This view of Jupiter's moon Io was captured by NASA's Galileo spacecraft. Slightly larger than Earth's moon, Io is the most volcanically active body in the solar system. Deposits of sulfurous materials, like sulfur dioxide frost, coat the surface in hues of yellow, white, grey and brown. Bright red materials and dark spots mark areas of recent volcanic activity usually associated with high temperatures and surface changes.
Because it has so much geologically activity, Io's surface is constantly changing. During the course of its long mission Galileo was able to observe as eruptions transformed this exotic landscape, teaching us about processes similar to those experienced by the early, highly volcanic earth.