Oh, duh. I guess I didn't read Emily's latest post carefully enough.

They look like portholes to me. Ancient starship.

It also occurs to me that the settling event that formed the ridge might also have produced parallel features nearby. I'm sure we'll have better data soon; the most likely explanation is "coincidence".

Hey, it just occurred to me that this could be a ring scar! Is Iapetus geometrically in the ring plane? How thick are the rings compared to the diameter of the moon?