Rendez-vous with Saturn

The first written mention of Saturn is attributed to the Assyrians around 700 BC. They described a planet that sparkled in the sky and called it "Ninib's star." In 1610, Galileo observed a strange form through his telescope - a planet that appeared to spread out at the sides.

In 1659, Dutch astronomer Christiaan Huygens found the explanation to this riddle - a series of rings circling the planet. He also discovered Titan, a natural satellite. A few years later, Jean-Dominique Cassini observed four other, smaller moons: Iapetus, Rhea, Tethys and Dione.

Many questions remain, such as how Saturn's rings formed, or whether Titan's atmosphere is comparable to Earth's. The Cassini-Huygens mission, launched in 1997, is the first devoted to the exploration of Saturn. NASA, which built the Cassini orbiter, is conducting the mission in collaboration with ESA, which supplied the Huygens probe.

The spacecraft and its instruments reached Saturn on 1 July 2004, after a journey of 7 years and 3.5 billion km. The Cassini orbiter is now collecting essential data on Saturn's and its satellites' structure and environment until 2017.

Europe’s Huygens probe plunged into Titan’s atmosphere in January 2005 and landed on its surface, making it the first explorer spacecraft to have conducted in-situ measurements on such a distant world. The radar images taken by Cassini, when it flew over Titan, revealed several pockets of liquid methane around the moon's northern and southern poles. More recently, traces of sodium were detected in ice particles in the vapour plumes of Enceladus, one of Saturn’s moons. This could point to the presence of a salty liquid ocean.

The Cassini-Huygens programme could in particular improve our understanding of the chemical mechanisms which led to the emergence of life on Earth.

^{Last updated: July 2010}