Melting Earth's Core

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Science  26 Apr 2013:
Vol. 340, Issue 6131, pp. 442-443
DOI: 10.1126/science.1236304

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Earth's predominantly iron core is under extreme pressures that range from 136 to 364 GPa (100 GPa ∼ 1 million atm). The core consists of an outer layer that is molten and a solid inner core. The temperature of the core region can be estimated if the melting temperature of iron under such extreme pressures can be determined. Pressures and temperatures corresponding to the conditions at the core can be generated in the laboratory by using two gem-quality single-crystal diamonds coupled with laser heating (see the figure). The challenge, however, is how to accurately determine the melting point under such extremes. On page 464 of this issue, Anzellini et al. (1) use fast in situ synchrotron x-ray diffraction to study melting in the laser-heated diamond-anvil cell. The accurate determination of the melting temperature of iron provides an important constraint on the core temperature, which is essential to understanding how the dynamic Earth works, including its heat budget, generation of its magnetic field, and the thermal evolution of the planet.