Iapetus: Moon of mystery
The puzzle of Saturn's most intriguing satellite may finally have been solved. Marcus Chown reports
Published: 17 August 2005
In Arthur C Clarke's novel, 2001: A Space Odyssey, Saturn's moon Iapetus plays a central role. It is the site of the star gate, the portal through which Dave Bowman - Clarke's modern-day Odysseus - journeys to meet his destiny in a far-flung corner of the universe. Clarke selected Iapetus for the star gate because, uniquely among bodies in the solar system, it has one face about 10 times brighter than the other. What better place to locate an artificial alien artefact than on a moon which gives every impression of being artificial itself?
The origin of Iapetus's Janus faces is one of the longest standing mysteries in the solar system, one that has persisted since the moon's discovery by the astronomer Giovanni Cassini in 1671. But the mystery may at last have been solved. The key turns out not to be an ancient encounter with an enigmatic extraterrestrial race but an ancient encounter with Saturn's spectacular system of rings.
The most important event in unravelling the mystery of Iapetus was the flyby of the moon by the Cassini space probe on 31 December 2004. The onboard cameras captured images of the crater-strewn moon in unprecedented detail. What those images revealed stunned planetary scientists back on Earth.
Stretching for 1,300km - almost a third of the way around the moon - was an extraordinary ridge. In places, it is 20km high - more than twice the height of Everest - and this is on a moon only 1,436km across, much less than half the diameter of our own Moon. The ridge follows the equator closely. And there is nothing like it anywhere else in the solar system.
http://news.independent.co.uk/world/science_technology/article306478.ece