FIGURE 5 Ir- and chondrite-normalized PGE composition of the primitive mantle (Becker et al. 2006) compared with the main groups of chondritic meteorites (A) and with impact rocks of lunar maria (B). Note that the primitive mantle estimate does not correspond to any known chondrite composition; only the strongly brecciated rocks in the heights around lunar maria, and contemporaneous with the 3.9-3.8 Ga late heavy bombardment recorded by the Moon's surface, provide a reasonably good match with the Becker et al. (2006) primitive mantle estimate.