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Space Science

Saturn's Moon Iapetus Has A 'Belt' 245

Posted by timothy from the it's-a-peach dept.
Believe writes "In another unexpected find by Cassini-Huygens, Saturn's moon Iapetus shows a bulging waistline. According to the story, the dark side of the moon is almost perfectly bisected by a tall, narrow ridge that runs for 1300 km (808 mi) and rises up to 20 km (12 mi) high. This height is amazing in such a small moon; it rivals Olympus Mons on Mars which is a body 5 times its size."
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Saturn's Moon Iapetus Has A 'Belt' More

Saturn's Moon Iapetus Has A 'Belt'

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  • deathstar? (Score:2, Interesting)

    by Phil246 ( 803464 )
    with that ridge on this pic : http://saturn.jpl.nasa.gov/multimedia/images/image -details.cfm?imageID=1270 it REALLY has a passing resemblance to a death star.
    did anyone else notice this?

  • So do I... (Score:5, Funny)

    by Black Parrot ( 19622 ) on Monday January 10, 2005 @04:55AM (#11308562)

    ...but you don't see it on the front page of Slashdot.

  • NASA... (Score:4, Funny)

    by Quaoar ( 614366 ) on Monday January 10, 2005 @04:58AM (#11308569)
    That's no moon.

  • Arthur C Clarke (Score:3, Interesting)

    by panurge ( 573432 ) on Monday January 10, 2005 @04:58AM (#11308570)
    ...I think it was had a story about a planet with a wall round the middle. (A long time ago now.) If there's any chance this wall has similar properties, we need to get a robot down there to take a look at it.
    • See the story The Wall Around the World [cloggie.org] written in 1953 by Theodore R. Cogswell. And look out for the Dark Man!
      (The Wall separated the technologists from the magicians.)

    • In fact in the novel of 2001 the Discovery goes to Saturn not Jupiter and in particular to Iapetus where as Clarke mentions there is an enormous visual discrepancy between the light side and the dark side ... of course in 2001 there was an eye like object on one side with a ginormous monolith as the pupil.

      Never read 2010 or 3001 (or whatever) so I don't know how this was resolved with Europa etc.

      • Re:Arthur C Clarke (Score:3, Informative)

        by kalidasa ( 577403 ) *
        The book 2010 was written as a sequel to the movie, not to the book. There are some things in the book from the book 2001 ("My god, it's full of stars!" wasn't in the movie - yes,I've checked a dozen times), but it discards Saturn and re-sets everything to Jupiter. The reason Jupiter was used in the movie? They couldn't get a convincing enough Saturn, and decided that by eliminating the ring by depicting Jupiter instead they'd simplify the FX issues.
        • They couldn't get a convincing enough Saturn, and decided that by eliminating the ring by depicting Jupiter instead they'd simplify the FX issues.

          As I recall, ACC said the Saturn effects were realistic, but so strange they weren't convincing -- fortunately they didn't let that argument sway them from zero g, silence in space, the sparse asteroid belt, and all the other true-to-life but counter-intuitive effects.

          The SFX guy however, Douglas Trumball, found a way to use Saturn effects he'd worked out when h

          • He did describing them as "unconvincing," true - though I don't remember the "realistic, but strange" part. Anyway, there are several places you could look, including *The Making of Kubrick's 2001*, Clarke's *Lost Worlds of 2001*, and I think there's an intro to 2010 (that's the most likely place).
            • If any of y'all wind up working for the parent poster, make sure to hold on to your hands....(from Arthur C. Clarke's _The Fountains of Paradise_ (1979))

    • Re:Arthur C Clarke (Score:4, Informative)

      by petterbergman ( 747245 ) on Monday January 10, 2005 @08:45AM (#11309088)
      There is a short-story by Clarke about a universe that contains only one sun and one planet, the universe is about as big as the planets orbit. The planet is constantly showing the same face toward the sun, it has a day-side, very hot, and anight side, very cold. Humans live around the equator where the temperature is right.

      In the book the universe actually ends somewhere around the north pole(dark side) of the planet and a long time ago humans built a great wall to hide the end of the universe... great short-story.
    • Having just read the very fine Red Mars [amazon.com] by Kim Stanley Robinson, he describes the spectacular collapse of a space elevator [wikipedia.org] causing a ring that went almost twice around the equator of Mars.

      Actually, the space elevator was actually one of Arthur C Clarke's ideas [space.com]

      The structure of the ring is a bit different from this one, but the location (along the equator) is the link.
    • Another book with a world with a wall around the middle. But it's probably not the one you are thinking of.

      Midnight at the Well of Souls.

    • I think you're thinking of Dr. Seuss... The Butter Battle Book anyone?
    • http://math.cofc.edu/faculty/kasman/MATHFICT/mfvie w.php?callnumber=mf319

  • Lucas be praised! (Score:5, Funny)

    by duffahtolla ( 535056 ) on Monday January 10, 2005 @04:58AM (#11308571)
    This [google.com] cant be coincidence.. [nasa.gov]

  • Why surprising? (Score:3, Insightful)

    by Velox_SwiftFox ( 57902 ) on Monday January 10, 2005 @05:01AM (#11308579)
    Why is it surprising that tall mountain ridges are found on small (relative to planets) moons, where there may be little weather and low gravity to cause their erosion?

    • Re:Why surprising? (Score:5, Interesting)

      by pe1rxq ( 141710 ) on Monday January 10, 2005 @05:09AM (#11308611) Homepage Journal
      It is surprising in the way these mountains are on the moon's equator and form a nice belt.
      That there is little erosion isn't a surprise, but the mountains origin is far more interesting.
      On earth mountains are all results of our molten core (plate tektonics and vulcanoes). There must be some process that created this moutain belt.

      Jeroen

      • Re:Why surprising? (Score:5, Interesting)

        by Vo0k ( 760020 ) on Monday January 10, 2005 @05:36AM (#11308693) Journal
        I have two theories...

        Less possible:
        What I'd look for are two large craters of similar size and same age (can be estimated by amount of erosion from later meteorites), placed on opposite sides of the moon, shifted from the surface of the intersection by similar distance in opposite directions. Strong enough hit could have just split the moon it two...

        More possible:
        The moon had its own ring, just like Saturn has. But the ring's rotation was slowed down by Saturn's gravity (the same way our Moon's rotation got stopped by Earth) and the ring was pulled by the moon's gravity down, on the surface, depositing all the material straight below its orbit.
        • The presence of Saturn itself would disrupt the formation of a ring around a small planetary body like a satellite, I would think. Not that I have done n-body simulation for this type of things.

          If not, then I'd bet the gravitational perturbation alone would increase perpendicular motion of this hypothetical ring in the plane of rotation (i.e., the ring would get puffed up).

          In any case, I'd look for geophysical reasons before invoking some "ring" theory.
          • Note the moon is stopped in its rotation around saturn (1day=1year) and the ring is right around its equator. That would be a strong coincidence for the forces to appear right there. On the other hand, this symmetrical layout would be about the only possible where Saturn's influence wouldn't "puff" the ring and could actually stabilize it in this position.
            • Tidal lock doesn't necessarily mean that the revolution of Iapetus is in the plane of the ring or Saturn's rotation (or is it so? I can't locate its ephemeris).

              Besides this object is so small that it is more likely to be part of Saturn's ring. Its gravitation field is not significant enough to trap a larger number of small bodies as Saturn does. And if you're saying that Saturn's ring particles gets deposited there, then that's probably not right either. As they decend onto the surface, it'd make a crater,

              • Re:Why surprising? (Score:3, Interesting)

                by Vo0k ( 760020 )
                Tidal lock doesn't necessarily mean that the revolution of Iapetus is in the plane of the ring or Saturn's rotation (or is it so? I can't locate its ephemeris).
                Actually Iapteus could orbit opposite to Saturn's location and perpendicular to the ring, it doesn't matter. What only matters is so its orbit axis was parell to its rotation axis when it had a normal daily cycle yet (no tilt), and paralell to its ring axis. (so tidal lock was changing speed, not direction of rotation). Nowadays when it's stopped it
          • There's no reason why a satellite can't have a satellite. A ring system is just another orbiting object (or rather, many, many objects). Planets in our solar system have moons, and rings, after all, and their orbits are not disrupted by the Sun. Therefore, it should be possible for a moon to have a natural satellite or ring system. I don't know that we've ever seen that in practice, but we did put a man-made orbiting vehicle around our own Moon.
        • Damn you and your plausible theories! I was hoping this would finally be the strange artifact that would have scientists announcing "we have finally found signs of extra-terrestrial intelligence". punk...
        • Both are doubtfull.

          Plate technonics tends to make subduction zones along arcs, not in straight lines. Volcanism outside of subduction zones tend to be in hot spots, not lines. So neither is likely to be the cause of this.

          I'd guess that the cause is core colapse. The crust got strong enough (relative to the size of the moon) to resist techtonics. The core shrunk through cooling or volcanism or both. Then the crust colapsed along the weekest line to take in the size. The weakest line was the equator. The po

          • Plate technonics tends to make subduction zones along arcs, not in straight lines. Volcanism outside of subduction zones tend to be in hot spots, not lines. So neither is likely to be the cause of this.

            Don't you think plate tectonics is specific to planets of volcanic core?
            Rules that apply to a planet with hot liquid core don't apply to cold bodies of debris stuck together.

            I'd guess that the cause is core colapse.
            Nice theory but what would be the reason for it to happen? And why is the line so straight

      • Re:Why surprising? (Score:2, Insightful)

        by rhennigan ( 833589 )
        I'm willing to bet there used to be a ring around the moon, that eventually fell out of orbit, piling up in a neat row around the equator. Then again, IANAKP (Knowledgable Person), so feel free to suggest why this might not be possible.
        • I'm willing to bet there used to be a ring around the moon, that eventually fell out of orbit, piling up in a neat row around the equator. Then again, IANAKP (Knowledgable Person), so feel free to suggest why this might not be possible.

          There is virtually no atmosphere, so no air braking. Orbits do degrade due to tidal friction, but just prior to fragments of a ring hitting the surface they'd still be in an orbit, moving very fast (1500 km/hr by my calculation). So if they did finally touch down to the sur


      • a giant mold line.
        Since we're all wildly speculating anyway.

    • Re:Why surprising? (Score:5, Interesting)

      by HuguesT ( 84078 ) on Monday January 10, 2005 @05:20AM (#11308643)
      For several reasons:

      On Earth mountains are caused by plate tectonics, i.e. disconnected area of crust floating on magma that run into each other, but such mechanism are impossible on small bodies because they cool too fast, i.e their crust quickly become too thick and form a single fused objet.

      Of course mountains can also be volcanoes, but similarly this implies magma that can rise to the surface, i.e a crust that is not too thick.

      The exception are moons close enough to their parent body so that internal heat can be sustained by tidal effects. This is the case on Io, for example.

      However there can only be tidal effects if the moon is rotating around itself at a different rate as it revolves around its parent body. For Iapetus, just like our moon, the two rates are the same and they always present the same face to their parent. This implies only minimal tidal effects due to the eccentricity of the orbit.

      Of course the mountain/volcano may have been formed a very long time ago when the moon wasn't as cool as it is now, probably this is the case for mount Olympus on Mars, however there is erosion on most planetary bodies even without atmosphere or low gravity, caused by the myriad of asteroid impact they sustain.

      One remaining option is impact by a large asteroid. We now have to come up with a reasonable impact scenario that can produce a feature similar to the one seen on Iapetus, which is indeed very strange.
      • One remaining option is impact by a large asteroid. We now have to come up with a reasonable impact scenario that can produce a feature similar to the one seen on Iapetus, which is indeed very strange.

        Easy: two big asteroids struck the moon simultaneously on both poles!
      • To set a thing or two straight about plate tectonics (not tektonics, or techtonics; parent got it right, about 5 other posts have not) on Earth, the pieces of lithosphere (crust+uppermost rigid mantle) float not on magma but on hotter, solid mantle rock that flows plastically and behaves like a fluid on long timescales. The magma that we observe coming to the surface is the result of partial melting (a few % only!) of this solid mantle rock. All of which has very little to do with the molten (outer) core of
  • The NASA summary says the ridge can reach 20km/12m wide. The height only reaches 13km/8m, only about half the actual height of Olympus Mons. Proportionally, though, it's about 2.5 times the size of Olympus Mons. Still very impressive.
    • Proportionally, though, it's about 2.5 times the size

      the height.

      Olympus is a single top. This is a ridge, very long.
      Comparing a lake 1km wide and a river 1km wide...
  • ... it ate too many MARS BARS

    Ahhhahahah! hahahaha! hahahaha...ooooo, just shoot me now.

  • Oh my, thousands of nerds will come out and rejoyce over this pic.

    Screw science tag; it's Star Wars, baby!

    [Literally, I expect to see little scientific discourse on this thread...so sad.]

  • Thanks (Score:4, Interesting)

    by scum-e-bag ( 211846 ) on Monday January 10, 2005 @05:22AM (#11308650) Homepage Journal
    Thanks.

    Stories like this make slashdot cool.

  • Kim Stanley Robinson's A Short, Sharp Shock (Score:3, Interesting)

    by boa13 ( 548222 ) on Monday January 10, 2005 @05:25AM (#11308659) Homepage Journal
    Coincidences are weird, sometimes.

    Kim Stanley Robinson is well known for his hard sci-fi Mars trilogy (Red Mars, Green Mars, Blue Mars). He has also written a small and memorable fantasy book, A Short, Sharp Shock [amazon.com], which takes place on a strange world covered by sea, almost perfectly bisected by a tall, narrow ridge that seems to run all around the world (but maybe only for 1300 km?) and that sometimes almost reaches the sea, sometimes climbs up to great heights (20 km maybe?).

    Just a coincidence, of course, but it's funny that a man who loves space in general and planets in particular would use an existing but at the time unknown geological feature as the basis of a fantasy book.
  • The ridge is 13km high and 20km wide.

  • I think I speak for many when I say... (Score:4, Funny)

    by solios ( 53048 ) on Monday January 10, 2005 @05:33AM (#11308682) Homepage
    o_O.

    It's a giant space WALNUT. :O

  • I'm a product designer (Score:4, Funny)

    by I7D ( 682601 ) <ian...shook@@@gmail...com> on Monday January 10, 2005 @05:51AM (#11308733) Homepage
    And that is definitely a parting line, just an artifact of the mold.

    • Re:I'm a product designer (Score:3, Funny)

      by Anonymous Coward
      Quite true. It was a budget moon so it is bound to have some minor issues.

      Sincerely,
      Magrathea planetary wharf

  • Size confusion (Score:5, Interesting)

    by Spy Handler ( 822350 ) on Monday January 10, 2005 @06:05AM (#11308761) Homepage Journal
    "This height is amazing in such a small moon; it rivals Olympus Mons on Mars which is a body 5 times its size."

    Article submitter didn't take Astronomy 101 apparently. Small planetoids tend to have more prominent geological features than larger planets because stronger gravity pulls everything together harder and flattens things out. For instance, Olympus Mons on Mars is much higher than any mountain on Earth precisely because Earth has stronger gravity.

    • Re:Size confusion (Score:2, Interesting)

      by ralphh ( 703108 )
      The submitter is rephrasing the JPL news release, which a implied a similar awe. In part: "No other moon in the solar system has such a striking geological feature. In places, the ridge is comprised of mountains. In height, they rival Olympus Mons on Mars, approximately three times the height of Mt. Everest, which is surprising for such a small body as Iapetus. Mars is nearly five times the size of Iapetus."

    • Re:Size confusion (Score:2, Informative)

      by SsShane ( 754647 )
      Also, Mars has a much thicker crust than Earth. Our mountains literally sink into the mantle when they reach a certain mass.
    • Other people just say Olympus Mons is much higher because its THE vlocano with the longest span of activity.

      While gravity makes planets to be round, it has not such a great effecct as that it "flattens" mountains.

      The difference between Himalaya and Olympus mons is: the former is a folding mountain, where two plates press against each other and the later is a shield vocano.

      If at all you could argue that "volcanos" behave different depending on gravity.

      Regards,
      angel'o'sphere
    • I don't think it is gravity alone which accounts for the size difference, but mainly weathering and erosion, for which you need an atmosphere. Earth has this in abundance, Mars relatively little, and Iapetus probably none at all. Gravity has nothing to do if there is no wind or rainfall to knock loose stones to begin with. (Of course, the gravity of the planet is a factor in whether it can retain an atmosphere to begin with...)
  • Forget the walnut jokes, and the deathstar jokes, a real idea, to be shot down with real science (I hope):

    1) Moon form as overall a solid shell, but has a core containing radioactive materials
    2) Due to composition, heat builds up faster than it escapes, and builds preasure as the center expands
    3) Preasure eventually causes outer solid shell to crack along the equator at the time, molten material flows out, and forms band, and solidifies, never to occur again.

    Thoughts?
    • Like all real science, it's too weird to adequately theorize. But I'll toss in my ignorance and say tidal stresses along the equator causes the cracking and extrusion of material.
      -aiabx

  • It's not a ridge, it's a seam... (Score:3, Funny)

    by matt_wilts ( 249194 ) <matt_wilts@@@hotmail...com> on Monday January 10, 2005 @06:40AM (#11308837)
    ..like a Russian Doll, open it up & there's another moon inside!

  • The Iapetusian Wall (Score:3, Funny)

    by TintinX ( 569362 ) on Monday January 10, 2005 @07:21AM (#11308913) Homepage
    This is a remnant from the Iapetusian Cold War, when the folk from the northern hemisphere were separated from those in the southern.
    Be grateful that Cassini-Huygens' lens isn't more powerful or you might have been able to make out David Hasselhoff standing on it singing a song about freedom.
  • Slartibartfast [bbc.co.uk] forgot to remove the glue that remained after merging the two half-sphere's together...
  • 1. It was originally two moons, of the same size. They collided, leaving a ridge at the join.

    2. It will become two moons, of the same size. It is in the process of mitosis.

    3. It is a giant cricket ball.

    4. This is the seam the mould left.

    5. There is no spoon. I mean, moon.

    6. Aliens did it as a display of power.

    7. We did it, millions of years ago, before nuking ourselves and starting again. As a warning to ourselves in the future, which we are now ignoring.

    8. Aliens did it for a joke.

    9. This is what t
  • ... cause it kept mooning passing ships.
  • THAT's where it's hiding it's intellectual property theft evidence!

    My best sig is this one.

  • Amazing? Why? (Score:4, Interesting)

    by slavemowgli ( 585321 ) on Monday January 10, 2005 @07:54AM (#11308956) Homepage

    his height is amazing in such a small moon

    Why? There is a limit on which heights are possible for a given celestial body (planets etc., that is, I'm not counting in stars here), and that limit is actually higher for a smaller body (for example, a volcano the size (height) of Olympus Mons wouldn't even theoretically be possible on earth).

  • Wrong turn (Score:3, Funny)

    by LS ( 57954 ) on Monday January 10, 2005 @08:46AM (#11309092) Homepage
    Looks like Bugs Bunny definitely took a wrong turn at Albuquerque...

    LS
  • http://saturn.jpl.nasa.gov/multimedia/images/image -details.cfm?imageID=1270

    Dare I say it?

    That's no moon....that's a space station!

    I believe we should start training our X Wing pilots to hit Womp Rats in Beggar's Canyon NOW.

  • Sensible non-death-star explanation (Score:4, Insightful)

    by adeyadey ( 678765 ) on Monday January 10, 2005 @08:59AM (#11309130) Journal
    Many of the smaller moons/asteroids are barely spherical, and having been hit so often, barely held together by gravity. given the size of the impact crater, it is possible this moon was nearly torn apart by that impact, and the belt is a relic of that event.

    Some of the smaller moons & asteroids out there are more like piles of rubble held together by gravity than solid bodies - thus the headaches in what to do if one were ever found to be on collision course with earth, since an attempt to move it of course would merely fragment the body..
  • If we find three rings braided into a ponytail, it's time to start stockpiling nukes in Washington.
  • http://saturn.jpl.nasa.gov/multimedia/images/image -details.cfm?imageID=1270

    Does it look like:

    a) the death star
    b) a lemon
    c) the suse logo

    ???
  • It was assembled - the two halves must join somewhere...
  • I have *real* trouble believing that's natural.

    Damn, we missed 'em by how many millions of years?

    mark

  • Second thoughts: I *know* what it looks like... (Score:3, Interesting)

    by whitroth ( 9367 ) <whitroth@5-cen t . us> on Monday January 10, 2005 @10:49AM (#11309827) Homepage
    Anyone read Kim Stanley Robinson's [Red/Green/Blue] Mars?

    Reminds me of the *big* space elevator cable that fell. If that caused lava flows/vulcanism in a line....

    mark
  • ...I find allegations that Iapetus has 'a bulging waistline' quite offensive and hurtful.

    Not untrue, you understand. Just hurtful.
  • ... Great Wall of Iapetus imaged by Western surveillance satellite.

    Film at 11
  • It is a very typical "failure mode" of the human mind. We see something coincidental that catches our attention, and assume that something fishy must be going on.

    We can rest assured in the fact that, for every moon that coincidentally has a ridge coinciding with its equator there are thousands of moons elsewhere which do not. The reason we notice the "unusual" arrangement is precisely because it is unusual. Unusual to the human mind, that is.

    How many mundane events happen to you on a daily basis? And ho

  • Why couldn't this moon have been formed by the collision of two similarly-sized bodies? Not a spectacular Industrial Lights and Magic collision, but suppose they were in the same (or similar) orbits that eventually converged? I imagine it as more of a crush than and crash.

    This might account for material not flying out. Additionally, it might account for the equatorial ridge, where mantle materials piled up on each other during the crushing gravitational embrace. As gravity pulled the new object closer to c

  • Iapetus' Belt - Proposed Explanations (Score:3, Funny)

    by wildsurf ( 535389 ) on Monday January 10, 2005 @04:00PM (#11313104) Homepage
    10. The moon was actually injection-molded.
    9. The hill is the remains of an ancient alien rail-gun launcher.
    8. Iapetus, in a fit of sibling jealousy, has attempted to grow its own rings.
    7. Percival Lowell accidentally based his sketches on the wrong planet.
    6. This is the planet from Kim Stanley Robinson's "A Short, Sharp Shock", without the oceans.
    5. The moon was tectonically separated aeons ago from Vallis Marineris.
    4. This is the solar system's frenulum.
    3. Ringworld deorbited here.
    2. Not much, just loosening its belt after the holidays.

    and..

    1. That's No Moon...

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