Basic Data

• Mean Distance from Sun: 1433.4 million km.
• Equatorial Radius: 60,268 km. (9.45 Earth)
• Mass: 5.68 x 10²⁶ kg. (95.2 Earth)
• Surface Gravity: 9.0 m/s² (0.91 Earth)
• Length of Year: 29.66 years
• Length of Day: 10h 32-47m

Wikipedia - Saturn

About Saturn

If Jupiter is the king of planets, Saturn is certainly the most interesting. It is the only planet with a huge, highly developed ring system (the other gas giants have rings, but they are thin, small and faint). It has a number of interesting moons. And the planet itself boasts of its own mysteries. An enormous hexagonal cloud structure, bigger than the Earth, surrounds the north pole. And the south pole is a titanic hurricane five thousand kilometers across, with a sharply defined eyewall and smaller "sub-storms" inside. Because Saturn's clouds are buried deeper in its atmosphere, beneath an outer haze, they are not as clearly seen. But observations have detected tremendous thunderstorms, crackling with lightning.

The rings are composed of vast quantities of ice chunks, ranging in size from pebbles all the way up to boulders around the size of a small car. Recent observations have suggested that the ring particles form clumps, which break apart over time and reform into new clumps. Interactions with Saturn's magnetic field produces the appearance of spokes, although the exact mechanism is still unknown.

The rings are maintained by a number of small "shepherd moons" which orbit inside and outside of the various ring divisions. Gravitational effects from these moonlets herd the ring particles, preventing them from spreading out and dissipating. One curious side effect that the rings have on some of these moons is the accumulation of large amounts of material on the equator, resulting in bodies that resemble flying saucers.

Saturn is the least dense of all the solar system's planets. As a result, in spite of being nearly a hundred times as massive as Earth, its surface gravity (more accurately, gravity at level of its atmosphere where the pressure is one bar, since it does not have a solid surface) is actually less than ours. Saturn is also the most "flattened" of all the planets, with a polar radius nearly 6000 kilometers less than its equatorial radius.

Saturn's Moons

Titan in natural color, seen from Cassini

Saturn possesses several interesting moons, such as: Titan, which has an atmosphere denser than Earth's; Enceladus, which has immense geysers spouting from its southern polar regions; Iapetus, with half of its surface covered with an unknown dark material, giving it a two-faced appearance; Rhea, believed to have a very faint ring system of its own.

Enceladus orbits in the middle of the thickest part of the E ring, and is believed to be responsible for replenishing it by means of material ejected from its south polar geysers.

Titan is the second largest moon in the solar system, and the only one to have a dense atmosphere. Surface air pressure is 1.6 times that of Earth, roughly equivalent to the pressure at the bottom of an Olympic class swimming pool. This atmosphere is composed mostly of nitrogen, with a few percent methane and traces of other gases. Because of the temperature, methane can exist in both liquid and gaseous states, and serves a function similar to that of water on Earth. Large lakes—even seas—of liquid hydrocarbons have been detected in the northern polar regions, using radar. A large lake known as Ontario Lacus has not only been seen by radar near the south pole, but has been determined to definitely contain ethane. At least one observation suggests that the layer of ethane is only a few millimeters thick; this would make sense if the lake were very sludgy, with only a thin skim of pure liquid at the top. Given the presence of complex hydrocarbons found on the surface at the Huygens landing site, this is not surprising.

The equatorial regions of Titan are covered in vast "seas" of sand composed of grains of water ice mixed with frozen hydrocarbons that have "snowed" out of the atmosphere. Prevailing winds caused by tidal forces from Saturn have created huge, parallel dunes that extend for hundreds of kilometers east and west, except when they curve around "islands" of bare ice that stick up above the sands. The Huygens probe photographed both the sandy lowlands and bare ice highlands during its descent. The lowlands strongly resembled a dry riverbed or lake bed, littered with eroded ice pebbles, and the highlands were carved with eroded channels, probably caused by runoff from infrequent, but fierce, methane rainstorms. Methane was detected evaporating from the sandy surface where the probe landed, indicating that the sand is probably wet underground, and the heat from the probe caused some of it to flash into steam and escape.

Observation from Earth

Saturn is the last planet that was known to ancients. The Greeks called it Kronos and the Babylonians knew it as Ninurta. The ancient Hebrews called it Shabbathai. When Galileo built his telescope and aimed it at Saturn, he was totally perplexed by what he saw and did not recognize the rings for what they were. Later, when changing seasons brought Saturn to equinox and the rings became vanishingly thin, he wondered "Has Saturn swallowed his children".

Later and greater telescopes finally allowed astronomers to recognize the rings as rings. Christiaan Huygens—who also discovered Titan—was the first to suggest a ring structure. Later, Giovanni Domenico Cassini determined that there were gaps in the rings, and the largest of these gaps, the Cassini Division, still bears his name.

Even today, after several visits by spacecraft, Saturn remains a favorite for telescope viewers.

Exploration of Saturn

Three spacecraft (Pioneer and both Voyagers) have made flybys of Saturn. And at the time of the writing of this page, the Cassini orbiter is still busy studying the planet and its moons. Cassini also brought with it the Huygens probe, which landed on Titan on January 14, 2005.