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Saturn’s Moon Dione Has An Ocean Just Under The Surface
published during a waxing gibbous moon.
10/10/2016

Saturn’s Moon Dione

Portrait of Dione– Saturn’s moon Dione is seen against the backdrop of the planet, with its rings visible in a faint line towards the center. Credit: NASA

It might not be as showy as other moons with subsurface oceans <cough> Enceladus <cough>, but that doesn’t mean that Saturn’s moon Dione can’t make a splash.

In an article published this week in the journal Geophysical Research Letters researchers announced that gravity data collected on a recent Cassini mission indicated that just like its more famous neighbor Enceladus (also a moon of Saturn), Dione has a subsurface ocean.

The findings show that unlike Enceladus’ juicy center which is relatively close to the surface, Dione’s ocean is buried much deeper. Researchers estimate that the ocean is likely about 100 kilometers (62 miles) below the surface.

Saturn’s Moon Dione

A global ocean on Enceladus—Though Enceladus has a much shallower crust, both it and Dione are believed to have subsurface oceans. Credit: NASA/JPL-Caltech

Dione is also less showy than its neighbor Enceladus, which spews forth large, observable plumes from its shallow subsurface oceans into space, originating from cracks in Enceledus’ surface. Images of Dione’s surface also show that it has similar cracks and fractures to the ones seen on Enceledus, suggesting that Dione, might have been more active in the past, much like its neighbor is today.

Other possible explanations of the unusual cracks on Dione’s surface have been raised before, with other papers attributing the odd features to the interaction of the moon with other similarly sized objects that exerted enough of a tidal pull on Dione to crack the surface.

But the researchers think that in this case, measurements of Dione indicate that the moon has a subsurface ocean surrounding an icy core, with a thick layer of icy material encasing the whole thing.
Saturn’s Moon Dione

The curve of Dione with Enceladus photobombing in the background. Credit: NASA/JPL-Caltech/Space Science Institute

Could it harbor life? With a long-lived liquid ocean (researchers think it’s been there for as long as the moon itself has existed), the existence of life on Dione is certainly a possibility that researchers are looking into.

“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.”

Unfortunately, it’s unlikely that researchers will get a close-up look at Dione anytime soon. While previous studies have shown that the moon does contain oxygen, other moons, like Enceladus, or Jupiter’s Europa have far more accessible subsurface oceans, which are either closer to the surface or are actively spewing material into space and would be more promising targets for future missions.

But hang in there Dione. We’ll get to you someday.