Measurements of the concentrations of 26Al in lunar rocks 15555 and 60025

The authors have measured the concentrations of 26Al in lunar rock samples 15555,859 and 60025,28 with a multidimensional gamma-ray spectrometer, obtaining concentrations of 167±14 and 255±10 dpm/kg for the two rocks, respectively. Computer modelings were carried out on both samples of the 26Al production rates from cosmic-ray bombardment using consistent values of cosmic-ray parameters and reasonable values of surface erosion to see if an inconsistency in values needed for a fit between measurement and modeling could be found which would suggest the presence of surface-implanted 26Al in one or both samples. The final result was that both of the samples could be fitted by the computer models using omnidirectional SEP flux and rigidity shape values of 125 protons/cm2/s>10 MeV and 125 MV/unit charge, respectively, and with the reasonable surface erosion rates of 0–0.24 mm/Myr for rock 15555,859, and 1.6 mm/Myr for 60025,28.