These two pictures of Uranus -- one in true color (left) and the other in false color -- were compiled from images returned by Voyager 2. The picture at left shows Uranus as human eyes would see it from the vantage point of the spacecraft. The darker shadings at the upper right of the disk correspond to the day-night boundary on the planet. Beyond this boundary lies the hidden northern hemisphere of Uranus, which currently remains in total darkness as the planet rotates. The blue-green color results from the absorption of red light by methane gas in Uranus' deep, cold and remarkably clear atmosphere.
The picture at right uses false color and extreme contrast enhancement to bring out subtle details in the polar region of Uranus. Uranus reveals a dark polar hood surrounded by a series of progressively lighter concentric bands. One possible explanation is that a brownish haze or smog, concentrated over the pole, is arranged into bands by zonal motions of the upper atmosphere.
Image Credit: NASA/JPL