Brittle ice shell thickness of Enceladus from fracture distribution analysis

Abstract

We determine the depth of fracture penetration in multiple regions of Enceladus by performing self-similar clustering and length distribution analysis of fractures. The statistical characterization of fault-population attribute, such as length and clustering, provide a productive avenue for exploring deformation rate, stress transmission mode, rheology of the medium, and mechanical stratification of the ice satellite. Through this analysis, we estimate the depth of the mechanical discontinuity of Enceladus' ice shell that is the depth to which fractures penetrate the brittle ice layer above the ductile one. In this work, we find that for the South Polar Terrain (SPT), the brittle ice shell interested by fracture penetration is about 30 km and corresponds to the total depth of the ice shell because the SPT has a very high thermal gradient and, hence, fractures likely reach the ocean-ice interface. In the other regions analyzed, the depth of fracture penetration increases from 31 to 70 km from the South Pole to northern regions up to 75°.