Jupiter, like the other gas planets, doesn't have solid surfaces. Rather its gaseous material simply becomes denser with depth. When we see the planet, what we see is the tops of clouds.
Jupiter is comprised of 90% hydrogen and 10% helium. There are also traces of water, methane, ammonia, and "rock". Our knowledge of the interior is sketchy because the current space probe, Galileo's probe only goes down 150 km below the cloud tops. It probably has a rocky core. Above this core is liquid metallic hydrogen, which makes up most of the planet.
Jupiter and the other gas planets have high-powered winds (on Jupiter-over 400 mph) which are in wide bands of latitudes. Chemical and temperature differences are responsible for the colored bands that we see. The light bands are called zones while the dark ones are called belts.
Jupiter has a huge magnetic field that is ten times stronger than the Earth's. The magnetosphere extends more than 650 million km. However, the magnetosphere is far from spherical---it extends just a few kilometers toward the sun.
In 1973, Pioneer 10 first visited Jupiter. It was soon followed by Pioneer 11, Voyager 1, Voyager 2, and Ulysses.
The vivid colors seen in the clouds of Jupiter are the result of discreet chemical reactions of the trace elements in Jupiter's atmosphere. The colors correlate with the cloud's altitude: the reds being the highest, followed by whites and browns, with blue being the lowest. Sometimes we see blues and browns because of holes in the upper layers. The Great Red Spot on Jupiter has been known to astronomers for more than 300 years. Its discovery is usually attributed to Cassini or Robert Hooke in the 17th Century. It is a turbulent storm on Jupiter. The Great Red Spot is an oval that is big enough to hold two Earth's. 
In 1610, Galileo discovered Jupiter's four large moons, Io, Europa, Calliso, and Ganymede. To this day, Jupiter has 16 known moons, the four large Galilean moons and 12 small ones. Jupiter is very gradually slowing down due to the tidal drag produced by the Galilean satellites. Also the same tidal forces are forcing them farther from Jupiter.
Jupiter Sites
Cool pictures of Jupiter.
Learn about the Galileo probe.
NSSDC Photo Gallery
Learn about the Galileo Project.
Jupiter Events
