Heating ocean moon Enceladus for billions of years / Cassini-Huygens / Space Science / Our Activities / ESA
http://www.esa.int/...ace_Science/Cassini-Huygens/Heating_ocean_moon_Enceladus_for_billions_of_years
Enough heat to power hydrothermal activity inside Saturn’s ocean moon Enceladus for billions of years could be generated through tidal
friction if the moon has a highly porous core, a new study finds, working in favour of the moon as a potentially habitable world.
A paper published in Nature Astronomy today presents the first concept that explains the key characteristics of 500 km-diameter Enceladus
as observed by the international Cassini spacecraft over the course of its mission, which concluded in September.
This includes a global salty ocean below an ice shell with an average thickness of 20–25 km, thinning to just 1–5 km over the south polar
region. There, jets of water vapour and icy grains are launched through fissures in the ice. The composition of the ejected material measured
by Cassini included salts and silica dust, suggesting they form through hot water – at least 90ºC – interacting with rock in the porous core.
These observations require a huge source of heat, about 100 times more than is expected to be generated by the natural decay of radioactive
elements in rocks in its core, as well as a means of focusing activity at the south pole.
The tidal effect from Saturn is thought to be at the origin of the eruptions deforming the icy shell by push-pull motions as the moon follows
an elliptical path around the giant planet. But the energy produced by tidal friction in the ice, by itself, would be too weak to counterbalance
the heat loss seen from the ocean – the globe would freeze within 30 million years.
