Other Saturnian Moons

The Saturnian system contains several smaller, irregular moons that we know very little about. These satellites are extremely small, and many were not discovered until the Voyager encounters with Saturn or by astronomers using the Hubble space telescope. Because of their small size, it is possible that some of these moons may be captured asteroids or comets. These recent discoveries bring the total number of Saturnian moons to 31. Below is a listing of the largest of these moons in the order of their orbit from Saturn. Images that appear on this page are the best available at this time. You may also access information on one of the moons by clicking on its name below:

Pan		Epimetheus		Helene
Atlas		Janus		Hyperion
Prometheus		Telesto		Phoebe
Pandora		Calypso

Pan

Pan is the innermost of Saturn's moons. It was named after the ancient mythical god of the woods, who had a human head and torso and the legs, ears, and horns of a goat. Pan was discovered by Mark R. Showalter in 1990 using data sent back by the Voyager spacecraft. It was discovered nine years after the Voyager encounter when unusual patterns in Saturn's A-ring predicted the size and location of a small moon. Pan orbits inside the Encke Gap of Saturn's A-ring. It acts as a shepherd satellite and is responsible for keeping the gap open. Not much is known about Pan at this time. The discovery of this small moon has led some astronomers to believe that there may be other moons within Saturn's rings yet to be discovered.

Atlas

Atlas is the second of Saturn's known moons. It was named after the Titan condemned by Zeus to carry the heavens on his shoulders. He was the son of Iapetus and the nymph Clymene and brother of Prometheus and Epimetheus. Atlas was discovered by R. Terrile in 1980 using images received from the Voyager spacecraft. It orbits Saturn near the edge of the A-ring and is believed to be a shepherd for this ring system. Very little is known about this tiny moon.

Cassini image of tiny Atlas (NASA/JPL/Space Science Institute)		Statistics for Atlas Discovered by...... R. Terrile Year of Discovery...... 1980 Diameter...... 28.5 x 23.6 x 12 miles (46 x 38 x 19 km) Mean Distance from Saturn...... 85,503 miles (137,640 km) Rotational Period...... unknown Orbital Period...... 0.602 days Orbital Eccentricity...... 0 Orbital Inclination...... 0 degrees Apparent Magnitude...... 18.0

Prometheus

Prometheus [pra-MEE-thee-us] is Saturn's third moon. In Greek mythology, Prometheus was a Titan who stole fire from Olympus and gave it to humankind. For this he was severely punished by Zeus. He was the brother of Atlas and Epimetheus. Prometheus was discovered in 1980 by S. Collins and others using images from the Voyager missions. It acts as a shepherd satellite for the inner edge of Saturn's F-ring. Prometheus is extremely elongated in shape and is covered with a number of ridges, valleys and craters. Some of these craters are measure up to 12 miles (20 km) across. Prometheus appears to be somewhat less cratered than some of its neighboring moons. Prometheus has a very low density. This indicates to astronomers that it is composed mainly of porous ice.

Pandora

Pandora [pan-DOR-uh] is the fourth of Saturn's known moons. In Greek mythology, Pandora was the first woman. She was bestowed upon humankind by Zeus as a punishment for Prometheus' theft of fire. She was the wife of Epimetheus, and was entrusted with a box containing all the ills that could plague mankind. She opened it out of curiosity and thereby released all the evils of human life. This was the fabled "Pandora's Box". Pandora was discovered by Collins and others using images from the Voyager spacecraft. It is the outer shepherd satellite for Saturn's F-ring. Pandora appears to be heavily cratered, with some of the craters as much as 19 miles (30 km) in diameter. It is much more heavily cratered than its nearby neighbor, Prometheus. Not much is known about Pandora at this time.

Epimetheus

Epimetheus [ep-eh-MEE-thee-us] is the fifth of Saturn's moons. It was named after the son of Iapetus and brother of Prometheus and Atlas. He was the also the husband of Pandora. Epimetheus was first discovered in 1966 by R. Walker. At the time, the discovery was somewhat confusing since Janus shares a similar orbit. In 1977, Fountain and Larson were able to show that there were actually two moons involved. Epimetheus has a very irregular shape and is covered with ridges, grooves and craters. Some of these craters are as large as 19 miles (30 km) in diameter. Epimetheus is considered to be co-orbital with Janus. This means that both moons share the same orbit of about 94,095 miles (151,472 km) from Saturn's center. As the two moons approach each other they exchange momentum and trade orbits with each other. Thus, the outer moon becomes the inner and vice versa. This exchange takes place about every four years. Astronomers believe that the Epimetheus and Janus may have formed from a single moon that was broken in two by some cataclysmic event.

Janus

Janus [JAY-nus] is Saturn's sixth moon. It was named after the ancient god of gates and doorways, who was often depicted with two faces looking in opposite directions. Janus was first discovered by the French astronomer Audouin Dollfus in 1966. Although he is credited with the discovery, it is not certain whether what he saw was Janus or Epimetheus. In 1978, Fountain and Larson were able to show that there were actually two moons in the same orbit. The surface of Janus is heavily cratered. Some of these craters approach 19 miles (30 km) in diameter. Its surface appears to be older than that of Prometheus and younger than that of Pandora. It has few linear features. Janus is co-orbital with Epimetheus. Both moons share the same orbit of about 94,095 miles (151,472 km) from Saturn's center. As the two moons approach each other they exchange momentum and trade orbits with each other. Thus, the outer moon becomes the inner and vice versa. This exchange takes place about every four years. Astronomers believe that the Epimetheus and Janus may have formed from a single moon that was broken in two by some cataclysmic event.

Telesto

Telesto [tah-LESS-toh] is the tenth of Saturn's moons. It was named after the daughter of Oceanus and Tethys in Greek mythology. Telesto was discovered by Smith, Reitsema, Larson and Fountain in 1980 based using ground-based observations. This moon and its cousin, Calypso, are known as Tethys Trojans. They travel around Saturn in the same orbit as Tethys about 60 degrees ahead and behind it. Telesto orbits in Telesto's leading Lagrange point, about 60 degrees ahead of Tethys. Very little is known about this small moon.

Calypso

Calypso [ka-LIP-so] is the eleventh of Saturn's moons. According to Greek mythology, Calypso was a sea nymph who delayed Odysseus by keeping him on an island for seven years. Calypso was discovered by Smith, Reitsema, Larson and Fountain in 1980 based using ground-based observations. This moon and its cousin, Telesto, are known as a Tethys Trojans. They travel around Saturn in the same orbit as Tethys about 60 degrees ahead and behind it. Calypso orbits in Telesto's trailing Lagrange point, about 60 degrees behind Tethys. Not much is known about this moon.

Helene

Helene is the thirteenth of Saturn's known moons. It was named after the Amazon who battled Achilles in Greek mythology. Helene was discovered in 1980 by P. Laques and J. Lecacheus from ground-based observations. Helene is considered a Trojan satellite of Dione because it shares the same orbit. it circles Saturn about 60 degrees ahead of Dione. This puts it in Dione's leading Lagrange point. Because if this, Helene is sometimes referred to as Dione B. very little is known about this moon at the present time.

Hyperion

Hyperion [hi-PEER-ee-en] is the sixteenth of Saturn's moons. In Greek mythology, Hyperion was a Titan. He was also the son of Gaea and Uranus and the father of Helios. Hyperion was discovered by Bond and Lassell in 1848. It is the largest irregular object in the Solar System. Most other moons of this size are spherical in shape. Astronomers believe that a collision with another object may have blasted away part of the moon, leaving behind the irregular fragment we see today. Hyperion has a very low density, which indicates that it is probably composed mainly of water ice with a small amount of rocky material. It has a low albedo, which seems to suggest that it may be covered with some type of dark material, possible from the moon Phoebe. The surface of Hyperion is heavily cratered, indicating that it is probably the oldest surface in the Saturnian system. The largest of these craters measures 75 miles (120 km) in diameter and 6.2 miles (10 km deep). One odd feature about Hyperion is the fact that its rotation is very chaotic. Its axis of rotation wobbles so much that its rotational period varies from one orbit to the next. It is the only known body in the Solar System known to do this. This chaotic rotation may be the result of its eccentric orbit combined with gravitational forces from Saturn.

Phoebe

Phoebe [FEE-bee] is the eighteenth and outermost of Saturn's moons. In Greek mythology, Phoebe was the virgin goddess of the hunt and the Moon, and the twin sister of the god Apollo. Phoebe was discovered in 1898 by William Henry Pickering. This moon orbits Saturn in a retrograde motion, which means the direction of its orbit is opposite that of Saturn's other moons. Phoebe appears to be roughly circular in shape, and has a very low albedo. In fact, its albedo is only 0.05, which makes it darker than coal. It is also very red in color. Some astronomers believe that Phoebe might be the source of dark material on Hyperion and Iapetus. This material may have been blasted away from Phoebe by meteor impacts. Phoebe rotates on its axis about once every nine hours. Because of this, its rotation is not synchronous. It does not show the same face to Saturn as do all of the other Saturnian moons except Hyperion. Astronomers believe that Phoebe may be a captured asteroid. Its composition resembles that of other dark carbonaceous asteroids. These asteroids are very primitive, and are thought to be composed of the original material that formed the Solar System. Since they are small, the Sun never heats them sufficiently to change their chemical composition. If this is true, then Phoebe would the first such object to ever be photographed at close range.