An Oceanic Mechanism for Geyser Formation on Enceladus

Abstract The tiger stripes of Enceladus are a sequence of four parallel and evenly-spaced fissures 130~km long which erupt water from a global subsurface ocean out into space. We present the first theory of their formation which links the observed surface to yet unexplored features of the oceanic environment below. Given one initial fissure, topography on the underside of the ice shell rubs periodically against the ocean due to the satellite's libration. This motion excites internal gravity waves which propagate down and reflect at a bottom boundary, reimpacting the underside of the shell at a fixed distance away from primary fissure. This impact generates heat through wave breaking which melts the ice, forming the next fissures in a chain of parallel stripes. We solve for the internal wave field, energy dissipated, and ice melted using linear gravity wave analysis, extending previous literature on gravity wave conversion. The dissipation predicted by the analytical theory matches nonlinear simulations using the MITgcm, especially when the flow remains subcritical. Dissipative regimes where new fissures can form are identified. Maintaining that formation occurs at the observed 35 km spacing, we discuss implications for ocean depth and stratification.