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Evidence for an early wet Moon from experimental crystallization of the lunar magma ocean

Nature Geoscience volume 10, pages 1418 (2017) | Download Citation

Abstract

The Moon is thought to have been covered initially by a deep magma ocean, its gradual solidification leading to the formation of the plagioclase-rich highland crust. We performed a high-pressure, high-temperature experimental study of lunar mineralogical and geochemical evolution during magma ocean solidification that yields constraints on the presence of water in the earliest lunar interior. In the experiments, a deep layer containing both olivine and pyroxene is formed in the first 50% of crystallization, β-quartz forms towards the end of crystallization, and the last per cent of magma remaining is extremely iron rich. In dry experiments, plagioclase appears after 68 vol.% solidification and yields a floatation crust with a thickness of 68 km, far above the observed average of 34–43 km based on lunar gravity. The volume of plagioclase formed during crystallization is significantly less in water-bearing experiments. Using the relationship between magma water content and the resulting crustal thickness in the experiments, and considering uncertainties in initial lunar magma ocean depth, we estimate that the Moon may have contained at least 270 to 1,650 ppm water at the time of magma ocean crystallization, suggesting the Earth–Moon system was water-rich from the start.

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Acknowledgements

We thank S. Matveev and T. Bouten for technical assistance on electron microprobe analyses and B. Lacet for sample preparation. P. Warren is thanked for constructive criticisms. This work was supported by a Netherlands Organization for Scientific Research (N.W.O.) Vici award to W.v.W. and a China Scholarship Council fellowship to Y.L.

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Affiliations

  1. Faculty of Earth and Life Sciences, VU Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands

    • Yanhao Lin
    • , Elodie J. Tronche
    • , Edgar S. Steenstra
    •  & Wim van Westrenen

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Contributions

W.v.W., E.J.T. and Y.L. designed the project. Y.L. and E.J.T. performed the experiments. Y.L., E.J.T. and E.S.S. performed sample analyses. All authors discussed the results. Y.L. and W.v.W. wrote the paper with input from all authors.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Yanhao Lin or Wim van Westrenen.

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https://doi.org/10.1038/ngeo2845

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