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Journal Article

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

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Citation

Münker, C., Pfänder, J. A., Weyer, S., Büchl, A., Kleine, T., & Mezger, K. (2003). Evolution of Planetary Cores and the Earth-Moon System from Nb/Ta Systematics. Science, 301, 84-88. doi:10.1126/science.1084662.


Cite as: https://hdl.handle.net/21.11116/0000-000D-D688-8
Abstract
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 less than 65%. Moreover, the Moon-forming impact can be linked in time with the final core-mantle equilibration on Earth 4.533 billion years ago.