By Ron Cowen
A new image taken by the Cassini spacecraft is putting the spotlight on Saturn’s split-personality moon Iapetus: half being bright, half being dark. Taken on July 3, just 3 days after the craft began its Saturn tour, the Cassini picture is the first image of the moon taken from space since the early 1980s.
Astronomers have known about this dichotomy ever since Italian-French astronomer Jean Dominique Cassini discovered Iapetus in 1672. He correctly surmised that the moon’s trailing hemisphere as it moves around Saturn is composed of highly reflective material but that the leading hemisphere is apparently without the glitter. That’s in contrast to the other 30 known moons of Saturn, as well as the moons of Jupiter, all of which tend to be brighter on their leading edges.