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takyon writes:

Data collected by the Cassini spacecraft during a 2011 flyby of Saturn's moon Enceladus suggests that an internal liquid ocean may be closer to the surface than previously thought. Ice near the south pole of Enceladus, where plumes of water vapor have been detected, was found to be up to 20 K warmer than expected:

"These observations provide a unique insight into what is going on beneath the surface. They show that the first few metres below the surface of the area that we investigated, although at a glacial 50-60 K, are much warmer than we had expected: likely up to 20 K warmer in some places," [Alice Le Gall] adds. "This cannot be explained only as a result of the Sun's illumination and, to a lesser extent, Saturn's heating so there must be an additional source of heat."

The detected heat appears to be lying under a much colder layer of frost, as no similar anomaly was found in infrared observations of the same region – these probe the temperature of the surface but are not sensitive to what is underneath. [...] Even if the observations cover only a small patch of the southern polar terrains, it is likely that the entire region is warm underneath and Enceladus' ocean could be a mere 2 km under the icy surface. The finding agrees well with the results of a recent study, led by Ondrej Cadek [DOI: 10.1002/2016GL068634] and published in 2016, which estimated the thickness of the crust on Enceladus. With an average depth of 18–22 km, the ice shell appears to reduce to less than 5 km at the south pole.

Thermally anomalous features in the subsurface of Enceladus's south polar terrain (open, DOI: 10.1038/s41550-017-0063) (DX)

Original Submission