title: Plutonium-fission xenon found in Earth's mantle
abstract: Data from mid-ocean ridge basalt glasses indicate that the short-lived radionuclide plutonium-244 that was present during an early stage of the development of the solar system is responsible for roughly 30 percent of the fissiogenic xenon excesses in the interior of Earth today. The rest of the fissiogenic xenon can be ascribed to the spontaneous fission of still live uranium-238. This result, in combination with the refined determination of xenon-129 excesses from extinct iodine-129, implies that the accretion of Earth was finished roughly 50 million to 70 million years after solar system formation and that the atmosphere was formed by mantle degassing.
authors.affiliation: J. Kunz, Institut de Physique du Globe de Paris, Laboratoire de Geochimie et Cosmochimie, Centre National de la Recherche Scientifique URA 1758, 4 place Jussieu, F-75252 Paris Cedex 05, France. T. Staudacher, Institut de Physique du.
authors.initials: J
authors.lastname: Kunz
authors.initials: T
authors.lastname: Staudacher
authors.initials: CJ
authors.lastname: Allegre