Saturn's Moons

Saturn has many moons (62 discovered as of 2012). The moons are: Titan, Rhea, Iapetus, Dione, Tethys, Enceladus, Mimas, Hyperion; Prometheus, Pandora (shepherd moons), Phoebe, Janus, Epimetheus, Helene, Telesto, Calypso, Atlas, Pan, Ymir, Paaliaq, Siarnaq, Tarvos, Kiviuq, Ijiraq, Thrymr, Skathi, Mundilfari, Erriapo, Albiorox, Suttung and 30 unnamed moons. Titan is the biggest moon; this moon has a thick nitrogen atmosphere.

Pan

Located within the Encke Gap in the rings

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
Mark R. Showalter/Voyager 2, 1990	133,583km	0.5750 days	10 km	unknown

Atlas

A shepherd satellite for Saturn’s A-ring.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
R. Terrile/Voyager 1, 1980	137,670 km	0.6019 days	18.5x17.2x13.5 km	unknown

Prometheus

A shepherd satellite for the inner edge of Saturn’s F Ring.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
S. A. Collins & D. Carlson/Voyager 1, 1980	139,353 km	0.613 days	74x50x34 km	unknown

Pandora

A shepherd satellite for the outer edge of Saturn’s F Ring.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
S. A. Collins & D. Carlson/Voyager 1, 1980	141,700 km	0.6285 days	55x44x31 km	unknown

Epimetheus

Covered by grooves, valleys, and craters over 30 km in diameter. Shares orbit with Janus (they are only separated by about 50 kilometers (31 miles)). Once every four years they approach each other, exchange some momentum and switch orbits.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
R. Walker/1966 and J. Fountain, S. Larson/1978	151,422 km	0.694 days	69x55x55 km	5.4 x 1017 kg

Janus

Heavily cratered (craters over 30 km in diameter). Shares orbit with Epimetheus (they are only separated by about 50 kilometers (31 miles)). Once every four years they approach each other, exchange some momentum and switch orbits.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
Audouin Dollfus, 1966	151,472 km	0.694 days	97x95x77 km	1.92 x 1018 kg

Mimas

Icy, heavily-cratered surface. Huge crater, Herschel, is 80 miles (130 km) wide. Herschel’s central mountain is 4 miles (6 km) tall, about 2/3 the height of Mount Everest. Very low temperatures (-200° C = -328°F).

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
William Herschel, 1789	185,520 km	0.942 days	209x196x191.4 km	3.75 x 1019 kg

Enceladus

Bright, smooth surface. Reflects almost all of the sunlight that hits it and is very cold ( -201° C = -330° F). 5 different types of terrain, suggesting a liquid interior: small craters, plains, fissures, corrugated terrain, and resurfaced areas.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
William Herschel, 1789	238,020 km	1.37 days	256x247x244.6 km	7 x 1019 kg

Tethys

Icy surface with craters, many cracks and plains. One huge ice trench, the Ithaca Chasma, is 40 miles (65 km) wide and extends over 3/4 of the way around the moon. A water-ice interior composition (density =1.21 gm/cm3). Surface temperature is -187° C = -305° F.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
G.D. Cassini, 1684	294,660 km	1.89 days	535.6x528x526 km	6.27 x 1020 kg

Telesto

Shares an orbit with Calypso; these 2 moons are also called the Tethys Trojans because they orbit Saturn in Tethys orbit, Telesto is 60° ahead of Tethys, Calypso is 60° behind Tethys.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
B. Smith, H. Reitsema, S. Larson, J. Fountain, 1980	294,660km (leads Tethys)	1.89 days	15x12.5x7.5 km	unknown

Calypso

Shares an orbit with Calypso; these 2 moons are also called the Tethys Trojans because they orbit Saturn in Tethys’ orbit, Telesto is 60° ahead of Tethys, Calypso is 60° behind Tethys.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
B. Smith, H. Reitsema, S. Larson, J. Fountain, 1980	294,660km (trails Tethys)	1.89 days	15.0x8.0x8.0 km	unknown

Dione

Icy surface with craters, plains and streaks of bright material. Some craters over 100 km wide. Its density is 1.43 gm/cm3, the densest moon of Saturn, indicating a large rocky core.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
G.D. Cassini, 1684	377,400 km	2.74 days	560 km	1.10 x 1021 kg

Helene

Shares orbit with Dione, leads it by 60°.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
P. Laques & J. Lecacheus, 1980	377,400 km (leads Dione)	2.74 days	18x16x15 km	unknown

Rhea

Icy surface with craters, plains and bright streaks. No atmosphere. Its density is 1.33 gm/cm3, indicating a small, rocky core covered with water-ice.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
G.D. Cassini,1672	527,040 km	4.52 days	764 km	2.31 x 1021 kg

Titan

Biggest moon of Saturn and second largest moon in Solar System (after Jupiter’s Ganymede). It is larger than the planets Mercury and Pluto. Titan has a thick mostly nitrogen atmosphere (with some methane) and an atmospheric pressure of 1.6 bars (60 percent greater than the Earth’s). This atmosphere with its heavy clouds obscures the moon’s surface. It may rain liquid methane. The surface temperature is about -178°C = -289°F.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
C. Huygens, 1655	1,221,830 km	15.9 days	2,575 km	1.3455 x 1023 kg

Hyperion

Hyperion is the largest-known irregular-shaped body. It has a reddish color. Surface marred with craters. Variable rotational period.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
W. & G. Bond/W. Lassell, 1848	1,481,100 km	21.27 days	180x140x112.5 km	2 x 1019 kg

Iapetus

A rocky moon that is partly bright and partly reddish in color. Craters on surface.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
G.D. Cassini,1671	3,561,300 km	79.33 days	718 km	1.6 x 1021 kg

Phoebe

Almost circular shape, reddish color. Orbits in a retrograde direction (opposite in direction to other satellites’ orbits). Rotates on its axis every 9 hours (this is unlike the other moons of Saturn, except Hyperion, which always show the same face to Saturn). Phoebe may be a captured asteroid.

Discovered	Distance from Saturn	Orbital Period	Radius	Mass
W. Pickering, 1898	12,952,000 km	550.48 days (retrograde orbit)	110 km	4 x 1018 kg