Evolution of Planetary Cores and the Earth-Moon System from Nb/Ta Systematics

@article{Mnker2003EvolutionOP,
  title={Evolution of Planetary Cores and the Earth-Moon System from Nb/Ta Systematics},
  author={Carsten M{\"u}nker and J{\"o}rg A. Pf{\"a}nder and Stefan Weyer and Anette B{\"u}chl and Thorsten Kleine and Klaus Mezger},
  journal={Science},
  year={2003},
  volume={301},
  pages={84 - 87}
}
It has been assumed that Nb and Ta are not fractionated during differentiation processes on terrestrial planets and that both elements are lithophile. High-precision measurements of Nb/Ta and Zr/Hf reveal that Nb is moderately siderophile at high pressures. Nb/Ta values in the bulk silicate Earth (14.0 ± 0.3) and the Moon (17.0 ± 0.8) are below the chondritic ratio of 19.9 ± 0.6, in contrast to Mars and asteroids. The lunar Nb/Ta constrains the mass fraction of impactor material in the Moon to… 
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