>>9588449Science. 1976 Dec 11;194(4271):1293-5.
The atmosphere of Mars: detection of krypton and xenon.
Owen T, Biemann K, Rushneck DR, Biller JE, Howarth DW, Lafleur AL.
Abstract
Krypton and xenon have been discovered in the martian atmosphere with the mass spectrometer on the second Viking lander. Krypton is more abundant than xenon. The relative abundances of the krypton isotopes appear normal, but the ratio of xenon-129 to xenon-132 is enhanced on Mars relative to the terrestrial value for this ratio. Some possible implications of these findings are discussed.