Mystery of Saturn’s Two-Faced Moon

Iapetus’ bizarre two-toned appearance, with one dark side and one bright side, has puzzled

astronomers since the moon was first discovered by Giovanni Domenico Cassini in 1671. To better understand how this oddball Saturn moon formed and evolved, researchers are now studying the temperature variation across Iapetus’ differing surfaces by measuring the moon’s microwave emissions. Previous studies using data from NASA’s Cassini spacecraft suggest that migrating ice makes half of Iapetus reflective and bright, while the other side is cloaked in dust and darkness. Paul Ries, a graduate student at the University of Virginia and a researcher at the National Radio Astronomy Observatory (NRAO) was trying to get something continuous to look at the thermal variations.To do this, Ries measured the amount of light produced by Iapetus and its pattern of microwave emissions. Essentially, most objects in the solar system are blackbody objects that absorb all the radiation that hits them, he explained. This observations of Iapetus showed a very different and unexpected pattern. As said Ries what he found was that the emissions were what we call flat, which means that as we go from one radio wavelength to another, the emissions were the same when we expect them to be declining. What that corresponds to is a very steep absorption. To improve his models of Iapetus, Ries looked a little closer to home, at previous studies that measured microwave emissions and temperature signals from our own planet. As said Ries in the specific case of Iapetus, this observations can help shed light on what’s going on in its formation and evolution. Iapetus certainly has some strange stuff that needs to be explained, so this is potentially very interesting for the future. But eventually, Ries would like to do observations of the outer solar system, the Kuiper Belt and beyond.