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The mystery xenon in Earth's atmosphere came from icy comets

The origin of the xenon in Earth's atmosphere has been a mystery for decades. Now, using data from the Rosetta spacecraft's tight orbits around a comet, researchers have determined that 22 per cent came from comets. This strengthens suspected connections between these celestial bodies and Earth's evolution.
The xenon gas in Earth's atmosphere contains more heavy isotopes than xenon in the solar wind or meteoroids, and for decades researchers couldn't figure out where this heavy component came from. The idea that it could have been brought here by comets was often suggested, but evidence was limited.
In 2014, the Rosetta spacecraft orbited the comet 67P/Churyumov-Gerasimenko mere kilometres from the surface, allowing it to sample the gas coming off the comet's ice patches. Bernard Marty at the University of Lorraine in France and his colleagues found that those gases closely matched the composition of Earth's heavy xenon.

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The Mysterious Case of the Missing Noble Gas

The evidence is in every 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 lighter noble gases, than meteorites similar to the rocky material that formed the Earth.
The missing-xenon paradox is one of sciences great whodunits.

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Earth's missing xenon could be hiding in quartz

What's happened to the Earth's missing xenon? For decades scientists have known that the abundance of xenon is curiously lower than predicted from comparisons with the other noble gases. Yet they have been unable to determine why. Now chemists in Canada have evidence that it is residing in the ground beneath our feet.
In 2005, researchers discovered that at high temperatures and pressures xenon seems to displace silicon in crystalline silicon dioxide, or quartz. The researchers proposed that xenon atoms swap places with silicon atoms, binding to the two remaining oxygen atoms either side. If this were the case, it could account for the loss of atmospheric xenon in the distant past, perhaps at a time of heavy meteorite bombardment of quartz in the Earth's crust.

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