Plutonium-244 dating VII. Initial abundances of uranium-235 and plutonium-244 in lunar samples

Re-examination of a vast amount of lead and xenon isotope data that have been accumulated since the Apollo 11 landing on the moon in July 1969 reveals that some of the lunar fines and breccia started to retain their radiogenic lead and fissiogenic xenon isotopes about 5 billion years ago when the ratios of²³⁵U and²⁴⁴Pu to²³⁸U in the early solar system were approximately 4 and 2 atoms per 10 atoms of²³⁸U, respectively.