This oozy, pockmarked image is the surface of Jupiter’s moon Io, from the first complete geologic map of the turbulent orb. Io is the most volcanically active place in the solar system, so it’s of great interest to geologists because its surface is continually refreshing and renewing. It’s the only celestial body where scientists have not seen any impact craters.
The U.S. Geological Survey published the Io map using data from four image mosaics, produced by the Voyager and Galileo missions. David Williams, a faculty research associate in the School of Earth and Space Exploration at Arizona State University, spent six years breaking the mosaics down to 19 different types of surface material. The map can now be used as a benchmark for further Io studies, allowing scientists to track how the moon changes.
Tidal forces among Jupiter, Io and its sister moons Ganymede and Europa cause wrenching movements in the moon’s crust, creating heat inside the moon and causing its volcanism.
The map, which is rendered in true color, includes lava flows, tholi (volcanic domes), moon calderas called paterae, and sulfur plains. You can download the whole thing here.