Short-lived radionuclides in the solar nebula

Several radionuclides with halflives as short as 10(5) years were present in the material from which the solar system formed. Those with halflives around 10(8) years and less have now decayed to extinction, but their prior presence can be inferred, chiefly from variations in the relative abundances of their daughter isotopes, in sufficiently ancient solid samples (meteorites) and in major planetary reservoirs. Their short lifetimes provide the finest available radiometric constraints on the chronology of nebular and planetary events in the early solar system and on nucleosynthetic events contributing to the presolar molecular cloud shortly before its collapse. The time between nucleosynthesis and meteorite formation is so short that it fosters induced collapse models, and the most recently added radionuclides may never have been well mixed with the rest of the presolar cloud.