Known Space -- Sol -- Saturn -- | Janus |
Janus is the sixth satellite of Saturn. Janus has an irregular shape with a size of 196 x 192 x 150 kilometers in diameter. It is heavily cratered with several craters 30 kilometers in diameter. The pervasive cratering indicates that its surface must be several billion years old. Prometheus appears to have fewer craters indicating a younger surface while Pandora appears to have an older surface. Janus has few linear features.
Janus and Epimetheus are "co-orbital" ... they share the same orbit of 151,472 kilometers from Saturn's center or 91,000 kilometers above the cloud tops. They are only separated by about 50 kilometers. As these two satellites approach each other they exchange a little momentum and trade orbits; the inner satellite becomes the outer and the outer moves to the inner position. This exchange happens about once every four years. Janus and Epimetheus may have formed from a disruption of a single parent to form co-orbital satellites. If this is the case, the disruption must have happened early in the history of the satellite system.
Orbital Distance: 151,500 km (average) Eccentricity: 0.007 Local Year: 0.695 days (16h 40m 48s) Orbital Velocity: 15.849 km/s Inclination: 0.140° Local Day: 0.695 days (16h 40m 48s) Axial Tilt: n/a Diameter: 196 km x 192 km x 150 km Composition: Ice Density: 0.68 g/cm3 Mass: 2.01 x 1015 tonnes (336/billion earths) Gravity: 0.0017 G Escape Velocity: 0.055 km/s Area: 100,000 km2 Surface Material: Mostly H2O ice Atmosphere: None Pressure: None Albedo: 0.80 Temperature: ???°C |