Saturn

Planet Profile

Mass (kg)............................................5.69 x 10^26
Diameter (km)........................................120660
Mean density (kg/m^3) ...............................690
Escape velocity (m/sec)..............................35600

Average distance from Sun (AU).......................9.539
Rotation period (length of day in Earth hours).......10.2
Revolution period (length of year in Earth years)....29.46

Obliquity (tilt of axis in degrees)..................26.7
Orbit inclination (degrees)..........................2.49
Orbit eccentricity (deviation from circular).........0.056

Mean temperature (K).................................88 K (1 bar level)

Visual geometric albedo (reflectivity)...............0.46
Atmospheric components...............................97% hydrogen, 
                                                      3% helium, 
                                                       .05% methane
Rings................................................Rings are 
        270,000 km in diameter, but only a few hundred meters thick. 
        Particles are centimeters to decameters in size and are ice (some
        may be covered with ice); there are traces of silicate 
        and carbon minerals. There are four main ring groups and three
        more faint, narrow ring groups separated by gaps called divisions.

Clouds and Spokes

Several dark spoke-like features can be seen across the broad B ring (left of planet). The moons Rhea and Dione appear as dots below and below left of Saturn, respectively. This photo was taken July 21, 1981, when the spacecraft was 33.9 million km (21 million mi) from the planet. Voyager 2 made its closest approach to Saturn on August 25, 1981.

Rings in Shadow

This image of Saturn was taken while the spacecraft was departing the Saturnian system. The planet's disk casts a shadow across the ring system. The visible side of the rings is directly illuminated by the sun. The broad dark band in the rings separates the outer A ring from the inner B ring. The C ring is much fainter and closer to the planet. The narrow F ring is just barely visible outside the A ring.

Braided Rings

Saturn's narrow F ring, just outside the main ring system, is a very complex structure. In this close-up view it is made up of two narrow bright rings and a fainter ring inside them. The bright rings contain bends, kinks, and bright clumps that give the illusion that these strands are braided. Scientists speculate that the clumps may contain mini moons. The F ring was photographed at a range of 750,000 km (470,000 mi).

Red Oval Cloud

This unique red oval cloud feature is visible in Saturn's southern hemisphere. The difference in color between the red oval and surrounding bluish clouds indicates that material within the oval contains a substance that absorbs more blue and violet light than the bluish clouds. The oval feature did not change in appearance for several months before this photo was taken on November 6, 1980 at a distance of 8,500,000 km (6,300,000 mi).

Three Moons

The disk of Saturn casts a shadow across its rings away from the sun. The satellites Mimas, Enceladus, and Tethys, seen as dots, all orbit Saturn in the plane defined by its rings and equator.

Saturn's Moons

Saturn and two of its moons, Tethys and Dione, were photographed by Voyager 1 at a distance of 13 million km (8 million mi). The shadows of Saturn's three bright rings are cast onto the cloud tops. The limb of the planet can be seen easily through the 3500 km (2170 mi) wide Cassini Division, which separates the A and B rings. The view through the much narrower Encke Gap, near the outer edge of the A ring is less clear. Closer to the planet is the faintest of Saturn's three main rings, the C ring or crepe ring, barely visible against the planet.

Cataclysmic Impact

Mimas, the innermost of Saturn's larger moons, was nearly shattered by a cataclysmic impact. From observing Mimas' crater Herschel, scientists speculate that the inner satellites of the outer planets have, in fact, been shattered and gravitationally reassembled many times in their geologic history. Herschel's walls are approximately 5 km (3.2 mi) high, parts of its floor measure 10 km (6.2 mi) deep, and its central peak rises 6 km (3.7 mi) above the crater floor. The diameter of this moon is 394 km (244 mi).

Global Mosaic

This global mosaic of Enceladus was assembled from images acquired by Voyager 2 during its close flyby of Saturn's second large satellite. Although Enceladus shows an abundance of impact craters in some areas, the lava flows near the center of the disk contain many fewer craters and cut some craters in half. This confirms the multiple stages or episodes of volcanism that formed and reformed the icy body's surface.

Bright Satellite

The surface of Enceladus resembles that of Jupiter's satellite Ganymede. Some areas are smooth and uncratered while others contain impact craters up to 35 km (22 mi) in diameter. Linear sets of grooves tens of kilometers long traverse the surface and are probably faults resulting from deformation of the crust. The uncratered regions are geologically young and may indicate that Enceladus has experienced a period of relatively recent internal melting. The satellite is about 500 km (310 mi) in diameter and has the brightest surface of any of Saturn's satellites.

Impact Craters

Tethys is approximately 1100 km (684 mi) in diameter and is densely populated with impact craters. One of these, above center, is surrounded by a hummocky ejecta blanket. Ithaca Chasma stretches from left center up toward the crater, covering three quarters of the circumference of Tethys.

Smooth Crust

In this image of Saturn's fourth large moon, Dione, the trailing hemisphere is visible. This region was protected from billions of years of impact-gardening, which obliterated old surface features in the leading hemisphere. Icy fluids escaped to the surface through breaks in the crust and formed giant crisscrossing, wispy, bright marks on the exterior.

Full Disk

Impact craters are visible records of the collision of cosmic debris. On Dione, the largest crater is less than 100 km (62 mi) in diameter and shows a well-developed central peak. The sinuous valleys may have formed when faults broke the moon's icy crust. Images in this mosaic were taken from a range of 162,000 km (100,600 mi) on November 12, 1980.

Water Ice

The density of Saturn's moon Rhea suggests that it is largely made of water ice with a small proportion of rocky material. Note that the ancient impact scars that ripped through the ice early after the formation of the solar system are still preserved to this day.

Obscure Titan

This view of Saturn's largest satellite was taken from a position looking almost directly back toward the sun at the Mercury-sized body. Titan's hydrocarbon-rich nitrogen atmosphere scatters sunlight in a forward direction over the limb around the entire disk. The surface of Titan is obscured due to a deep cloud layer. The diameter of Titan is 5150 km (3200 mi).

Irregular Body

Scientists believe that this small irregular satellite may once have been a piece of a larger satellite. Hyperion measures approximately 370 x 280 x 225 km (229 x 174 x 140 mi) and orbits outside of Titan.

Global Dichotomy

The leading hemisphere of Iapetus is covered by extremely dark material, whereas the trailing hemisphere is covered with bright material. This dichotomy puzzled the discoverer, astronomer Giovanni Cassini, who noted that the satellite was visible only from one side of its orbit. Two models have been proposed to explain this. The first proposes that dark material from Phoebe, a dark exterior moon, falls onto Iapetus from orbit. The second model says that the dark material erupted from the interior of Iapetus into a low area in the leading hemisphere.

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