Surface-to-ocean exchange by the sinking of impact generated melt chambers on icy ocean worlds

Impacts into icy bodies often generate near-surface melt chambers and thermal perturbations that soften the ice. We explore the post-impact evolution of nonpenetrating impacts into Europa’s ice shell. Numerical 5 simulations of viscous ice deformation show that dense impact melts founder before refreezing. If the transient cavity depth exceeds half the ice shell thickness, over 40% of the impact melt drains into the underlying ocean. Drainage occurs through a continuous porous conduit from the near-surface to the ocean on timescales of 103 10 to 104 years. The drainage of impact melts to the ocean occurs for all ice shell thicknesses and ice viscosities explored, suggesting that melt foundering is a natural consequence of impacts on icy worlds. Post-impact vis15 cous deformation is an important process on icy worlds, which modifies crater morphology, affects cryovolcanism, creates conduits through the ice for surface-to-ocean exchange, and may supply oxidants required for habitability to the subsurface ocean.