Determination of the half-life of 41Ca from measurements of Antarctic meteorites

Using accelerator mass spectrometry (AMS), we have determined the half-life of 41Ca from the decrease of its concentration with terrestrial age in five Antarctic meteorites and a recent fall. The meteorites were selected on the basis of their 36Cl concentrations (measured on the same aliquots as used here), which showed a span of terrestrial ages of ≅ 600 ka, and on the basis of other cosmogenic-nuclide concentrations which indicated that the meteorites had small pre-atmospheric sizes (so that the samples were negligibly shielded from primary cosmic rays), and sufficiently long irradiation times in space that the concentrations of 41Ca and 36Cl were in secular equilibrium prior to the meterorites' fall to Earth. Based on the decrease of 41Ca relative to 36Cl (t1/2=301±2 ka), we infer that the half-life of 41Ca is 103±7 ka. (orig.)