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Saturn's Moon Enceladus Has Global Subsurface Ocean

Posted by Soulskill on from the pack-a-swimsuit dept.

An anonymous reader writes: NASA's Cassini probe has made another fascinating discovery: Enceladus, one of Saturn's moons, has an underground ocean spanning its entire globe. Researchers were trying to explain why the moon wobbles as it orbits Saturn, and they eventually came to the conclusion that its outer shell must be completely detached from its core. "The mechanisms that might have prevented Enceladus' ocean from freezing remain a mystery. Thomas and his colleagues suggest a few ideas for future study that might help resolve the question, including the surprising possibility that tidal forces due to Saturn's gravity could be generating much more heat within Enceladus than previously thought."

35 of 72 comments (clear)

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    2. Re:Slashdot ads by TWX · · Score: 1

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      --
      Do not look into laser with remaining eye.
    3. Re:Slashdot ads by TWX · · Score: 1

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      --
      Do not look into laser with remaining eye.
    4. Re:Slashdot ads by Tablizer · · Score: 1

      You are clicking the check-box wrong. -Steve J.

      --
      Table-ized A.I.
    5. Re:Slashdot ads by Opportunist · · Score: 1

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      --
      We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
    6. Re:Slashdot ads by Opportunist · · Score: 1

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      --
      We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
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      --
      Lost at C:>. Found at C.
  2. Perpetual energy machine by RenHoek · · Score: 2

    I'm sure I'm wrong considering the laws of thermodynamics and all, but if a moon is heated by gravitational shifting, does this go on for ever? I.e. is this a perpetuum mobile?

    1. Re:Perpetual energy machine by WalksOnDirt · · Score: 2

      ... if a moon is heated by gravitational shifting, does this go on for ever?

      No, the orbit eventually decays.

      --
      a,e,i,o,u and sometimes w and y (at be if of up cwm by)
    2. Re:Perpetual energy machine by Tablizer · · Score: 5, Insightful

      It's NOT obvious because it's very gradual and there are multiple potential places the energy can be transferred from, such as Saturn's spin rate, the moon's orbital momentum, the moon's (past) rotation, the rings, and/or nearby moons. Resonance based energy transfer can be quite unintuitive.

      --
      Table-ized A.I.
    3. Re:Perpetual energy machine by Brett+Buck · · Score: 5, Informative

      No. Energy is being taken out every time. At some point it will become tidally locked, just like the Moon (of earth) and then the heating will stop.

         

    4. Re:Perpetual energy machine by Anonymous Coward · · Score: 1

      Tidal heating still goes on from non-circular orbits, uneven mass distribution (e.g. the wobbling), and slightly from other moons if they get close enough.

    5. Re:Perpetual energy machine by Zorpheus · · Score: 1

      What happened with our moon is that its rotation got tidally locked and that its orbit became larger. When all orbits just get large no motion will stop though.

    6. Re:Perpetual energy machine by Applehu+Akbar · · Score: 1

      I betcha that the rocky core of Enceladus is radioactive, as the Earth is, and that this is the heat source we are looking for.

  3. Unknown energy by Spinalcold · · Score: 2, Interesting

    and yet again a moon/planet is getting power by some unknown mechanism, Pluto was the other recent find. This is fascinating news! I wonder if it could be a combination of many, many small factors. Physicists (and I am studying it as an undergrad) are very prone to hacking off small factors when calculating things, thinking small factors don't contribute to the overall result, and most of the time they don't. But all the tiny factors like neutrino's, radioactive particles, other stars, gamma rays, etc etc, is there any way that the combined contribution could add up to the energy, or even a part of it, that we are failing to find? The rest of that unknown could be...I don't know, one of those energy's we are still trying to figure out, like Dark Energy or the new evidence for the Z', W' force...

    I'm just throwing spit at a wall here cause it's fun. And fascinating.

    1. Re:Unknown energy by Anonymous Coward · · Score: 1

      I guess you're not very far along in your physics studies, because you seem to lack a basic grasp of how sciene works. If for some reason you wish to posit the theory that Enceladus' ocean is kept unfrozen by the cumulative effect of energy from neutrinos and cosmic rays and such (and traditionally one would first eliminate more likely theories before going for the fringe stuff), by all means do so. Do some back-of-the-napkin calculations to figure out how much energy would be required from all those trace sources, and try to work out if your theory is in any way credible. That would be quite a lot of energy, by the way.

      And by the way, we are not "failing to find" the energy heating Enceladus' ocean - that would emply that we have had ample opportunity to look for it, which we have not. We have had minimal opprtunity to study Enceladus. Cassini has taken our knowledge a long way forward, and the chances are that with further study, perhaps from a future probe, we will easily be able to figure out where the energy comes from.

    2. Re:Unknown energy by Anonymous Coward · · Score: 1

      It is not an unknown mechanism. Io is tidally locked but is heated from tidal forces due to orbit eccentricity (that is maintained due to other moons). Enceladus has half the orbital distance of Io and is in a more eccentric orbit, so it shouldn't be a surprise that it is tidally heated. The big thing is knowing what is made of to have some idea what that heating does.

    3. Re:Unknown energy by Rei · · Score: 1

      Haha, that's exactly my attitude too :) It's almost a running joke that you launch a probe to anything in space and find out that it has an unexpectedly large amount of energy input ;) And I agree with your assessment that there's probably no single factor, just a lot of different energy sources that people haven't thought of. Unfortunately, humans tend to go into each situation with the blinders of experience, expecting things to be like that which we've already seen. The reality can be incredibly different, and space seems to have no shortage of interesting things to throw at us.

      Pluto, for example, has a couple of nonconventional sources for driving tectonics. One is its wild temperature swings over the course of its year, shrinking and then expanding its crust. Potentially more powerful is the hundred-something kilograms of nitrogen it loses every second; over geological timeperiods, it amounts to the loss of hundreds to thousands of meters of nitrogen from the whole planet, that's a massive amount of subsidence. Probably the best theory for what's going on right now (caveat: this is still VERY early in the process!) is that Pluto has a relatively thin water ice crust across the whole planet, underlain with a mantle of heavier, viscous-flowing nitrogen ice, which reaches the surface at Sputnik Planum (the "heart") and where impacts have pierced through the water crust. The loss of nitrogen where it's exposed drives its motion (through relaxation), causing a rise in the form of the convection cells at Sputnik and subduction on the opposite side of the planet. Deeper than the nitrogen layer would be a water ice layer (during Pluto's formation, at some point the nitrogen would have been a liquid ocean atop a heavier water ice layer). Now that the nitrogen is solid, it's heavier than the water ice, so the deeper layer is only stable when at great enough depth. As the nitrogen mantle boils off, the outer surface of the deeper water ice layer becomes unstable and chunks break off and are entrained into the nitrogen like xenoliths, slowly floating up along the convection cell borders and reaching the surface as "floating ice mountains". These then, over geological timeperiods, wash to the shore and collect on the chaos terrain.

      Like anything we've ever seen before? Hell no! But I fully expect nature to do this to us again and again.

      Think of the periodic table, of all of the elements that are reasonably common in the universe, and the chemical forms they usually take. There's a lot of them. Now picture the full range of possible temperature and pressure combinations across the universe - it's vast. Now think of the phase diagram for each chemical, of all of the different possibilities. Now factor in time, how the temperature and pressure experienced by a body can change depending on the circumstances.

      Yeah, there's a *lot* of bloody possibilities out there! Metals plating out into giant dendritic spires, superconducting seas, natural nuclear reactors kicking off rainbow-glowing clouds and rivers... it's almost impossible to imagine all of the potential diversity.

      Here's one: picture a close binary world, far from its star - so with a temperature not greatly over the cosmic background. At these temperatures, helium - the second most common element in the universe - could readily pool into oceans, with a thin helium atmosphere. Neat enough on its own. But if the larger party in the binary was eating helium from the atmosphere of the smaller body (or other method of losing the atmosphere), then this would be evaporatively cooling the smaller body. I ran some calculations a while back and found that due to the low rate of radiative heat exchange at such cold temperatures, it's quite possible for the helium on the smaller body in the right conditions to evaporatively cool below helium's lambda point - aka the ocean would become a superfluid - flowing with zero velocity, climbing over obstacles in thin surface layers with ease, creating powerful boiloff fou

      --
      "This administration is so incompetent that they cover their tracks with bigger tracks." - Seth Meyers
    4. Re:Unknown energy by Rei · · Score: 1

      That said, I don't think that, say, gamma rays, neutrinos, etc would ever be a relevant energy source. But things that people don't immediately think of certainly could be. For example, in the above Pluto case: if you have a heavier nitrogen ice layer over a lighter water ice layer, and a chunk of the ice breaks through and floats to the surface... that's an energy input. That's moving the system to a lower energy state. In Enceladus, one energy source that's now believed to be going on is serpentinization of a deeper rock layer, creating an ultrabasic soda ocean and releasing hydrogen gas. And of course, as the hydrogen rises, that too is another release of energy.

      --
      "This administration is so incompetent that they cover their tracks with bigger tracks." - Seth Meyers
    5. Re:Unknown energy by Spinalcold · · Score: 1

      Thanks for your very informative response. That superfluid calculation is extremely fascinating! For some reason I never thought of superfluids in moons and other objects, I have a tendency to think of that as specifically a man made thing--my bad!

      I highly doubt neutrinos would actually be a heating source as well, I was just naming off mechanisms off the top of my head, not being series. As for gamma's, not in any large manner either, I was instead imagining VERY small pockets of heating, melting a small amount of ice. Yeah, not really a moon powering source.

  4. Frozen Fish by Anonymous Coward · · Score: 1

    No. Energy is being taken out every time. At some point it will become tidally locked, just like the Moon (of earth) and then the heating will stop.

     

    Then all the fish freeze.

    1. Re:Frozen Fish by idontgno · · Score: 1

      Unless the Monolith implodes the planet into an artificial star.

      ALL THESE WORLDS ARE YOURSâ"EXCEPT EUROPA. AND ENCELADUS. THAT TOO. ATTEMPT NO LANDINGS THERE

      --
      Welcome to the Panopticon. Used to be a prison, now it's your home.
  5. I wonder if there are dead fish at the south pole? by Aku+Head · · Score: 3, Interesting

    The geysers could spit them out and they would fall back to the surface. We need an orbiter to fly through those plumes and measure what is in them.

  6. Re:Saturn's spinning slows by mister_playboy · · Score: 1

    Every large moon in the Solar System is tidally locked, Enceladus included.

    --
    Do what thou wilt shall be the whole of the Law ::: Love is the law, love under will
  7. Subsurface Ocean by nospam007 · · Score: 1

    Mmmmh, aren't _all_ oceans subsurface if you really consider it?

  8. Re:Life everywhere by peragrin · · Score: 1

    mars lost more than it's atmosphere, it lost it's central core heating too.

    no terraforma of mars until you can figure out how to jump start it's core with nukes.

    --
    i thought once I was found, but it was only a dream.
  9. Re:Saturn's spinning slows by Anonymous Coward · · Score: 1

    Look into how heating on Io works. Io is tidally locked, but in a slightly non-circular orbit which provides plenty of tidal heating (the orientation isn't perfectly locked when the speed varies over the orbit and forces change as the moon moves slightly further and closer to the planet). Io's orbit stays eccentric because of interactions with other moons, so they behave as a system slowly losing energy. Enceladus has a smaller, more eccentric orbit than Io.

  10. Even more bizzare sub surface ocean! by 140Mandak262Jamuna · · Score: 4, Interesting
    That is nothing man, nothing. There is a planet with a huge subsurface ocean of iron! Yes, iron in liquid form, molten iron. It is roiling too. And because iron is magnetic the oceanic currents of this iron ocean creates a powerful magnetic field. The magnetic field powerful enough to deflect the charge particle wind from its parent star several at a distance of several planetary diameters away. The entire planet behaves as thought it has a permanent bar magnet placed along its axis! Further more these iron ocean current weaken over time, change directions and flip the polarity of the planetary magnet.

    This ocean of molten iron exists just 1% of the planetary radius below the surface. Most people don't realize how close they are to this bizarre weird incredible iron ocean.

    --
    sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
    1. Re:Even more bizzare sub surface ocean! by Anonymous Coward · · Score: 1

      This ocean of molten iron exists just 1% of the planetary radius below the surface.

      Umm, more like 45% of the radius down. The mantle is a slowly forming, more plastic like rock, while the liquid iron outer core is much further down.

    2. Re:Even more bizzare sub surface ocean! by 140Mandak262Jamuna · · Score: 1

      Thanks for the correction. Confused magma with the iron core. Still such an ocean of iron is closer than most people think.

      --
      sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
  11. Re:More disgusting... by Applehu+Akbar · · Score: 1

    "Republican corporate welfare. Children are starving to death, but they instead want to funnel money by the truckload to corporations under the excuse of 'science'"

    Meanwhile, the other guys defund science because of their hippie-chick fear of everything 'radioactive' or 'biological', or because the Hawaiian volcano god might be offended. Whatever your politics, if you want those children to be fed, you need to defend science.

  12. All these worlds... by seven+of+five · · Score: 2

    All these worlds are yours, except Euro^H^H^Hnceladus.
    Attempt no landings there.

  13. What are the chances... by Type44Q · · Score: 1

    I wonder what the chances are that, like Earth, it might have a core that's undergoing slow fission...

  14. Pluto Pump [Re:Unknown energy ] by Tablizer · · Score: 1

    The speculation on Pluto's dynamic surface is that as it cycles closer and further from the sun, the substances on its surface change densities relative to each other, creating a kind of pumping action.

    For example, at the furthest point from the sun, substance A may be denser than substance B. But it could reverse near the closest point to the sun if A expands more than B under the increased heat (at that temperature). Thus A is pushed beneath B for part of the orbit, and then B is pushed beneath A for the other part. This push/pull action against uneven terrain creates a natural pump which smushes stuff all around, giving the melted-plastic look we find at Pluto.

    --
    Table-ized A.I.