Iapetus, ring-thief?

The Cassini-Huygens spacecraft sent pics of the odd place, Iapetus. There was a pic last year that showed some odd, equatorial mountains on its far side, and the new set shows there's an equatorial ridge that wraps around at least half the moon. Here's a view:

My idea is that this is a record of an ancient ring-eating event. The scientists are arguing over whether this is a chain of volcanoes, or compression fractures. Someone on the team will propose its ring emplaced, you watch. How tall is the ridge? It has been reported to be 20km high, on a worldlet only 1400km in diameter. If you stood on top of this ridge, you'd see the curvature of Iapetus. You'd be able to look out over 75,000 square km, about 150km in all directions. Something the same proportions on the Earth would be 180km tall (roughly 115 miles, or more than 40 miles higher than SS1's hop).

If there were Saturnian Rings as far out as Iapetus' orbit, they'd be enormous. Viewed from Earth, they would have been about 2/3 the width of our moon's diameter.