The Cassini Spacecraft
After an epic journey of seven years and 3.5 billion kilometres, the Cassini spacecraft entered Saturn orbit on July 2004. The Cassini-Huygens mission is a $3 billion, 4-year tour of Saturn, its rings and many of its 40-odd known moons. No other spacecraft had been near the solar system's second largest planet since the Voyager flybys of the 1980s. Launched in October 1997, the joint US-European spacecraft is the largest and most sophisticated interplanetary vessel ever built. Cassini weighs as much as an adult male African elephant and is around the size of a 30-seater school bus. The most spectacular highlight of the mission so far is its visit to Titan, Saturn's largest moon. ESA's Huygens probe was released by Cassini and descended through the dense atmosphere of Titan in January 2005. It became the first probe to land on such a distant world. Huygens discovered a strikingly Earth-like landscape of hills and branching valleys, though the peaks are ice and the intermittent rivers carry liquid methane. Cassini has also seen clouds and old shorelines, as well as evidence for deserts, an ice volcano and a possible lake of methane near the south pole. But there has been no sign of the methane seas or oceans once expected.
Saturn Superstorm From a Distance
Cassini scientists have seen something like this before. In 2006, the spacecraft observed Saturn's south pole, where a storm two-thirds as wide as Earth was raging. That vortex was the first place in the solar system other than Earth where astronomers saw eye-wall clouds, a typical feature of hurricanes in which a bank of clouds towers above the central pit.
Now, the springtime sun reveals a similar vortex swirling in the north. Astronomers think these storms form in the same way as hurricanes, with warm, moist air rising from lower cloud layers. The storms may be permanent, or could come and go with the seasons.
