|Color-ratio Composite of the SSI LUNMOS6-7 Mosaic|
Original Caption Released with Image:
Shown here is a false-color image of the Moon constructed from data acquired by Galileo in December of 1992. The colors are produced by displaying three color ratios in red, green, and blue. Color ratios cancel out the effects of albedo variations and topographic shading, so subtle color variations related to composition are enhanced. The full dataset consists of mosaics in six spectral bands, with central wavelengths (in nanometers) of 410 (violet), 560 (green), 670 (red), 756, 889, and 990. The image shown here consists of the color ratios 756/410 displayed as red, 756/990 as green, and 415/756 as blue. As a result, the red and blue intensities are controlled by visible color, whereas the green intensity in controlled by the relative depth of the 1000 nm absorption band; both fresh soil exposures and soils rich in mafic minerals (pyroxene and olivene) appear greenish (or orange if the visible color is relatively red; blue-green if the visible color is relatively blue). The distinctive bright spots are fresh craters such as Tycho (bottom center), which may be bright blue, green, or orange, depending on the mineralogy. Many of the craters are surrounded by reddish rings, probably due to thin veneers of glassy impact melt. The youngest large craters are surrounded by bright blue ejecta and rays. The large orange areas (upper left) consist of iron-rich mare lavas, whereas extensive deep-blue areas consist of titanium-rich mare lavas. The darkest blue (or purplish) spots (center) consist of "dark-mantle" deposits, from explosive volcanic eruptions, which are rich in titanium and relatively rich (for the Moon) in volatiles. There is considerable interest in exploiting the dark mantle deposits to extract oxygen, helium, and other elements. The extensive reddish areas consist of highland materials, rich in the mineral plagioclase.
Image processing by the U.S. Geological Survey, Flagstaff, Arizona.