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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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hendric
post Sep 8 2006, 05:54 PM
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I still don't see how the two divergent ridges get created by a decaying ring. The orbital speed of the ring at low altitude would not be the same as the rotational velocity of a proto-Iapetus. So, how do the angled ridges get created?? If the ring was at an angle to Iapetus, as it descended it would not stay above a single location.

I favor a tectonic explaination. We have symmetrical ridges here on Earth due to seafloor spreading. Seems like a reasonable explaination to me. The question would be why would there be a single crack along a great circle? Maybe Iapetus had a Europa-like episode with a shallow ocean, and as it slowly froze it expanded/contracted enough to crack open. Without nearby moons and tides, the crack went around the planet symmetrically.


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tasp
post Sep 9 2006, 05:10 AM
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QUOTE (hendric @ Sep 8 2006, 12:54 PM) *
I still don't see how the two divergent ridges get created by a decaying ring. The orbital speed of the ring at low altitude would not be the same as the rotational velocity of a proto-Iapetus. So, how do the angled ridges get created?? If the ring was at an angle to Iapetus, as it descended it would not stay above a single location.



The single location is the highest spot along the Iapetan equator. That is what synchronizes the emplacement of the diverging features.

For every rotation of Iapetus, the highest spot along the Iapetan equator penetrates the ring plane twice. Once as it crosses from north to south, and again 180 degrees later when the high spot penetrates the ring plane crossing from south to north.

The lowest edge of the ring descends (via the 'bump' or dynamical ring spreading process) during the interval the high spot is not in the ring plane. As the highest spot passes through the ring plane, the chunks comprising the low edge of the ring impact the high spot, making it higher. The 'spray' from the impact interacts with materials still in orbit immediately above the high spot, decelerating them, and causing them to contact the surface downrange of the highspot, along the ground track of the ring at that time. This also explains why all three ridges taper downward from the high end.

That's why the 2 diverging attendent ridges are identical (less subsequent cratering damage), and are 'keyed' to the highest spot along the equator.


Note: inclined features in the ring or a small shift in the spin axis of Iapetus during emplacement will produce the same result, 2 diverging attendent ridges. I am not sure how to distinguish between shifting the axis of Iapetus a few degrees and inclined features in the ring. I think the 2 causes will produce identical features.

I cannot imagine an internal process that can create perfectly matched attendant ridges to the main ridge structure as elegantly as the emplacing ring with either an inclined element, or a small shift of the Iapetan spin axis during the emplacement.



I also note, it appears to my inexperience eye that the high end of the ridge structure is antipodal to the sub-Saturn point of Iapetus. Is the ridge structure massive enough to be the deciding factor in aligning Iapetus to Saturn? (as mass distribution in earth's moon does to earth?)



Does anyone with more computer graphics savy than me (that would be everyone else) want to take a stab at modeling this process for all to see?
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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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