A Proposed Model for Cryovolcanic Activity on Enceladus Driven by Volatile Exsolution

Abstract

There is considerable interest in sending a mission to Enceladus to sample its erupting materials, which are sourced from its ocean, a proposed habitable environment. However, we lack resolution between competing ascent and eruption models, which offer differing consequences and challenges for mission sampling and access strategies. We report a new Enceladus ascent and eruption model, “Cryo-Erupt,” where ascent from ocean to jet is driven by the exsolution and expansion of dissolved gases from ascending water within conduits. This mechanism shares many similarities with some forms of terrestrial activity, including explosive silicate volcanism, cold-water geysers and “limnic” eruptions. This preliminary study suggests that this mode of ascent and eruption is viable and broadly consistent with a range of observations including the apparent co-existence of point- (jet) and fissure- (curtain) sourced activity as well as strong contrasts in velocity and ice-to-vapor ratio between the plume and the jets feeding it. However, it requires the co-existence of a sublimation plume as an additive component to the broader plume. The outcomes of the Cryo-Erupt model differ in terms of conduit physical and chemical processes from previously proposed boiling interface eruption models, for example, predicting larger dynamic pressures and narrower conduits, which could present challenges for direct robotic access. Due to the lack of a static boiling interface or wall condensation, bulk composition is unlikely to change appreciably during ascent from the ocean-conduit interface to the jet, potentially simplifying the interpretation of samples collected in space or on Enceladus’ surface.