Particle entrainment and rotating convection in Enceladus’ ocean

Abstract

Observations from Cassini have identified nanometer-sized silica grains in Saturn’s E-ring although their origin is unclear. Tidal deformation within Enceladus’ silicate core has been predicted to generate hot hydrothermal fluids that rise from the core-ocean boundary and traverse the subsurface ocean. This raises the possibility that the particles observed by Cassini could have been produced by hydrothermal alteration and ejected via the south polar plumes. Here, we use an analytical model to quantify potential for particle entrainment in Enceladus’ ocean. We use scaling relations to characterize ocean convection and define a parameter space that enables particle entrainment. We find that both the core-ocean heat fluxes and the transport timescale necessary to drive oceanic convection and entrain particles of the observed sizes are consistent with observations and predictions from existing thermal models. We conclude that hydrothermal alteration at Enceladus’ seafloor could indeed be the source of silica particles in Saturn’s E-ring.

The nanometer silica grains that were detected by Cassini in Saturn’s E-ring can be explained by hydrothermal activity on Enceladus’ seafloor and upward transport through the ocean, according to analytical modeling of convection and particle entrainment in Enceladus’ ocean.