Iapetus was the location of the Second Monolith in novelization of 2001: A Space Odyssey
Clarke even got right the large circular feature on the moon, plus the fact that Saturn's rings were made up of many rings like a phonograph record, not just a few sections as believed in 1968.
Clarke also hinted that Iapetus was so strongly dark and light because the Monolith ETI made it that way to serve as a beacon of sorts for the day humanity could travel in space.
Food for thought. Maybe we need a dedicated Iapetus mission too.