Mysteriously, most of the gas xenon that scientists expected to find in Earth’s atmosphere is missing. Now, researchers say they might have the answer to this puzzle: This noble gas, which usually does not bond with other atoms, may chemically react with iron and nickel in Earth’s core, where it’s held. Xenon is a noble gas, so, like other noble gases, such as helium and neon, it is mostly chemically inert. Scientists have long analyzed xenon to study the evolution of Earth and its atmosphere.
Strangely, atmospheric levels of xenon are more than 90 percent less than scientists would have predicted based on levels of other noble gases such as argon and krypton. [8 Chemical Elements You’ve Never Heard Of]
“The missing xenon paradox is a long-standing question,” said study author Yanming Ma, a computational physicist and chemist at Jilin University in Changchun, China. Although some researchers have suggested that this “missing” xenon may have escaped from the atmosphere into space, the majority of scientists think it is hidden in the Earth’s interior. However, investigators have long failed to find a way in which Earth might incorporate this gas into chemically stable compounds —. For instance, there is no known way for ice or sediments might to rically capture xenon on Earth, meaning it should just escape into the atmosphere.
Past research had suggested Earth’s core might hold xenon. However, “all the previous attempts to implicate the capture of xenon in the Earth’s core have failed,” Ma said. Earth’s core, which contains about one-third of the planet’s mass, is made of iron and nickel. In 1997, scientists reported experiments that suggested xenon would not react with iron.
“Through a careful analysis of their work, however, we found that the experiment was carried out only up to 150 gigapascals, a pressure far from the Earth’s inner-core pressure of 360 gigapascals,” Ma said. (In comparison, 1 gigapascal is more than nine times greater than the pressure at the bottom of the Mariana Trench, the deepest part of the ocean.)