Approaching Iapetus - what makes it two-faced?

h2ouniverse · Sep 13, 2007

And what if Hyperion was the source, and not a recipient of the dark material? For the canyon: are we sure this is the shadow that we see? not bands of dark material?

3488 · Sep 13, 2007

Hi Joel, AFAIK, Hyperion is not the source. Could be wrong, but it does appear to be contaminents from Titan's atmosphere. The canyon, does look like a real gash. Sure there is darker & lighter material, but it is a real feature. Just wonder what it is? Impact related or internally formed?? Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

h2ouniverse · Sep 13, 2007

Is it parallel to equator or N/S? (theory of equatorial ridge as a structural relaxation)

vogon13 · Sep 13, 2007

Regarding the Iapetan equator, we see two general 'forms', (neglecting crater damage) a highly organized and symmetrical 'wedge ramp' and somewhat disorganized 'piles'. How does this 'jibe' with looking at these forms in regards to emplaced ringage? We can imagine a disorganized 'mess' of debris in orbit about Iapetus as a result of a glancing impactor collapsing to the Laplacian plane. This is established science, Laplace having worked this out a very long time ago. Upon establishment of the planar form of debris in orbit over the equator, the dynamical ring spreading process asserts itself. Again, this is established science, (refer to the Planetary Rings chapter in The New Solar System) angular momentum is transported radially across the breadth of the ring plane by (gentle) collisions amongst the constituent ring particles in adjacent orbits. The effect lowers the low edge of the ring system towards the surface, and lofts the high edge towards the Roche limit. This process is 'slow', however. Iapetus, uniquely isolated among the solar systems major satellites, is well protected against gravitational tidal effects of other bodies, and the longevity of the ring system is assured for long enough such that it evolves to a the final state we see today. Upon commencement of the spreading process, the low edge of the ring system slowly descends towards the surface. A key point to understanding the eventual disposition of these materials, is to understand the amount of contraction of the lowest circle of the ring is much less than the average radius of the ring paricles themselves per orbit. In 2 hours 55 minutes, the drop might be millimeters, but realize the particles size might be 1 meter or more. Now contemplate the ring lowering towards the absolute highest spot along it's equatorial ground track. On a given orbit, a specific particle might clear the high spot by 1 millimeter. In this case, the particl <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>

3488 · Sep 14, 2007

Thank you very much Vogon. I had to read your post a few times to fully understand, but I do get it now. Yes I agree, that the Voyager Mountains are the result of a collapsed ring. I already thought so from the earlier high reso images because. 1). There are many landslides, evidence of accumulation of loose material (rules out cryovolcanisn). 2). Lack of flow like features (many of these images are more than sharp enough to show such features), also consistant with accumulation of loose material. 3). Deep, drilled in craters on the Voyager Mountains, suggesting impactors meeting relatively little resistance on impact. Where as this does not show elsewhere on Iapetus. 4). Also many craters on the flanks of the Voyager Mountains, show signs of slumping, consistant also with slippage of loose material. This has been a most fascinating encounter, one of the major highlights of the entire mission. Iapetus Voyager Mountains 2,519 KM. Iapetus from 39,965 KM. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

anthmartian · Sep 14, 2007

I too totally agree with the collapsed ring theory. It was my favourite explanation pre encounter, and has been reinforced by what we've seen so far. The first thing i thought of when seeing the Voyager Mountains, with their slumped craters, and fine dusty composition, were the views we have seen in the past of Phobos. Which we know to have a thick covering of very fine dusty regolith. http://www.spaceguarduk.com/phobos~1.jpg The large craters on the Voyager's remind me too of Stickney crater on Phobos to look at. Weighing all that up, i tend to agree these mountains are composed of very fine material. <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

tdamskov · Sep 14, 2007

I tend to agree with the ring emplacement theory but I think there are still some issues that need to be ironed out. - The ramp. I can't quite visualize why the material would emplace itself in a ramp and not a fan like structure (facing away from incoming impacts)? As the ring material comes down I imagine it might form a barrier instead, deflecting material along the sides. I'm not saying a ramp isn't plausible but why would the ramp go on for that long instead of a series of smaller piles, and why would it be riddled with craters on the flat top and still have steep, slumped flanks that look like landslides? Particles rolling off the sides of the ramp might do a number of things but I don't see a steep flank as the obvious result. - Why would the ring only touch down at one point? There are many unknowns here and if these orbiting chunks keep bumping each other, many of them should obtain orbits with very different inclinations, particularly when the first particles start to impact. Not sure here. I could be completely off track. It bugs me that we see absolutely no evidence of the ring on the far side of the moon. - At 1500 Km/h, any material touching down at only a few mm/sec might bounce and/or roll quite far, particularly if it has some coherence. The gravity and resulting friction is so low, many particles would simply skip and hit somewhere else. They could for all we know bounce half way around the moon since they're almost at escape velocity to begin with. - On those triangular piles... I'm skeptical that they would immediately form a triangular cross section; the ring should have at least some horizontal width and as the piles build up, a lot of material away from the equator would start hitting the flanks of the piles, then rolling off and forming more of a flat, rounded profile - or a series of humps. At least that's how I visualize it. Complicating the analysis is the heavy cratering that has altered the sh

jaxtraw · Sep 14, 2007

Regarding what the particles might do, it's a pity we don't have a research grant and some facilities. We could do some useful, and fun! experimental studies firing particulates from a "gun" in a vacuum and very low G <img src="/images/icons/smile.gif" />

tdamskov · Sep 14, 2007

I couldn't agree more <img src="/images/icons/smile.gif" />

brellis · Sep 14, 2007

Could be a Cool thing to do on or from ISS <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

lysol · Sep 14, 2007

Im letting my imagination run wild here. And the first thing that came to mind is it's a space ship. I mean, its orbit is all funky compared to the other moons. Certain symmetry to it is weird like the ridge. No way could that be from rings "falling". that ridge is nearly straight freaking up. And plus i doubt there isnt even enough of a gravitational pull to hold those rings it its gravity well in the event of a collision in the first place. So I think its a space ship. Its hollow inside...and whatever atmosphere there was, had a blow out somewhere at the surface...and that white stuff is the water vapor that turned to snow.

MeteorWayne · Sep 14, 2007

That's just plain silly. It's not hollow, otherwise it wouldn't be as massive as it is. Please descibe how it's orbit is "funky" The symmetry of the ridge has two possible mechanisms that both can make sense, either a collapsed ring, or extrusion from a shrinking moon; from the observations, the collapsed rig is in the lead right now. If you wish to speculate on it being a space ship, please start a thread in Phenomena, where such a discussion belongs. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

tdamskov · Sep 14, 2007

I was actually going to make a tongue-in-cheek remark on his post, then changed my mind to an extremely sarcastic one and finally realized that responding to such a load of rubbish was just a waste of time.. <img src="/images/icons/smile.gif" /> I'm still astounded at the images sent from Iapetus. Almost impossible to believe that such an insignificant object could be so interesting!

anthmartian · Sep 14, 2007

tdamskov, you're absolutely right. It takes me back to the Voyager encounters. it was the planets we were all excited about seeing. In many cases the moons were far more exciting and interesting. The Voyager's instantly made the solar system a bigger more fascinating place with each planetary encounter. Now, probes such as Cassini carry on that tradition, building on the excitement. The more we see, the more questions we have, the more we want to know. That thrills me! Iapetus has thrilled me this week, that's for sure! <img src="/images/icons/smile.gif" /> I know whats coming with every event, in as much as i am going to be astounded, that makes the anticipation and the revelations of each fly past as thrilling as the complete surprise's delivered to us by Voyager's 1 and 2. <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

3488 · Sep 14, 2007

Hi MeteorWayne, Thanks for rebutting that troll post. I do not feel well enough right now to be bothered to rebutt it myself. A couple of days ago, my health took a sudden dive (although I am OK now, just a bit shaken up by it) & can just do without nonsense like that appearing on what is undoubtably, one of the best threads ever to appear on SDC. Anyhow, back on topic, I quite like this one Iapetus from 39,263 KM. I have reduced the brightness, but increased the contrast, to bring out detail in the white terrain on this dappled part of Iapetus. The white area is far from smooth & appears to have a rippling effect, that is not normally visible on the regular images. I am awaiting the gravity data with a lot of interest. Iapetus is obviously slightly out of round, even without the Voyager Mountains. Its average shape appears to be 1,467 KM / 912 miles across the equator & 1,440 KM / 895 miles through the poles. The gravity data will be very interesting. Cassini passed close enough to get a handle on whether or not Iapetus is differentated (has a core, mantle & crust) or is a homogenous mix of ice & rock. Also the SAR image swathe will be good to see also, along with the multispectral images & readings when that is released. Hi tdamskov, I would like to say a big thank you to you for your excellent animation of the Voyager Mountains. You animation of the Cassini images, shows how the shape & altitude of those mountains change with longitude. I will be watching your movie many times, to see what I can fathom out. I have reposted your link here, as your original post is now a few pages back & may get missed by other readers. http://www.td4.dk/space/Ia</safety_wrapper <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

jaxtraw · Sep 14, 2007

I just can't get past the sharp distinction between black and white on this surface. It can't be any kind of drifting dust, can it?

anthmartian · Sep 15, 2007

jaxtraw : I know the best, closest most interesting images of places on Iapetus where we see white and dark are from around 7,000 km. Not the closest during the encounter. But i agree, the borders between the light and dark look very defined, from that distance at least. I suppose true "drifting" would imply it has taken place in a significant atmosphere. But, we have seen streaks of material settling on the ground at places like Triton ( from the geysers there ) . Our views may be tainted by images from the MRO, where we see dark wind blown material over another type of surface. Of course, we cannot get that here. Another place i have seen one colour ontop of another is on our Moon, in features such as the rays from the crater Tycho. But, in that case of course this was due to an impact. I do not know how things would play out in a vacuum, in very low G regarding a material settling on the surface without any dramatic event like a geyser or impact effecting it. Way back in this topic, i noticed some of the early views of the white material reminded me of pictures from Earth of glacier fields taken from orbit. It just gave that impression of a sharply defined edge of material moving across a landscape as a glacier would. http://anthmartian.googlepages.com/white-on-dark.jpg/white-on-dark-full.jpg So far. From what i have observed from imagery, and from what i have read here. I believe, the Voyager mountains are caused by a collapsed ring. That also provided the dark carbonaceous / organic material seen today on the moon. I support the ideas put forward here that the ring material has spread over the moon over a long period due to impacts on the Voyager mountains, spreading this fine dusty dark material all over. Could the white be a recycled version of the original Iapetus surface? This was a regular <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

vogon13 · Sep 15, 2007

I tend to agree with the ring emplacement theory but I think there are still some issues that need to be ironed out. - The ramp. I can't quite visualize why the material would emplace itself in a ramp and not a fan like structure (facing away from incoming impacts)? As the ring material comes down I imagine it might form a barrier instead, deflecting material along the sides. I'm not saying a ramp isn't plausible but why would the ramp go on for that long instead of a series of smaller piles, and why would it be riddled with craters on the flat top and still have steep, slumped flanks that look like landslides? Particles rolling off the sides of the ramp might do a number of things but I don't see a steep flank as the obvious result. Our experience with things 'splatting' are all influenced by our having grown up in an atmosphere. The ringage particles emplacing on Iapetus did so in a vacuum, and we are looking at an almost entirely ballistic phenomena as a result. Having said that, there is a slight north/south (horizontal) dispersion to the resulting debris generated at the trifurcation point. We see the effects of this in the slight but steady relaxation of the angle of repose of the sides of the ridge as we travel towards the short end, and additionally, in the north/south (horizontal) dispersion of the emplaced materials in the Voyager Mountains region. - Why would the ring only touch down at one point? There are many unknowns here and if these orbiting chunks keep bumping each other, many of them should obtain orbits with very different inclinations, particularly when the first particles start to impact. Not sure here. I could be completely off track. It bugs me that we see absolutely no evidence of the ring on the far side of the moon. The collapse of a variously randomly inclined orbiting debris cloud to a tight planar form over the equator is established science, Laplace having wor <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 · Sep 15, 2007

I would like to present a case for revisiting Iapetus during the Cassinin extended mission. The 'tiger scratches' appear to me to be a new kind of feature, something we have not seen elsewhere in the solar system. (I am of the opinion the 'tiger stripes' of Enceladus, while unique, are unrelated) Their enormous size, and their 'chasmatic' form are intriguing. I note an apparent radial orientation to 'Joan' (aka, Landslide Crater) and also proximity to 'Joan'. I am finding it suggestive that the 'scratches' are resultant of compression of deep Iapetan materials in the same direction of the flight path of the impactor that formed 'Joan'. These materials, finding no other release for those compression forces, have bulged upward and fractured the overlying surface materials. We have noted other clues around Iapetus that it is unusually rigid, and has been rigid for an apparent uniquely long interval. We might be seeing another indication of that rigidity here. These scratches, chasms actually, might be the deepest 'cracks' (as a percentage of the radius of the object) in a solar system body we will ever find. High resolution imagery of the sides and depths of these features can potentially give us a look at materials we might not be able to study for centuries. Additionally, if UV scans, or radar, or any other instrument on Cassini can be used productively here, they should be. Illumination angles and space craft viewing angles will be critically important here. I realize an additional flyby of Iapetus is 'iffy' at best, and designing a flyby to optimize study of this feature makes that even more difficult to accomplish, however, the uniqueness of this feature make for a particularly strong case in reviewing the Cassini extended mission for possible encounter opprotunities. <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>

spin0 · Sep 16, 2007

Hi all, I downloaded all Cassini's raw images and compiled a Iapetus flyby-video of them. I did use artistic licence and changed a bit the order of images to get more fluid motion (eg. mountain ridge & Voyager mountains). It gives you an idea where all the images were taken and how they link to each other. And it looks quite cool <img src="/images/icons/cool.gif" /> Link to the video: http://www.youtube.com/watch?v=baaGOqIJaFM And here's a downloadable hi-res (500x500) version: http://files-upload.com/files/502810/Iapetus-divx6.avi BTW, my first post - just joined the forum. <img src="/images/icons/smile.gif" /> I also made some interesting mosaics of the transition zone between dark and light sides of Iapetus. But they're quite large, should I post them to the forum? <div class="Discussion_UserSignature"> </div>

anthmartian · Sep 16, 2007

spin0 : welcome. <img src="/images/icons/smile.gif" /> I am at this moment making a video of the encounter. May i use your clip on that project? Which will be full DVD res when complete? Also if you would like to contribute to anything like that i am involved in an ongoing DVD project with other members here. You can post here, or PM here if you are interested. Ok, back to the theories.... Does nobody here support the rapid cooling theory for the Voyager Mountains? Iapetus's fast rotation and extreme heat causing the equatorial bulge? it has been modelled, and from what i believe as long as isotopes ( aluminum-26 and iron-60 ) were present, which have a short life span geologically speaking, the model does work, and fit. These isotopes produce extreme heat, but when they ran out of life this would have lead to a very fast freezing of Iapetus. basically, the moon would have been frozen in the shape we see it now, literally frozen in the shape of its primordial form. http://solarsystem.nasa.gov/news/display.cfm?News_ID=22235 <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

spin0 · Sep 16, 2007

<blockquote>In reply to:<hr />spin0 : welcome. I am at this moment making a video of the encounter. May i use your clip on that project? Which will be full DVD res when complete? Also if you would like to contribute to anything like that i am involved in an ongoing DVD project with other members here. You can post here, or PM here if you are interested. <hr /></blockquote> Thank you. Yes, feel free to use my flyby-clip. The credit of the images belong to assosiated space agencies, I only put them together. And yes, I'm very much interested in contributing to the project, I'll PM. BTW: Your site is amazing! Thants! <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

3488 · Sep 16, 2007

I too Vogon. Lets see what I can do. I too would love to see another super close approach to Iapetus. Anyway, I have cropped & enlarged a portion of the Voyager Mountains shot from 2,519 KM. A BIG image. 4.3 MB. A much smaller 48 KB image here. This is becoming more & more compelling that the Voyager Mountains are made of very loose material. The profiles are extremely smooth (probably age related also, like the Lunar Mountains), deep drilled, slumping craters & landslips. Also the large crater on the mountain clearly displays streaking. I agree, Iapetus itself is solid. Frozen very hard indeed. No evidence of ANY cryovolcanism whatsoever. Difficult to say, if Iapetus has never had, or all evidence has been destroyed by subsequent cratering. What ever, Iapetus has been inactive for at least 4GY IMO. Just awaiting the gravity data, which will give some insight as to whether or not Iapetus is a diffrentiated object, with a core, mantle & crust, or is a homegenous mix of ice & rock. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

3488 · Sep 16, 2007

Hi Anthmartian, I think the problem is, would Iapetus have gathered enough of these isotopes to enable the heating required. Also the Voyager Mountains, appear to be made of loose material. If the Voyager Mountains, were indeed compressional, due to a rapidly rotating young Iapetus, which froze in its youth, would have the same enormous structural strength as the surrounding surface, The evidence is apparent for that strength in the crust of Iapetus, wide, shallow craters, terracing, etc, but the Voyager Mountains are a tall pile of loose rubble. Why that discrepancy? Just my thoughts with the evidence thus far gathered. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

anthmartian · Sep 16, 2007

Andrew, i am a subscriber to the collapsed ring theory. I feel if the mountains were to have been turned into loose, fine material by erosion due to impacts, there would be nothing left of them. It seems logical to me that they were constructed of this material from the word go. I am just putting the alternatives out there. *L* Although i believe this alternative was in favour, pre Encounter on Sept 10th, not after. Due to evidence seen in images. But apparently those isotopes has been found in many asteroids. <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

Approaching Iapetus - what makes it two-faced?

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