Images taken by NASA's Galileo spacecraft with different angles of sunlight help scientists interpret the three- dimensional shape of structures on Jupiter's moons. This pair shows a mountain named Tohil Mons on the innermost of Jupiter's four large moons, Io. The top image was taken at low resolution and a low Sun angle during Galileo's third orbit, in 1996. Because the Sun is low, topographic features on the mountain can be recognized from the shadows they cast.
Labels indicate the peak of the mountain and two volcanic depressions, called paterae.
The topography is almost indistinguishable, but many more details can be discerned. By combining several observations in this manner, Galileo scientists are able to study Io's mountains and to learn about their evolution and their relationship to Io's volcanoes.