780 Encyclopedia of the Solar System
FIGURE 10 Orthographic projections of the lunar near and far sides: (a) Elevation; (b–d)
abundance (weight fraction) of selected elements. The map data are superimposed on a shaded
relief image. (FeO data courtesy NASA Planetary Data System ; image courtesy United States
Geological Survey.)relief image, is shown in Fig. 10a. The far side includes
the feldspathic highlands and the SPA basin. The near side
consists of major basins, including Procellarum and Im-
brium, which contain mare basalts. The mare basalts are
rich in Fe, with the highest concentrations occurring in
western Procellarum (Fig. 10b). The low abundance of FeO
in the highlands, which are rich in plagioclase feldspar,
reflects a significant lunar geochemical trend in which
mafic silicate minerals are displaced by plagioclase, which is
Fe-poor.