The extinct p-process nuclide 146Sm serves as an astrophysical and geochemical chronometer through measurements of isotopic anomalies of its α-decay daughter 142Nd. Based on analyses of 146Sm/147Sm α-activity and atom ratios, we determined the half-life of 146Sm to be 68 ± 7 (1σ) million years, which is shorter than the currently used value of 103 ± 5 million years. This half-life value implies a higher initial 146Sm abundance in the early solar system, (146Sm/144Sm)0 = 0.0094 ± 0.0005 (2σ), than previously estimated. Terrestrial, lunar, and martian planetary silicate mantle differentiation events dated with 146Sm-142Nd converge to a shorter time span and in general to earlier times, due to the combined effect of the new 146Sm half-life and (146Sm/144Sm)0 values.
Publication Source (Journal or Book title)
Kinoshita, N., Paul, M., Kashiv, Y., Collon, P., Deibel, C., DiGiovine, B., Greene, J., Henderson, D., Jiang, C., Marley, S., Nakanishi, T., Pardo, R., Rehm, K., Robertson, D., Scott, R., Schmitt, C., Tang, X., Vondrasek, R., & Yokoyama, A. (2012). A shorter 146Sm half-life measured and implications for 146Sm-142Nd chronology in the solar system. Science, 335 (6076), 1614-1617. https://doi.org/10.1126/science.1215510