Saturn's moon Dione harbors a subsurface ocean

Saturn’s moon Dione harbors a subsurface ocean
Dione with Saturn and its rings in the background. This image was taken by the Cassini spacecraft on 17 August 2015. Credit: NASA/JPL-Caltech/Space Science Institute

A subsurface ocean lies deep within Saturn's moon Dione, according to new data from the Cassini mission to Saturn. Two other moons of Saturn, Titan and Enceladus, are already known to hide global oceans beneath their icy crusts, but a new study suggests an ocean exists on Dione as well.

In this study, researchers of the Royal Observatory of Belgium show gravity data from recent Cassini flybys can be explained if Dione's floats on an located 100 kilometers below the surface. The ocean is several tens of kilometers deep and surrounds a large rocky core. Seen from within, Dione is very similar to its smaller but more famous neighbor Enceladus, whose south polar region spurts huge jets of water vapor into space. Dione seems to be quiet now, but its broken surface bears witness of a more tumultuous past. The study is published online this week in Geophysical Research Letters.

The authors modeled the icy shells of Enceladus and Dione as global icebergs immersed in water, where each surface ice peak is supported by a large underwater keel. Scientists have used this approach in the past but previous results have predicted a very thick crust for Enceladus and no ocean at all for Dione. "As an additional principle, we assumed that the icy crust can stand only the minimum amount of tension or compression necessary to maintain surface landforms", said Mikael Beuthe, lead author of the new study. "More stress would break the crust down to pieces."

Saturn’s moon Dione harbors a subsurface ocean
Dione with Enceladus in the background. This image was taken by the Cassini spacecraft on 8 September 2015. Credit: NASA/JPL-Caltech/Space Science Institute

According to the new study, Enceladus' ocean is much closer to the surface, especially near the south pole where geysers erupt through a few kilometers of crust. These findings agree well with the discovery last year by Cassini that Enceladus undergoes large back-and-forth oscillations, called libration, during its orbit. Enceladus' libration would be much smaller if its crust was thicker. As for Dione, the new study finds it harbors a deep ocean between its crust and core. "Like Enceladus, Dione librates but below the detection level of Cassini,'' said Antony Trinh, co-author of the new study. "A future orbiter hopping around Saturn's moons could test this prediction."

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." The ocean of Dione seems to be too deep for easy access, but Enceladus as well as Jupiter's moon Europa are generous enough to eject water samples in space, ready to be picked up by a passing spacecraft.

The club of "ocean worlds"—icy moons or planets with subsurface oceans in common parlance—gains new members with each new mission to the outer solar system. Three ocean worlds orbit Jupiter, three orbit Saturn and Pluto could also belong to the club, according to recent observations of the New Horizons spacecraft. The approach to modeling planetary bodies used in this study is a promising tool to study these worlds if we can measure their shape and gravity field, according to Mikael Beuthe. "Future missions will visit Jupiter's moons, but we should also explore Uranus' and Neptune's systems", he said.

Saturn’s moon Dione harbors a subsurface ocean
Representation of the interior of Enceladus with icy crust, ocean and solid core. ROB researchers think that Dione may also have a subsurface ocean. Credit: NASA/JPL-Caltech/Space Science Institute

Explore further

Image: Enceladus and its paper-thin crust

More information: Mikael Beuthe et al. Enceladus' and Dione's floating ice shells supported by minimum stress isostasy, Geophysical Research Letters (2016). DOI: 10.1002/2016GL070650
Journal information: Geophysical Research Letters

Provided by Royal Observatory of Belgium
Citation: Saturn's moon Dione harbors a subsurface ocean (2016, October 5) retrieved 22 October 2019 from https://phys.org/news/2016-10-saturn-moon-dione-harbors-subsurface.html
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Oct 05, 2016
"Future missions will visit Jupiter's moons, but we should also explore Uranus' and Neptune's systems", he said."

I, for one, could not agree more.

Oct 05, 2016
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Oct 05, 2016
Proposing a subsurface ocean seems to be the new flavor of faddish groupthink these days. And why not? It fits all of the stereotypical narratives, and we won't know the truth of the matter for many decades to come.

Oct 05, 2016
Proposing a subsurface ocean seems to be the new flavor of faddish groupthink these days. And why not? It fits all of the stereotypical narratives, and we won't know the truth of the matter for many decades to come.


Nothing to do with groupthink - that's what you lot do. Hanging on the every word of unqualified mythologists.
By contrast, these people actually understand science, and apply it in ways that don't break the laws of physics. And, of course, by following the evidence. I'm not saying this particular proposal will hold up - we'll see. However, it is pretty much a given at Europa and Enceladus. No need to run around inventing all sorts of electric woo to try to explain the things we see at Io, Europa, Enceladus etc, etc.
And I've yet to see alternative hypotheses that make any scientific sense from the EU nutjobs. Despite continually asking for them. As I've said before; no one to do the science, and no desire to tie themselves down to actual predictions.

Oct 05, 2016
As the gravitational models fail to reflect reality, unseen "dark" oceans are invented. The dark ages of astronomy continue...

Oct 05, 2016
As the gravitational models fail to reflect reality, unseen "dark" oceans are invented. The dark ages of astronomy continue...


As opposed to the EU explanation of everything, which has so far failed to explain a single thing. Mind you, you can't explain anything if you don't publish it. And you'll never explain anything as long as scientifically challenged mythologists are doing the non-science for you. Just repeat after them: "It's all electric, it's all electric." Do this until your brain turns to plasma and escapes through your ears.

Oct 05, 2016
I might be wrong, so maybe somebody can set me straight. But it sure seems that the scientists are getting a lot of mileage out of this Cassini mission. It seems like some really cool new stuffs shows every couple of months or so, for years now. Is it remarkable fruitful or is it just me thinking it is?

Oct 05, 2016
I might be wrong, so maybe somebody can set me straight. But it sure seems that the scientists are getting a lot of mileage out of this Cassini mission. It seems like some really cool new stuffs shows every couple of months or so, for years now. Is it remarkable fruitful or is it just me thinking it is?


Yep, and it's been out at Saturn for 12 years! Less than a year to go though. The discoveries at Titan and Enceladus are the highlights for me.
Not all that surprising that it's been fruitful, as we didn't know an awful lot about the system until we got there. Mind you, there were some pretty good predictions about Titan, regarding the lakes and its atmosphere.

Oct 05, 2016
Uncle Ira, you are not wrong. The Cassini mission has been an incredible success by almost anyone's definition.

I realize it would take a large launch vehicle, and thus cost more money, but I would LOVE to see a Cassini-like mission for Uranus and another for Neptune. We know so little about these worlds and their moons compared to Saturn, I can only imagine the science returns would be phenomenal. If I could add one thing to Cassini going forward, it would be to carry more then one Huygens-type probe. How cool would it be to carry, for example, six probes whose targets could be selected after arrival? You discover something amazing, specify the communications parameters and launch a Huygens-type probe to find out more. After I came up with this fine idea, I realized that Star Trek had beaten me to it by a half century or so. Voyager even had different classes of probes for different situations.

Oct 07, 2016
You calling somebody dumb is like Hawking calling someone using crutches a cripple
@bschitthead
lets see, so, what you are saying is:
"Cripple" = a lame or partly disabled person or animal; one that is disabled or deficient in a specified manner
http://www.merria.../cripple

Crutch = a mobility aid that transfers weight from the legs to the upper body. It is often used for people who cannot use their legs to support their weight, for reasons ranging from short-term injuries to lifelong disabilities
https://en.wikipe...i/Crutch

a person on crutches is, by definition, one that is disabled or deficient in a specified manner, thus can be called crippled

so it's an accurate label that defined something clearly, concisely and without ambiguity

therefore what you've said above is: Phys1 has made a clear, concise accurate label that is not ambiguous and clearly applies to the intended target who practices pseudoscience

clear as day to me!

Oct 08, 2016
Taking sloppy meaning at face value, not.going.to.happen.

How about Hawking goading a cripple for being a cripple? The mentally ill have cognition. Isn't veridical, doesn't correspond to useful level of social functioning, is full of delusions, but it's cognition.

BS is obviously deeply disturbed and conflicted. Yes, incapable of picking the winner in a one horse race, but it's still "thinking". I guess it's just sloppy shorthand for "learn to think in a logical manner that reaches veridical conclusions". Yeah. Not going to happen. So...what's your issue that you think he might? Or are you just poking the caged animal to see it grunt? That mind really has to be a prison, you know. Isn't that punishment enough?

But if you must twist the knife, ignore him. I will bet you anything you want to wager that he goes to troll someplace else. Wasn't your goal to reduce the misinformation? Well? Starting to think you're sadistic.

Oct 08, 2016
Point well taken, Ira!

Oct 08, 2016
Just to be clear about the penultimate post, CD and HA are quite willful in their ignorance, I can see your point of calling them out, and agree they should be publicly hung by the balls and flogged at dawn.

And not for being non-conformist to anticipate the usual whinge, but for being VERY conformist within their little club and willfully corrupting the public corpus scientiae. They are intellectual vandals. I have no problem with public whippings for vandals, as agrees Galileo, who they love to fantasize would see them as a kindred spirit. He wouldn't. He detested vandalism and pseudoscience. Go take a plasma enema, is my guess at what he'd say to the EU acolytes.

Oct 13, 2016
Water, Water, Everywhere! BUT Nary a single sign of life about :-( !
So frustrating for big bang materialists that the expected spontaneous rising of life from the ground/pond scum via random chemical and physical processes all by itself does not seem to be observable anywhere.

Earth overflows with life but the rest of the solar system[and by silly extrapolation, the galaxy] is as barren as can be. How totally frustrating that must be.

Oct 13, 2016
Water, Water, Everywhere! BUT Nary a single sign of life about :-( !
So frustrating for big bang materialists that the expected spontaneous rising of life from the ground/pond scum via random chemical and physical processes all by itself does not seem to be observable anywhere.

Earth overflows with life but the rest of the solar system[and by silly extrapolation, the galaxy] is as barren as can be. How totally frustrating that must be.


Oh dear, yet more creationists being allowed out on day release.

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