 Because xenon is a <unk> for two parent isotopes , xenon isotope ratios in meteorites are a powerful tool for studying the formation of the solar system . The iodine @-@ xenon method of dating gives the time <unk> between nucleosynthesis and the condensation of a solid object from the solar nebula . In 1960 , physicist John H. Reynolds discovered that certain meteorites contained an isotopic anomaly in the form of an overabundance of xenon @-@ 129 . He inferred that this was a decay product of radioactive iodine @-@ 129 . This isotope is produced slowly by cosmic ray <unk> and nuclear fission , but is produced in quantity only in supernova explosions . As the half @-@ life of 129I is comparatively short on a <unk> time scale , only 16 million years , this demonstrated that only a short time had passed between the supernova and the time the meteorites had solidified and trapped the 129I . These two events ( supernova and <unk> of gas cloud ) were inferred to have happened during the early history of the Solar System , as the 129I isotope was likely generated before the Solar System was formed , but not long before , and <unk> the solar gas cloud with isotopes from a second source . This supernova source may also have caused collapse of the solar gas cloud . 
