History

(Gr. xenon, stranger) Discovered in 1898 by Ramsay and Travers in residue left after evaporating liquid air. Xenon is a member of the so-called noble or "inert" gases. It is present in the atmosphere to the extent of about one part in twenty million. Xenon is present in the Martian atmosphere to the extent of 0.08 ppm. the element is found in the gases evolved from certain mineral springs, and is commercially obtained by extraction from liquid air. 
A Periodic Table of the Elements at Los Alamos National Laboratory