Callisto
Moon· orbits Jupiter
Callisto is the outermost Galilean moon and among the most heavily cratered bodies known — an ancient, dark, only partly differentiated mix of rock and ice that may conceal a deep ocean.
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Key facts
Mass
1.08 × 10²³ kg
0.018 M⊕
Radius
2,410 km
1.39× wider than our Moon
Surface gravity
1.24 m/s²
13% of Earth's gravity
Day length
16.7 days
Orbit around Jupiter
16.69 Earth days
Science
Physical
- Mass
- 1.08 × 10²³ kg · 0.018 M⊕
- JPL / IAU mean radii; spacecraft-tracked GM where measured
- Radius
- 2,410 km · 1.39× wider than our Moon
- JPL / IAU mean radii; spacecraft-tracked GM where measured
- Density
- 1,834 kg/m³ · 1.8× water
- Computed from mass and radius
- Surface gravity
- 1.24 m/s² · 13% of Earth's gravity
- Computed from mass and radius
- Escape velocity
- 2.44 km/s · 22% of Earth's escape velocity
- Computed from mass and radius
Orbit around Jupiter
- Distance from Jupiter
- 1,882,700 km
- From JPL orbital elements
- Orbital period
- 16.7 days
- From JPL orbital elements
- Eccentricity
- 0.007
- From JPL orbital elements
- Inclination to Jupiter's Laplace plane
- 0.30 °
- From JPL orbital elements · The Laplace plane is the one a moon's orbit precesses about: close in it is the planet's equatorial plane, the plane of the rings, and further out it tilts toward the planet's own orbit.
Rotation
- Rotation period
- 16.7 days
- Tidal locking
- Tidally locked to its parent
Temperature
- Mean
- 134 K (-139 °C)
Composition
- Bulk composition
- A nearly uniform mixture of rock and water ice, only partly differentiated, possibly over a deep salty ocean.
Radiation & temperature
- Insolation
- 0.0353 S⊕ · 4% of the sunlight Earth receives
- Computed from the distance to the Sun (inverse-square; Earth's sunlight = 1), before any atmosphere.
- Bond albedo
- 0.12 · reflects 12% of incoming sunlight
- Equilibrium temperature
- 117 K (-156 °C)
- Computed from albedo + distance from the Sun (airless black body)
- Measured mean temperature
- 134 K (-139 °C)
- Greenhouse warming
- +17 K
- Measured temperature minus the airless equilibrium — the greenhouse effect
Discovery & history
- Discovered
- January 7, 1610
- By
- Galileo Galilei
- Method
- Visual discovery (telescopic)
- Name
- Callisto, a nymph and companion of Artemis loved by Zeus.
The outermost Galilean moon, found in 1610. Its ancient, heavily cratered surface is among the oldest in the Solar System.
Images
Images from open archives · credit shown per image