IS EARTH'S 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's 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's core, Yanming Ma of Jilin University in Changchun, China, and colleagues used a supercomputer to model the element's reactivity. Xenon would not normally react with iron – which makes up 85 per cent of the core – but at pressures of about 300 gigapascals and temperatures of about 6000 °C, found in Earth's core, the two seemed attracted to one another.
A compound can form from one xenon and three iron atoms. Because it has lower energy than the sum of the pure elements' energies under those conditions, it is the preferred state (arxiv.org/abs/1309.2169).
Ma's team found that xenon could even react with nickel, a minor component of the core. "Earth's core is a natural reservoir for xenon," Ma says. So it could be that iron's hot embrace is to blame for Earth's missing xenon.
This article appeared in print under the headline "Xenon and iron, a match made in the core"
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