The dark and light side of Iapetus. Credit: NASA/JPL/Space Science Institute
Although Saturn’s moon Iapetus was first discovered in 1671 by Giovanni Cassini, its behavior was extremely odd. Cassini was able to regularly find the moon when it was to the west of Saturn, but when he waited for it to swing around to Saturn’s east side, it seemed to vanish. It wasn’t until 1705 that Cassini finally observed Iapetus on the eastern side, but it took a better telescope because the side Iapetus presented when to the east was a full two magnitudes darker. Cassini surmised that this was due to a light hemisphere, presented when Iapetus was to the west, and a dark one, visible when it was to the east due to tidal locking.
With the advances in telescopes, the reason for this dark divide has been the subject of much research. The first explanations came in the 1970′s and a recent paper summarizes the work done so far on this fascinating satellite as well as expanding it to the larger context of some of Saturn’s other moons.
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Read the rest of What’s up with Iapetus? (780 words)
© jvois for Universe Today, 2011. |
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