Saturn
Starting at the interior, with a temperature around 2.5 x 104K, the temperature decreases to a temperature of 135K at the surface of the layer of molecular hydrogen (see section 1.7.). The temperature continues to decrease through the clouds to a minimum. This minimum is locate within the tropopause, at 100 mbar, and has temperature of about 85K. The area above this level coincides with the atmospheric haze explained above. The temperature actually increases from this point due because of the decreasing density.
The planet also has an ionosphere. At altitudes of 2200 km and 2800 km, observation shows areas of increased electron concentration. The level at 2800 km is higher, indicating that the ionosphere exists at that level.
Saturn releases about twice as much heat to space as it receives from the sun. This "extra" heat is a result of two processes. First, the gradual gravitational compression of the planet, called the Kelvin-Helmholtz mechanism. Second, "raining" of helium within the planet provides the additional energy. A detailed explanation of these processes exists.
As a whole, the planet is 75% hydrogen, 25% helium, with traces of water, methane, ammonia, and solids. These solids are similar in composition to the primordial solar nebula, from which the solar system was formed. The core of Saturn is made of rock, surrounded by a liquid metallic hydrogen layer and then a layer of molecular hydrogen (H2). (Molecular hydrogen is the state at which pure hydrogen exists, even on earth.) This makes the core similar to that of Jupiter. There are also traces of ice.
Near the surface, winds can reach a velocity of 500 meters per second, (1800km/h)! These winds generally blow from west to east at the equator, but above 35 degrees, the winds alternate in direction depending upon location. In 1990, the Hubble Space Telescope (HST) discovered a large white spot that was not present when the Voyager spacecraft were there. This white spot is believed to be a large storm.
Saturn rotates about its axis every 10 hours, 39 minutes, 24 seconds, which gives rise to the oblate nature of the planet. It orbits the sun every 29.46 earth years at an average distance from the sun of 9.539AU. (One astronomical unit (AU) is equal to the average distance between the Earth and the Sun.) This means that the Saturnian year is 29.46 times longer that the Earth year.
