Nd of the Moon (original) (raw)

The Moon likely accreted from melt and vapor ejected during a cataclysmic collision between Proto-Earth and a Marssized impactor very early in solar system history. The identical W, O, K, and Cr isotope compositions between materials from the Earth and Moon require that the material from the two bodies were well-homogenized during the collision process. As such, the ancient isotopic signatures preserved in lunar samples provide constraints on the bulk composition of the Earth. Two recent studies to obtain high-precision 142 Nd/ 144 Nd ratios of lunar mare basalts yielded contrasting results. In one study, after correction of neutron fluence effects imparted to the Nd isotope compositions of the samples, the coupled 142 Nd-143 Nd systematics were interpreted to be consistent with a bulk Moon having a chondritic Sm/Nd ratio Neodymium isotope evidence for a chondritic composition of the Moon. Science 312, 1369-1372]. The other study found that their data on the same and similar lunar mare basalts were consistent with a bulk Moon having a superchondritic Sm/Nd ratio [Boyet M. and Carlson R. W. (2007) A highly depleted Moon or a non-magma origin for the lunar crust? Earth Planet. Sci. Lett. 262,[505][506][507][508][509][510][511][512][513][514][515][516]. Delineating between these two potential scenarios has key ramifications for a comprehensive understanding of the formation and early evolution of the Moon and for constraining the types of materials available for accretion into large terrestrial planets such as Earth.