A TRAVELLER arrived at Saturn in May, ready to write the book on the planet鈥檚 intricate rings, stormy atmosphere and many moons.
Within weeks, the space probe Cassini revealed that Saturn鈥檚 outermost large moon, Phoebe, is a would-be comet captured by the gas giant鈥檚 gravity. Had it slipped Saturn鈥檚 grasp, Phoebe would have come close enough to the sun to start evaporating, growing a coma and tail that would have blazed far brighter than Hale-Bopp.
On 1 June, Cassini passed a milestone in its mission, flying through a gap in Saturn鈥檚 rings before going into orbit. A close-up of the rings revealed spirals and scallops caused by the subtle gravity of Saturn鈥檚 small moons, and knife-sharp edges and fibrous structures that are still unexplained. Traces of dust on the icy particles making up the rings hint that different rings may have slightly different origins. Perhaps several wanderers from the outer darkness, less cautious than Phoebe, have strayed too close to Saturn and been shattered by its gravity.
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In October, Cassini gave us the first clear images of Titan, which till then had been the largest stretch of unexplored territory in the solar system. Hidden under orange-brown smog are intricate patterns of light and dark terrain, with lobes, broad streaks, narrow cracks or ridges, and bright 鈥渋slands鈥�.
Much more will be revealed as Cassini swoops past Titan 43 more times. We will also learn the secrets of many of Saturn鈥檚 other moons, peer deep inside the planet with instruments that might detect its rocky heart, and discover whether a metallic layer of liquid hydrogen is generating its magnetic field.
