Spectral Mapping of Mare Mosciviense, Lunar Farside, from Clementine Uvvis

Background: The Clementine mission provided the first high resolution mul-tispectral image data set of the far side of the Moon. While near side surface morphological units have been studied extensively from earth based spectral measurements, this is the first opportunity to examine the compositional properties of far side areas. Moscoviense is one of the prominent large impact basins on the lunar far side centered on (147 deg 27E, 26 deg 27N), approximately 445 km in diameter. The geo-morphology is complex possibly resulting from sequences of explosive volcanism, mare emplacement by effusive volcan-ism, and subsequent smaller impacts as discussed in [1]. The terrain exhibits great variation in brightness, color and texture on a very small (several hundred meter) to large (ten to hundred km) scale. Analyses and Preliminary Results: We are using Clementine UVVIS multispectral images for compositional mapping of the Moscoviense basin and surrounding areas. The data have been calibrated, image planes co-registered and mosaiced at the USGS, Flagstaff [2]. The five image bands are centered at 0.415, 0.750, 0.9, 0.95 and 1.0 microns. For this preview study we shrunk the original image by a factor of four, to 474 m/pixel resolution. Preliminary results from linear mixture modeling indicate that at least five spectral endmembers are needed for a decent model fit to this area. Further, spatially coherent spectral units are distinguishable through spectral classification. A preliminary classification map is shown in Figure 1 (original figure in color). The units are as keyed in Figure 2, which shows average spectra of the training areas for each spectral unit. The unit names indicate the types of locations where training spectra were extracted. The spectra look generally consistent with those in [3] and [4]. The known major surface units appear to be compositionally distinct too, and in general agreement with albedo and color ratio images [5]. The basin floor is covered by three distinguishable mare deposit units (A, B, C) which are all relatively dark, exhibit increasing redness from A to C, and are likely to be of different ages [1].