The icy plains, shown here in bluish hues, subdivide into units with different albedos at infrared wavelengths probably because of differences in the grain size of the ice. On Io Volcanic hot spots and auroral emissions glow on the dark side of Jupiter's moon Io in the image at left. It is the best and highest-resolution image ever acquired of hot spots or auroral features on Io. The mosaic at right of 1979 Voyager images is shown with an identical scale and projection to identify the locations of the hot spots seen in the Galileo image. The grid marks are at 30 degree intervals of latitude and longitude.
North is to the top.
Greenish areas seen near the limb, or edge of the moon, are probably the result of auroral or airglow emissions of neutral oxygen or sulfur atoms in volcanic plumes and in Io's patchy atmosphere.