A proposed cryovolcanic eruption model for Enceladus' plume

There is considerable interest in sending a mission to Enceladus to sample its erupting materials, which are transported either directly or indirection from its ocean, a likely habitable environment. However, we lack of clear resolution between candidate ascent and eruption models, which offer differing consequences and chellenges for mission sampling and access strategies. We report a new Enceladus ascent and eruption model – referred to as the multi-component multi-phase (MCMP) model – where the dominant driving eruption mechanism has been mostly neglected in published work: the exsolution from liquid water and expansion of dissolved volatile gases during vertical conduit flow from Enceladus’ ocean. This mechanism shares many similarities with some forms of terrestrial activity, including explosive silicate volcanism, cold-water geysers and “limnic” eruptions driven by rapid exsolution of dissolved CO2. The outcomes of this model differ it terms of conduit physical and chemical processes from previously proposed boiling interface eruption models, with greater dynamic pressures and the narrowest predicted conduits presenting different challenges for direct robotic access to the ocean. Due to the lack of a static boiling interface or wall condensation, bulk composition is unlikely to change appreciably during ascent from ocean-conduit interface to jet, potentially simplifying the interpretation of samples collected in space or on Enceladus’ surface. However, it should be noted that this does not preclude other locations and modes of fractionation, sequestration and transport from ocean to plume.