A Shorter 146Sm Half-Life Measured and Implications for 146Sm-142Nd Chronology in the Solar System

TL;DR

This study measures a shorter half-life for 146Sm, impacting the timing of early solar system events and refining chronometers used in astrophysics and geochemistry.

Contribution

It provides a new, more accurate half-life for 146Sm, altering previous age estimates of planetary differentiation and solar system chronology.

Findings

146Sm half-life is 68 ± 7 million years, shorter than previous estimates.

Higher initial 146Sm abundance in the early solar system.

Revised ages for planetary differentiation events are earlier than previously thought.

Abstract

The extinct p-process nuclide 146Sm serves as an astrophysical and geochemical chronometer through measurements of isotopic anomalies of its alpha-decay daughter 142Nd. Based on analyses of 146Sm/147Sm alpha-activity and atom ratios, we determined the half-life of 146Sm to be 68 \pm 7 (1sigma) million years (Ma), which is shorter than the currently used value of 103 \pm 5 Ma. This half-life value implies a higher initial 146Sm abundance in the early solar system, (146Sm/144Sm_0 = 0.0094\pm0.0005 (2sigma), 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.