Enceladus: An estimate of heat flux and lithospheric thickness from flexurally supported topography.

Abstract

We have identified flexural uplift along a rift zone of the Harran Sulci, Enceladus, using Cassini stereo-derived topography. Modeling the topography on the basis of a flexed broken elastic plate yields an effective lithospheric thickness of 0.3 km and, combined with the strength envelope, a mechanical lithospheric thickness of 2.5 km with heat fluxes of 150-220 mW/m2 at the time of formation. The heat fluxes are comparable with average heat fluxes measured in Enceladus’ active south polar area and correspond to heat fluxes derived via models of unstable extension of the lithosphere in this area. Surface porosity can reduce the heat fluxes to an estimated minimum of 40-50 mW/m2. Crater-size frequency counts and a lunar-like impact chronology fix the time of formation of the rift zone at 3.5 Ga from present-day.