Enceladus does and does not have a global ocean

By Phil Plait | June 24, 2009 4:40 pm

In 2005, the Cassini space probe orbiting Saturn surprised astronomers when it detected geysers of water spewing from the icy moon Enceladus. This week, in a University of Colorado study of the geysers spewing from Enceladus, astronomers found the water lacked sodium. They observed it using the 10 meter Keck and 4 meter Anglo Australian ground-based telescopes, and detected very little if any sodium in the geysers. If the plumes originated from an undersurface ocean then they are expected to have sodium in them. Instead, given the unsalty nature of the geysers, they surmise there may be pockets of liquid water under the surface which evaporates into space, or it could be from crustal plates of surface ice rubbing against each other.

Plumes from Enceladus

[rewind noises]

In 2005, the Cassini space probe orbiting Saturn surprised astronomers when it detected geysers of water spewing from the icy moon Enceladus. This week, in a JPL and Max Planck Institute for Nuclear Physics study of the outermost ring of Saturn, astronomers found the ring particles contained sodium. They observed it using the Cassini spacecraft, and detected sodium salts in the rings. This ring is known to be replenished by Enceladus’s geysers. If the plumes originated from an undersurface ocean then they are expected to have sodium in them. Given the salty nature of the rings, they surmise there must be a global ocean under the surface which shoots water into space where it replenished that ring.


Uh, say what? Which is it?

Beats me. I’m a violent star-explodey kind of guy, not an exooceanologist. I imagine the authors of the two papers have their opinions on both studies, and I’d love to hear what they have to say. I’d also like to see the spectra obtained by the no-salt-in-the-plumes team first (because a non-detection of something is always on shakier ground than a positive detection of something) before I would come to any conclusions.

But thus is science. Two observations, two good teams, two very different conclusions. That’s what it’s like on the cutting edge… and we’ll need more observations to cut through all this. Happily, as Cassini orbits the Saturn system it will be passing directly through the plumes at least twice more, giving astronomers that many more chances to see what’s happening on that tiny little moon so far away.

Image: NASA/Cassini

CATEGORIZED UNDER: Astronomy, Cool stuff

Comments (59)

  1. Davidlpf

    Could there this be a situation where once annd while you get geysers from the ocean below to supply the salt water and then the surface emitting the non-salty water as well.

  2. IVAN3MAN

    Maybe Enceladus has monosodium glutamate in it? ;-)

    I’ll get my coat and see myself out…

  3. T.E.L.

    Interesting. When Cassini buzzed through a geyser about a year ago, the mass-spec didn’t detect sodium then either.

    Perhaps the supply of sodium is all used up, and more can’t be shipped in until the interplanetary truckers strike is settled.

  4. Why ocean has to be salty at the first place? Can’t it be a fresh water ocean?

  5. Crux Australis

    I like Davidlpf’s hypothesis.

  6. Davidlpf

    But before the trucks arrive the Vogons have to make a hyperspace expressway here.

  7. John Baxter

    Phil, please keep us up to date as this plays out.

    If we accept both observation sets as correct (which seems to me to be a good starting point), then
    1. as T.E.L says, the sodium is used up
    or 2. there are two different types of geysers at different times, and U Colorado happened to see the sodium-free ones each time they looked
    or 3. there is another source of ring sodium (saucer exhaust, kids flushing …, oh, never mind).

  8. Davidlpf

    Or the salts were ions carrying gigantic currents through space and got attracted to the rings by the electric field they obvious have and got deposited.

  9. I believe that the going theory is that the sodium is locked up in the water crystals. You wouldn’t see it from the ground, but you would from a mass-spec, which breaks up the water.

    Also, I think that Cassini did see the sodium quite a while ago, T.E.L, they’re just able to publish it now. But it’s extremely late and I could be wrong. Ask me again tomorrow.

  10. hoorray for the team pro-oceans

    boo for the team pro-dull boring planet

    science should be more like a soccer match cheering crowd, have it’s facts based on what we wish it could be true.

  11. Davidlpf

    I do not wish for either one the facts will stand on their own, my idea was just a guess from the infomation preented I did not know about the other theory.

  12. IVAN3MAN

    @ #9. Davidlpf,

    You haven’t gone turncoat on us and gone over to the “Electric Universe” camp, have you? ;-)

  13. Davidlpf

    No, but spending way too much time on their websites.

  14. Sili

    Considering that Na is absolutely everywhere when you want to do spectroscopy, it’s pretty impressive not to see it. Perhaps they overcorrected the background?

    Still – It’s good to see Science in action. I sorta hoped they had to peer review eachother’s papers.

  15. New astronomical findings are important to keep track of, especially if you are required to complete a science fair project during the upcoming school year. Print out blogs, like this one, clip magazine and newspaper articles and also take notes on documentaries that come up during the summer on astronomical topics.

  16. Maybe this is a silly question, but why does it matter? Couldn’t it be a fresh-water ocean, or lake?

  17. Curious…

    And perhaps might give some idea of how troublesome things can be for those of us who look for more complex chemicals. Even simple sodium can be ellusive!

  18. Tom

    “Uh, say what? Which is it?” LOL Exactly what I thought. Miss print???

  19. Jack Mitcham

    If it’s a “fresh water ocean,” where does the sodium in the JPL study come from? I love astronomy. :)

  20. @ Phil

    ” I’m a violent star-explodey kind of guy”

    Speaking of explodey things, did you happen to see the ISS pictures of Sarychev Peak volcano? Awesome…

    click my name for the link to Daily Mail ONLINE for the pics and storey

    I know it’s off topic but…

  21. Enceladus is a homeopathic planet that is self-succussing. The salt has now been diluted out of the planet and all it needs to become a solar system panacea is a nice sugar coating. . .

    Are the plumes initially liquid water that freezes to ice crystals, or is it a mass of ice that from the surface that is ejected? If it is liquid water, might it be possible for a salty layer, with it’s lower freezing point to liquify first – and thus be ejected first?

  22. ndt

    Is it possible the sodium was already in the ring, and the non-salty water from the plume froze around salty dust particles?

    Also, are there any more missions to Saturn in the planning stages?

  23. @alexandre van de sande
    science should be more like a soccer match cheering crowd, have it’s facts based on what we wish it could be true.

    That is the cool thing about science. It doesn’t matter which side you choose when the results are in you get to change sides. Everybody wins. Unlike religion where you must dogmatically stick to your side in defiance of the evidence.

  24. MadScientist

    Phil: what state of sodium are people attempting to detect? If it’s neutral atomic sodium I would ignore any earth-based attempts at detection; there is so much sodium in the ‘sodium layer’ (~80km altitude) that a peek at the solar spectrum shows two black stripes where the yellow doublet is expected to be. If a source as bright as the sun can’t get photons through to the ground at those frequencies, I doubt you’ll have any luck with much fainter sources.

    On the other hand, if people are looking for sodium while bound to something else (like chlorine) that really makes life miserable. I can dissolve salt in water and add any number of ligands to shift the absorption all over the place. Not to mention of course the very low number of photons available at the earth as compared to instruments near Saturn, and add to that the interference of the earth’s atmosphere (scattering + absorption).

    I would need to know more about the experimental procedures used before saying anything with any confidence, but offhand I’d have more confidence in instruments orbiting saturn than in earth-based measurements.

  25. deyja

    This has nothing to do with the post, but I saw a interview on the weird things blog, and the skepticism part overall drew my attention. You said you wanted proof, well, here it is, if it can be called proof: http://www.therealpresence.org/eucharst/mir/engl_mir.htm and overall, I’d like to draw your attention to Lanciano´s miracle: http://www.therealpresence.org/eucharst/mir/english_pdf/Lanciano1.pdf I would like for it to be read completely before commenting.

  26. Dave

    Hi Phil,

    As you know, sometimes, putative detections are simply statistical fluctuations in the number of photons that disappear with better data.
    Example:
    http://adsabs.harvard.edu/abs/2005ApJ…629..700N
    followed by
    http://adsabs.harvard.edu/abs/2007ApJ…656..129R

    But, I do agree with you: since we know where in the spectrum to look for sodium, the probability of a chance random deficit of photons — at precisely the right wavelength — that mimics sodium absorption is quite low.

  27. IBY

    Whatever the answer is, it is still a really cool moon to study about. I mean really, it has those geysers and weird cracks.

  28. StevoR

    maybe its a Quantum ocean / structure?

    Until we “collapse the wave form” by observing it, could Enceladus be both oceanic and non-oceanic … ? Just like Schrodinger’s half-dead /half alive cat!

    BTW. Why do oceans have to have salt in them? Could it be that they formed out of Na (Sodium)-free material? Could it be just H20 with Na well NA? (Not Appplicable.)

    Plus what about the magnetic field readings – don’t they require salty oceans where there’s no hot metal core? Does Enceladus have a detectable magnetic field and if so does it imply salt /non-salt / ocean / no ocean for this little moon?

    @ 26 IBY : cool? Enceladus is well below freezing! Literally and metaphorically!
    (At least surface temperature ~wise.)

    Incidentally those “weird cracks” are termed “tiger stripes” and /or Sulci (plural form – the singular form =sulcus) as well. These “tiger stripes” are also individually named features tagged after South West Asian / Islamic World cities, eg. Baghdad Sulcus, Cairo Sulcus.

    —–
    Two mentions of Schroedinger’s cat in two posts now .. Hmm .. can I get a Schroedinger hatrick!?)

  29. Voltaire-o'-2009

    @ 24 Shane:

    “That is the cool thing about science. It doesn’t matter which side you choose when the results are in you get to change sides. Everybody wins. Unlike religion where you must dogmatically stick to your side in defiance of the evidence.”

    Also unlike religion & even cooler, the two sides can agree to get along together without thinking the other side are devil-led infidels or evil heretics who must be killed for their “unbelief” in what “our” side says …

    Science has no “Holy Wars” – although even for the religious “Holy War” is surely an oxymoron!?

  30. SpriteSuzi

    @1 Robbie:
    Thanks for posting that link. Those volcano photos taken from the ISS are stunning, and I had not heard anything about the eruption. I’m in New Zealand, and even with reading the NZ Herald, LA Times, and NYTimes (all online…) I still miss out on lots of cool science news! Thx again.

  31. Rob

    @deyja — I am confused — what are you trying to accomplish here again? If you are trying to show how silly some religious fools are capable of being and how religion can override our common sense, you have provided some compelling evidence. If you are trying to provide proof of religion, you have failed miserably — you have provided us with a 400 year old account of a mythical event that “happened” 900 years before it was written down. You get an F- for that post.

    Moving on — I second the question posed by IvanPankov and MichaelL — does an underground “ocean” need to be salty? I could be wrong but this seems like more geocentric foolishness (i.e. many still assume that all life in the Universe will be carbon based and require H20). I mean, to call it an ocean as such it would have to be salty, but why couldn’t there exist a massive, ocean sized fresh water lake? I am sure that the scientists researching this know far better than I, and I would be interested if anyone here could clarify.

  32. Robert Carnegie

    Although most of the scientists with interesting personal theories cling onto their theory when the weight of evidence, um, pulls the other way. (Can whitey get a metaphor?)

  33. Robert Carnegie

    Re life, -we’re- salty. Lick your skin. Suck on a cut. Therefore, life as we know it…

    Another romantic idea that seduces scientists who should be more attentive to the “ugly fact” side of the enterprise is that we are big walking bags full of ocean. Well, if you put it better than that it’s romantic. The idea that our heredity goes all the way back to the sea. We are seventy per cent water, folks. But, as I say, scientifically misleading.

  34. lets blame this on the superposition of different eigenstates – so let’s just collapse the wave function of the system!

  35. Rob

    @Robert Carnegie — “Re life, -we’re- salty. Lick your skin. Suck on a cut. Therefore, life as we know it… “

    Exactly… life as we know it… I think that we need to come to grips with the fact that when we find life out there, it will most certainly not be life as we know it. We ought to be thinking outside the box to try to anticipate what life could look like and where else it could exist. I am sure we will still be almost completely blindsided by how different life will be elsewhere regardless, but the more foresight we have the better. It is silly to assume that life not only needs water to flourish, but salty water at that.

  36. Andrew

    We don’t have the foresight to be able to predict what life that is not like us would look or act like. We don’t even do a very good job of predicting what existing terrestrial life will do. So, while it is fun to speculate about what might be out there, it isn’t very efficient, especially given the number of non-carbon/water/DNA based life forms that we have found on Earth.

    Lack of evidence is not proof but given the preponderance of the evidence we do have, there is no reason to assume that life doesn’t need salt water and carbon to form. Granted, one example throws everything else into question, but we don’t have one yet, even on a planet as diverse and full of life as we have. If a non-carbon based life form could form why wouldn’t it form here, as well?

  37. Stone Age Scientist

    :?: Hmmm, I was just wondering, given the age of the planets, is the theory of ice plates rubbing against each other even feasible? I mean that scenario can’t go on forever without the ice vastly diminishing itself due to friction; particularly when the resulting vapors escape into space. Since water still spews forth from the planet (not yet depleted), what are the chances that these phenomenon are actually recent events?

    Btw, Phil, as per the sentence below,

    If the plumes originated from an undersurface ocean then they are expected to have sodium in them.

    :arrow: What makes scientists expect that Enchilada’s subsurface ocean contains sodium? I thought the geological components of other planets/moons were totally different from that of Earth? Take Titan, for example, which is supposed to have seas/lakes of methane.

  38. llewelly

    5. Ivan Pankov,
    June 24th, 2009 at 5:13 pm:

    Why ocean has to be salty at the first place? Can’t it be a fresh water ocean?

    Water is reactive enough to (slowly) dissolve metals, especially sodium, out of rocks, especially if the water flows occasionally. So fresh bodies of water do not stay fresh unless they are draining into another body of water (which must be at lower altitude.) If there’s a fresh body of water under Enceladus’ icy surface, it must also be connected to a salty body of water underneath the ice. (There is a known network of lakes under the thickest parts of the Antarctic ice sheet, so I don’t think this suggestion is a stretch.) If the two teams measured plumes from different locations, it’s possible one plume is from a fresh body of water, and the other is from a salty body of water.

    My prior paragraph assumes the plumes come from liquid water beneath the ice. Over long time scales, the salt will tend to move to lower altitudes. So any plume with salt in is most likely from deep beneath the ice, and thence from a body of water which is at a local minimum in altitude, and not being drained. A plume without salt could be from a higher altitude (but still beneath the ice) body of water, or it could come from surface melt.

    To put this another way – salt in the plume is evidence of an under-ice ocean (or at least an under-ice salty lake), but no salt in the plume is not evidence against an under-ice ocean – it’s just a lack of evidence for an under-ice ocean.

  39. llewelly

    What makes scientists expect that Enchilada’s subsurface ocean contains sodium? I thought the geological components of other planets/moons were totally different from that of Earth?

    Well – an Enchilada without sodium isn’t as flavourful.

  40. amphiox

    #37 – Rob

    Salt isn’t just NaCl, it includes all ionic compounds. Life isn’t made of water, it’s made of stuff dissolved in water.

    Life without salt means life with no charged particles, which means no charge gradients across membranes and no acid-base chemistry, among other things. In short, water is only useful for life because it is so good at dissolving charges. Life that does not require salt in water is going to be life that doesn’t require water at all.

  41. amphiox

    Also, at least here on earth, the working definition of ‘ocean’ is a large body of salty water. A large body of fresh water is called a lake. Though of course on earth we don’t have large bodies of fresh water as big as say the Pacific Ocean, and so we don’t actually have a term for that.

  42. Gary Ansorge

    Rob:

    The only other atom I know of that can re-combine in the complex ways of carbon is silicon so, maybe, life might also be based on silicon however, I read a a recent article(Darn: can’t find it again)
    that linked the formation of ten basic amino acids to the second law of thermodynamics and showed how those were the most likely to form in any carbon based ecosystem, implying no matter where carbon life forms, it will most likely have (at least) those ten amino acids in common.

    I’ve seen no research attempting to form amino acid like structures with a silicon base. That doesn’t mean it’s impossible, but silicon is the second most common metaloid in earthes crust(at 26 %) just behind oxygen. With that much availability, you’d think it would be a major component of life,especially since it, like carbon can either accept or donate 4 electrons from its outermost electron shell, but it isn’t, so maybe life can’t be based on it. I guess we’ll either have to build such active molecules in the lab or wait until we can send probes to likely star systems looking for such,,,

    GAry 7
    PS Salt water oceans or fresh water lakes,,,both are likely on Enceladus,,,

  43. BMcP

    Obviously we need more data, let’s send more probes! :)

    I am serious, you can’t have too much space exploration.

  44. Stone Age Scientist

    llewelly @ #39, if the force came from beneath the ocean, shouldn’t that also drive the settling salt up to the surface, along with the water? It seems the two teams share the common scenario of an upheaval(s) within or on the surface of the moon (eg, crust movements which translate to quakes, or heat that enables the “spewing” evaporation). Would the process of settling even be possible in such a restless environment as this? Please bear.

    BTW, when you said ‘surface melt,’ were you referring to the process of sublimation?

  45. David L

    Enceladus does and does not have a global ocean. I’m glad that’s settled.

  46. brntoki

    I suppose this will all get changed with future study anyway, but as I understood from some earlier reading (and I may not have understood it very well, to be honest… ), is that both readings are thought, at least by some, to be correct, and that they actually, together, point a little more toward an underwater ocean hypothesis.

    I think the point was that, with Cassini, it was a little more capable of discerning the makeup of the plumes, while the earth based observances were less able. If, therefore, the earth based observance also showed the salt, then it would have to have been more abundant. In that case, an underwater ocean with a less dense salt content would be the less likely scenario. There would need to be some source of water with much higher concentrations of salt. Since only Cassini was able to detect the salt, however, it is thought that something more akin to an ocean (lots-‘o-water, relatively little salt) is more likely.

  47. Yes, it’s quite clearly a quantum ocean, or rather a Dirac sea.

  48. Flying sardines

    Actually its a “mantle piece sea” – a sea that’s part of the Enceladese mantle … ;-)

    The crust of Enceladus is frozen ice – perhaps thinner in some spots than others.

    That’s assuming that the liquid waters there and is a “sea” in extent rather than being a “mantle piece ocean” or “mantle piece lake” – or not there at all.

    (Not saying its is or not, we just don’t know yet – lets send another spacecraft to find out as suggested here by 45 BMcP!)

    Incidentally, as asked by 29 StevoR :

    What about Enceladus having a magnetic field?

    Does it have one and, what, if anything, does that tell us about whether Enceladus has a (salty or not) sub-surface ocean?

    Also could one explanation be that the sodium is there but just at much lower concentrations than oceans here – perhaps diluted by a lot more oxgyen and hydrogen in the water?

  49. Plutonium being from Pluto

    Maybe Enceladus has just drunk all its soda already!? ;-)

    Or perhaps it just doesn’t like fizzy drinks? ;-)

  50. brntoki

    Did I say “underwater ocean”? Repeatedly?

    Wow! Sleep first, post later, I guess.

  51. To the best of my knowledge, Enceladus does not have an intrinsic magnetic field. And I don’t think we’ve detected an induced field, yet, either. But it may have one and we just need to get closer to detect it, too.

  52. Buzz Parsec

    Shane and Voltaire…

    Maybe somebody cleverer than me should do a comparison of science and religion based on George Carlin’s comparison of baseball and football…

    In religion, when people disagree, they get to burn each other at stakes. In science, when people disagree, they get to find out who (if anyone) is right. Then they can all agree and if they had any bets on the matter, the losers and feed the winners steaks (and beer.)

    We can all do much better than this…

  53. Torbjörn Larsson, OM

    I think life on Enceladus is a rather remote likelihood anyway, since the composition of the organics found in the plumes is AFAIU raw comet-like. Life would have processed that material for sure.

    But of course it is always good to find conditions amenable for life, such as nutrient-rich subsurface oceans!

    @ brntoki, thanks for making a plausible (and promising!) synthesis.

    Did I say “underwater ocean”?

    No worries, it sounds like a rather poetic term for oceans under a water ice cover.

  54. Flying sardines

    @ 53. John Weiss :

    To the best of my knowledge, Enceladus does not have an intrinsic magnetic field. And I don’t think we’ve detected an induced field, yet, either. But it may have one and we just need to get closer to detect it, too.

    Okay so its more data needed but not yet so far as we know. Thanks. :-)

    @ 52. brntoki Says:

    Did I say “underwater ocean”? Repeatedly?

    Yes you did – twice – so technically repeated once NOT repeat~edly. ;-)

    Wow! Sleep first, post later, I guess.

    Well I’m NOT going to say anything; half of my posts are typed while I’m more asleep than awake anyway.

    Seriously, I’ve seen a lot worse posts than your one above here … a lot. Don’t sweat it. :-D

  55. khms

    # 30. Voltaire-o’-2009

    Science has no “Holy Wars” – although even for the religious “Holy War” is surely an oxymoron!?

    A Holy War is what you get when someone manages to convince people it’s not an oxymoron.

  56. Jason A.

    Andrew #38:

    If a non-carbon based life form could form why wouldn’t it form here, as well?

    Because if carbon based life formed here first, it would outcompete any up-and-coming non-carbon life into nonexistence. Even primitive life of one form (carbon based here) is a superior competitor for resources than proto-life chemistry. It all has to do with who was here first. The reason all life on Earth now is carbon based is because it all descended from the first kind of life to form here.

    Though I totally agree with the sentiment that we should concentrate on looking for what we know how to look for. And carbon based complex molecules are more likely than silicon because carbon can bond with other carbon directly while silicon uses a silicon-oxygen-silicon alternating sequence.

  57. Sven

    Nasa’s APOD seems to cover this issue today:
    http://antwrp.gsfc.nasa.gov/apod/

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