London: Saturn moons Titan and Enceladus are already known to hide oceans beneath their icy crusts, but a new study suggests a subsurface ocean lies deep within Dione as well.
The findings, based on new data from the Cassini mission to Saturn, suggest that Dione harbours a deep ocean between its crust and core.
In this study, researchers of the Royal Observatory of Belgium showed gravity data from recent Cassini flybys can be explained if Dione's crust floats on an ocean located 100 kilometres below the surface.
The ocean is several tens of kilometres deep and surrounds a large rocky core.
The researchers believe that Dione's ocean has probably survived for the whole history of the moon, and thus offers a long-lived habitable zone for microbial life.
"The contact between the ocean and the rocky core is crucial," said Attilio Rivoldini, co-author of the study.
"Rock-water interactions provide key nutrients and a source of energy, both being essential ingredients for life," Rivoldini noted.
Seen from within, Dione is very similar to its smaller but more famous neighbour Enceladus, whose south polar region spurts huge jets of water vapour into space.
Dione seems to be quiet now, but its broken surface bears witness of a more tumultuous past.
The study findings were published online in the journal Geophysical Research Letters.
The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency.
After almost 20 years in space, the Cassini mission will end on September 15, 2017, NASA recently said.