Ancient moon of JupiterA benchmark for planetary history
Callisto
Callisto's crater-saturated surface records one of the oldest landscapes in the Solar System.
- Host
- Jupiter
- Type
- Ancient icy moon
- Mean diameter
- 4,821 km
- Mean orbital radius
- 1,882,700 km
- Orbital period
- 16.69 days
- Surface gravity
- 1.24 m/s²
- Radiation
- Lower than inner Jovian moons
- Ocean evidence
- Possible subsurface ocean
Callisto up close
NASA imagery
A landscape without renewal
Callisto has almost no visible tectonic activity or volcanic resurfacing. Impact after impact has saturated its surface, erasing older terrain and building a record that may span billions of years.
Bright spots mark fresh craters and ejecta. Their distribution helps scientists estimate the size and age distributions of objects that have struck the Jovian system.
An ocean far below
Callisto's interior likely contains a deep ocean beneath more than 100 kilometres of ice and rock, but the evidence is less direct than for Europa or Ganymede.
Because Callisto sits outside Jupiter's strongest radiation belts, it is sometimes discussed as a possible future base for studying the Jovian system. Any mission would still face extreme cold and distance.
Worth knowing
Callisto is the third-largest moon in the Solar System after Ganymede and Titan.
Its surface is one of the most heavily cratered landscapes known.
A day on Callisto lasts about 16.7 Earth days because it is tidally locked.
Watch and explore
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The Most Battered World in Space SpaceAtlas
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Research & further reading
Mission imagery and measurements are interpreted alongside orbital data. Follow the source links for the current NASA overview and precise satellite parameters.