Jupiter's moon Io is arguably one of the most volcanically active bodies in the Solar System. The reason, according to NASA's page Scientists to Io: Your Volcanoes Are in the Wrong Place is believed ...
Iapetus's hemisphere facing Saturn is dark, whereas the opposite one is bright. Could a cryo-volcano be the reason behind this colour difference in Iapetus's hemispheres?
This question is somewhat related to my earlier question How are the compositional components of exoplanet atmospheres differentiated?, but this about a specific surface-atmospheric phenomena - ...