Brine Migration and Impact-Induced Cryovolcanism on Europa

Despite evidence for plumes on Jupiter's moon Europa, no surface features have been definitively identified as the source of the plumes to date. Furthermore, it remains unknown whether the activity originates from near-surface water reservoirs within the ice shell or if it is sourced from the underlying global ocean. Here we investigate brine pocket migration, studied previously in the context of sea ice on Earth, as a process for transporting brine along thermal gradients. We show that the fracture system located in the center of Europa's Manannán crater is consistent with the formation of a subsurface brine reservoir. After the initial impact, residual aqueous melt concentrated via brine pocket migration as the target material cooled. Freezing and overpressurization then resulted in a cryovolcanic eruption. The volume of the emptied reservoir and the critical composition at the end of migration provide further constraints on the average salinity of Europa's ice shell.