Letter | Published:

Direct measurement of thermal conductivity in solid iron at planetary core conditions

Nature volume 534, pages 99101 (02 June 2016) | Download Citation

Abstract

The conduction of heat through minerals and melts at extreme pressures and temperatures is of central importance to the evolution and dynamics of planets. In the cooling Earth’s core, the thermal conductivity of iron alloys defines the adiabatic heat flux and therefore the thermal and compositional energy available to support the production of Earth’s magnetic field via dynamo action1,2,3. Attempts to describe thermal transport in Earth’s core have been problematic, with predictions of high thermal conductivity4,5,6,7 at odds with traditional geophysical models and direct evidence for a primordial magnetic field in the rock record8,9,10. Measurements of core heat transport are needed to resolve this difference. Here we present direct measurements of the thermal conductivity of solid iron at pressure and temperature conditions relevant to the cores of Mercury-sized to Earth-sized planets, using a dynamically laser-heated diamond-anvil cell11,12. Our measurements place the thermal conductivity of Earth’s core near the low end of previous estimates, at 18–44 watts per metre per kelvin. The result is in agreement with palaeomagnetic measurements10 indicating that Earth’s geodynamo has persisted since the beginning of Earth’s history, and allows for a solid inner core as old as the dynamo.

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Acknowledgements

We acknowledge experimental assistance from H. Marquardt. This work was supported by the NSF (grant numbers DMR-1039807, EAR-1015239, EAR-1520648 and EAR/IF-1128867), the Army Research Office (grant 56122-CH-H), the Carnegie Institution of Washington, the National Natural Science Foundation of China (grant number 21473211), the Chinese Academy of Science (grant number YZ201524), the University of Edinburgh, and the British Council Researcher Links Programme. Portions of this research were carried out at the light source Petra III at DESY, a member of the Helmholtz Association (HGF).

Author information

Author notes

    • Zuzana Konôpková

    Present address: European XFEL GmbH, Notkestrasse 85, DE-22607 Hamburg, Germany.

Affiliations

  1. DESY Photon Science, Notkestrasse 85, DE-22607 Hamburg, Germany

    • Zuzana Konôpková
  2. School of Physics and Astronomy and Centre for Science at Extreme Conditions, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK

    • R. Stewart McWilliams
    •  & Natalia Gómez-Pérez
  3. Departamento de Geociencias, Universidad de Los Andes, Bogotá, Colombia

    • Natalia Gómez-Pérez
  4. Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, 350 Shushanghu Road, Hefei, Anhui 230031, China

    • Alexander F. Goncharov
  5. Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington DC 20015, USA

    • Alexander F. Goncharov

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Contributions

Z.K., R.S.M. and A.F.G. designed and conducted experiments. R.S.M. reduced raw data. Z.K. and N.G.P. performed finite-element modelling. N.G.P. performed error analysis and geophysical calculations. All authors wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Zuzana Konôpková or R. Stewart McWilliams or Natalia Gómez-Pérez or Alexander F. Goncharov.

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https://doi.org/10.1038/nature18009

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