Limited direct fluid exchange between the deep subsurface ocean and the shallow subsurface environment of Europa

Abstract Numerous satellites in the outer solar system, including Europa, possess vast subsurface oceans beneath their icy exteriors. Previous studies have proposed that liquid water from Europa’s deep ocean may ascend through dikes and pool as sills within the shallow subsurface. Such reservoirs could create transient habitable environments and may be directly linked to the formation of surface features such as chaos terrain and lenticulae. Here, we couple high resolution laminar and fully turbulent fluid thermal simulations to test whether such dikes can deliver the required volumes before freezing. Our results indicate that the volume of water capable of ascending through dikes before freezing and sealing the conduit is insufficient to account for the hypothesized surface features. When turbulence is included, heat loss within the ascending column of liquid water increases by up to four orders of magnitude, driving supercooling enough to trigger frazil ice formation and rapid conduit clogging. Our results suggest that direct fluid exchange between Europa’s deep ocean and shallow subsurface is minimal and that in-situ melting may be the primary source of any shallow liquid water, if present. Notably, this also implies that shallow liquid reservoirs, if encountered by future missions, may not reflect the geochemical signature of the underlying ocean.