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Does Enceladus Have an Active Core with Hydrothermal Circulation?

Presentation #509.08 in the session Icy Moons Interior and Ice Shell (Oral Presentation)

Published onOct 23, 2023
Does Enceladus Have an Active Core with Hydrothermal Circulation?

A geophysical orbiter at Enceladus could address the ocean’s present-day habitability, and whether organic and volatile materials in the plume can be explained by ongoing hydrothermal activity. Post-Cassini, there remains a debate over whether the extreme heat observed at the Tiger Stripes is generated in the ice, which might require a non-hydrothermal explanation for the silica nano-grains found in Saturn’s E-ring. A key part of the strategy to constrain the extent of hydrothermal activity would be to refine the global heat budget and determine where the heat is localized. An onboard thermal imager could constrain the global thermal emission, and its spatial distribution. InSAR and high-resolution imaging could constrain the deformation, rheology, and topography of the ice shell, revealing the total heat generated in the ice and along the Tiger Stripes. The detailed gravity field would reveal the complex tidal response of Enceladus from shape and potential to degree 10. Such an investigation would constrain the density of the ocean to within 1%, equivalent to about 10 ppt in salinity, which would help distinguish between high and low salinity models in the published literature. The new bounds on ocean and ice thickness/shape would constrain the remaining tidal heating below the ice, including the rheological state of the rocky interior and associated topographic variations from hydrothermal processing. The combined information would enable modeling to assess any additional heating in the ocean.

The investigation of heating would also address how the moon’s habitability might have changed through time. Detecting substantial core heating would point to a longer-lived ocean at Enceladus, and thus to a great capacity for life to develop and evolve. This baseline present day state is needed to understand whether the Enceladus interior has been undergoing water rock-interaction only recently, if at all, or if hydrothermalism and water-rock interaction have continued for 4 Gyr or more.

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