- Io:
- Diameter: 3,643 km (2,264 miles)
- Orbit:
- Average Distance from Jupiter: 421,700 km (261,000 miles)
- Orbital Period: 1.8 days
- Composition: Primarily silicate rock with a thin atmosphere of sulfur dioxide.
- Surface Features: Extremely volcanically active with hundreds of volcanoes and sulfurous deposits.