The interior of Enceladus one year after Cassini
Abstract
While the observation of a large-scale plume emitted by Enceladus occurred early after the insertion of the Cassini spacecraft around Saturn, a coherent view on the interior processes that power and feed this activity started emerging only in the latest year of the mission. Thanks to a flexible payload as well as multiple flybys during the extended mission, analyses of Enceladus data (composition of materials originating from the moon's interior, geophysical measurements and long series of surface images) composed a view where a global salty ocean is present underneath an ice crust of very uneven thickness (20-25 km in average, less than 5 km beneath the south pole, more than 30 km in some equatorial regions). Density of the rock core implies a significant (water-filled) porosity. Furthermore, several independent chemical clues indicate that high-temperature (>363 K) hydrothermal processes probably occur at present, deep in the moon. In this presentation, we show that tidal deformation within a rock core filled with interstitial liquid water can produce a sufficient amount of heat to enable the persistence of a global ocean, for at least tens of Myr. Thermal convection of interstitial water within the tidally heated core leads to strongly focused hot upwellings, especially beneath the poles. Modeled temperatures agree with the range inferred from compositional measurements by Cassini that indicate water-rock interaction and might be detected in the gravity data. Powerful hotspots (several GW) are thus predicted at the seafloor. While ocean dynamics partly filter this strongly heterogeneous heat flux at the seafloor, our models demonstrate that heat supply to the base of the ice shell is expected to be largest in regions coinciding with the lowest ice thickness - the transport time of organic products by ocean thermal vents would match the constraints derived from Cassini measurements (typically a few months).
- Publication:
-
European Planetary Science Congress
- Pub Date:
- September 2018
- Bibcode:
- 2018EPSC...12..662C