LucidBeast writes "Xenon, the second heaviest of the noble gasses, is only found in trace amounts in the atmosphere. Atmosphere contains less xenon than other lighter noble gasses. Missing xenon has perplexed scientists and it has been speculated that it is hiding in the Earth's mantle. Now, a group at the University of Bayreuth in Germany thinks it might have found the answer. It turns out that xenon does not dissolve easily into magnesium silicate perovskite, and thus it cannot hide there. Because it had no place to hide, it is now gone forever."