Galilean moon · moon of Jupiter
Callisto
The outermost Galilean moon, with one of the oldest and most heavily cratered surfaces in the Solar System.
- Distance from Earth today
- 815.7 million km5.452 AU · light: 45 min 21 s
- Distance from the Sun today
- 795.2 million km5.316 AU
- As of
- 4 November 2026position from NASA/JPL orbital elements
Where it is today
Top view of the plane of Earth’s orbit, compressed distance scale. Open on the big map with the time slider →
Facts
- Diameter
- 4,821 km
- Mass
- 107,566 × 10¹⁸ kg
- Density
- 1,834 kg/m³
- Mean distance from the planet
- 1,882,700 km
- Orbital period
- 16.7 days
- Orbital eccentricity
- 0.0070
- Orbital inclination
- 0.3°
Source of the figures: JPL SSD – Planetary Satellites (public domain).
Discovery: 1610 – Galileo Galilei
Description
Callisto is the second-largest moon of Jupiter and the outermost of the four discovered by Galileo. Unlike its siblings, it is not locked in an orbital resonance and receives little tidal heating, so its dark surface has remained almost unchanged for billions of years and is saturated with impact craters. Its most striking feature is Valhalla, a giant impact basin surrounded by concentric rings. Measurements by the Galileo spacecraft hinted that a salty ocean may exist deep beneath its crust. Because it lies outside Jupiter's most intense radiation, Callisto has often been suggested as a future base for exploring the Jovian system.