NASA has used photos gathered during the Galileo Solid-State Imaging (SSI) experiment in 1995 and 1998. The colours have been enhanced to create a complete image that resembles how the moon would look to a human observer.
Near-infrared, green and violet filters were combined to create the realistic view. Gaps in the original image have been filled by NASA, using surrounding terrain and colours. The cracked surface is due to broken ice refreezing in different patterns, creating a terrain of criss-crossed ridges.
"Colour variations across the surface are associated with differences in geologic feature type and location. For example, areas that appear blue or white contain relatively pure water ice, while reddish and brownish areas include non-ice components in higher concentrations.
"The polar regions, visible at the left and right of this view, are noticeably bluer than the more equatorial latitudes, which look more white. This colour variation is thought to be due to differences in ice grain size in the two locations."
– Jet Propulsion Laboratory, California Institute of Technology, NASA