Its distinctive rings have mystified astronomers since Galileo's observations in the 17th century. The small chunks of ice and rocky material that orbit Saturn's equatorial area may be debris from the planet's birth or remnants of asteroids or moons that came too close and broke apart. Jupiter, Neptune, and Uranus also are adorned with rings, but theirs are much smaller and fainter. Like Jupiter, Saturn has a Red Spot, although it's only one-third the size. Every 30 years, astronomers have observed spectacular white spots that cover a major portion of the planet.
Scientists believe they are clouds of ammonia-ice crystals that bubble to the top of the atmosphere.
Titan Saturn has 21 known moons, more than any other planet. As Cassini approaches Titan, it will deploy the 800-pound Huygens probe, named after Christiaan Huygens, who discovered the moon in 1655. The craft will enter the atmosphere and a parachute will deploy to slow its descent. The probe also will generate some 1,100 radar images of the moon's surface, which will be relayed to the main spacecraft for retransmission to Earth. Titan is the size of a small planet and one of a few moons in the solar system to have an atmosphere.