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'. The prominent heart-shaped red feature surrounds a massive volcano called Pele. The red colour probably represents recent fragmental volcanic material (pyroclastics), again sulphurous in chemistry. This image was made in near infrared, green and ultraviolet light by the Galileo spacecraft in June 1996.