Orbiting the giant planet Jupiter is the fascinating moon, Io, one of four moons discovered by Galileo in 1610. One look at Io and it is obvious that something unusual is going on there. Its mottled surface is a collage of colors-yellow, orange, red, and blackish browns - which make it look somewhat like a gigantic pizza. The explanation for this remarkable color palette is found down on the surface. Volcanoes! Io is literally bursting with volcanic activity. Volcanoes spew out vast amounts of sulfurous material which cover Io's Iandscape. Io's surface coloration reflects the various colors that sulfur takes on at different temperatures.
Fiery volcanoes pepper Io's landscape, and massive lava flows spread out over enormous distances. From its surface, geyserlike eruptions eject dust and gas hundreds of kilometers into space, which fall back to the ground in elegant umbrella-shaped plumes. Some of the hottest temperatures in the solar system outside of the sun are found here, and yet most of the surface is bitterly cold.
Intense radiation from Jupiter's atmosphere over the course of the mission has severely damaged Galileo's computer circuitry and has resulted in failure of the spacecrafts computer systems. In order to prevent the possibility of the crippled spacecraft contaminating the environment of Io's neighboring moon, Europa, which may harbor a liquid water ocean beneath its surface, the spacecraft will plunge into the atmosphere of Jupiter on September 21, 2003. At that time, after a tremendously successful eight year tour of the Jovian system, the Galileo mission will come to an end.
Photo Credit: NASA/JPL
Illustration Credit: NASA/JPL
Date created June 6, 2000
Last updated June 5, 2003