AOPP Seminar - Exploring stratification, freshening, and particulate transport within Enceladus’ subsurface ocean

Enceladus – moon of Saturn – hides a global ocean of water beneath its icy exterior and is a prime target in the search for life. Geyser-like plumes erupting from its south polar ice shell eject ocean material into space, providing a means to probe its composition, a target of future missions. Yet, it is unclear if plume material can be assumed representative of conditions at Enceladus’ depths, where hydrothermal environments conducive for life have been hypothesised. 

In this work, we highlight the role of ocean stratification (non-convecting regions of ocean) which if present within Enceladus, could isolate the plumes from the ocean bottom, yielding plume material that misses components present at depth. Using theoretical models verified with 2D global ocean numerical simulations, we show that Enceladus’ south polar ocean should be stratified if a steady state ice shell is assumed, delaying the arrival of hydrothermal products at the plumes by 100’s to 100’000s of years. Furthermore, it is shown how melting of the south polar ice shell, required if it is in steady state, could freshen the plume source by several g/kg relative to the bulk ocean. Implications of these findings for existing and future interpretation of plume material are discussed.