Xenon is the second heaviest of the Noble gasses. The lighter ones—Neon, Argon, and Krypton—are all present in the atmosphere at about the level expected from predictions of primordial concentration. Big old Xenon, though, is missing in action, with about 90% unaccounted for.
Where did the misplaced Xenon go? Previous attempts at explanations include Xenon entrapment in water, ice, or sediments, or possibly escape from the atmosphere into space. All have proven untenable. Read More ›