‘Wobbly’ Saturn moon suggests global ocean © NASA/JPL-Caltech

‘Wobbly’ Saturn moon suggests global ocean

Scientists studying images from the Cassini space probe discover an ocean below the icy surface of Enceladus covering the whole of the Saturn-moon’s inner core.

Given humans are 60 per cent water, it’s no wonder we feel a little wobbly in the morning every now and again, but this logic has been applied on a massive level to Enceladus, one of the moons of Saturn that is being studied by the Cassini space probe.

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By studying the wobble of the moon as it orbits Saturn, scientists have found that the only explanation for its magnitude is that deep below the frozen outer shell is an ocean, ebbing and flowing around its rocky core.

Previous analysis of Enceladus has suggested that there was at least a lens-shaped sea in the moon’s polar region, but the new research, published in the journal Icarus, has confirmed that this body of liquid covers the whole moon. Images collected by Cassini over the last seven years were studied and carefully mapped so that slight changes in the moon’s orbit could be spotted and these results showed the all-important wobble.

“This was a hard problem that required years of observations, and calculations involving a diverse collection of disciplines,” says Peter Thomas, a Cassini imaging team member at Cornell University “but we are confident we finally got it right.”

The question now facing scientists looking at Enceladus is why the ocean remains liquid and not frozen like the surface above it, though Thomas suggests that Saturn’s gravity could be causing more heat within the moon than previously thought.

As the Cassini mission approaches the end of its tour of Saturn, it will make its deepest-ever dive over the Enceladus, passing only 49km above the surface through one of the moon’s icy plumes. Who knows, maybe it’ll find some signs of life beneath the waves?


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