Recently, the Cassini spacecraft has detected ongoing geologic activity near the south pole of Saturn''s moon Enceladus. In contrast, the satellite''s north-polar region is heavily cratered and appears to have been geologically inactive for a long time. We propose that this hemispheric dichotomy is caused by interior dynamics with degree-one convection driving the south-polar activity. We investigate a number of core sizes and internal heating rates for which degree-one convection occurs. The numerical simulations imply that a core radius of less than km and an energy input at a rate of 3.0 to 5.5 GW would be required for degree-one convection to prevail. This is within the range of the observed thermal power release near Enceladus'' south pole. Provided that Enceladus is not fully differentiated, degree-one convection is found to be a viable mechanism to explain Enceladus'' hemispheric dichotomy. [Copyright &y& Elsevier]