The hemispheric dichotomy of surface tectonics and heat flux on Enceladus

Enceladus exhibits a strong tectonic contrast between its South Polar Terrain (SPT), which is young and geologically active, and its northern hemisphere, which is relatively ancient and stable. Previous global three-dimensional spherical models of convection exhibit patterns that are symmetrical around the equator and fail to explain the formation of a hemispheric dichotomy. Here we present global threedimensional spherical models of convection in Enceladus’ ice shell to show that convection in Enceladus’ ice shell with plasticity and irregular core geometry can self-consistently generate a hemispheric dichotomy in tectonics and heat flux. With a spherical core, convection produces global overturning, which cannot explain the regional confinement of Enceladus’ current tectonic activity to the SPT. Models with appropriate non-spherical core geometry and plasticity tend to produce overturning confined to the South Polar Terrain or regional overturning in different regions at different times, which can explain the tectonic dichotomy and local age differences on Enceladus. Our models predict heat flows up to 5–10 GW during active episodes, consistent with Cassini observations.