The area surrounding the Apollo 16 landing site has been imaged using the Clementine UVVIS data. Figure 2 is an Apollo metric photograph showing the landing site. The lunar module Orion touched down at 9 degrees S, 15.5 degrees E, approximately equidistant between the north and south ray craters. The Calyey Plains are an important region to study because samples collected during the Apollo 16 mission are used to calibrate orbital spectral data.
Combining the 415-, 750-, and 950-nm mosaics as blue, green and red channels respectively yields a true-color composite image of the landing site. The Moon's natural color is a faint red/brown. The blue tint seen in the Descartes mountains is the result of fresh ejecta from the crater Dollond E. Fresh crater ejecta is typically blue because it has not hand enough time to develop large amounts of iron-rich, red glass (agglutinates).
Ratioing the individual wavelength mosaics subdues brightness effects due to albedo and topography, and highlights color differences related to soil mineralogy and maturity. The red channel is controlled by the 750/415 ratio and is sensitive to soil maturity. The 750 to 950 ratio is sensitive to the presence of mafic minerals and is displayed as the green channel. Areas that are blue (415/750)in the image are the result of fresh soils or in mare, a concentration of the mineral illmenite (FeTiO3). Topographic features tend to be be washed out because Clementine images were taken at high sun angles. For this reason, the multispectral image is combined with the metric photograph. This allows correlations between the surface morphology and the spectral signatures.
The 750- and 950-nm images are combined to produce a quantitative map of FeO concentration accurate to approximately 1 weight percent. This map shows that the Cayley Plains and the Descartes Mountains appear to have similar compositions. The image shows that the amount of FeO in the Cayley plains to be approximately 4-5 weight percent. This calculation in consistent with return samples from this region.