This is a picture of Io, a moon of Jupiter. Io is covered with sulfur compounds ejected by volcanoes which continually erupt all over Io. Io is the most volcanically active body in the solar system.
Io orbits very close to Jupiter. As it goes around, the fact that Jupiter is pulling more strongly on one side (the closer side) of Io than the other squeezes and distorts Io, generating heat. This heat is responsible for all the volcanoes on Io.
PtyS 106 is the course that talks the most about Io.
PtyS 403, PtyS 407, and PtyS 411 also partly deal with Io.
Some other places you can find information on Io include:
