These Dawn FC (framing camera) composite images show the spectacular spectral diversity of Vesta's surface. The FC has 7 color filters which allow it to image Vesta in a number of different wavelengths of light. Being able to image in many wavelengths enhances features and colors that would otherwise be indistinguishable to the human eye. The left image shows a RGB color composite image of Vesta. RGB stands for red, green and blue and in this case red is the 750nm filter, green is the 920nm filter and blue is the 980nm filter. Nm stands for nanometers and is a measure of the wavelength of light. The images from these 3 filters were combined into this one RGB composite image, which enhances Vesta's coloration. The right image is also a RGB composite image. This time red is the ratio of the brightness at a wavelength of 750nm to the brightness at 440nm; green is used for the ratio of the brightness at 750nm to 920nm and blue is used for the ratio of the brightness at 440nm to 750nm. These ratios have all been picked for specific scientific purposes. The green shows the relative strength of a particular mineralogical characteristic, the ferrous absorption band, at 1000nm so that a brighter green color signifies a higher relative strength of this band. The blending between the red and blue heightens the color range of visible light.
Photo credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA