Low viscosity of the Earth's inner core

AB Belonoshko and J Fu and T Bryk and SI Simak and M Mattesini, NATURE COMMUNICATIONS, 10, 2483 (2019).

DOI: 10.1038/s41467-019-10346-2

The Earth's solid inner core is a highly attenuating medium. It consists mainly of iron. The high attenuation of sound wave propagation in the inner core is at odds with the widely accepted paradigm of hexagonal close-packed phase stability under inner core conditions, because sound waves propagate through the hexagonal iron without energy dissipation. Here we show by first-principles molecular dynamics that the body- centered cubic phase of iron, recently demonstrated to be thermodynamically stable under the inner core conditions, is considerably less elastic than the hexagonal phase. Being a crystalline phase, the body-centered cubic phase of iron possesses the viscosity close to that of a liquid iron. The high attenuation of sound in the inner core is due to the unique diffusion characteristic of the body- centered cubic phase. The low viscosity of iron in the inner core enables the convection and resolves a number of controversies.

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