The ultraviolet-light image taken with UVIS (left) was taken during a flyby in December 2004. A visible light image taken on the same date is shown on the right for reference. The ultraviolet image indicates water ice abundance across the surface: the bright north polar terrain (shown in red) is the iciest region in this view. Away from the pole, as the color shifts to blue, less water ice is present in the surface. The darkest terrain, which includes very little water ice, is shown in light blue. The dark sky background viewed during the observation is shown as purple in this color scheme. Credit: NASA/JPL/University of Colorado/Space Science Institute