Saturn is a major planet, very similiar to Jupiter. The main body of Saturn consists of hydrogen, and its mean density is ruffly 0.69 g/cm cubed, the lowest of any planet. Also Saturn's atmosphere consists mainly of hydrogen, but the proportions of other gases differ from that of Jupiter. The flattening of Saturn at its poles is very striking. This is caused by the rapid rotation of the planet. (1 rotation in 10 hours and 40 minutes) Saturn's equatorial diameter is 120,660 km; the poles diameter is 98,000 km.
The pattern of belts found on Saturn is less distinct than Jupiterís and it is only through special processing of photos that detailed formations show up clearly. The differences are caused due to the differences in thermal processes affecting the atomsphere's circulation, chemical processes, and meteorological happenings. It is far colder on Saturn. The top cloud layer has an approximate temperature of -130 C, but the ratio between its thermal energy radiated from the interior to that received from the Sun is 2:1 (as compared to Jupiters ratio of 1:1). The stronger proportion of internal energy can cause greater ascending currents and efficient blending of the atmosphere. This may be the cause for the extreme velocity of wind currents, up to 1,800 km/h, that are found around Saturnís equatorial belt.
Since the early 17th century when they were discovered, Saturnís rings were one of the greatest mysteries of our Solar System. In 1980 and 1981 Voyagers 1 and 2 photographed the rings in unexpected detail, which only added to the number of questions. Since the 19th century it has been known that Saturnís rings consisted of numerous objects from that of grains of dust to boulders of various sizes.
The belts are produced by the circulation of the atmosphere. The light zones consist of cooler clouds at a greater height. The dusky belts are more transparent. The coloration of the belts on Jupiter show up very well in pictures taken by probes at close range. The colours are caused by various compounds that are created at specific temperatures, and thus at certain heights in the planets atmosphere. The temperature in the upper most cloud layer in -140 C , but in the lower layers it rises to 0 C.