Letter | Published:

The isotopic nature of the Earth’s accreting material through time

Nature volume 541, pages 521524 (26 January 2017) | Download Citation

Abstract

The Earth formed by accretion of Moon- to Mars-size embryos coming from various heliocentric distances. The isotopic nature of these bodies is unknown. However, taking meteorites as a guide, most models assume that the Earth must have formed from a heterogeneous assortment of embryos with distinct isotopic compositions1,2,3. High-precision measurements, however, show that the Earth, the Moon and enstatite meteorites have almost indistinguishable isotopic compositions4,5,6,7,8,9,10. Models have been proposed that reconcile the Earth–Moon similarity with the inferred heterogeneous nature of Earth-forming material, but these models either require specific geometries for the Moon-forming impact11,12 or can explain only one aspect of the Earth–Moon similarity (that is, 17O)1,2,3. Here I show that elements with distinct affinities for metal can be used to decipher the isotopic nature of the Earth’s accreting material through time. I find that the mantle signatures of lithophile O, Ca, Ti and Nd, moderately siderophile Cr, Ni and Mo, and highly siderophile Ru record different stages of the Earth’s accretion; yet all those elements point to material that was isotopically most similar to enstatite meteorites. This isotopic similarity indicates that the material accreted by the Earth always comprised a large fraction of enstatite-type impactors (about half were E-type in the first 60 per cent of the accretion and all of the impactors were E-type after that). Accordingly, the giant impactor that formed the Moon probably had an isotopic composition similar to that of the Earth, hence relaxing the constraints on models of lunar formation. Enstatite meteorites and the Earth were formed from the same isotopic reservoir but they diverged in their chemical evolution owing to subsequent fractionation by nebular and planetary processes13.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

References

  1. 1.

    & Equilibration in the aftermath of the lunar-forming giant impact. Earth Planet. Sci. Lett. 262, 438–449 (2007)

  2. 2.

    , & A primordial origin for the compositional similarity between the Earth and the Moon. Nature 520, 212–215 (2015)

  3. 3.

    & The feeding zones of terrestrial planets and insights into Moon formation. Icarus 252, 161–174 (2015)

  4. 4.

    et al. Oxygen isotopic evidence for vigorous mixing during the Moon-forming giant impact. Science 351, 493–496 (2016)

  5. 5.

    , , , & The proto-Earth as a significant source of lunar material. Nat. Geosci. 5, 251–255 (2012)

  6. 6.

    , & Testing Earth–Moon isotopic homogenization with calcium-48. Lunar Planet. Sci. Conf. XXXXVI, 2436 (2015)

  7. 7.

    , , , & Contributors to chromium isotope variation of meteorites. Geochim. Cosmochim. Acta 74, 1122–1145 (2010)

  8. 8.

    et al. The chemical composition of the Earth: enstatite chondrite models. Earth Planet. Sci. Lett. 293, 259–268 (2010)

  9. 9.

    Stable-isotopic anomalies and the accretionary assemblage of the Earth and Mars: a subordinate role for carbonaceous chondrites. Earth Planet. Sci. Lett. 311, 93–100 (2011)

  10. 10.

    & Mass fractionation laws, mass-independent effects, and isotopic anomalies. Annu. Rev. Earth Planet. Sci. 44, 709–783 (2016)

  11. 11.

    & Making the Moon from a fast-spinning Earth: a giant impact followed by resonant despinning. Science 338, 1047–1052 (2012)

  12. 12.

    Forming a Moon with an Earth-like composition via a giant impact. Science 338, 1052–1055 (2012)

  13. 13.

    , , , & Planetary and meteoritic Mg/Si and δ30Si variations inherited from solar nebula chemistry. Earth Planet. Sci. Lett. 427, 236–248 (2015)

  14. 14.

    , , , & Stochastic late accretion to Earth, the Moon, and Mars. Science 330, 1527–1530 (2010)

  15. 15.

    et al. Highly siderophile elements were stripped from Earth’s mantle by iron sulfide segregation. Science 353, 1141–1144 (2016)

  16. 16.

    , & Broad bounds on Earth’s accretion and core formation constrained by geochemical models. Nat. Geosci. 3, 439–443 (2010)

  17. 17.

    , & Tungsten isotopic evolution during late-stage accretion: constraints on Earth–Moon equilibration. Earth Planet. Sci. Lett. 292, 363–370 (2010)

  18. 18.

    , & Systematics of metal–silicate partitioning for many siderophile elements applied to Earth’s core formation. Geochim. Cosmochim. Acta 75, 1451–1489 (2011)

  19. 19.

    , , , & Core formation and core composition from coupled geochemical and geophysical constraints. Proc. Natl Acad. Sci. USA 112, 12310–12314 (2015)

  20. 20.

    , , , & Heterogeneous accretion and the moderately volatile element budget of Earth. Science 328, 884–887 (2010)

  21. 21.

    et al. Accretion and differentiation of the terrestrial planets with implications for the compositions of early-formed Solar System bodies and accretion of water. Icarus 248, 89–108 (2015)

  22. 22.

    & 142Nd evidence for early (>4.53 Ga) global differentiation of the silicate Earth. Science 309, 576–581 (2005)

  23. 23.

    et al. A nucleosynthetic origin for the Earth’s anomalous 142Nd composition. Nature 537, 394–398 (2016)

  24. 24.

    , , & Molybdenum isotopes and the building blocks of the Earth. Lunar Planet. Sci. Conf. XXXXVII, 2639 (2016)

  25. 25.

    & A perspective from extinct radionuclides on a young stellar object: the Sun and its accretion disk. Annu. Rev. Earth Planet. Sci. 39, 351–386 (2011)

  26. 26.

    & 60Fe-60Ni chronology of core formation in Mars. Earth Planet. Sci. Lett. 390, 264–274 (2014)

  27. 27.

    et al. The major-element composition of Mercury’s surface from Messenger X-ray spectrometry. Science 333, 1847–1850 (2011)

  28. 28.

    & Silicon isotope evidence against an enstatite chondrite Earth. Science 335, 1477–1480 (2012)

  29. 29.

    & Origin of the Moon in a giant impact near the end of the Earth’s formation. Nature 412, 708–712 (2001)

  30. 30.

    , , & Lunar tungsten isotopic evidence for the late veneer. Nature 520, 534–537 (2015)

  31. 31.

    , & Tungsten isotopic evidence for disproportional late accretion to the Earth and Moon. Nature 520, 530–533 (2015)

  32. 32.

    , , & Geochemical arguments for an Earth-like Moon-forming impactor. Phil. Trans. R. Soc. Lond. A 372, 20130244 (2014)

Download references

Acknowledgements

S. Jacobson provided the PDFs for the Rubie et al. model15 and J. Siebert and J. Badro provided assistance during development of the code to reproduce their model19. Discussions with A. Morbidelli, D. Rubie, A. Campbell, F. Ciesla, R. Yokochi, M. Roskosz, N. Greber and C. Burkhardt were greatly appreciated. J. Hu double-checked all the derivations and codes used in this contribution. This work was supported by NSF (CSEDI, grant EAR1502591; Petrology and Geochemistry, grant EAR1444951) and NASA (LARS, grant NNX14AK09G).

Author information

Affiliations

  1. Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637, USA

    • Nicolas Dauphas

Authors

  1. Search for Nicolas Dauphas in:

Competing interests

The author declares no competing financial interests.

Corresponding author

Correspondence to Nicolas Dauphas.

Reviewer Information Nature thanks W. Bottke, R. Carlson and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Extended data

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    This file contains derivations of the equations used in the main text and Mathematica code used to calculate the partitioning of moderately siderophile elements in the model of ref. 19.

Excel files

  1. 1.

    Supplementary Table 1

    This table contains a compilation of isotopic anomalies in planetary materials.

About this article

Publication history

Received

Accepted

Published

DOI

https://doi.org/10.1038/nature20830

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.