142Nd: New Insights into the Formation of Terrestrial Planets and the Earth's Composition and Dynamics

Abstract: 142Nd is the decay product of the extinct radionuclide 146Sm (t_1/2 = 103 Ma). Geochemists’ standard model of Earth‘s composition predicts the terrestrial Sm/Nd ratio is chondritic, and therefore that the terrestrial 142Nd/144Nd ratio is chondritic. Work over the last half decade has shown that the Earth, Moon, and possibly Mars have non-chondritic 142Nd/144Nd. This brings into question the standard compositional model and suggests the birth of terrestrial planets is a particularly violent affair.