Io. Enhanced-colour view of Io, innermost of the 'Galilean' moons of Jupiter. The orange and yellow colours come from various forms and compounds of sulphur which cover most of the surface. The white areas are thought to be sulphur dioxide 'frost'. Just upper right of centre is a large black feature called Loki. This is thought to be a 250km-wide lake of sulphur, with a large 'raft' of solid sulphur floating in it. Loki is a volcanic feature, plumes of ejected material being seen in earlier Voyager images. This image was made in near infrared, green and ultraviolet light by the Galileo spacecraft in June 1996.