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Huge Ocean Confirmed Underneath Solar System's Largest Moon

Posted by samzenpus on from the under-the-sea dept.

sciencehabit writes The solar system's largest moon, Ganymede, in orbit around Jupiter, harbors an underground ocean containing more water than all the oceans on Earth, according to new observations by the Hubble Space Telescope. Ganymede now joins Jupiter's Europa and two moons of Saturn, Titan and Enceladus, as moons with subsurface oceans—and good places to look for life. Ceres, the largest object in the asteroid belt, may also have a subsurface ocean. The Hubble study suggests that the ocean can be no deeper than 330 kilometers below the surface.

21 of 117 comments (clear)

  1. Life by hooiberg · · Score: 4, Insightful

    How did life start on earth? Water, with trace elements, under pressure, with a magnetic field to protect against the worst of the solar radiation.
    And what have we here? Water, with trace elements, under pressure, with a magnetic field to protect against the worst of the solar radiation.

    1. Re:Life by abies · · Score: 5, Insightful

      Except it is not a solar radiation you need protecting against (Sun is very far), but Jupiter radiation. Unfortunately despite magnetosphere, Ganymede gets around 8 rem of radiation per day (http://en.wikipedia.org/wiki/Colonization_of_the_outer_Solar_System#Ganymede), which is bit too much for life as we know it. Fortunately, it is not going to be an issue 300km below the surface - but at that depth, you don't need magnetosphere anyway.

      I think that biggest problem for life there would be availability of energy. 300km of crust is probably shielding external energy too well, so internal heat would be probably only viable source of that. Might be not enough to sustain life (or even more, to produce it randomly)

    2. Re:Life by hooiberg · · Score: 5, Insightful

      On the other hand, heat built up by tidal forcing of Jupiter will also not be able to escape easily, through such a thick crust. Remember that we have many deep-ocean creatures on earth, where there is no light, and the water is so cold that it is barely liquid. (zero to three degrees Celsius).

      Actually, it has been estimated there are so many deep-ocean species, that bioluminescence might be the most common method of communication on earth.

    3. Re:Life by itzly · · Score: 2

      And all we need to do to take a sample is a launch a probe with a 300 km long drill bit. Easy peasy.

    4. Re:Life by Rei · · Score: 3, Insightful

      And you know that those are the requirements for LAWKI how? Ignoring the fact that there could be entirely different requirements for other entirely types of life elsewhere, you have no clue how the earliest forms of life on Earth began.

      If Titan's natural abiotic organic chemistry laboratory offers any clues, for example, the start of life could have come because of ionizing solar radiation, and in the absence of water, and only later developed into our present form. On Titan solar ionizing radiation builds complex organic compounds, some having been measured at over 10000 daltons, of carbon, hydrogen, and nitrogen, which raises the potential of catalytic cycles.

      There have been countless proposed mechanisms for the earliest forms of autocatalysis that could have led up to the theoretical RNA world that could have led to our present world. And orders of magnitude more not yet conceived that could potentially have done it. It's silly to pretend that we have any clue exactly what the requirements are for the earliest "ancestor" to life on Earth. We don't know whether it developed in an ocean, on land, in a lake, in the soil, in rocks deep underground, in the troposphere, in the exosphere, in space... we really don't know. We don't know where it developed and we don't know what it was, and we don't know if it was the only way life could form (but I'd wager "no").

      --
      "Are you hungry? I haven't eaten since later this afternoon." -- Primer
    5. Re:Life by Rei · · Score: 5, Interesting

      I should add that we need to think better about how we want to think about early life, what's likely to lead to an evolutionary path.

      On one hand, we have self replicators like the misfolded prions of BSE. Injected into a healthy human, a single misfolded prion can begin taking others in the person's body and misfolding them, leading to a catalytic cycle that spreads like a virus and eventually kills the person. One could conveive that if there were a wide range of "roughly prion-like" chemicals in some primordial soup, that their variations in folding could lead to evolutionary adaptation with time.

      Is this reproduction some realistic sort of form of protolife? By far most people would say no. Prions are large, complex proteins; the concept of an early world containing large amounts of this exceedingly specific complex protein, or even proteins not exactly the same but still similar enough for reproduction, is exceedingly unlikely.

      On the other hand, let's look at something like tin pest. Objects made of pure tin are stable at warmer temperatures, but at low temperatures they can develop something called "tin pest" where tiny spots break out, and then over the course of months expand and eat up the object, breaking it down into dust, like bacterial colonies spreading across a petri dish. This is a low-temperature stable allotrope of tin which catalyzes its own formation to reproduce itself.

      Is this reproduction some realistic soft of form of protolife? By far, most people would say no. Contrary to prions, it's input is quite simple: plain, ordinary tin. It's easy to picture where this specific case or other natural cases like it could occur in some early world. But its problem is different: it's too specific. Tin pest seems unlikely to, say, mutate and start catalyzing the production of phospholipids or similar. It's just one self-catalytic reaction, with no real possibility for alterations.

      The earliest forms of protolife surely lie somewhere on the spectrum in-between these two endpoints - not with such glaringly simple inputs as tin pest, such that your reaction is too simple to have any chance of it mutating without outright dying off, but not with inputs so complex as prions that you're unlikely to ever find significant quantities in nature. Surely the earliest forms were some sort of middle ground.

      But what they were, specifically? This is totally and utterly unknown at this time.

      --
      "Are you hungry? I haven't eaten since later this afternoon." -- Primer
    6. Re:Life by TapeCutter · · Score: 5, Interesting

      The four Galilean moons are interesting from an evolutionary POV.
      Io - Molten sulphur on the surface, purple volcanoes all over it.
      Europa - Deep water ocean, thin crust, very active plate tectonics.
      Ganymede - Europa with a deep dish crust and cooler core.
      Callisto - A rock.

      So it would seem that gas giants may have their own "goldilocks zone" when they are orbiting in the colder regions of their host system. So the "average" solar system may have 3-4 "habitable zones" rather than just one.

      --
      And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
    7. Re:Life by Anonymous Coward · · Score: 4, Insightful

      On the other hand, heat built up by tidal forcing of Jupiter will also not be able to escape easily, through such a thick crust.

      Heat "build-up" is not enough, you need a heat gradient with some sort of heat flow. Life and chemistry doesn't bypass thermodynamics. If the water and ground below it is very even, with the gradient in solid material above, there might not be enough of an energy source to allow life to form.

    8. Re:Life by s_p_oneil · · Score: 2

      Or if the surface is ice, with enough energy to melt through 300km of it. It still might need a 300km long antenna to tell us if it finds anything. I doubt a signal would go through 300km of solid ice very well.

    9. Re:Life by dissy · · Score: 2

      But let us reword your position for a moment to point out the folly (currently at least) in its usefulness.

      Here in my home country, if I desired a hamburger I happen to know from experience that most restaurants will have such a thing to sell to me. Ignoring jokes about McDonalds not having real food for just a moment, I know they are the most common place around to find a hamburger at.

      Then you come along and (correctly, but uselessly) point out that the laws of physics do not rule out the possibility of finding a hamburger sitting around in some random persons back yard, and so such places should all be equally searched as well.

      Yet if you or I were to travel to a country we have never been to before and happened to desire a hamburger, we would search out a restaurant knowing the chance of finding a hamburger there, even without ever having visited a restaurant in that country before.

      No one is actually arguing that it wouldn't be possible to find a hamburger in a random persons backyard (although many would argue if it would be a good idea to eat it :P ) but from experience we know the odds of finding one in such a place are much much lower than compared to a restaurant.

      Likewise, we know life on earth is more likely to be found in water than not.
      That doesn't mean there is NO life outside of the water at all, just that the odds of finding it in water are higher than finding it elsewhere.

      Again, no one is actually arguing that water is required for life in general, only that our sample of one shows a much higher chance of finding it, and our sample size of one is all we have to formulate characteristics to actually look for and detect.

      So looking for life in water, that is similar to life on earth, is what we have the best description of (as crappy as it may be) and so the best chance of actually detecting, and our one sample shows it as the highest likelihood of occurring in water.

      This is why we look for water and use the characteristics of life we have to match on - because it gives the best chance of success.

      As our samples of majorly differing life forms increases and our characteristics to match on increase, we will have better odds of success looking elsewhere.

      But with our current knowledge and technical level, it makes no sense to search for hamburgers in random back yards when we can search in restaurants first.

      You always aim for the low hanging fruit first, then move on to the harder to reach fruit after.
      You have to learn to walk before you can run.
      Insert additional cheesy proverbs here (especially if they make good hamburger toppings! sorry, I think I'm hungry)

      Just because searching for life as we know it in water is the first step does not exclude all the other harder to detect steps, it only delays them until later, hopefully to a time we are better equipped to do so both with technology and our knowledge.

      It's also worth pointing out that no one is actually forcing you to look in the most common places for the things we know how to detect - you are free to look anywhere you like for things you can't describe, if you so wish.
      It's just that your odds of success are so drastically lower, even compared to the already seemingly low chances in finding life in water on another world, that few people would be willing to throw money at you for the task.

      And that, put simply, is why we look for water on other worlds in our search for life.

    10. Re:Life by MachineShedFred · · Score: 2

      it could leave a repeater at the top of the shaft before it starts boring in. It sends a low power signal to that, which then boosts it with a high-gain directional which stays pointed at Earth, or even a satellite with another repeater.

      Yes, that's all very heavy, but so is 300km of cable

      --
      Slashdot still doesnâ(TM)t support Unicode after it was added to the HTML standard in 1997.
    11. Re:Life by MightyMartian · · Score: 2, Informative

      Keep in mind that there is virtually no evidence for panspermia.

      --
      The world's burning. Moped Jesus spotted on I50. Details at 11.
    12. Re:Life by mrchaotica · · Score: 2

      Some of them do. The ones that don't, however, rely (as far as we know) on 'marine snow', which would not exist on Ganymede.

      --

      "[Regarding the 'cloud,'] ownership was what made America different than Russia." -- Woz

    13. Re:Life by skastrik · · Score: 2

      The four Galilean moons are interesting from an evolutionary POV. Io - Molten sulphur on the surface, purple volcanoes all over it. Europa - Deep water ocean, thin crust, very active plate tectonics. Ganymede - Europa with a deep dish crust and cooler core. Callisto - A rock.

      Yes, I imagine the birds will have quite different types of beaks.

  2. Finally! by Pikoro · · Score: 5, Funny

    Finally a reason to kick-start manned space exploration! Think of what can be learned! If there is life on these moons, then that means that it will also die. Dead plants means ocean floor sediment. That means there could be oil there! We now have a reason!

    --
    "Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
  3. Re:That can't be right... by Anonymous Coward · · Score: 2, Insightful

    because the Greens tell us that we'll soon have used up all the water on the Earth,

    When you slap labels on your "enemies" and then ascribe to them absurd positions you're doing yourself a disservice. You stop thinking rationally and dismiss any notion that doesn't already fit with your ideas.

  4. Re:That can't be right... by Thanshin · · Score: 4, Funny

    I'm pretty sure that's going to be the most stupid thing I read all day. ...

    Ok. I HOPE, that's the stupidest, but I have a budget meeting in less than an hour, so I'm not really that confident.

  5. Re:So an ocean so deep that... by Rei · · Score: 4, Interesting

    Realistically, it's hard to picture any method that would work other than a nuclear reactor melting itself down through the surface. But then you've got the question of how to handle communications back to the top. That's a *lot* of ice to transmit through.

    A 330km cable frozen into the ice that reforms above would be very heavy (tens of thousands of tonnes even if very lightweight), complex to feed, and probably have an unacceptable risk of breakage from shifting / settling ice.

    I guess if you considered extremely low bandwidth acceptable you could use a neutrino pulse based transmission method straight from the probe.

    Perhaps instead of 330km of cable you could drop behind hundreds of RTG-powered SLF radio repeaters (or thousands of ULF repeaters, or tens of thousands of VLF repeaters...). That'd still be of course incredibly heavy (not just for the power and radio equipment, but for the very sizeable antennae), but that'd likely be more workable than a single 330km cable.

    I guess the last option that comes to mind would be to use exceedingly low frequency RF to try to go straight through the ice from the probe itself, less than 1Hz. But surely we're talking an antenna spread out over hundreds of square kilometers to be able to do that.

    --
    "Are you hungry? I haven't eaten since later this afternoon." -- Primer
  6. Re:So an ocean so deep that... by Rei · · Score: 2

    Hmm, it just occurred to me, yet one more possibility, and probably the most realistic: Fully autonomous probe. No through-the-ice communication. Contains ballast tanks. Heavier than ice when the ballast tanks are full, lighter than ice when they're empty. Mission: probe melts its way down, explores, flushes its ballast tanks with compressed air so that it's buoyant, then melts its way back to the surface. *Then* it can transmit everything that it discovered.

    --
    "Are you hungry? I haven't eaten since later this afternoon." -- Primer
  7. Re:So an ocean so deep that... by Muad'Dave · · Score: 2

    ... SLF radio repeaters ...

    Why try to brute force RF down at the DC level? Why not head to the other end of the spectrum and use lasers? If that water is relatively pure and there are few bubbles in the ice, I think lasers would win the size/weight to comm distance race.

    BTW I love the idea of a modulated neutrino beam, except how much mass would it take to even modulate it enough to be detected?

    --
    Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
  8. Kola Superdeep Borehole by DarthVain · · Score: 2

    Considering the deepest we've been able to bore a hole on earth with all the resources available (like air, gravity, equipment, people, etc...) was just over 12.2km deep they have a way to go...

    http://en.wikipedia.org/wiki/K...

    I was trying to come up with an analogy of something impossibly far away, more so than boring a 330km hole, on a frozen moon, on another planet, and failed.