Site hosted by Build your free website today!


Semimajor Axis of Orbit 422,000 km
Siderial Revolution Period 1d 18h 28m
Orbit Eccentricity 0.004
Orbital Inclination 0.0
Radius 1815 km
Visual Magnitude 5.0

Io, the innermost of the Galilean satellites, is the most volcanically active object in the solar system. Volcanoes on the satellite spew molten sulfur and sulfur dioxide hundreds of kilometers into space. It then solidifies and falls back to the surface as a sort of "snow" of sulfur compounds. The reason that Io is so volcanically active is that it is being heated by the strong gravitational pull of Jupiter, which melts the materials at the center of the satellite.