Mean orbital velocity: 6 miles (9.6 km) per second
Inclination of axis: 26.73 degrees
Orbital eccentricity: 0.056
Orbital inclination: 2.49 degrees
Diameter at equator: 74,990 miles (120,660 km)
9.41 x Earth's diameter
Oblateness: 0.102
Mass: 5.69 x 10^26 kg
95.1 x Earth's mass
Volume: 8.15 x 10^14 km^3
752 x Earth's volume
Density: 0.69 g/cm^3
0.127 x Earth's density
Surface gravity: 11.3 m/s^2
1.16 x Earth's gravity
Escape velocity: 22.1 miles (35.6 km) per second
Mean surface temperature: -292 F / -180 C / 93 K (at cloud tops)
Maximum apparent diameter as seen from Earth: 20.9"
Albedo: 0.46
Number of known satelites: 18
Mean diameter of Sun as seen from Saturn: 3' 22"
Satellite data
Pan (S18)
Mean distance from center of Saturn: 83,000 miles (133,600 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 0.576 days
Orbital eccentricity: 0
Orbital inclination to Saturn's equator: 0 degrees
Diameter: 12 miles (20 km)
Mass: unknown
Density: unknown
Escape Velocity: 0.006 mile (0.01 km) per second
Maximum apparent diameter as seen from Saturn: unknown
Atlas (S15)
Mean distance from center of Saturn: 85,560 miles (137,670 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 0.602 days
Orbital eccentricity: 0.002
Orbital inclination to Saturn's equator: 0.3 degrees
Diameter: 23 x 21 x 27 miles (37 x 34 x 27 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.009 mile (0.015 km) per second
Maximum apparent diameter as seen from Saturn: unknown
Prometheus (S16)
Mean distance from center of Saturn: 86,600 miles (139,350 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 0.613 days
Orbital eccentricity: 0.004
Orbital inclination to Saturn's equator: 0.0 degrees
Diameter: 92 x 62 x 42 miles (148 x 100 x 68 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.03 mile (0.05 km) per second
Maximum apparent diameter as seen from Saturn: unknown
Pandora (S17)
Mean distance from center of Saturn: 88,100 miles (141,700 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 0.629 days
Orbital eccentricity: 0.004
Orbital inclination to Saturn's equator: 0.05 degrees
Diameter: 68 x 55 x 39 mi. (110 x 88 x 62 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.02 mi (0.035 km) per second
Maximum apparent diameter as seen from Saturn: unknown
Epimetheus (S11)
Mean distance from center of Saturn: 94,110 miles (151,420 km)
Inclination of Axis: unknown
Rotation period: unknown
Orbital period: 0.694
Orbital eccentricity: 0.009
Orbital inclination to Saturn's equator: 0.34 degrees
Diameter: 86 x 68 x 68 miles (138 x 110 x 110 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.03 mile (0.45 km) per second
Maximum apparent diameter as seen from Saturn: unknown
Janus (S10)
Mean distance from center of Saturn: 94,140 miles (151,470 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 0.695 days
Orbital eccentricity: 0.007
Orbital inclination to Saturn's equator: 0.14 degrees
Diameter: 118 x 121 x 96 miles (190 x 194 x 154 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.045 mi (0.075 km) per second
Maximum apparent diameter as seen from Saturn: unknown
Mimas (S1)
Mean distance from center of Saturn: 115,300 miles (185,540 km)
Inclination of axis: 0 degrees
Rotation period: 0.942 days
Orbital period: 0.942 days
Orbital eccentricity: 0.020
Orbital inclination to planet's equator: 1.52 degrees
Diameter: 247 miles (398 km)
Mass: 4.5 x 10^19 kg
Density: 1.2 g/cm^3
Escape velocity: 0.10 mi (0.16 km) per second
Maximum apparent diameter as seen from Saturn: 10' 54"
Enceladus (S2)
Mean distance from center of Saturn: 147,940 miles (238,040 km)
Inclination of axis: 0 degrees
Rotation period: 1.370 days
Orbital period: 1.370 days
Orbital eccentricity: 0.004
Orbital inclination to Saturn's equator: 0.02 degrees
Diameter: 310 miles (498 km)
Mass: 8.4 x 10^19 kg
Density: 1.2 g/cm^3
Escape velocity: 0.12 mile (0.2 km) per second
Maximum apparent diameter as seen from Saturn: 10' 36"
Tethys (S3)
Mean distance from center of Saturn: 183,140 miles (294,670 km)
Inclination of axis: 0 degrees
Rotation period: 1.888 days
Orbital period: 1.888 days
Orbital eccentricity: 0.0
Orbital inclination to Saturn's equator: 1.1 degrees
Diameter: 650 miles (1,046 km)
Mass: 7.5 x 10^20 kg
Density: 1.21 g/cm^3
Escape velocity: 0.25 mile (0.4 km) per second
Maximum apparent diameter as seen from Saturn: 17' 36"
Telesto (S14)
Mean distance from center of Saturn: 183,140 miles (294,670 km)
(Leads Tethys by 60 degrees)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 1.888 days
Orbital eccentricity: 0.0
Orbital inclination to Saturn's equator: 1 degree
Diameter: 19 x 16 x 10 miles (30 x 26 x 16 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.006 mile (0.01 km) per second
Maximum apparent diameter as seen from Saturn: unknown
Calypso (S13)
Mean distance from center of Saturn: 183,140 miles (294,670 km)
(Trails Tethys by 60 degrees)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 1.888 days
Orbital eccentricity: 0
Orbital inclination to Saturn's equator: 1 degree
Diameter:19 x 10 x 10 miles (30 x 16 x 16 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.006 mi (0.01 km) per second
Maximum apparent diameter as seen from Saturn: unknown
Dione (S4)
Mean distance from center of Saturn: 234,570 miles (377,420 km)
Inclination of axis: 0 degrees
Rotation period: 2.737 days
Orbital period: 2.737 days
Orbital eccentricity: 0.002
Orbital inclination to Saturn's equator: 0.02 degees
Diameter: 696 miles (1,120 km)
Mass: 1.05 x 10^21 kg
Density: 1.43 g/cm^3
Escape velocity: 0.3 mile (0.5 km) per second
Maximum apparent diameter as seen from Saturn: 12' 24"
Helene (S12)
Mean distance from center of Saturn: 234,570 miles (377,420 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 2.737
Orbital eccentricity: 0.005
Orbital inclination to Saturn's equator: 0.15 degrees
Diameter: 22 x 21 x 17 miles (36 x 34 x 28 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.006 mi (0.01 km) per second
Maximum apparent diameter as seen from Saturn: unknown
Rhea (S5)
Mean distance from center of Saturn: 237,560 miles (527,040 km)
Inclination of axis: 0 degrees
Rotation period: 4.518 days
Orbital period: 4.518 days
Orbital eccentricity: 0.001
Orbital inclination to Saturn's equator: 0.35 degrees
Diameter: 950 miles (1,528 km)
Mass: 2.49 x 10^21 kg
Density: 1.33 g/cm^3
Escape velocity: 0.37 mile (0.6 km) per second
Maximum apparent diameter as seen from Saturn: 10' 42"
Titan (S6)
Mean distance from center of Saturn: 759,390 miles (1,221,860 km)
Inclination of axis: 0 degrees
Rotation period: probably 15.945 days
Orbital period: 15.945 days
Orbital eccentricity: 0.029
Orbital inclination to Saturn's equator: 0.33 degrees
Diameter: 3,201 miles (5,150 km)
Mass: 1.35 x 10^23 kg
Density: 1.88 g/cm^3
Escape velocity: 1.6 miles (2.2 km) per second
Maximum apparent diameter as seen from Saturn: 17' 10"
Hyperion (S7)
Mean distance from center of Saturn: 920,510 miles (1,481,100 km)
Inclination of axis: unknown
Rotation period: unknown
Orbital period: 21.277 days
Orbital eccentricity: 0.104
Orbital inclination to Saturn's equator: 0.43 degrees
Diameter: 224 x 174 x 140 miles (360 x 280 x 226 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.12 mile (0.2 km) per second
Maximum apparent diameter as seen from Saturn: 43"
Iapetus (S8)
Mean distance from center of Saturn: 2,213,360 miles (3,561,300 km)
Inclination of axis: 0 degrees
Rotation period: 79.331 days
Orbital period: 79.331 days
Orbital eccentricity: 0.028
Orbital inclination to Saturn's equator: 14.7 degrees
Diameter: 892 miles (1,436 km)
Mass: 1.88 x 10^21 kg
Density: 1.16 g/cm^3
Escape velocity: 0.44 mile (0.7 km) per second
Maximum apparent diameter as seen from Saturn: 1' 48"
Phoebe (S9)
Mean distance from center of Saturn: 8,051,000 miles (12,954,000 km)
Inclination of axis: unknown
Rotation period: approx. 0.4 days
Orbital period: 550.4 days
Orbital eccentricity: 0.163
Orbital inclination to Saturn's equator: 150 degrees
Diameter: 137 miles (220 km)
Mass: unknown
Density: unknown
Escape velocity: approx. 0.06 mile (0.1 km) per second
Maximum apparent diameter as seen from Saturn: 3"
Planet composition
With a density only 0.69 times that of water, Saturn is the least dense of all the planets. (Terrestrial planets like Earth , Mercury, Venus, and Mars have densities closer to 5 times that of water.) Saturn's mass, however, is 95 times greater than Earth and is second only to Jupiter.
Like Jupiter, Saturn is believed to have a relatively small, rocky core, although Saturn may also have a layer of water, methane, and ammonia ices surrounding its core. Two thick layers of liquid hydrogen surround the central regions. In the lower layer, the pressure is so great that hydrogen behaves like a metal. As is the case with Jupiter, it is thought that the motion and circulation of this metallic layer give rise to Saturn's magnetic field. A gaseous atmosphere of hydrogen and helium lies above the upper layer of liquid hydrogen.
Rocky Core: radius of 13000 km
Liquid Helium Layer: 2000 km thick
Liquid Metallic Hydrogen Layer: 26000 km thick
Liquid Hydrogen Layer: 18000 km thick
Hydrogen and Helium Gas Layer: 1500 km thick
Topography
A wide range of cloud systems exist in Saturn' atmosphere. Several persistent symmetric white, brown, and red ovals have been observed at various latitudes and are believed to be a product of mixing methane, ammonia, and sulfur. Atmospheric bands colored yellow, brown, and black are the result of molecules, which were destroyed by ultraviolet sunlight and violent lightening, being mixed together by Saturn's dynamic weather patterns. The red band is probably produced by phosphine.
Two main atmospheric beltsù North Equatorial (Latitude +20) and South Equatorial (Latitude -20)ùare always visible, and aurora are common between 78 and 80 Latitude in both hemispheres. The major cloud features in Saturn's northern hemisphere are the Brown spot (1, 5,00 km in diameter) and Big Bertha (the largest spot, measuring 10,000 by 6,000 km). Saturn's southern hemisphere features Anne's Spot (5,000 by 3,000 km).
Compared with Jupiter, Saturn's features are low-contrast. This is explained in part by Saturn's lower temperatures and weaker gravity. The lower temperature means that the condensation point for a compound such as ammonia is reached at higher pressure (lower altitude or greater atmospheric depth) on Saturn.
Atmosphere
Hydrogen is the most abundant element in Saturn's atmosphere (about 94% by volume), followed by helium (about 6%). Traces of ammonia, phosphine, methane, ethane, acetylene, ammonium hydrosulfide, and water vapor are also present. A wide range of cloud systems exist in Saturn's atmosphere, with clouds of different compositions typically occurring in different layers (as seen in the diagram to the left).
The winds at Saturn's equator have been measured at 1,770 km (1,100 miles) per hour. These powerful winds, as well as other dynamic weather patterns, mix different molecules together to produce atmospheric bands colored yellow, brown, and black. Saturn's atmospheric features are not as colorful as those of Jupiter, probably because different chemical reactions predominate at Saturn's cooler temperatures. Despite the 27 inclination of the axis of rotation, Saturn's winds are symmetrical with respect to the equator. This indicates that the weak radiation received from the Sun only slightly affects atmospheric motion.
Magnetic fields and gravity
Like other planetary magnetic fields, the magnetic field generated by the liquid metallic hydrogen in Saturn's interior is very similar to that created by a simple bar magnet with north and south poles. Unlike other planets, however, Saturn's magnetic axis is aligned to within 1 degree of the spin axis.
The bow shock is approximately 24 Saturn radii away from the planet on the side closest to the Sun. On the opposite side of the planet, the magnetic field becomes very stretched and forms the magneto tail. The magneto tail extends for hundreds of radii away from Saturn; at a distance of 25 Saturn radii, the diameter of the tail is 80 Saturn radii.
Titan has no intrinsic magnetic field; therefore it has no electrically conducting and convecting liquid core. Its interaction with Saturn's magnetosphere creates a magnetic wake behind Titan. The big satellite also serves as a source for both neutral and charged hydrogen atoms in Saturn's magnetosphere.
Surface gravity on Saturn is 1.19 times the gravity on Earth.
Orbit and rotation
Saturn orbits in a very eccentric pattern at a mean distance of 1,427 million km from the Sun. It has a very rapid axial rotation of 10 hours 15 minutes, and an orbital period of 10,759.2 days (29.46 Earth years).
Moons and/or rings
Saturn has more than 20 known satellites, more than any other planet in the solar system. All of Saturn's satellites contain a high percentage of ice, but each is unique: Dione is dense; Mimas is marked by a crater 1/3 the size of the satellite; Enceladus has a smooth surface; Hyperion has an irregular shape; and Phoebe has a retrograde rotation. The largest satellite, Titan, has a dense, nitrogen-based atmosphere that makes it unique among all the solar system satellites. Researchers believe that solar radiation may be converting methane in Titan's atmosphere to ethane, acetylene, and (in combination with nitrogen) hydrogen cyanide, the building block of amino acids. These conditions may be similar to the conditions present on Earth between three and four billion years ago, but scientists believe that Titan's temperature is too low to permit further organic evolution.
Saturn is also surrounded by a series of seven named major rings (" A" through "G"), which have variable compositions. Researchers speculate that the rings were formed when a large object encountered Saturn early on in the solar system's evolution and broke into tiny fragments that spread around the planet. Alternatively, it is possible that a single, large satellite orbiting Saturn was destroyed by a collision with another object such as an asteroid. There is growing support for the theory that the rings represent debris associated with Saturn as the planet evolved from the original solar nebula, and that the debris was never part of another body.
The main rings A, B, and probably contain water ice in pieces ranging from tiny grains to blocks several tens of meters in diameter. Together the main rings span a width of about 275,000 km. Rings A and B are divided by the Cassini Division, a gap as wide as North America (nearly 4,000 km). Ring C, known as the Crepe or Dusky Ring, is semi-transparent.
Some of the known rings were not discovered by land-based observers. Pioneer 11 first detected Ring F and the Voyager probes added G and E, which are both very tenuous. The Voyagers also provided proof that there are literally thousands of rings within the minor divisions in major rings.
Mythology
Named for Cronos, father of Zeus (Jupiter). Most satellites are named for Titans who, according to Greek mythology, were brothers and sisters of Saturn. Janus is named for the two-faced Roman god who could look forward and backward at the same time. Epimetheus was named for the backward looking god. Mimas for a titan felled by Hephaestus (or Ares) in the war between the titans and Olympian gods. In that same war, Enceladus was crushed by Athene and earth piled on top of him became the island of Sicily. Tethys was the wife of Oceanus and mother of all rivers and Oceanids. Dione was the sister of Cronos and mother (by Zeus) of Aphrodite. Rhea, another sister of Cronos, was also his wife. Hyperion and Iapetus were also titans.
Discovery and exploration
Saturn, named for Jupiter's father, the first ruler of Olympus, is the most remote planet known to ancient people. The first recorded observations were made in Mesopotamia in the mid-7th century BC when Saturn occulted the Moon. Galileo Galilei is credited with the first observations of the disk itself in 1610. And in 1659, the rings were accurately described for the first time by Christiaan Huygens. G.D. Cassini, director of the Paris Observatory, first noted the gap in the rings in 1675, now known as Cassini's Division. The cause for the division was first explained by the "zones of avoidance" theory (the same as theory used to describe the reason for gaps between minor planets and asteroids between the Sun and Mars and Jupiter), developed in 1866 by Daniel Kirkwood.
In modern times, Saturn has been visited by Pioneer and Voyager probes: Pioneer 11 visited in September 1979. Voyager 1 in November 1980; Voyager 2 in August 1981. Exploration of the planet will continue with the Cassini mission, a combined effort by NASA and the European Space Agency scheduled for launch the latter part of the 1990s.
