Saturn, the Solar System's Major Ring Bearer

Saturn's History and Naming

Saturn was the Roman name for Cronus, the lord of the titans in Greek mythology. Saturn happens to be the root of the English word "Saturday."

Physical Characteristics of the Planet Saturn

Saturn is a gas giant made up mostly of hydrogen and helium. Saturn is the second largest planet, big enough to hold more than 760 Earths, and is more massive than any other planet except Jupiter, roughly 95 times Earth's mass. However, Saturn has the lowest density of all the planets, and is the only one less dense than water — if there were a bathtub big enough to hold it, Saturn would float on top.

Although the other gas giants in the solar system — Jupiter, Uranus and Neptune — also have rings, those of Saturn are without a doubt the most extraordinary. The largest one to date spans up to 200 times the diameter of the planet.

Saturn is the farthest planet from Earth visible to the naked human eye. The yellow and gold bands seen in the planet's atmosphere are the result of super-fast winds in the upper atmosphere, which can reach up to 1,100 miles per hour (1,800 kilometers per hour) around its equator, combined with heat rising from the planet's interior.

Saturn spins faster than any other planet except Jupiter, completing a rotation roughly every 10-and-a-half hours. This rapid spinning causes Saturn to bulge at its equator and flatten at its poles — the planet is 8,000 miles (13,000 kilometers) wider at its equator than between the poles.

Saturn's most recent curiosity may be the giant hexagon circling its north pole, with each of its sides nearly 7,500 miles (12,500 kilometers) across — big enough to fit nearly four Earths inside. Thermal images show it reaches some 60 miles (100 kilometers) down into the planet's atmosphere. It remains uncertain what causes it.

Orbital Characteristics of the Planet Saturn

• Composition & Structure
  • Atmospheric composition (by volume)
    •  96.3 percent molecular hydrogen, 3.25 percent helium, minor amounts of methane, ammonia, hydrogen deuteride, ethane, ammonia ice aerosols, water ice aerosols, ammonia hydrosulfide aerosols
  • Magnetic Field
    • Saturn has a magnetic field about 578 times more powerful than Earth's.
  • Chemical composition
    • Saturn seems to have a hot solid inner core of iron and rocky material surrounded by an outer core probably composed of ammonia, methane, and water. Next is a layer of highly compressed, liquid metallic hydrogen, followed by a region of viscous hydrogen and helium. This hydrogen and helium becomes gaseous near the planet's surface and merges with its atmosphere.
  • Internal structure
    • Saturn seems to have a core between about 10 to 20 times as massive as the Earth.

• Orbit & Rotation

Average Distance from the Sun

English: 885,904,700 miles

Metric: 1,426,725,400 km

By Comparison: 9.53707 times that of Earth

Perihelion (closest)

English: 838,519,000 miles

Metric: 1,349,467,000 km

By Comparison: 9.177 times that of Earth

Aphelion (farthest)

English: 934,530,000 miles

Metric: 1,503,983,000 km

By Comparison: 9.886 times that of Earth

(Source: NASA.)

Saturn's Moons

Saturn has at least 62 moons. Since the planet was named after Cronus, lord of the titans in Greek mythology, most of Saturn's moons are named after other titans, their descendants, as well as after giants from Gallic, Inuit and Norse myths.

Saturn's largest moon, Titan, is slightly larger than Mercury, and is the second-largest moon in the solar system behind Jupiter's moon Ganymede. Titan is veiled under a very thick, nitrogen-rich atmosphere that might be like what Earth's was long ago, before life. While the Earth's atmosphere extends only about 37 miles (60 kilometers) into space, Titan's reaches nearly 10 times as far.

These moons can possess bizarre features. Pan and Atlas are shaped like flying saucers, Iapetus has one side as bright as snow and one side as dark as coal, and Enceladus shows evidence of "ice volcanism," spewing out water and other chemicals. A number of these satellites, such as Prometheus and Pandora, are shepherd moons, interacting with ring material to keep rings in their orbits.

Saturn's Rings

Galileo was the first to see Saturn's rings in 1610, although from his telescope they resembled handles or arms. It took Dutch astronomer Christiaan Huygens, who had a more powerful telescope, to propose that Saturn had a thin, flat ring.

Saturn actually has many rings made of billions of particles of ice and rock, ranging in size from a grain of sugar to the size of a house. The rings are believe to be debris left over from comets, asteroids or shattered moons. Although they extend thousands of miles from the planet, the main rings are typically only about 30 feet thick. Cassini revealed vertical formations in some of the rings, with particles piling up in bumps and ridges more than 2 miles (3 kilometers) high.

The rings are generally named alphabetically in the order they were discovered. They are usually relatively close to each other, with one key exception caused by the Cassini Division, a gap some 2,920 miles (4,700 kilometers) wide. The main rings, working out from the planet, are known as C, B and A, with the Cassini Division separating B and A. The innermost is the extremely faint D ring, while the outermost to date, revealed in 2009, could fit a billion Earths within it.

Mysterious spokes have been seen in Saturn's rings, which might form and disperse over a few hours. Scientists have conjectured these spokes might be composed of electrically charged sheets of dust-sized particles created by small meteors impacting the rings or electron beams from the planet's lightning. Saturn's F Ring also has a curious braided appearance — it is composed of several narrow rings, and bends, kinks, and bright clumps in them can give the illusion that these strands are braided.

Research & Exploration

The first spacecraft to reach Saturn was Pioneer 11 in 1979, flying within 13,700 miles (22,000 kilometers) of it, which discovered the planet's two of its outer rings as well as the presence of a strong magnetic field. The Voyager spacecraft discovered the planet's rings are made up of ringlets, and sent back data that led to the discovery or confirmation of the existence of nine moons.

The Cassini spacecraft now in orbit around Saturn is the largest interplanetary spacecraft ever built, a two-story-tall probe that, at 6 tons in weight (5,650 kilograms), is roughly equal in mass to an empty 30-passenger school bus. It discovered plumes on the icy moon Enceladus, and carried the Huygens probe, which plunged through Titan's atmosphere to successfully land on its surface.

Saturn's Gravitational Impact on the Solar System

As the most massive planet in the solar system after Jupiter, the pull of Saturn's gravity has helped shape the fate of our system. It might have helped violently hurl Neptune and Uranus outward. It, along with Jupiter, might alos have slung a barrage of debris toward the inner planets early in the system's history.

Possibility of Life

The life found on Earth could not live on Saturn, and scientists doubt that any form of life exists there.

RELATED: See our Solar System Planets overview, or our broader Solar System Facts overview, or learn more about each of the other planets: Mercury, Venus, Earth, Mars, Jupiter, Uranus, Neptune and the demoted dwarf planet Pluto.