Iapetean geoid, Sea level Options

[Rob Pinnegar]

There's been a fair amount of speculation that Iapetus' despinning, from its initial rapidly-rotating configuration to its current tidally-locked one, might have taken a long time, and that Iapetus might be the only major Saturnian moon that froze *before* it was despun. This has been presented as a possible explanation for Iapetus' strange shape.

Well, there are at least two huge basins on Iapetus that, while rugged, have relatively flat floors: the big one in Cassini Regio that faces Saturn, and the one in the southern part of Roncevaux Terra. Has anyone checked to see whether the "best fits" to the shapes of these basin floors match the curvatures of surrounding parts of the moon? If either of those basins formed before Iapetus was completely despun, their shapes might match some ancient Iapetean geoid, not the current one (some allowance for "slump" would be necessary here).

Given the bashed-up state of the basins, Iapetus' crazy shape, and our very incomplete knowledge of its gravitational field, I don't know whether this would even be possible. It might be worth a look, though.