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On a ring origin of the equatorial ridge of Iapetus
Guest_AlexBlackwell_*
post Aug 29 2006, 06:18 PM
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Wing Ip just had an interesting Iapetus-related paper published in GRL.
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ngunn
post Sep 10 2006, 08:05 PM
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So much to reply to (no, it isn't driving me to distraction - far from it) - but only a few minutes available. On no ridge rings on Pluto or Charon - I agree, unfortunately, but there's always an outside chance since we don't really know their histories. Anyhow Pluto will get one when Charon disintigrates. smile.gif

On the intimate details of ring emplacement - very good, I'm almost buying it. However I don't think the basic thesis would be under serious threat even if your details turn out to be wrong.

I'm going to go away and extend my d cubed times m over M table to some more objects, like Ceres and the moons of Uranus. Will post anything interesting I find.
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tasp
post Sep 11 2006, 02:42 AM
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QUOTE (ngunn @ Sep 10 2006, 03:05 PM) *
On the intimate details of ring emplacement - very good, I'm almost buying it. However I don't think the basic thesis would be under serious threat even if your details turn out to be wrong.



I don't know how thoroughly I have cosidered this topic (I don't know what I don't know, after all) but I have gone over quite a few variations of all this.

Before I encountered and understood the differential ring spreading process as outlined in the New Solar System book, I labored trying to figure out a mechanism to get the ring down on the surface of Iapetus. I considered Iapetus' remoteness from perturbing bodies to imply an extremely long lived ring system. Cool if we want to see one in this epoch, but it doesn't help explain the pictures we have now. I put a great deal of effort into establishing that Iapetus is not to far off the mark from Triton and Pluto to have had an extremely tenuous atmosphere eons ago when the sun was somewhat dimmer. The atmospheric drag emplaced the ring. Unfortunately, that generates a feature that doesn't look like the ridge system on Iapetus.

I have also spent time gyrating the center of mass of Iapetus during the ring emplacement. I get thinking of precessing the axis of a gyroscope as analogous to Iapetus unbalancing during emplacement. The ring system just isn't massive enough, and/or emplaced quickly enough to do anything bizarre to the Iapetan spin axis. While interesting to think about, it doesn't really help us understand how the ring descended and emplaced the ridge structure.

I do have some technical trades backgrounds, and frequently thought of lathes, specifically, machining the inside of a cylindrical piece of metal. Interesting analogy, but tough to explain on a messageboard.

The diverging attendent ridges I consider to be the 'brass ring' here. Explain them, and you have the whole thing nailed down air tight. Realizing that inclined structures in the ring could emplace just like that, and alternatively, that Iapetus could have it's spin axis deflected by a few degrees during emplacement (perhaps by a big impactor) and generate the exact same feature again was fun.

The ring idea seems to tell all actually.

The ring particles actually orbited in the same direction as the ridge tapers downward. (Assuming the pics aren't inverted and I understand the orientation of everything here, as seen on the map earlier in this thread, from left to right)

It would have been possible, and perfectly safe, to stand directly beneath the ring during emplacement in what I call landslide basin. One could have actually approached the ring fairly closely from the sides too, but having meter sized boulders whizzing past your face at just under 1000 MPH would have been a bit scary. Even discerning motion in the ring system would have been difficult from far enough away for the unaided human eye.

I am thinking the rings were white, or light colored. And the fine grooving we see in Saturn's rings would have been greatly diminished here, or absent entirely. Having the inner edge of the ring descending so low to the surface (no corresponding dusky ring analog here) would have presented a very different appearance from Saturn's rings. (and to my aesthetics, less visually appealing, they would not seem to be floating above the moon, but rather resting upon it).


Due to the pretty intense 'meat grinder' effect of lofting the materials in the first place, then collapsing to the Laplacian plane, followed by the incessant bump and grind of the dynamical ring spreading process, I suspect the ring particles to have been pretty uniform size wise, although I don't know if we are talking walnut sized chunks or Volkswagen sized chunks.

The upper edge of the ring, I feel, was rather constrained at or near the Roche limit. Drag forces would have always been sapping energy from the ring system, and the ring spreading process would have worked primarily on the low side of the ring, not the top. We wouldn't have seen any little moons spun off the high side. And as it follows, the entire ring system would have eventually emplacedonto the Iapetan surface.


The absolute fastest the ring system could have emplaced, would, I feel, be in the hundreds of years range. There are some formulas for figuring ring spreading speed, but I will let others chew numbers for this. Heck, an upper limit for ring emplacement time might be up to many thousands of years, but not millions. That some 'straggler' chunks in the ring plane might have persisted for longer periods isn't too important, this all happened billions of years ago (no I am not going to do crater counts to calculate surface ages, either) anyhow, and are nowhere near as interesting as the main phase of the emplacement process.


What a fun moon this has turned out to be. Hope Allen gets lucky and photographs some especially weird and bizarre Kuiper belt objects!
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Posts in this topic
- AlexBlackwell   On a ring origin of the equatorial ridge of Iapetus   Aug 29 2006, 06:18 PM
- - volcanopele   okay, now a ring around Iaptetus is an interesting...   Aug 29 2006, 06:20 PM
- - AlexBlackwell   Here's an interesting passage from the conclud...   Aug 29 2006, 06:25 PM
- - Michael Capobianco   Does the paper address why the equatorial ridge do...   Aug 29 2006, 06:40 PM
|- - David   QUOTE (Michael Capobianco @ Aug 29 2006, 06...   Aug 29 2006, 07:05 PM
|- - Decepticon   QUOTE (Michael Capobianco @ Aug 29 2006, 02...   Aug 29 2006, 11:56 PM
|- - JRehling   Roughly speaking, I guess the fact that the ridge ...   Aug 30 2006, 01:07 AM
- - jsheff   Would this process also explain the albedo assymet...   Aug 29 2006, 07:06 PM
|- - tasp   QUOTE (jsheff @ Aug 29 2006, 02:06 PM) Wo...   Sep 10 2006, 01:35 AM
- - AlexBlackwell   QUOTE (Michael Capobianco @ Aug 29 2006, 08...   Aug 29 2006, 07:44 PM
- - tasp   An object skimming the surface of Iapetus will hav...   Aug 30 2006, 05:11 AM
- - AlexBlackwell   There was a brief blurb about this paper yesterday...   Aug 30 2006, 07:53 PM
- - Rob Pinnegar   I guess this idea probably originated with those i...   Aug 30 2006, 09:41 PM
|- - tasp   QUOTE (Rob Pinnegar @ Aug 30 2006, 04:41 ...   Aug 30 2006, 11:29 PM
- - dvandorn   Does Iapetus' ridge have to have been created ...   Aug 31 2006, 12:04 AM
|- - tasp   Maintaining focus (or collimation) of the strand ...   Aug 31 2006, 03:02 AM
|- - David   I think I understand the idea to be one of a low-v...   Aug 31 2006, 07:23 AM
- - ngunn   Under the scenario proposed I would expect volatil...   Aug 31 2006, 10:00 AM
|- - ugordan   QUOTE (ngunn @ Aug 31 2006, 11:00 AM) Cou...   Aug 31 2006, 11:18 AM
|- - ngunn   QUOTE (ugordan @ Aug 31 2006, 12:18 PM) M...   Aug 31 2006, 11:50 AM
|- - ugordan   The point I was trying to make is the greatest tem...   Aug 31 2006, 12:08 PM
|- - ngunn   QUOTE (ugordan @ Aug 31 2006, 01:08 PM) A...   Aug 31 2006, 12:38 PM
- - ngunn   One other point - the 'catastrophic atmosphere...   Aug 31 2006, 01:06 PM
- - tasp   Invoking an atmosphere above a certain very low de...   Aug 31 2006, 01:27 PM
|- - ngunn   QUOTE (tasp @ Aug 31 2006, 02:27 PM) Invo...   Aug 31 2006, 02:01 PM
|- - The Messenger   QUOTE (tasp @ Aug 31 2006, 07:27 AM) I al...   Sep 3 2006, 11:22 PM
|- - ngunn   QUOTE (The Messenger @ Sep 4 2006, 12:22 ...   Sep 4 2006, 10:13 AM
||- - The Messenger   QUOTE (ngunn @ Sep 4 2006, 04:13 AM) Why?...   Sep 6 2006, 03:21 AM
||- - ngunn   QUOTE (The Messenger @ Sep 6 2006, 04:21 ...   Sep 6 2006, 08:15 AM
|||- - JRehling   A comment on followup missions: Whatever future mi...   Sep 6 2006, 12:02 PM
|||- - ugordan   QUOTE (JRehling @ Sep 6 2006, 01:02 PM) A...   Sep 6 2006, 12:29 PM
|||- - mchan   QUOTE (ugordan @ Sep 6 2006, 05:29 AM) Tr...   Sep 6 2006, 11:15 PM
|||- - ugordan   QUOTE (mchan @ Sep 7 2006, 12:15 AM) I do...   Sep 7 2006, 06:58 AM
||- - TritonAntares   Hi, let us anticipate the equatorial ridge was bui...   Sep 6 2006, 08:51 AM
||- - ugordan   The ridge is ancient which means the ring is also ...   Sep 6 2006, 09:03 AM
|||- - ngunn   QUOTE (ugordan @ Sep 6 2006, 10:03 AM) Pe...   Sep 6 2006, 12:41 PM
||- - ngunn   QUOTE (TritonAntares @ Sep 6 2006, 09:51 ...   Sep 6 2006, 09:05 AM
||- - tasp   QUOTE (TritonAntares @ Sep 6 2006, 03:51 ...   Sep 9 2006, 02:32 PM
|- - JRehling   QUOTE (The Messenger @ Sep 3 2006, 04:22 ...   Sep 5 2006, 04:44 PM
- - tasp   And this, consider the oblique impactor that may h...   Aug 31 2006, 01:33 PM
- - ngunn   Note the following sentence already quoted by Alex...   Aug 31 2006, 02:52 PM
- - tasp   I am having trouble seeing how the precipitating l...   Aug 31 2006, 03:56 PM
- - Rob Pinnegar   You mention "attendant ridges". This was...   Aug 31 2006, 05:20 PM
- - ngunn   On multiple ridges - perhaps the emplacement of th...   Sep 1 2006, 11:26 AM
- - tasp   I admit a certain favoring of an oblique impact kn...   Sep 1 2006, 01:45 PM
- - ngunn   This discussion has become really interesting. I...   Sep 1 2006, 02:52 PM
- - ngunn   Just found John Rehling's rather nice diagram ...   Sep 4 2006, 01:49 PM
|- - TritonAntares   Hi, I've just been back from a 1-week-vacation...   Sep 5 2006, 10:27 AM
- - ngunn   I did ask the other day for someone to re-post an ...   Sep 6 2006, 02:08 PM
|- - ugordan   QUOTE (ngunn @ Sep 6 2006, 03:08 PM) I di...   Sep 6 2006, 02:15 PM
- - djellison   Links to that place are not a good idea. Can peop...   Sep 6 2006, 02:13 PM
|- - ngunn   QUOTE (djellison @ Sep 6 2006, 03:13 PM) ...   Sep 6 2006, 02:31 PM
|- - Themisto   QUOTE (ngunn @ Sep 6 2006, 04:31 PM) Sorr...   Sep 6 2006, 03:06 PM
- - djellison   That's better We used to worry about mention...   Sep 6 2006, 03:10 PM
- - ngunn   OK let's see if this works.. http://www.aaw-d...   Sep 6 2006, 03:45 PM
- - tasp   3 intersecting ridges, all describing segments of ...   Sep 6 2006, 06:47 PM
|- - ngunn   QUOTE (tasp @ Sep 6 2006, 07:47 PM) The f...   Sep 7 2006, 08:51 AM
- - tasp   Some of the criteria that seem to be needed for us...   Sep 7 2006, 02:58 PM
|- - ngunn   QUOTE (tasp @ Sep 7 2006, 03:58 PM) Some ...   Sep 7 2006, 03:45 PM
- - tasp   We may find Iapetan like ridge structures on a per...   Sep 7 2006, 03:03 PM
|- - TritonAntares   Hi, before we should keep on speculating whether t...   Sep 7 2006, 03:50 PM
|- - ngunn   QUOTE (TritonAntares @ Sep 7 2006, 04:50 ...   Sep 8 2006, 10:44 AM
|- - ugordan   I have absolutely no idea on which internal proces...   Sep 8 2006, 11:05 AM
||- - ngunn   QUOTE (ugordan @ Sep 8 2006, 12:05 PM) I ...   Sep 8 2006, 12:04 PM
|||- - ugordan   QUOTE (ngunn @ Sep 8 2006, 01:04 PM) On g...   Sep 8 2006, 12:25 PM
|||- - ngunn   QUOTE (ugordan @ Sep 8 2006, 01:25 PM) It...   Sep 8 2006, 12:45 PM
|||- - ugordan   Yeah, but why would it flatten itself along the eq...   Sep 8 2006, 12:50 PM
||- - Rob Pinnegar   Two things today: QUOTE (ugordan @ Sep 8 200...   Sep 8 2006, 01:56 PM
|- - ynyralmaen   QUOTE (ngunn @ Sep 8 2006, 12:44 PM) So, ...   Sep 8 2006, 11:34 AM
||- - ngunn   QUOTE (ynyralmaen @ Sep 8 2006, 12:34 PM)...   Sep 8 2006, 12:12 PM
|- - tasp   QUOTE (ngunn @ Sep 8 2006, 05:44 AM) So, ...   Sep 8 2006, 01:33 PM
- - Bill Harris   This has been a fascinating discussion. Before Ca...   Sep 8 2006, 12:56 PM
- - ngunn   Hello Bill - nice to know it's not just the 4 ...   Sep 8 2006, 01:18 PM
|- - tasp   QUOTE (ngunn @ Sep 8 2006, 08:18 AM) Hell...   Sep 8 2006, 01:40 PM
- - tasp   Some where here at UMSF is a nice map of Iapetus (...   Sep 8 2006, 02:27 PM
- - tasp   I will note that Iapetus is subject to the smalles...   Sep 8 2006, 02:30 PM
|- - ugordan   However, the surface gravity at Iapetus is also va...   Sep 8 2006, 02:38 PM
- - tasp   I also point out that the New Solar System books...   Sep 8 2006, 02:36 PM
- - tasp   Virtually all solar system objects are believed to...   Sep 8 2006, 02:52 PM
- - ngunn   Is this the one? http://photojournal.jpl.nasa.gov/...   Sep 8 2006, 02:54 PM
|- - tasp   QUOTE (ngunn @ Sep 8 2006, 09:54 AM) Is t...   Sep 8 2006, 02:59 PM
|- - ugordan   Iapetus is undeniably oblate, but the question is ...   Sep 8 2006, 03:04 PM
|- - tasp   QUOTE (ugordan @ Sep 8 2006, 10:04 AM) Ia...   Sep 9 2006, 05:31 AM
- - hendric   I still don't see how the two divergent ridges...   Sep 8 2006, 05:54 PM
|- - TritonAntares   QUOTE 37th DPS Meeting, 4-9 September 2005 Session...   Sep 8 2006, 08:29 PM
||- - tasp   QUOTE (TritonAntares @ Sep 8 2006, 03:29 ...   Sep 9 2006, 05:28 AM
||- - ngunn   QUOTE (TritonAntares @ Sep 8 2006, 09:29 ...   Sep 9 2006, 08:59 AM
||- - tasp   QUOTE (ngunn @ Sep 9 2006, 03:59 AM) . . ...   Sep 9 2006, 01:56 PM
||- - ngunn   QUOTE (tasp @ Sep 9 2006, 02:56 PM) I hav...   Sep 9 2006, 09:56 PM
|- - tasp   QUOTE (hendric @ Sep 8 2006, 12:54 PM) I ...   Sep 9 2006, 05:10 AM
- - tasp   Also, check out the big elongated crater at 0 to 3...   Sep 9 2006, 05:35 AM
- - tasp   Just noticed I did not address moonlets below sync...   Sep 9 2006, 09:00 PM
- - tasp   I am thinking we aren't going to see an Iapeta...   Sep 10 2006, 01:00 AM
- - tasp   Speaking of New Horizons, how far out can it produ...   Sep 10 2006, 01:11 AM
- - tasp   Regarding perturbations of a possible Iapetan ring...   Sep 10 2006, 05:08 PM
- - Michael Capobianco   Well, I'm still a bit skeptical as well. For o...   Sep 10 2006, 05:18 PM
- - tasp   Of course, the most interesting bit of the ridge s...   Sep 10 2006, 06:00 PM
- - ngunn   So much to reply to (no, it isn't driving me t...   Sep 10 2006, 08:05 PM
- - tasp   QUOTE (ngunn @ Sep 10 2006, 03:05 PM) On ...   Sep 11 2006, 02:42 AM
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