Moon of Jupiter
Diameter: 3660 km
Distance: 421700 km (mean)
Period: 1.769 days
Eccentricity: 0.0041
Inclination: 0.05°
Magnitude: 5

Io is the innermost of Jupiter's 'Galilean Satellites' and the most volcanically active body in the solar system with over 400 known volcanoes producing plumes of sulfur and sulfur dioxide reaching up to 500 km into space. They are kept active by Jupiter's tremendous tidal force and its own tidal heating. Io's surface counts about 100 mountains, but hardly any crater, and if produced, they will soon be filled with lava.