Key facts
- Mean diameter
- 3,643.2 km
- Mass
- 8.93 × 10^22 kg (0.015 Earths)
- Surface gravity
- 1.796 m/s² (0.183 g)
- Escape velocity
- 2.56 km/s
- Mean temperature
- -130 °C
- Rotation period
- 42.456 hours
- Orbital period
- 1.769 days
- Mean distance from Jupiter
- 0.4217 million km
Atmosphere
Negligible or extremely thin.
Composition and structure
Rock and ice.
Discovery and exploration
Hundreds of active volcanoes; lava lakes and sulfur plumes up to 400 km high.