On a ring origin of the equatorial ridge of Iapetus Options

[Guest_AlexBlackwell_*]

Wing Ip just had an interesting Iapetus-related paper published in GRL.

[tasp]

3 intersecting ridges, all describing segments of great circles about Iapetus.

Not to belabor the point, but there is not an internal geological process that gives a whit about great circles configured this way. The feature 'shouts' external orbital causation. Consider precession of the rotation axis of Iapetus (or inclined structures in orbit above), syncronization of the deposition process as the highest spot on the equator passes through the ring plane twice per rotation. The ground track per the relevant orientations of the ring, equator, highest spot along the equator, and precession (or inclined structure) is where the ring emplaces.

{Sorry for the crappy diagram}

---<-----

[ngunn]

The feature 'shouts' external orbital causation.

Absolutely, and this is the central wonderful realisation which should set us looking for similar structures elsewhere. The detailed argument beyond that point though: it's plausible but do you really think it's conclusive, case closed? I think that's claiming too much.

Incidentally on the search for similar structures - I don't just mean ridges. More generally we should look out for distinctive equatorial topography of any kind that might have had a ring origin. The specific type of formation will depend on circumstantial details of the process but great circles will be the giveaway.