Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Potassium isotopic evidence for a high-energy giant impact origin of the Moon

Nature volume 538, pages 487–490 (2016)Cite this article

Subjects

Abstract

The Earth–Moon system has unique chemical and isotopic signatures compared with other planetary bodies1,2,3; any successful model for the origin of this system therefore has to satisfy these chemical and isotopic constraints. The Moon is substantially depleted in volatile elements such as potassium compared with the Earth and the bulk solar composition4, and it has long been thought to be the result of a catastrophic Moon-forming giant impact event5. Volatile-element-depleted bodies such as the Moon were expected to be enriched in heavy potassium isotopes during the loss of volatiles; however such enrichment was never found6. Here we report new high-precision potassium isotope data for the Earth, the Moon and chondritic meteorites. We found that the lunar rocks are significantly (>2σ) enriched in the heavy isotopes of potassium compared to the Earth and chondrites (by around 0.4 parts per thousand). The enrichment of the heavy isotope of potassium in lunar rocks compared with those of the Earth and chondrites can be best explained as the result of the incomplete condensation of a bulk silicate Earth vapour at an ambient pressure that is higher than 10 bar. We used these coupled constraints of the chemical loss and isotopic fractionation of K to compare two recent dynamic models that were used to explain the identical non-mass-dependent isotope composition of the Earth and the Moon. Our K isotope result is inconsistent with the low-energy disk equilibration model7, but supports the high-energy, high-angular-momentum giant impact model8 for the origin of the Moon. High-precision potassium isotope data can also be used as a ‘palaeo-barometer’ to reveal the physical conditions during the Moon-forming event.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: K isotope compositions of the Earth, the Moon and meteorites.
Figure 2: K isotope compositions versus the K/U ratio for the Earth and the Moon.
Figure 3: Proposed models for the post-giant-impact state to explain the identical non-mass-dependent isotope compositions of the Earth and the Moon.

Similar content being viewed by others

References

  1. Ringwood, A. E. Origin of the Earth and Moon (Springer, 1979)

  2. Wiechert, U. et al. Oxygen isotopes and the moon-forming giant impact. Science 294, 345–348 (2001)

    Article  CAS  ADS  Google Scholar 

  3. Zhang, J., Dauphas, N., Davis, A. M., Leya, I. & Fedkin, A. The proto-Earth as a significant source of lunar material. Nat. Geosci. 5, 251–255 (2012)

    Article  CAS  ADS  Google Scholar 

  4. Taylor, S. R. Lunar and terrestrial crusts: a contrast in origin and evolution. Phys. Earth Planet. Inter. 29, 233–241 (1982)

    Article  CAS  ADS  Google Scholar 

  5. Canup, R. M. Simulations of a late lunar-forming impact. Icarus 168, 433–456 (2004)

    Article  CAS  ADS  Google Scholar 

  6. Humayun, M. & Clayton, R. N. Potassium isotope cosmochemistry: genetic-implications of volatile element depletion. Geochim. Cosmochim. Acta 59, 2131–2148 (1995)

    Article  CAS  ADS  Google Scholar 

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

    Article  CAS  ADS  Google Scholar 

  8. Lock, S. J. et al. A new model for lunar origin: equilibration with Earth beyond the hot spin stability limit. In Proc. 47th Lunar Planet. Sci. Conf. (Lunar and Planetary Science Institute, 2016)

  9. Wasserburg, G. J., Macdonald, G. J., Hoyle, F. & Fowler, W. A. Relative contributions of uranium, thorium, and potassium to heat production in the Earth. Science 143, 465–467 (1964)

    Article  CAS  ADS  Google Scholar 

  10. Anders, E. & Grevesse, N. Abundances of the elements: meteoritic and solar. Geochim. Cosmochim. Acta 53, 197–214 (1989)

    Article  CAS  ADS  Google Scholar 

  11. Arevalo, R., McDonough, W. F. & Luong, M. The K/U ratio of the silicate Earth: insights into mantle composition, structure and thermal evolution. Earth Planet. Sci. Lett. 278, 361–369 (2009)

    Article  CAS  ADS  Google Scholar 

  12. Halliday, A. N. & Porcelli, D. In search of lost planets – the paleocosmochemistry of the inner solar system. Earth Planet. Sci. Lett. 192, 545–559 (2001)

    Article  CAS  ADS  Google Scholar 

  13. Sharp, Z. D., Shearer, C. K., McKeegan, K. D., Barnes, J. D. & Wang, Y. Q. The chlorine isotope composition of the Moon and implications for an anhydrous mantle. Science 329, 1050–1053 (2010)

    Article  CAS  ADS  Google Scholar 

  14. Paniello, R. C., Day, J. M. D. & Moynier, F. Zinc isotopic evidence for the origin of the Moon. Nature 490, 376–379 (2012)

    Article  CAS  ADS  Google Scholar 

  15. Kato, C., Moynier, F., Valdes, M. C., Dhaliwal, J. K. & Day, J. M. D. Extensive volatile loss during formation and differentiation of the Moon. Nat. Commun. 6, 7617 (2015)

    Article  ADS  Google Scholar 

  16. Wang, K. & Jacobsen, S. B. An estimate of the bulk silicate earth potassium isotopic composition based on MC-ICPMS measurements of basalts. Geochim. Cosmochim. Acta 178, 223–232 (2016)

    Article  CAS  ADS  Google Scholar 

  17. Barnes, I. L. et al. Isotopic abundance ratios and concentrations of selected elements in some Apollo 15 and Apollo 16 samples. Proc. Lunar Planet. Sci. Conf. 4, 1197–1207 (1973)

    ADS  Google Scholar 

  18. Garner, E. L., Machlan, L. A. & Barnes, I. L. The isotopic composition of lithium, potassium, and rubidium in some Apollo 11, 12, 14, 15, and 16 samples. In Proc. Sixth Lunar Sci. Conf. 1845–1855 (Lunar and Planetary Science Institute, 1975)

  19. Church, S. E., Tilton, G. R. & Wright, J. E. Volatile Element depletion and 39K/41K fractionation in lunar soils. Abstr. Lunar Planet. Sci. Conf. 7, 146–148 (1976)

    ADS  Google Scholar 

  20. Li, W., Beard, B. & Li, S. Precise measurement of stable potassium isotope ratios using a single focusing collision cell multi-collector ICP-MS. J. Anal. At. Spectrom. 31, 1023–1029 (2016)

    Article  CAS  Google Scholar 

  21. Schauble, E. A. Applying stable isotope fractionation theory to new systems. Rev. Mineral. Geochem. 55, 65–111 (2004)

    Article  CAS  Google Scholar 

  22. Yu, Y., Hewins, R. H. & Alexander, C. M. O.’D. & Wang, J. Experimental study of evaporation and isotopic mass fractionation of potassium in silicate melts. Geochim. Cosmochim. Acta 67, 773–786 (2003)

    Article  CAS  ADS  Google Scholar 

  23. Richter, F. M., Mendybaev, R. A., Christensen, J. N., Ebel, D. & Gaffney, A. Laboratory experiments bearing on the origin and evolution of olivine-rich chondrules. Meteorit. Planet. Sci. 46, 1152–1178 (2011)

    Article  CAS  ADS  Google Scholar 

  24. Young, E. D. Assessing the implications of K isotope cosmochemistry for evaporation in the preplanetary solar nebula. Earth Planet. Sci. Lett. 183, 321–333 (2000)

    Article  CAS  ADS  Google Scholar 

  25. Clayton, R. N. Oxygen isotopes in meteorites. Annu. Rev. Earth Planet. Sci. 21, 115–149 (1993)

    Article  CAS  ADS  Google Scholar 

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

    Article  CAS  ADS  Google Scholar 

  27. Melosh, H. J. New approaches to the Moon’s isotopic crisis. Phil. Trans. R. Soc. A 372, 20130168 (2014)

    Article  CAS  ADS  Google Scholar 

  28. Zindler, A. & Jacobsen, S. B. Rethinking lunar formation: back to the future? In Proc. 41st Lunar Planet. Sci. Conf. Abstract No. 2702 (Lunar and Planetary Institute, 2010)

  29. Pahlevan, K., Stevenson, D. J. & Eiler, J. M. Chemical fractionation in the silicate vapor atmosphere of the Earth. Earth Planet. Sci. Lett. 301, 433–443 (2011)

    Article  CAS  ADS  Google Scholar 

  30. Canup, R. M., Visscher, C., Salmon, J. & Fegley, B., Jr. Lunar volatile depletion due to incomplete accretion within an impact-generated disk. Nat. Geosci. 8, 918–921 (2015)

    Article  CAS  ADS  Google Scholar 

  31. Langmuir, C. H., Bender, J. F. & Batiza, R. Petrological and tectonic segmentation of the East Pacific Rise, 5°30′–14°30′ N. Nature 322, 422–429 (1986)

    Article  CAS  ADS  Google Scholar 

  32. Jacobsen, S. B. & Wasserburg, G. J. Nd and Sr Isotopic Study of the Permian Oslo Rift. Report No. 78-701, 194–196 (US Geological Survey, 1978)

  33. Jacobsen, S. B. & Dymek, R. F. Nd and Sr isotope systematics of clastic metasediments from Isua, West Greenland: identification of pre-3.8 Ga differentiated crustal components. J. Geophys. Res. 93, 338–354 (1988)

    Article  CAS  ADS  Google Scholar 

  34. Strelow, E. W. E. & Von, S. Toerien, F. & Weinert, C. H. S. W. Accurate determination of traces of sodium and potassium in rocks by ion exchange followed by atomic absorption spectroscopy. Anal. Chim. Acta 50, 399–405 (1970)

    Article  CAS  Google Scholar 

  35. Humayun, M. & Clayton, R. N. Precise determination of the isotopic composition of potassium: application to terrestrial rocks and lunar soils. Geochim. Cosmochim. Acta 59, 2115–2130 (1995)

    Article  CAS  ADS  Google Scholar 

Download references

Acknowledgements

This work was funded by the NASA Emerging Worlds program (NNX15AH66G). K.W. acknowledges financial support from the Harvard Origins of Life Initiative Postdoctoral Fellowship during his time at Harvard. We thank NASA JSC and CAPTEM for providing lunar samples and M. Petaev, S. Stewart, S. Lock and B. Jolliff for discussions.

Author information

Authors and Affiliations

  1. Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, 02138, Massachusetts, USA

    Kun Wang & Stein B. Jacobsen

  2. Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, 63130, Missouri, USA

    Kun Wang

Authors
  1. Kun Wang
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Stein B. Jacobsen
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

S.B.J. and K.W. () designed the study. K.W. performed the analysis. K.W. and S.B.J. wrote the manuscript.

Corresponding author

Correspondence to Kun Wang.

Additional information

Reviewer Information Nature thanks A. Treiman and E. Young for their contribution to the peer review of this work.

Extended data figures and tables

Extended Data Figure 1 The estimation of the pressure effect on α.

The experiments on K isotope fractionation during evaporation and condensation are very limited. One study22 conducted evaporation experiments on chondritic analogue materials in a high vacuum (around 10−9 atm) and at various higher pressures (1 × 10−5, 9 × 10−5, 7.2 × 10−5, 1.8 × 10−5, 1.8 × 10−4, 1.4 × 10−3, 1.3 × 10−2 and 1 atm). One of their major observations is that the degree of K isotope fractionation during evaporation decreases with higher pressures. Another study23 indicates that not only the pressure but also the composition (that is, H2, He, CO2) of the surrounding gas would affect the degree of K isotope fractionation. Here the red dots show the calculated effective Rayleigh fractionation factors based on the experimental data22,23 versus pressures. The effective Rayleigh fractionation factor is correlated with pressures and the observed value from this study suggests a >10 bar pressure during the loss of K from the Moon. Note that because not all the experiments are conducted at the same surrounding gas environment and the composition of the surrounding gas would also affect the effective fractionation factor (downward arrows in the figure), the correlation between the effective fractionation factor and pressure is not perfect. This >10 bar pressure from this study is at best a first-order estimation.

Source data

Extended Data Figure 2

An artist’s rendering of the two recent models of the origin of the Moon and their implications for K isotopes. Scenario 1 is from ref. 7; scenario 2 is from ref. 8.

Extended Data Table 1 K isotope compositions of terrestrial igneous rocks
Full size table
Extended Data Table 2 K isotope compositions of carbonaceous chondrites
Full size table
Extended Data Table 3 K isotope compositions of Apollo lunar samples
Full size table

PowerPoint slides

Source data

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Wang, K., Jacobsen, S. Potassium isotopic evidence for a high-energy giant impact origin of the Moon. Nature 538, 487–490 (2016). https://doi.org/10.1038/nature19341

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature19341

This article is cited by

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.

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing