Enceladian Song of Ice and Vapour: Experimentally Modelling the South Polar Terrain as a Giant Heat Exchanger

Cassini’s observations of Enceladus revealed active water-vapour and ice-grain plumes emerging from the Tiger Stripes, but the physical link between plume observables and the subsurface fracture system remains uncertain. Here, we present a new way to approach this problem derived from our laboratory experiments of the South Polar Terrain, which is seen to behave as a giant single-stream heat exchanger.

We performed a new experimental campaign using the CLAM setup, in which water vapour is driven through cooled 3D-printed crevasse analogues under low-pressure conditions. The experiments show a strong coupling between wall temperature, channel diameter, phase change, and plume evolution. We find that lower wall temperature increases the velocity of the vapour flow, while reducing our crevasse analogue diameter lowers its temperature.

We interpret these results with a "heat exchanger" model that follows the energy balance of vapour rising through icy crevasses, including convective cooling against cold walls, kinetic cooling from flow acceleration, and latent heat release from condensation and ice accretion. Using dimensionless heat-transfer parameters, we connect measurable plume properties such as mass-flow rate, vent temperature, velocity, and solid fraction to possible crevasse geometries and ice-shell thicknesses.

When applied to Enceladus, we show that our model can be used as a tool to identify which plume-origin scenarios are physically plausible. They suggest that the velocity and temperature of the jets can be directly linked to the crevasse depth and cross-section area. Our approach can therefore provide a direct link between plume's characteristics and crevasses morphology and can be expanded toward more realistic fracture geometries, evolving ice accretion, briny sources, and both jet-like and curtain-like eruptions, which will be instrumental to prepare plume models for future ocean-world missions.