Agitated by Jupiter's gravity, Io is a cauldron of volcanism, spewing out silicate lava, sulfur, and sulfur dioxide. Its irregular orbit around the gas giant creates strong tidal forces within Io, causing its surface to rise and fall by as much as 100 meters. The volcanic activity constantly remodels this small moon, flooding its surface with molten material and pockmarking it with new eruptions.
This landscape is assembled from images taken by the 1979 Voyager spacecraft and by the Galileo craft, which cruised the Jovian system in the late 1990s and early 2000s. A major international expedition to Jupiter's moons is in the planning stages, but the space agencies intend to focus on the icy moons Europa and Ganymede.