Earth's Missing Noble Gas Xenon May Not Be Lost After All

In this NASA handout, the umbra, or moon's shadow, passes over Earth during the total eclipse on August 21, 2017. New research suggests that xenon might be hiding inside the Earth. NASA via Getty Images

Xenon, one of Earth's rarest and most mysterious gases, has left scientists puzzled for decades. They've long thought that the Earth's atmosphere should contain more of the noble gas, but new research has shown that it might be here after all—it's just hiding far away from us.

In an effort to solve what scientists often call "the missing Xe paradox" a team of international researchers examined the theory that xenon is tucked away deep inside our planet's core. Previous findings have found that just like the other six noble gases—argon, helium, neon, krypton, radon and oganesson—xenon is unreactive, meaning it doesn't mix well with other compounds or elements. However, under certain circumstances, it may actually react.

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"When xenon is squashed by extreme pressures, its chemical properties are altered, allowing it to form compounds with other elements," Sergey Lobanov, study co-author and researcher at the Institute for Mineral Physics at Stony Brook University, said in a statement.

Lobanov and his colleagues tested their theory by using advanced technology to mimic the condition of Earth's core. They then successfully attempted to get xenon to react with the metals nickel and iron, both of which are abundant in Earth's center. Under extremely high temperatures and pressure, the elements reacted, according to the findings published in the journal Physical Review Letters.

"Our study provides the first experimental evidence of previously theorized compounds of iron and xenon existing under the conditions found in the Earth's core," Alexander Goncharov, study co-author and staff scientist at Carnegie Institution for Science, said in a statement.

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However, the same reaction likely wouldn't have been seen billions of years ago when the Earth was forming, Goncharov explains. Rather, as the planet's internal pressure and temperature increased over the years, new compounds were able to be made.

There are still many questions to be answered. The team is now investigating whether a two-part formation process played a role in trapping xenon when the Earth first formed and then once conditions were altered, later allowed xenon reactions to occur.

"There are many more systems and paradoxes to resolve," Elissaios Stavrou, study co-author and Lawrence Livermore National Laboratory physicist, said in a statement. "We look forward to writing new chapters about extreme physicochemical phenomena."