Cosmic Scale
Callisto
Moon of Jupiter · 778 million km from the Sun
How big is Callisto?
Callisto is about 4,821 km across.
See Callisto in 3D, at true scale
Callisto is the most heavily cratered object in the Solar System — a surface so old and so unchanged that it records four billion years of impacts. It orbits far enough out to sit mostly outside Jupiter's fierce radiation belts.
At a glance
| Diameter | 4,821 km |
|---|---|
| Mass | 1.08 × 10²³ kg |
| Diameter compared with Earth | 0.378 × Earth |
| Orbits | Jupiter, every 16.7 days |
| Surface age | About 4 billion years |
| Valhalla basin | Rings out to 1,900 km |
| Discovered | 1610, Galileo |
Good to know
- Its low radiation makes it the usual choice in studies of where a crewed base in the Jupiter system might go.
- It probably has a salty ocean 100 km or more beneath the surface.
- Unlike Io, Europa and Ganymede, it is not caught in the tidal resonance that heats them.