Xenon

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The Mysterious Case of the Missing Noble Gas
Xenon has almost vanished from Earth's atmosphere.Geoscientists think it might have disappeared in space
By Ewen Callaway and Nature magazine  | Thursday, October 11, 2012 | 8

Image: htx.pppl.gov

From Nature magazine

The evidence is inevery breath of air, but answers are harder to come by. Xenon, the second heaviest of the chemically inert noble gases, has gone missing. Our atmosphere contains far less xenon, relative to the lighternoble gases, than meteorites similar to the rocky material that formed the Earth.
The missing-xenon paradox is one of science’s great whodunits. Researchers have hypothesized that the element islurking in glaciers, minerals or Earth’s core, among other places.
“Scientists always said the xenon is not really missing. It’s not in the atmosphere, but it’s hiding somewhere,” says inspector, sorry,professor Hans Keppler, a geophysicist at the University of Bayreuth in Germany. He and his colleague Svyatoslav Shcheka are the latest geoscientists to tackle the case, in a report published todayin Nature.

Elementary, my dear Watson

They went looking for answers in minerals. Magnesium silicate perovskite is the major component of Earth’s lower mantle — the layer of molten rock between thecrust and the core, which accounts for half the planet’s mass. The sleuthing scientists wondered whether the missing xenon could be squirreled away in pockets in this mineral. “I was quite sure that itmust be possible to stuff noble gases into perovskite,” says Keppler. “I suspected xenon may be in there.”
The researchers tried dissolving xenon and argon in perovskite at temperatures exceeding1,600 ºC and pressures about 250 times those at sea level. Under these extreme conditions — similar to those in the lower mantle — the mineral sopped up argon yet found little room for xenon.
Those...