Did a giant impact and a crashing submoon form the bizarre ridge around Iapetus?

Of all the weird things we've seen in our solar system — and it's a long list — I think near the top would be the bizarre and very large ridge of mountains stretching all the way around Saturn's moon Iapetus.

And I do mean bizarre. It wraps around the moon's equator, is nearly continuous, and is punctuated by individual peaks some of which are 20 kilometers high! That's over twice as tall as Mt. Everest. And it's wide, too, in some places about 200 kilometers across. Images of the ridge from th...