Geochemistry

Expelled Xe

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Science  25 Apr 2014:
Vol. 344, Issue 6182, pp. 340
DOI: 10.1126/science.344.6182.340-b
CREDIT: L. ZHU ET AL., NATURE CHEMISTRY (20 APRIL 2014) © NATURE PUBLISHING GROUP

Based on the distribution of other noble gases, Earth's atmosphere is apparently depleted in Xe. Although some may have been lost to space, Earth's interior—the original source of atmospheric gases—could also act as a reservoir by preferentially holding onto Xe as the planet formed and differentiated. Because of the size of the mantle, it would be an ideal candidate; however, it is unclear whether Xe reacts with the major Si-rich phases of the mantle at the corresponding pressures and temperatures. Zhu et al. performed total energy calculations at the extreme temperature and pressure conditions of Earth's inner core to determine that Xe reacts with Fe and Ni, the two dominant constituents of the solid inner core. Crystal structure predictions found several stable phases of Xe-Fe/Ni alloys, including the stable phases of XeFe3 and XeNi3, suggesting that the inner core may be Earth's missing reservoir of Xe.

Nat. Chem. 10.1038/NCHEM.1925 (2014).

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