Interesting facts
  • Io has hundreds of volcanoes, and is the most geologically-active object in our Solar System.
  • This is a result of tidal heating in Io’s interior, caused by gravitational forces from Jupiter and its other large moons.
  • Io is in orbital resonance with Europa and Ganymede: for every orbit of Ganymede, Europa orbits twice and Io orbits four times.

You can view these links to learn more about Io and the Galilean moons:
The Io image on this page (with Jupiter behind) was taken in 2001 by the Cassini probe, and is courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Goddard Space Flight Center.

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