PU-244, SUPERNOVA AND HOT ATOM CHEMISTRY

Re-examination of a vast amount of xenon isotope data reveals that the carbonaceous chondrites and some of the lunar fines began retaining t heir xenon when the ratio of Pu-244 to U-238 in the solar system was 0 .113 to 0.262 (atom/atom) about 4,900 million years ago. Excess Xe-129 from the decay of I-129 is conspicuously missing in most of these sam ples, indicating that either a) the last supernova exploded more than 150 to 200 million years prior to the time the carbonaceous chondrites began to retain their xenon, or b) fine-grained interstellar diamond crystals found in the carbonaceous chondrites may have played the role of a 'fission product catcher' for a quantitative retention of Pu-244 fission xenon, while allowing the excess Xe-129 from the weak-beta de cay of I-129 to escape from the meteorites.