Io Volcanic Moon of Jupiter

Io is one of the four largest moons of the planet Jupiter. This rocky world is volcanically active with over 400 active volcanoes fueled by gravitational induced tidal forces. Io was discovered in 1610 by Galileo and has been photographed by numerous NASA spacecraft including the two Voyagers, Galileo, Cassini-Huygens, New Horizons and Juno, as well as the Hubble Space Telescope.