Iron and titanium abundance and maturity degree distribution on the lunar nearside

New digital images of the lunar nearside albedos at 0.42, 0.65, 0.75, and 0 .95 mu m derived from telescopic data were used to map the abundance and di stribution of iron, titanium, and maturity degree on the lunar nearside. De veloping the approach by P. Lucey et al. (1995, Science 268, 1150), a metho d of separating contributions of the Fe and Ti abundance and maturity degre e to spectral properties of the lunar surface is presented. The main object ive of the method is an analysis of the 3D correlation diagram of optical c haracteristics of regolith material with the aim of choosing a coordinate s ystem providing the best correlations of these characteristics with Fe and Ti abundance (data for the Surveyor, Luna, and Apollo landing sites) and wi th maturity degree (laboratory measurements of lunar samples by E. Fischer and C. Pieters (e.g., 1996, J. Geophys. Res. 101, 2225). To find the coordi nates, a geometrical optics model of light scattering in particulate media enabling to calculate the absorption coefficient from albedo measurements i s used. An analysis of the correlation diagram FeO-TiO2 provides two maps c haracterizing optical types of the lunar nearside. In particular, the maps show that the basalts of Mare Serenitatis and Mare Tranquillitatis are not widely extended on the lunar nearside. The maturity degree, parameter I-s/F eO, was also mapped. Regions with I-s/FeO less than or equal to 50 are youn g craters surrounded by ray systems, whereas the condition I-s/FeO greater than or equal to 70 corresponds to regions associated with Copernicus eject a, western boundaries of Mare Tranquillitatis and Mare Serenitatis, and a p ortion of the south highland. The new map of FeO distribution on the lunar nearside was used to study a correlation between iron content and distribut ion of remanent magnetism over the lunar surface. The relationship obtained has a reverse behavior: the lower the iron content, the higher the magneti sm. (C) 1999 Academic Press.