Iapetus (moon)
Iapetus in true color, as imaged by the Cassini orbiter in September 2007. Iapetus's unusual two-tone coloration can be seen, along with its massive equatorial ridge on the right limb. | |
| Discovery | |
|---|---|
| Discovered by | G. D. Cassini |
| Discovery date | October 25, 1671 |
| Designations | |
Designation | Saturn VIII |
| Pronunciation | /aɪˈæpətəs/ |
Named after | Ἰαπετός Īapetus |
| Adjectives | Iapetian /aɪəˈpiːʃən/ |
| Orbital characteristics | |
| Periapsis | 3462252 km |
| Apoapsis | 3659387 km |
| 3560820 km | |
| Eccentricity | 0.0276812 |
| 79.3215 d | |
Average orbital speed | 3.26 km/s |
| Inclination |
|
| Satellite of | Saturn |
| Physical characteristics | |
| Dimensions | 1,492.0 × 1,492.0 × 1,424 km |
| 734.4±2.8 km | |
| 6777600 km2 | |
| Mass | (1.8056591±0.0000544)×1021 kg |
Mean density | 1.0887±0.0127 g/cm3 |
| 0.223 m/s2 (0.0228 g) (0.138 Moons) | |
| 0.573 km/s | |
| 79.3215 d (synchronous) | |
| 0° | |
| Albedo | 0.05–0.5 |
| Temperature | 90–130 K |
| 10.2–11.9 | |
Iapetus (/aɪˈæpətəs/) is the outermost of Saturn's large moons. With an estimated diameter of 1,469 km (913 mi), it is the third-largest moon of Saturn and the eleventh-largest in the Solar System. Named after the Titan Iapetus from Greek mythology, the moon was discovered in 1671 by Giovanni Domenico Cassini.
A relatively low-density body composed mostly of ice, Iapetus is home to several distinctive and unusual features, such as a striking difference in coloration between its dark leading hemisphere and its bright trailing hemisphere, as well as a massive equatorial ridge that runs three-quarters of the way around the moon.