Variations within the Northern Imbrium Noritic Deposits

and principal rock types (colors). (a) Reflectance. Maturity trends in norite (red) and mare (green) are indicated by solid (fresh), dashed (intermediate), and dotted (degraded) lines. (b) Scaled reflectance (same spectra as a). Spectra have been scaled (multiplicative) to unity at 750 nm. This scheme emphasizes trends in band strength and shape, which are apparent for all three suites of spectra. Band strength decreases with maturity in norite and mare, and generally with crater size (Figure 1) in central peaks. Fig. 1: NIN region. Base image is a Clementine 750 nm albedo image in a simple cylindrical projection. The northern portion of Imbrium basin is visible at the bottom of the image. Suites of small crater spectra analyzed are indicated by dots (green for mare, red for anorthositic norite (NIN)). Larger symbols indicate example spectra used in Figs. 2 & 3. Labels for these special craters are in white. The four large craters are indicated by triangles (central peak spectra). Their diameters in km are (west to east): 130 (Pythagoras), 59 (Carpenter), 70 (Philolaus), 50 (Anaxagoras). VARIATIONS WITHIN THE NORTHERN IMBRIUM NORITIC DEPOSITS. P. J. Isaacson and C. M. Pieters, Dept. of Geological Sciences, Brown University, Providence RI 02912. [[email protected]].