While I can't answer your question, a broader search for "polygonal cratering" and the like came up with several papers mentioning numerous polygonal craters (including but not limited to the hex) on Mercury, Venus, Mars, Luna and other moons, and Earth (possibly most discernible being the 4-sided Barringer's Crater aka Meteor Crater in Arizona). And, of course, there are the dynamic pentagonal/hexagonal polar forms such as on Saturn. Unfortunately, most of the papers that I browsed through didn't have pictures and were mostly concerned with conventional geophysical type explanations of the phenomenon, i.e. impact, vulcanism, etc.redeye wrote: If the hexagonal craters on Iapetus are formed by instabilities in the plasma stream that laid down the crater in the first place, why do we not see more of these formations in our solar system? Apart from one or two on our own moon I have been unable to find any others.