National Geographic : 1998 Aug
IMAGEPROCESSINGBYMARKLEMMON,UNIVERSITYOFARIZONA,TUCSON(ABOVEANDRIGHT);MARKLEMMONANDJUSTINMAKI,JPL(BELOW) Blue sky at night... The setting sun tints the sky blue (above) as light is scattered by particles of air borne red dust. Similarly, scattering by tiny water-ice particles lends a blue hue to wispy high-altitude clouds passing overhead near dawn (right). Gray clouds (below), colored by icy dust particles, give an overcast morning an Earthly qual ity-on a clear day the Martian sky is butterscotch.