Saturn was the most distant of the five planets known to the ancients. In 1610, Italian astronomer Galileo Galilei was the first to gaze at Saturn through a telescope. To his surprise, he saw a pair of objects on either side of the planet. He sketched them as separate spheres and wrote that Saturn appeared to be triple-bodied. Continuing his observations over the next few years, Galileo drew the lateral bodies as arms or handles attached to Saturn. In 1659, Dutch astronomer Christiaan Huygens, using a more powerful telescope than Galileo's, proposed that Saturn was surrounded by a thin, flat ring. In 1675, Italian-born astronomer Jean-Dominique Cassini discovered a 'division' between what are now called the A and B rings. It is now known that the gravitational influence of Saturn's moon Mimas is responsible for the Cassini Division, which is 4,800 kilometers (3,000 miles) wide.
Like Jupiter, Saturn is made mostly of hydrogen and helium. Its volume is 755 times greater than that of Earth. Winds in the upper atmosphere reach 500 meters (1,600 feet) per second in the equatorial region. (In contrast, the strongest hurricane-force winds on Earth top out at about 110 meters, or 360 feet, per second.) These super-fast winds, combined with heat rising from within the planet's interior, cause the yellow and gold bands visible in the atmosphere.
Four NASA spacecraft have been sent to explore Saturn. Pioneer 11 was first to fly past Saturn in 1979. Voyager 1 flew past a year later, followed by its twin, Voyager 2, in 1981.
The Cassini spacecraft is the first to explore the Saturn system of rings and moons from orbit. Cassini entered orbit on Jun. 30, 2004 and immediately began sending back intriguing images and data. The European Space Agency's Huygens Probe dove into Titan's thick atmosphere in January 2005. The sophisticated instruments on both spacecraft are providing scientists with vital data and the best views ever of this mysterious, vast region of our solar system.
Cassini-Huygens is an international collaboration between three space agencies. Seventeen nations contributed to building the spacecraft. The Cassini orbiter was built and managed by NASA's Jet Propulsion Laboratory. The Huygens probe was built by the European Space Agency. The Italian Space agency provided Cassini's high-gain communication antenna. More than 250 scientists worldwide are studying the data streaming back from Saturn on a daily basis.
For more information in Saturn, see the Nasa Solar System Exploration: Saturn webpage and the The Cassini-Huygens Mission to Saturn and Titan webpage.
Nasa Solar System Exploration: Saturn; The Cassini-Huygens Mission to Saturn and Titan, 08/2007 (web page)