Callisto
4,821 kmacross
Callisto is 4,821 km across and orbits Jupiter at 1,882,700 km, once every 16.7 days. One of the most heavily cratered worlds known — a four-billion-year-old surface that has simply kept the score.
▶ Visit Callisto in 3D
Why this moon matters
Callisto is the solar system’s museum piece: geologically dead for around four billion years, its surface has simply accumulated craters — including Valhalla, a multi-ringed impact scar nearly 3,800 km across. Orbiting outside Jupiter’s worst radiation belts, it is regularly proposed as the least-hostile site for a future human outpost in the Jovian system.
Nothing has resurfaced Callisto since before complex life existed on Earth. Its face is the solar system’s oldest unedited photograph.
Callisto by the numbers
Diameter
4,821 km
Distance from Jupiter
1,882,700 km
Orbit period
16.7 days
Rotation
tidally locked
Surface gravity
1.24 m/s²
Temperature
−139 °C
Orbital speed
8.2 km/s
Sunlight travel time
43 minutes
In the interactive view you can fly to Callisto directly and ride along as it circles Jupiter.
Keep going
✓ Facts verified July 2026
Every figure on this page is a real, rounded value checked against primary sources. Found something out of date? See how we keep it accurate.