IS EARTH鈥橲 core playing cupid? It seems that xenon, a normally inert gas, can pair up with iron under the extreme conditions there. This could explain why our planet appears to lack xenon.
The atmosphere contains just 1/20th of Earth鈥檚 expected total xenon, as revealed by analyses of meteorites that should have a similar make-up to Earth.
To see if the missing xenon is trapped in the planet鈥檚 core, of Jilin University in Changchun, China, and colleagues used a supercomputer to model the element鈥檚 reactivity. Xenon would not normally react with iron 鈥� which makes up 85 per cent of the core 鈥� but at pressures of about 300 gigapascals and temperatures of about 6000 掳C, found in Earth鈥檚 core, the two seemed attracted to one another.
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A compound can form from one xenon and three iron atoms. Because it has lower energy than the sum of the pure elements鈥� energies under those conditions, it is the preferred state ().
Ma鈥檚 team found that xenon could even react with nickel, a minor component of the core. 鈥淓arth鈥檚 core is a natural reservoir for xenon,鈥� Ma says. So it could be that iron鈥檚 hot embrace is to blame for Earth鈥檚 missing xenon.
This article appeared in print under the headline 鈥淴enon and iron, a match made in the core鈥�
