SATURN
Saturn is a gas giant. It's structure is very similar to jupiter's core is composed liquid rock. Next comes a layer of liquid hydrogen. It is under such high 
pressure that the nature of the hydrogen changes, and is able to conduct electricity like metal. This generates the planet's magnetic field.
The layer on top of this is ordinary liquid hydrogen. Next, the hydrogen thins out into the gaseous atmosphere. It is composed of mainly hydrogen and helium with trace amounts of methane, water, ammonia, and hydrogen sulfide.
Interestingly, Saturn creates some of its own heat, but in a much different way than Jupiter. Scientists believe that the hydrogen and helium are slowly separating out, like vinegar and oil when left to sit. In Saturn's case, the heavier helium is slowly making its way through the hydrogen, generating heat (from friction) as it goes.
Saturn has something like Jupiter's Great Red Spot, but it is a Great White Spot. Nothing is currently known about the phenomenon, but it is probably similar to the Great Red Spot in the way it has formed. Besides this, Saturn's outer atmosphere is not nearly as turbulent as Jupiter's. This is because, being about two times farther away from the sun, it receives approximately 1/4 as much as energy from it. Less energy means that there is less to power atmospheric phenomenon.
Atmosphere
Saturn is basically one big atmosphere - as far as we know, there is no real surface to the planet. Its composition is nearly all H2; the rest is approximately:
- H2: 96.3±2.4%
- He: 3.25±2.4%
- CH4: 0.45±0.2%
- NH3: 0.0125±0.075%
- HD: 0.011±0.0058%
- C2H6: 0.0007±0.00015%
Besides this, aerosols of ammonia ice, water ice, and ammonia hydrosulfide exist in the atmosphere.
The temperature at 1 bar is approximately 134 K, and at 0.1 bar it is 84 K. The density at 1 bar is 190 g/m3. Below 30° latitude, wind speeds range up to 400 m/s, and above that only 150 m/s. The scale height of the Saturnian atmosphere is about 59.5 km.
Unique Characteristics
Saturn has a few unique features:
- First, it is the least dense of all the planets. If there were a bathtub big enough to fit Saturn in, the planet would float.
- Second is Saturn's magnificent ring system. This system has four sections. The farthest out, F, was discovered during the Voyager mission. Moving towards Saturn, next is the A section, and this section makes up about half the diameter of the entire system. Then comes the Cassini Division, between A and B, which is the large gap visible in most photographs. Next is the B ring, which has raised parts, caused by the planet's magnetism. These appear as spokes. In-between B and C, there is a small division called Enck's Division. The C ring is transparent. Farther in, there are very small ring particles which are slowly spiraling in towards the planet.
The rings were probably formed relatively recently - several thousand years ago - when two of Saturn's satellites crashed together. The ring systems of the other gas giants probably formed the same way, only much earlier, which is why they are mostly gone; most of their rings have fallen into their planet's atmosphere. In about 100,000,000 years, Saturn's rings will probably be gone, too. See the table below for data on its rings. - Another interesting property of Saturn is how it generates heat. As seen in the table below, the average temperature of Saturn is approximately 130 K. However, due to the equation for thermal equilibrium (below), it should only be about 80 K. This extra heat is generated due to its gas slowly separating. Like an oily salad dressing, the gases in Saturn's atmosphere are very slowly separating, with the lighter gas rising up and the heavier gas falling down. As this happens, friction between the molecules heats the gas, accounting for the extra heat.