Volcano World Io
This color image of Jupiter's moon Io was taken by the Galileo orbiter. It clearly shows the blistered, volcanic surface of this tortured moon. Gravitational tidal forces cause Io to stretch as it orbits the planet. This created friction, which heats up the interior of the moon. Active volcanoes spit out liquid sulfur and other material that give Io its unique colors. The color of this image has been enhanced slightly to bring out more details.
NASA / JPL / University of Arizona