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Earth science

Another energy source for the geodynamo

Nature volume 529, pages 288–289 (2016)Cite this article

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Magnesium is not usually considered to be a constituent of Earth's core, but its presence there has now been proposed to explain an ongoing enigma — the identity of the energy sources that drive our planet's magnetic field. See Letter p.387

Turbulent flow in Earth's liquid-iron core generates the planet's magnetic field through a process known as the geodynamo. This process is sustained by energy drawn from the core as it slowly cools1. Thermal convection is thought to be crucial, but revised estimates2,3 of thermal conductivity in liquid iron at high pressure have called into question the adequacy of the commonly cited energy sources1. On page 387 of this issue, O'Rourke and Stevenson4 propose a solution to this energy crisis. They argue that if magnesium had dissolved in the liquid iron at high temperature when the core formed, then subsequent precipitation of magnesium-bearing minerals on cooling would be an important source of energy. The authors' theory warrants a serious reassessment of magnetic-field generation in other rocky (terrestrial) planets.

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Figure 1: Possible processes at the boundary between Earth's liquid core and rocky mantle.

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  1. Bruce Buffett is in the Department of Earth and Planetary Science, University of California, Berkeley, Berkeley, California 94720-4767, USA.,

    Bruce Buffett

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  1. Bruce Buffett
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Correspondence to Bruce Buffett.

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Buffett, B. Another energy source for the geodynamo. Nature 529, 288–289 (2016). https://doi.org/10.1038/529288a

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