Galileo and the atmosphere of Callisto

NASA reveals recent findings from the unmanned Galileo orbiter touring Jupiter and its moons, including the discovery of a tenuous atmosphere surrounding the outermost large moon of Jupiter, Callisto. The thin layer of carbon dioxide surrounding Callisto completes the set: Galileo has detected an atmosphere of one kind or another around each of Jupiter’s four Galilean moons, some of which are large enough to be planets. As for how the atmosphere is sustained in the extremely hostile environment around Jupiter, scientists speculate that the CO2 could be emitted from beneath Callisto’s own crust.