+ NASA Home > Facts > Exploring the Universe

Did you know that the Cassini-Huygens Mission is an international collaboration between three space agencies and 17 nations contributed to building the spacecraft? More than 250 scientists worldwide will study the data collected. Saturn's beautiful rings are not solid. They are made up of particles of ice, dust and rock -- some as tiny as grains of sand, some much larger than skyscrapers. The Compton Gamma Ray Observatory was safely de-orbited and re-entered the Earth's atmosphere on June 4, 2000. Any pieces that survived landed in a remote area of the Pacific Ocean. It's pretty windy on Saturn. Winds around the planet's equator can reach 1,800 kilometers (1,118 miles) per hour. In comparison, the fastest winds on Earth reach only about 400 kilometers (about 250 miles) per hour. Four days after it was launched, the Deep Space 1 spacecraft was about 1,000,000 kilometers (about 600,000 miles) from Earth. To fly that far in a jet, you would have to fly for 6 weeks without stopping! Although other planets have rings too, Saturn's rings are the only ones that are visible from Earth even with a small telescope. To communicate with distant spacecraft, NASA's Deep Space Network uses antenna with a diameter of up to 70 meters (230 feet). That is almost as big as a football field. Saturn, the "Ringed Planet," is so far away from the Sun that it receives only about 1/80th the amount of sunlight that we receive here on Earth. Yes, the Sun appears much smaller from there. It's a small world. More than 1,000 Earths would fit into Jupiter's vast sphere. Scientists are particularly interested in Saturn's moon Titan because it's one of the few known moons with its own dense atmosphere. Titan's atmosphere is also thought to be very similar to what Earth's atmosphere was a long time ago. By learning about Titan, we'll learn about our own planet. When the Cassini-Huygens spacecraft arrives at Saturn, it will be traveling so fast that engineers will need to burn the spacecraft's engines for 97 minutes just to slow it down. If mission engineers don't do this, the spacecraft would keep on going, instead of entering the orbit around Saturn. A penumbral eclipse is the outer shadow in a zone where the Earth blocks part, but not all, of the Sun's rays from reaching the Moon. In contrast, the inner or umbral shadow is a region where the Earth blocks all direct sunlight from reaching the Moon. Titan is the largest of Saturn's moons. It is the second largest moon in the solar system. In fact, it is larger than both Mercury and Pluto. Equinox literally means "equal night." On an equinox, the sun is above the equator, so both the northern and southern hemispheres of the Earth receive about the same amount of sunlight, and day and night are the same length. Because Saturn is tilted, when its rings are facing Earth edge-on they "disappear" from our view. We now know this happens every 14 years or so, but poor Galileo questioned his sanity when they "disappeared" and then "reappeared" a few years later. Galileo, launched in 1989, was the first U.S. spacecraft to orbit Jupiter. Galileo entered Jupiter's orbit in 1995. Saturn is huge. It is the second largest planet in our Solar System. Only Jupiter is bigger. If you could line them up, more than nine Earths would fit across Saturn. Through his spyglass, in 1609 Galileo saw that there were spots on the Sun, imperfections on the Moon, and that the Milky Way was composed of millions of faint stars. His most stunning (and controversial!) discovery was of satellites orbiting Jupiter, dashing the concept that the Earth was the center of the Universe. Saturn's moon Iapetus (eye-AP-eh-tuss) is a very curious moon -- it seems to have a split personality! One hemisphere is covered with material darker than black velvet, while the other side is covered with material brighter than snow. Ganymede, one of the moons of Jupiter, is the largest moon in our Solar System. + View more NASA Facts