Q: Why send a probe to Saturn?

A: Saturn is a fascinating planet for many reasons, but its rings and its many moons are the main things scientists are interested in studying. Its biggest moon, Titan, is the only moon in the solar system that has its own atmosphere. A previous probe, Voyager, flew past Saturn, but there has never been a probe put into orbit around the planet.

Q: What are Saturn's rings made of?

A: Billions of sand-sized ice and dust particles to rocks as big as buildings make up the rings that orbit Saturn at varying speeds. There are hundreds of rings, thought to be the remnants of comets, asteroids or moons that shattered before they reached the planet.

Q: How long did it take Cassini to get to Saturn?

A: Seven years. Cassini launched from Kennedy Space Center on Oct. 15, 1997.

Q: What will Cassini do during its orbit?

A: Cassini's instruments can be classified as remote and microwave remote sensing instruments, and fields and particles instruments. These are all designed to record significant data and take a variety of close-up measurements. Cassini will use its instruments to look at Saturn's atmosphere in different light wavelengths, as well as "feel" things about magnetic fields and tiny dust particles.

Q: Why is Cassini carrying the Huygens probe?

A: Scientists couldn't resist the chance to plunge a probe into Titan's atmosphere. When the Huygens probe falls from Cassini and plunges through Titan's atmosphere to land on its surface, it will send back readings, giving researchers a better handle on exactly what elements make up the moon's atmosphere.

Q: What will happen when the probe drops?

A: The 319-kilogram (703-pound) Huygens probe is a fully-operational laboratory. In December, it will start a 22-day coast to Titan's surface. In January 2005, three sets of parachutes will slow the probe enough so that it can do experiments from the surface.