Saturn moon Dione’s subsurface ocean and growing hopes for ET life

Liquid water is considered a key ingredient to life as it is known on the Earth, and hence, finding out that the ringed Saturn’s offspring Dione — one among a somewhat crowded family, along with Enceladus and Titan — also has an ocean under its thick icy crust increases speculation among enthusiasts about the presence of life across the Solar System.

By analyzing gravity data received from the NASA/ESA unmanned spacecraft Cassini, a group of astronomers of the Royal Observatory of Belgium recently announced that they have detected a liquid ocean, some 32 kilometers deep, far beneath Dione’s icy surface.

The plain-looking Dione, first discovered in 1684, is 1,122 kilometers in diameter and is considered the 15th largest moon in the solar system. Its two siblings, the featureless Titan and the snowball Enceladus, have already been known to have subsurface oceans, with the latter spewing huge jets of water vapor into space thorough its numerous geysers situated on its south pole.

One major difference between Dione’s ocean and those of the other two satellites, according to researchers, is that Dione’s body of water is located far deeper underneath the surface than those of Titan and Enceladus. But the common feature among all three is that the liquid oceans have been there thanks to hydrothermal activities deep inside the moons.

The two smaller moons, Enceladus and Dione, undergo massive back-and-forth oscillations, called libration, creating heat enough to sustain water in its liquid form, during their orbits around the Saturn and due to the giant’s immense gravity.

“Like Enceladus, Dione librates but below the detection level of Cassini. A future orbiter hopping around Saturn’s moons could test this prediction,” said Antony Trinh, the co-author of the new study.

The findings of the research also showed that unlike Titan, the icy shells of Enceladus and Dione are actually colossal icebergs, as large as their entire crusts, immersed in subsurface oceans, where each covering ice peak is supported by a massive underwater keel.

Like the ocean of Enceladus, Dione’s ocean has probably been there for the whole history of the moon, and, therefore, has provided sufficient time to life’s building blocks to be coalesced, paving the way for the possible emergence of at least extraterrestrial microbial life forms.

“The contact between the ocean and the rocky core is crucial. Rock-water interactions provide key nutrients and a source of energy, both being essential ingredients for life,” said Attilio Rivoldini, another author of the study.

With technology at its current levels, researchers may never gain access to Dione’s ocean and its possible life in the near future; but the case is different for Enceladus, whose pouring water gives an opportunity for astronomers to detect life via future missions to Saturn.

The possible life found in Saturn’s moons and also in Jupiter’s Europa, another candidate for harboring life in the Solar System, could be chemically different from the one on the Earth and even from the life that once flourished on the Mars.

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