Magnesium oxide might go metallic in super-Earths

Published in Chemistry World, 22 Nov 2012

We take the Earth’s magnetic field for granted, but it is the only thing protecting us from the sun’s bombardment of lethal charged particles. Now, however, it seems there may be more planets outside our solar system with protective magnetic fields than previously thought. That’s the implication of a US study, which has demonstrated that the common planetary mineral magnesium oxide turns into a metallic liquid at high pressure.

Magnesium oxide is one of the simplest oxides present in terrestrial planets such as the Earth, as well as in the cores of giant planets such as Jupiter. Scientists are therefore keen to understand how its properties change under high temperatures and pressures. Theoretical predictions suggest that at very high pressures (0.3 to 0.7TPa) it should transform from a structure like sodium chloride, where each magnesium ion has six adjacent oxygen ions, to a structure like caesium chloride, where each magnesium ion has eight adjacent oxygen ions. Theory also predicts that at very high temperatures, typically greater than 5000K, magnesium oxide should turn into a liquid. […]

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