146Sm

Samarium-146 (146Sm) is a radioactive isotope of the element samarium. It has a mass number of 146 and decays by alpha emission to 142Nd. The half-life is about 103 million years, placing its decay on timescales relevant to the early solar system rather than modern Earth.

Natural occurrence and production are limited. 146Sm is not produced or maintained in detectable amounts today on Earth due to its relatively short half-life. It is believed to have been synthesized in stellar environments such as supernovae and asymptotic giant branch stars and became part of the material that formed the solar system. In meteorites and early planetary materials, the decay of 146Sm to 142Nd left measurable isotopic signatures that can be studied to understand early processes.

Applications and significance include its use in radiometric dating. The 146Sm-142Nd decay system provides a chronometer for early solar system events and planetary differentiation. By analyzing Nd isotopic compositions and Sm/Nd ratios in meteorites and terrestrial rocks, scientists can place constraints on the timing of crust formation and melting episodes within the first tens to hundreds of millions of years after solar system formation. The system is particularly valuable for investigating the chronology of differentiation in planetary bodies and for refining models of solar system evolution.