Approaching Iapetus - what makes it two-faced?

j8hart · Jan 26, 2005

I came up with a theory I think might explain the ring of mountains round the equator of Iapetus. Suppose a smallish object, say 10Km in diameter, fell into Iapetus when Iapetus was very young and had not had time to form a crust. Iapetus being a ball of liquid at this point in time the object might initially burry itself some distance below the surface. Suppose further that the object was less dense than Iapetus and had a higher melting point than the liquid it fell into. Over time the object might float up to the surface, perhaps encountering the crust which could have formed in the mean time. Now trapped inside the crust of Iapetus, the object might be slowly moved to the equator by the centrifugal force of Iapetus’s spin. Once at the equator, but still inside the crust, the bumping of the object against the inner surface of the crust could eventually force out the ring of mountains. Eventually the object might become stuck in one place, break apart, or perhaps it’s still in there bumping around. What do you think? OK it's a crazy idea, but then the ring of mountains is a crazy feature and I susspect it will take a crazy idea to explain it!

claywoman · Jan 26, 2005

Well my theory is that Iapetus is a large walnut, from the huge walnut tree. when it ripened if fell from the tree, got caught in Saturn's gravitational field....If you crack it, there will be more walnut then the world can eat, with a sweet, chocolate flavor because its been circling the 'Milky way for a while....

j8hart · Jan 27, 2005

I’ve read the giant walnut theory already, and I like it, and you probably have as much chance of being right with it as I do with my bumping around inside theory. When I first saw them, I said to myself “Oh my God! It’s a gigantic Kinder-Surprise!" However the problem with both giant walnuts and giant Kinder-Surprise is that they both suggest that Iapetus is the product of some very advanced civilisation. I say this in the case of walnuts because an organic walnut is not spherical, and has a distinct knobbly shape, compare: 1) Organic walnuts: http://www.fotosearch.com/IGS217/is083-013/ With 2) Iapetus: http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1270 So I’m afraid that if it is a walnut, it is almost certainly a GM walnut, created by the alien equivalent on Monsanta by selecting spherical genes and rejecting knobbly genes. For this reason I doubt my local Natural-Winkel (organic food store) would want anything to do with it. As much as I enjoy reading all theories about these mountains I’m looking for ones which explain the essential features which marks these mountains as different from any others I know of, that is to say: A) The symmetry. I.e. They are not only an arc of a circle (if not a whole circle) but an arc of an almost perfect circle whose centre looks like it corresponds almost exactly with the centre of the moon itself. B) The fact that they are, according to NASA “almost exactly parallel to the equator within a couple of degrees”. C) The fact that they are so big. The various NASA articles say in one place “over 13 Km” and in another “reaches 20 Km high”. Everest is a little under 9Km high, and that is from sea level. These mountains appear to rise to up to 20Km from a sta

j8hart · Feb 1, 2005

Yes, this could explain the two faces (though I prefer the idea that Iapetus swept through dust falling towards Saturn from an impact on another moon further out since that would explain why the dark face is the leading face). However what I am really interested in is the ring of mountains. Anyone have any comments on my bumping object inside the moon theory? Anyone have any other theories?

nexium · Feb 8, 2005

The mountains are toxic waste layed down in straight rows. The other rows were smoothed out (The dark color or the light color) The galaxtic EPA caught them and confiscated their equipment before they finished spreading out the last row of piles. Neil

astrophoto · Feb 8, 2005

Do we know of any type of materials that might darken when bomarded with radiation? Perhaps being the leading face makes the material darken somehow?

vogon13 · Feb 8, 2005

Suspect tholins from Titan would fill the bill for just such a material. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Feb 8, 2005

Didn't realize 'bumping around inside Iapetus' was not a joke, sorry. I don't feel qualified to comment on your theory, and I'm having trouble phrasing why I feel that way so that I won't get a moderator ad hominem zap. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

j8hart · Feb 9, 2005

I fully appreciate your problem vogon13, as I said myself in my first post it’s a crazy idea. I doubt it is the right explanation. And I have no objection to other people agreeing with me on that one <img src="/images/icons/wink.gif" /> . However when you look at the alternatives they all seam just as unlikely. Take, for example, the idea of Iapetus having had it’s own ring which collapsed onto the surface to form the mountains. I can see that working in deep space away from the gravitational influence of other bodies, but I just don’t see a ring falling in a straight line in a system like Saturn’s. It also has too much of an “it happens or it does not happen” feel to it for me. In other words if it is possible for moons to have rings which collapse to form a chain of mountains round the equator then why aren’t there chains like that all over the solar system. If it’s not possible, then it will not explain the ring of mountains on Iapetus. In my view the real explanation is going to be something with a good deal of improbability built in. In a sense it was the craziness of the theory that lead me to post it. For it to work an object with certain properties would have to have impacted Iapetus at just the right time.

silylene old · Feb 9, 2005

While everyone is posting "unusual" ideas for the circumferential mountain chain, well I thought I'd post the other really nutty idea that came to my mind when I first saw it: The unusual equitorial mountain chain was caused by the impact damage resulting from the collapse of a space elevator ! Well, just kidding...but this would make a good basis for a SF short story, wouldn't it? <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

vogon13 · Feb 9, 2005

Perhaps your theory not crazy enough to be true. I like the idea of a ring around Iapetus. That it turned out to be a temporary Iapetan feature is sad, would love to see composite picture of Iapetus, its' ring and ringed Saturn in background. Moons of Uranus may be hiding equatorial ridge segments as Voyager II only looked at sunward pointing polar regions of satellites. Very few asteroids are apparently spherical enough for me to be tempted to advocate looking for orbitally decayed ring residue on them, but will still be quite happy if the are eventually discovered there, anyhow. Wouldn't gavitational effects from other bodies be a factor in 'bringing down' a ring system? Tidal effects would bump up eccentricities of orbits of ring particles. A very low circular orbit wouldn't intersect surface, a very low slightly eccentirc orbit would. I had speculated previously in this thread about an extremely thin Iapetus atmosphere produce by a high cratering rate during ring system epoch. This might provide a gentle braking effect to slowly bring down the ring structure. I suspect ring structure (if real) to experience passages thru Saturn's magnetosphere as a drag force on orbit, too. A major cratering impact on Titan (equivalent to more than 100MT) would be expected to blow a great deal of Titan atmosphere into space, this gas, I'm thinking, might interact with solar wind and/or Saturns' magnetic field and wind up out around Iapetus. Doesn't have to happen very often as we apparently have 4000000000 years for this to all occur. I don't have a Pixar animation suite to play with making videos of my ideas, just a 47 year old 2 lobe original wet spongy processor, with no upgrades planned. Orbitally decayed ring shouldn't be too hard to simulate. If I had more than one old turntable (for you youngsters, a turntable plays records)(BTW, records are what we had before SACD, DVD-A, and CD) I would probably be out do <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Feb 9, 2005

Coming up next on FOX: WHEN SPACE ELEVATORS GO BAD!! Too bad Irwin Allen is dead. Julie Hagerty could play the brave scientist predicting disaster, and Brett Spiner could play the sympathetic, yet misunderstood alien. This movie is just begging for a very cute, but completely impractical robot, too. Excellent book idea. Oh by the way, anybody have any idea what really happens when a space elevator falls down? Wrap around planet? Fall in a conical pile? Part flings off into space? Hits Charro in a cheesy movie? Idunno <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

j8hart · Feb 10, 2005

"Wouldn't gavitational effects from other bodies be a factor in 'bringing down' a ring system? Tidal effects would bump up eccentricities of orbits of ring particles. A very low circular orbit wouldn't intersect surface, a very low slightly eccentirc orbit would." Yes, but my concern is that the eccentricities would be 3 dimensional. I.e. by the time the orbits intersect with the surface the distribution of those intersects would be over considerably more than the one and a half degrees of arc covered by the mountains. The ring might start out in the equatorial plain, but as it collapses would it collapse in the equatorial plain? I make it about 1.5 degrees, please excuse me if I’m wrong. But there is also the problem of landslides to consider. I’d say the distribution would have to be well within the 1.5 degrees to form such a sharp ridge.

nexium · Feb 10, 2005

Diamonds are transparent (white in quantity) Radiation disrupts the bonds result in specs of black soot. Likely a few other materials also darken under intence radiation. Silver chloride does, and other chemicals used to make photographs. In the reverse, red phosphorous would likely lighten due to radiation converting it to yellow phosphorous. Neil

vogon13 · Feb 10, 2005

Appreciate input on this, am still pondering your post. Will throw out some ideas and let you mull, too. * Thought of this today: Our moon exhibits a small 'dither' regarding how steadily one face is presented earthward. Astronomers can take advantage of this and photograph 59% of lunar surface from earth. Does Iapetus do this relative to Saturn? I dunno. Suspect enormous number of seemingly bad navigation pictures Cassini is taking of all the moons might be useful in tracking down loose ends in all the satellites orbital calculations. Not sure if libration of Iapetus during ring deposition would produce some kind of detectable trait to ridge structure that could be clincher for proving ring collapse idea. Wish I knew more about nutation and precession, feel these words are significant too. *Orbits of ring particles governed overwhelmingly by gravity of Iapetus. Just no other object nearby except Hyperion and Phoebe and Titan and they don't get very close at all. But unless something interacts with ring, it will stay put (the ring, silly). *If comet Shoemaker / Levi had smacked Saturn instead of Jupiter, would have been neat to watch comet zap holes in rings and then watch holes 'fill in' due to differential rotation effect. Note: hole in ring is about the only effect an object passing through ring would produce (assuming low mass object, not a black hole or something weird like white dwarf star). Incoming debris may have thwapped Iapetan ring too. *Assuming ring came down, and it took a long time (million years?) during that time, Iapetus is going to get thwacked by comets and other debris. If impact is off center (and virtually all impacts will be) Iapetus might have a slight change in the direction its axis points. There being no mechanical connection with the ring system as a whole and Iapetus, the ring system will stay 'fixed' where it is (if it is precessing, librating, nutating or just plain wobbling, I suspect <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Feb 14, 2005

Upon reflection may not have fathomed j8hart completely regarding width of ridge structure and would like to clarify something I'm pretty sure I have incorrect. Inclined structure(s) in a possible Iapetan ring system, when projected onto the surface would not produce a multi-ridged feature. The analog would best be examined by considering the outer ring of Uranus. It is more inclined to the equator of Uranus than the other rings (it is also more eccentric, but that is less important). This outer inclined ring precesses around Uranus. That is, if you were at longitude 120 deg. and saw the outer ring at its most northerly extension, it would not stay there, the highs and lows, so to speak, would slowly move around the planet. I feel an inclined structure in orbit around Iapetus would have a similar precessional path and as (if) it 'came down' would spread to either side of the equator. I believe this is the point j8hart was making and I didn't fathom implication of his remark until today. Excellent point. 'Moving' Iapetus, under the descending ring is how you get the multi ridge characteristic on the surface. Large off center impacts will adjust axis of Iapetus slightly, therefore, equator will move underneath ring as it descends, making the multi ridge feature. The implications of this might be that once fully mapped and understood, the scientists studying this ridge feature should be able to identify specific impact crater(s) on Iapetus surface as having been the specific one(s) that occured during ring collapse and 'adjusted' axis of Iapetus. Big earthquake in Indonesia 'wobbled' earth detectably (changed spin period detectably too) big impact on small body like Iapetus would have similar and/ or bigger effect. Note orbit plane of objeccts around earth did not shift in response to earthquake, they didn't feel ISS move few feet when earthquake hit, ISS crew would have noted even slight perturbation in ISS trrajectory <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

j8hart · Feb 17, 2005

Actually that was not my point, I was thinking more along the lines of what happens to individual particles of ring material as they decay out of the ring. Which you dealt with in your previous post. I agree though, it is an “Excellent point”. Summarising my problems with a decaying ring… A) First you have to have a ring round an object that is 3.1459e-04 Earth masses (I make the gravitational acceleration at the surface about 25cm/s^2, and escape velocity about 600m/s). I have no idea if this is realistic or not, but it does seem from the evidence that ring systems are a feature of much more massive objects. Though I accept that for all I know all the planets and many of the moons in the solar system may have had rings at one point, but only objects of about 10 Earth masses can retain them. B) Following on from A) if it was true that a ring could be sustained long enough to decay to for the mountains then it seams likely that several objects in the solar system would have such an equatorial ridge. Mars, say, for example. It’s about 1e-1 Earth Masses, which makes it about 318 times as massive as Iapetus. If Iapetus once had a ring which collapsed onto its surface, why not Mars? I can think of good reasons for eliminating some objects. For example, I accept that the Earth and the Moon could be eliminated because the mechanics of the Earth/Moon system might rule out a ring forming round either of them or if it did it might make the collapse particularly chaotic. I also accept that the strong tidal effects of the Sun might rule out such a feature on Mercury or Venus. But there are still about 6 objects more massive than Iapetus which we know do not have an equatorial ridge were perhaps we should expect one if a collapsing ring was the explanation. OK not a great argument I’ll admit. C) Lets imagine the ring in place. Suppose it’s in the plain of the equator, and composed of many small objects all on near circular orbits in the same pl

vogon13 · Feb 18, 2005

Possible Mars ring ? I'm salivating. Actually, Martian atmosphere was/is thick enough and minimum Martian orbital velocity high enough to vaporize infalling (possible) ring material. Iapetus seems to be spherical enough, preserves an apparently maximally ancient surface, and has a low enough orbital velocity to allow this admittedly unlikely feature to form. Had our moon a ring at its formation, molten surface conditions probably destroyed every last trace. Also, proximity to earth may have disrupted ring formation process very early in process. Iapetus is uniquely distant from Saturn which I am now starting to realize may be significant. Assuming Mimas ( or better yet, Miranda) to be a coalesced object formed of big chunks, maybe no ring or one that was incorpaorated into object as it coalesced. Enceladus seems to be resurfaced. Tethys seems to have had some geology do something that resulted in that enormous canyon system. Io and Europa seem to be inappropriate places to look for a ring derived ridge. Suspect if Callisto and/or Ganymede had a ring system it would have came down during liquid (molten?) surface epoch. Sorry this is so disjointed, got in late just wanted to get some ideas in to thread for you to consider before I fall asleep. Keep working on this! <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

jmilsom · Feb 18, 2005

I have also been pondering the debate on this thread and have a few points and questions: 1. It seems to me quite probable that the two astounding features on Iapetus are linked. Working with this assumption, the theories that can be applied narrow down considerably. Referring to Alex Blackwell’s early summary of the leading theories, I feel the first (exogenic origin /dust is coming in over a long time) is unlikely as it does not explain the ‘ridge’ feature. 2. Somewhere above (cannot find it now), someone mentioned that the images indicate that the dark material is laid ‘over’ the icy veneer. Is this confirmed now? This obviously writes off the second bunch of theories (asymmetric exogenic influence removes thin ice veneer from leading side) and also the fourth (i.e. endogenic origin / dark material from the interior). 3. I like the idea being explored of ‘accumulated residue of a decayed ring’ first raised by Yurkin and extensively teased out by Vogon13. This fits into the third group of theories (exogenic origin / dust debris originates from a major single event). Specifically theory 3b that the dust debris comes from a collision with Iapetus itself. However, this idea has many flaws as pointed out by j8hart. Personally I favour theory 3c from AlexBlackwell above. I.e. that these features were formed somehow by dust and debris from a collision of an outer Saturnian satellite with a heliocentric object with the result of a retrograde debris cloud crossing Iapetus’ orbit. To form both features, this debris ‘cloud’ would need to be flattened and makes such an impact highly coincidental. Some questions to help my thinking: - Do any moons of the gas giants have observable moonlets? If not, why not? - On a small body, what realistically is the likelihood of ejecta going into orbit after a direct impact? A glancing impact? These questions to me have relevance to Vogon13’s ideas above. - Could a small c <div class="Discussion_UserSignature"> </div>

bokmakierie · Feb 18, 2005

I have this crazy idea that Iapetus is a "siamese twin"! Two moons that have bonded in the dim distant past while they were still in a semi-solid state and colliding at low speed. This would explain the ridge along the equator as well as the differce in appearance of the two halves.

tom_hobbes · Feb 18, 2005

Don't be so silly Bob! It's obviously a die-cast Death Star, that's the welding seam along the middle. <div class="Discussion_UserSignature"> I wish I could remember But my selective memory Won't let me - Mark Oliver Everett </div>

jmilsom · Feb 18, 2005

Ha Ha! I must confess that was the first thought that occurred to me! It is like n old weathered death star. It has a central seam and a large crater in the upper hemisphere that would match the giant laser port! <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

jmilsom · Feb 18, 2005

No post has appeared on any of the boards for the last ten minutes. I cannot resist. This is officially the 10,000th post on the Space Science and Astronomy board! <div class="Discussion_UserSignature"> </div>

vogon13 · Feb 18, 2005

A ring around Saturn distant enough from Saturn to intersect Iapetus' orbit wouldn't form in a collimated enough fashion, nor remain collimated long enough over time to form such a narrow ridge feature as we see on Iapetus, IMHO. Iapetus is around 1500 km in diameter and its orbit radius is 3500000 km. Small target, much space. Now let me hasten to add, debris blasted from Saturn satellites is probably all over Saturn system, I feel that Iapetus does encounter it, but I think the analogy would be closer to earth and how it experiences meteor streams and swarms as it goes around the sun. I do expect Iapetus rover to find materials on Iapetus of external origin, but scattered randomly everywhere. The ring ridge, IMHO, is just overwhelmingly more likely to have formed from a nice tight ring system around Iapetus. Would speculate the mechanism postulated inOdysseus collision that apparently produced earths moon, possible collision object that created Charon around Pluto, was also factor in putting large amount of debris in orbit around Iapetus. In this case, if a satellite formed, it wound up somewhere else in Saturn system, but leftover debris from that event, interacted with itself and settled down into an equatorial ring around Iapetus that then slowly orbitally decayed onto surface of Iapetus. I am considerably less sure about 'staining' of leading hemisphere of Iapetus. Suspect Titan atmosphere derived materials as source, but don't have that same gut feeling as to how it transpired. Have speculated major impacts, as Cassini radar has just revealed, can exceed the Teller treshold for blasting gas from Titan into space. Getting this material (with its tholins, and/ or polymeric orange stuff) to Iapetus is something I don't have a good feel for. Would Saturns magnetotail bathe Iapetus once every 80 days with solar degraded materials escaped from Titan's atmosphere? <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Feb 19, 2005

do any of the moons of..... have observable moonlets? Interesting topic. From large leading hemisphere craters on Mimas, Tethys, and apparently Callisto(Asgard and Valhalla features) we are probably on pretty firm ground regarding co-orbital objects in the past that have been 'snuffed' and of course, objects like Mimas, Tethys and Diones co-orbitals that are still around (is Cassini going to take pix of any of these interesting objects besides Epimetheous?). While not exactly satellites of moons, the orbit sharing (essentially a 1/1 resonance) makes these secondary objects more intimate with their 'host' objects than the run of the mill 'rock in space'. Leading and trailing trojan asteroids of Jupiter have similar orbit sharing properties. Does Jupiter ever snarf one? I dunno, seems likely the occaisional collision or perturbation could mess up orbit enough to drop a Trojan in to Jupiter. Just had a thought. What if Asgard and Valhalla formations are exactly the same age? Binary relationship? Co-orbital sub-moon with a satellite? Weird. I have seen speculation the elongated craters in Martian equatorial region may be from lost 'brothers' (stablemates?) of Phobos and Deimos. As for an actual satellite of a moon around a gas giant, nothing current in the inventory, but I would expect binary captured asteriods in outer realms of satellite systems to be discovered someday, in similar proportion to mainbelt binary asteroids, like Ida and Dactyl. (or Gaspra, you know which one I mean). By way of example, Apollo 16 released a small satellite in low orbit around moon during early seventies, and although on an orbit apparently good enough for a manned capsule, it fell out of orbit in less than 2 months, most likely due to perturbations of earth and sun. My impression is once a probe in lunar orbit looses station keeping ability, its orbit grows more elliptical over time until it clobbers surface. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

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