ABUNDANCE AND DISTRIBUTION OF IRON ON THE MOON

The abundance and distribution of iron on the moon is derived from a n ear-global data set from Clementine. The determined iron content of th e lunar highlands crust (similar to 3 percent iron by weight) supports the hypothesis that much of the lunar crust was derived from a magma ocean. The iron content of lower crustal material exposed by the South Pole-Aitken impact basin on the lunar farside is higher (similar to 7 to 8 percent by weight) and consistent with a basaltic composition. T his composition supports earlier evidence that the lunar crust becomes more mafic with depth. The data also suggest that the bulk compositio n of the moon differs from that of the Earth's mantle. This difference excludes models for lunar origin that require the Earth and moon to h ave the same compositions, such as fission and coaccretion, and favors giant impact and capture.