Xenology

Abstract

Work in the field of xenon isotope abundances in meteorites is discussed in the context of current theories about the formation of the heavy elements and the early history of the solar system. Using a model in which the special (Xe129*) anomaly is due to decay of I129 produced in the principal galactic synthesis, we conclude that meteorites Abee and Richardton began to retain radiogenic xenon 52 m.y. after the cessation of nucleosynthesis. The xenon-retentive phase (probably chondrules, from results obtained by Merrihue) of the Bruderheim meteorite was formed 17 m.y. earlier, a result which depends very little on the model chosen for the origin of the I129. An iron meteorite appears to have cooled about 200 m.y. later than Abee. The general anomalies in meteorites, including carbonaceous chondrites, are not fixed but vary with release temperature in a heating experiment, suggesting that components of different isotopic composition are being fractionated in the release of the gas. A search for fissionogenic xenon in meteorites has yielded very definite evidence of two components of xenon in some meteorites, especially convincing results being presented for chondrules from the Bjurböle meteorite.