Enceladus flyby

By Phil Plait | October 10, 2008 1:16 pm

Just yesterday, the Cassini spacecraft passed an incredible 25 kilometers (16 miles) off the surface of Saturn’s weird moon Enceladus. This icy ball has plumes of water jetting up from its south pole region, emanating from a series of parallel cracks nicknamed tiger stripes. Cassini flew right through these plumes! The images taken have not been fully processed yet, but the Cassini folks have released a few of the raw images. Here’s one:

Cassini raw view of Enceladus

Wow. The surface of Enceladus is entirely covered with ice; see how few craters there are? That means the surface is "new"; if it were older there would be lots more craters. That means the moon is recently (or continuously) resurfaced, which in turn means a dynamic process almost certainly involving water and a liquid interior. The cracks and plates look to be due to ice floes. We see the same sort of thing here on Earth and on Jupiter’s frozen moon Europa.

This flyby was not designed to get great images, but to use other sensors to directly sample and investigate the composition of the plumes. Another flyby will happen on Halloween, October 31, and that one will focus — so to speak — on imaging. So stay tuned! There is a lot more coolness to come.


Comments (41)

Links to this Post

  1. Ruwe foto’s van Enceladus en Astroblogs | October 11, 2008
  1. Deepsix

    Awesome image. Makes me cold just looking at it.

  2. Elmar_M

    Hey Phil!
    Do you have a quick explanation why it is water and not some other substance that liquifies/freezes at the low temperatures this far away from the sun? Was that determined by spectroscopy?
    I mean a lot of things make ice that far away from the sun. For all we know it could be methane…

  3. Elmar_M

    Oh, the image is very cool (in more than one way, brrrr 😉 ). 25 kilometres is awefully close, how big (diameter) is that moon?

  4. Celtic_Evolution

    I just continue to be fascinated by this moon… I wonder what the resurfacing cycle is… how often is the entire surface “slate” wiped clean…

  5. Jimi

    That moon is obviously populated by a race of avid skiers…
    Or possibly sledders or snowmobilers.
    Just look at all those tracks!

  6. wow, this is awesome. and I believe the “sniffing” that cassini did this flyby found a mix of water and other stuff, so that’s probably a good piece of evidence that the ice is waterice.

    seems water, and even liquid water, isn’t soooooo horribly rare, at least in our solar system :-)

  7. err, i meant the last flyby… :-p

  8. It’s stunning, and the thought that life may be possible on it, astounding.

  9. Stuart

    No alien polar bears? What a disappointment! Seriously though, amazing pictures, would love to know some of the secrets that surface holds.

  10. JSug

    Mmmmmm…. I love me some chicken Enceladus.

  11. Wow, that canyon screams “CANYON” more than a normal 2D image would.

  12. Jeffersonian

    Mercury’s cool but that has me really excited. Could not some of the smaller craters simply be filled and leveled with ice and therefore indiscernible?

  13. Naomi

    Whoa o.o

    (Although, admittedly, my first thought was someone shoving a plastic bag full of water in a freezer – I swear I’ve seen that type of cracking before XD OMG NASA FAKED THE ENCELADUS FLYBYS.)

    Any conclusions on what they learnt from the plumes?

  14. RJ

    That is definately one of the coolest pictures I’ve seen in a while.

  15. @ Elmar_M

    The mean diameter of Enceladus is 504.2 km (± 0.2 km).

  16. Elmar_M
  17. Scientists have just discovered the method by which Enceladus is constantly resurfaced:


  18. Sebastian

    FLYby indeed! To put this into perspective: 25km is just about twice the height regular passenger jets travel here on earth.
    This is just incredible. Those pictures are simply awe-inspiring…. and hopefully, somewhat of a(nother) cornerstone for the further exploration of the solar system. There is still so much to see out there…

  19. Crudely Wrott

    Whaahoo! Go to the CICLOPS link above and look at photos 3 and 4. I overlaid 4 onto 3 by aligning the walls of the canyons and the striations. I think I’m looking at a very large and long lived outflow from the canyon that is flowing to the right. The apparent spreading of the outflow, possible compression ridges, and a remarkably cyclic “downstream” appearance all look familiar. But completely different. ‘Course, it is another world entirely. ;D

    Thanks again, Phil.

  20. themadlolscientist

    LOL @ Michael L!

    How strong are the tidal forces from Saturn? Are they enough to deform the moon and crack its surface? To heat it up and melt the ice so it’s floating on a layer of liquid water?

  21. dkary

    Most of the discussions I’ve seen suggest that the interior of Enceladus is probably a little “mushy”, but not really liquid except possibly around the tiger stripes region at the south pole.

  22. Crudely Wrott

    Yeah. And mushy stuff might just flow like the pictures suggest.

    I wonder what it would do if you could shake it?

  23. vinayak Aatreya

    Its amazing to see cassini so close to encla…. Is it really water or methane. Let’s wait for more info.

  24. This is an abstract from Wikipedia — Enceladus (moon):

    Moons in the extensive satellite systems of gas giants often become trapped in orbital resonances that lead to forced libration or orbital eccentricity; proximity to the planet can then lead to tidal heating of the satellite’s interior, offering a possible explanation for the activity. […]

    Enceladus orbits Saturn at a distance of 238 000 km from the planet’s center and 180 000 km from its cloud-tops, between the orbits of Mimas and Tethys, requiring 32.9 hours to revolve once (fast enough for its motion to be observed over a single night of observation). Enceladus is currently in a 2:1 mean motion orbital resonance with Dione, completing two orbits of Saturn for every one orbit completed by Dione. This resonance helps maintain Enceladus’s orbital eccentricity (0.0047) and provides a heating source for Enceladus’s geologic activity. […]

    [Assuming that Enceladus is a differentiated body, i.e., a silicate core with a water-ice mantle, subsequent heating from the decay of certain radioactive elements] and tidal heating would raise the temperature of the core to 1000 K, enough to melt the inner mantle. However, for Enceladus to still be active, part of the core must have melted too, forming magma chambers that would flex under the strain of Saturn’s tides. Tidal heating, such as from the resonance with Dione or from libration, would then have sustained these hot spots in the core until the present, and would power the current geological activity.

    Click on my name for the direct link to the article and a more detailed explanation with cool pix.

  25. SLC

    Here is an example of an exciting scientific event which did not involve manned space flight. One can only speculate as to he scientific discoveries that could be achieved if manned space flight were deemphasized in favor of Cassini type explorations. But of course, physicists like Bob Park and Steven Weinberg who tirelessly point this out don’t know what they are talking about.

  26. madge

    SNOWBALL FIGHT! You think they got apres ski bars there that serve hot schnapps and mulled wine? Awesome series of pix. Can’t wait till they finish evaluating the data from the Cosmic Dust Analyzer that sampled the plume.

  27. StevoR

    Excellent news – great week for space exploration with this &themESENGER fly-past of Mercury. 8) 😀

    SLC & others dissing manned spaceflight I don’t think the two (humans or robots) are necessarily mutually exclusive but rather could be considered complementary. As an Sf fan Ilike tothink of this as the preliminary reconnosience by Robots before we humans eventuallyget out there.

    The otherway of thinking may be -how much coooler if there werereal people aboard ashipinvestigating Encleadus -how much mor ecould theyspot and acton and do? 😉

    One day hopefully, whenthetechnology has grown betertr and the travel times dropped I’d love to see people on Enceladus.

    (Or would the radiation level be too high? I know the Jovian Gaililean moons are all deeply radioactive because of Jupiter’s equivalent of the Van Allen belts – is this as bad at Saturn?)

    Anyway, fornowe I’m justmarvelling over these images and those of Mercury and proiud to see both encounters atopposite ends of our solarsystem have gone so well. :-) 8)

    THX Bad Astronomer.

  28. StevoR -Correcting

    Yeck. Flippin’ typos .. Sigh


    I meant :

    Excellent news – great week for space exploration with this & the MESSENGER fly-past of Mercury succeeding.

    @ SLC & others dissing manned spaceflight : I don’t think the two (humans or robots) are necessarily mutually exclusive but rather that they could be considered complementary.

    As an SF fan, I like to think of this as the preliminary recconnosance (spelling?) by our robot proxies before we humans eventually get out there in the flesh.

    The other way of thinking may be this : How much cooler would this be if there were real living people aboard a ship investigating Encleadus – how much more could they spot and act on and do?

    One day hopefully, when the technology has grown better and the travel times dropped, I’d love to see people land on Enceladus.

    (Or would the radiation level be too high? I know the Jovian Gaililean moons are all deeply radioactive because of Jupiter’s equivalent of the Van Allen belts – is this as bad at Saturn?)

    Anyway, for now I’m just marvelling over these images and those of Mercury too and proud to see both encounters at opposite ends of our solar system* have gone so well.

    THX Bad Astronomer.

    PS Thinking of Mercury are all the images / info. from that fly-by in now or is there more still to come? Did they find that volcano suggested by the Arecibo data? (See ‘MESSENGER fly-by tonight’ thread here.)

    * Yeah I know strictly speaking Mercury is at one end but Pluto – or Eris or Sedna is at the other NOT Saturn. Spekaing metaphorically or poetically here.

  29. @SLC repeats ad nauseam: “But of course, physicists like Bob Park and Steven Weinberg who tirelessly point this out don’t know what they are talking about.”


  30. SLC

    Re shane

    I suggest that Mr. shane from Australia who apparently, like Dr. Plait is all in favor of manned space flight, not comment on US taxpayers who have to shell out for this activity. He who pays the piper calls the tune and Mr. shane in Australia isn’t paying the piper.

  31. Reverend J

    Can’t wait to see what the Mass Spec data shows!

  32. SpikeNut

    Looks like a left-over baked potato.

  33. Gary Ansorge

    So much water, so much reaction mass for a nuclear rocket,,,

    GAry 7

  34. @SLC,
    Good on ya SLC mate, is that the best you can do? As I mentioned you sound like a broken record. Really. We got it the first time. Now you bring nothing more to conversation than snide remarks and ad homs. We, the great unwashed masses of the intertoobs, do have opinions. Sometimes they have to do with US policy. Deal with it. You might be surprised to find that some Australians and Canadians and Nigerians and Kazaks and Burmese, et al also have an opinion on who your next president should be. We don’t vote in your elections either.

    So you don’t like your taxes going to stuff you don’t like? Waaah. Stuff happens. You do realise though that Australia and NASA have had for decades a long standing partnership in operations and facilities in Australia? Facilities, operations and the support of manned space flights and the purely robotic space missions? What? Can it be that Australian tax payers have a stake too?

    Look, I’ll put it in a way you might understand. Some people don’t want to pay for any space exploration at all while there is poverty on earth. What would you say to them? I would suggest your arguments would be very similar to ours, those who believe in manned space exploration.

    He who pays the piper, Mr. SLC from the USA, may call the tune but it doesn’t mean we can’t hum along or dance to that tune.

    By the way I have no comment on US taxpayers.
    Well, except for this, are the 40% of Americans who do not pay tax entitled to an opinion? Or are you of the opinion that should be no representation without taxation?

  35. John Weiss

    Why is it water ice and not some other ices? Actually, you do get other hydrogen compounds freezing in the outer solar system. However, oxygen is the most abundant element in the solar system after hydrogen and helium. Given that, water is expected to be the second most abundant molecule (after hydrogen), so its ices should be more common than methane and ammonia. (There are other, more subtle reasons that water would be more common in a given location involving physical properties like freezing points, but that’s the biggest one.)

    And yes, spectra show that these guys are mostly water ice. I don’t think that there are any confirmed detections of ammonia on Enceladus yet, for example.

  36. IVAN3MAN

    @ John Weiss

    According to Wikipedia — Enceladus (moon), the Ion and Neutral Mass Spectrometer (INMS) and the Ultraviolet Imaging Spectrograph (UVIS) both confirmed that the plumes emanating from Enceladus’s south pole region is, indeed, water vapor, but no ammonia was detected in the vented material by INMS or UVIS; however, simple and complex hydrocarbons such as propane, ethane, and acetylene were detected.

  37. @GAry 7: “So much water, so much reaction mass for a nuclear rocket”

    So you’d ruin the pristine space environment with nukes and radiation? How are the poor alien mothers going feel when their alien babies are born with 10 tentacles instead of eight?

  38. Gary Ansorge

    So? They’d have to learn to count in decimal instead of octal.

    GAry 7

  39. Buzz Parsec

    Jimi and Madge, Have you seen “A Grand Day Out” (first Wallace and Gromit film)? BTW, Bob Park and Steven Weinberg hated it. :-)


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