New theory may explain the lack of xenon in Earth’s atmosphere

Nature : Xenon is the second heaviest of the inert noble gases, but is not present in Earth’s atmosphere in proportions consistent with its presence in meteorites made of material similar to early Earth. The “missing” xenon is generally theorized to be trapped in minerals in Earth’s lower mantle. However, a team led by Hans Keppler and Svyatoslav Shcheka of the University of Bayreuth in Germany showed that xenon was not easily trapped in one such mineral, magnesium silicate perovskite. The tests led Keppler and Shcheka to suggest that during Earth’s formation, lighter noble gases were trapped, but xenon escaped from the atmosphere. The researchers show that the proportions of noble gases in the atmosphere correspond to the gases’ solubility in the mineral they tested. However, the theory may not fully explain why heavier isotopes of xenon are more present than lighter ones. And it may not accurately explain the similar lack of xenon on Mars.