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 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.  

Martian atmospheric dust is a major driver of weather, with feedbacks between atmospheric dust distribution, circulation changes from radiative heating and cooling driven by this dust, and winds that mobilize surface dust and distribute it in the atmosphere. Wind-driven mobilization of surface dust is a poorly understood process due to significant uncertainty about minimum wind stress, and whether saltation of sand particles is required. This study utilizes video of six Ingenuity helicopter flights to measure dust lifting during helicopter ascents, traverses, and descents. Dust mobilization persisted on take-off until the helicopter exceeded 3 m altitude, with dust advecting at 4-6 m/s. During landing, dust mobilization initiated at 2.3-3.6 m altitude. Extensive dust mobilization occurred during traverses at 5.1-5.7 m altitude. Dust mobilization threshold friction velocity of rotor-induced winds during landing are modelled at 0.4-0.6 m/s (factor of two uncertainty in this estimate), with higher winds required when the helicopter was over undisturbed terrain. Modeling dust mobilization from >5 m cruising altitude indicates mobilization by 0.3 m/s winds, suggesting non-saltation mechanisms like mobilization and destruction of dust aggregates. No dependence on background winds was seen for the initiation of dust lifting, but one case of takeoff in 7 m/s winds created a track of darkened terrain downwind of the helicopter, which may have been a saltation cluster. When the helicopter was cruising at 5-6 m altitude, recirculation was seen in the dust clouds.