Plutonium-244 in the early solar system

This paper presents results of noble gas, fission track, and petrographic investigations of inclusions in the Allende meteorite, most notably a single large coarse-grained ''high temperature condensate'' type inclusion. Discussion of the data focuses on the problem of whether or not /sup 244/Pu actually was present in the early solar system, rather than being represented principally by fission xenon imported into the solar system in interstellar grains. The fission xenon content of the large inclusion corresponds to a /sup 244/Pu//sup 238/U ratio of 0.0161 +- 0.0019 at time of formation, 4.5 x 10/sup 9/ yr ago. Approximately 30% of this /sup 244/Pu has produced visible fossil fission tracks in the major mineral phases; these decays must have occurred within the solar system, establishing a firm lower limit to the amount of /sup 244/Pu which was present in the solar system. The actual value is almost certainly substantially greater than this lower limit.