Aster › Space program › Janus
Janus
Position on the route: 46/130 · level needed 126 · journey (Mk0 engine) 24.6 h
By the numbers
| Size | ≈ 203 × 185 × 152 km |
|---|---|
| Year | 16.7 hours |
| Distance | 151,472 km |
| Found | 1966, Dollfus |
The story
Janus and Epimetheus are the Solar System’s oddest pair: they share nearly the same orbit. When the inner moon catches up with the outer one they do not collide but swap places: about every four years, one moves into the other’s orbit. Audouin Dollfus found Janus in 1966; that they were two separate bodies was shown later by Voyager.
About 179 km, cratered, with a density of 0.63 g/cm³: very porous. It circles just outside the rings, at the edge of Saturn’s A ring.
Missions
- Voyager 1 and 2 (1980–81)
- Cassini (2004–2017): close flybys
Colony note
Close to the rings; weak gravity. A station for the rings.
What probes bring back
- It shares one orbit with Epimetheus: about every four years they swap places, each drawing back before it can overtake the other.
- About 179 km, heavily cratered and low in density (0.63 g/cm³); found by Dollfus in 1966.