Ca-41 in the early solar system

Abstract

Ca-Al-rich refractory inclusions (CAIs) from the Efremovka carbonaceous chondrite contain excess K-41 that correlates with their Ca-40 contents. Our results suggest the presence of Ca-41 (mean life approximately 0.15 Myr) in the early solar system and an initial Ca-41/Ca-40 ratio of (1.5 +/- 0.3) x 10<SUP>-8</SUP> in the Efremovka CAIs at the time of their formation. The excess K-41 is not due to the production of Ca-41 by secondary neutrons during the cosmic-ray exposure of the Efremovka meteorite. A 'fossil' origin of the excess is not compatible with the magnitude of the observed excess and its correlation with Ca-40. Observation of excess K-41 in CAIs constrains the time interval between the cessation of nucleosynthetic input to the solar nebula and the formation of CAIs to less than a million years.