Calcium isotope evidence for the formation of early condensates in the Solar System from unmixed reservoirs with distinct nucleosynthetic origins

Abstract

Calcium-aluminum rich inclusions (CAIs) are the oldest condensates in the Solar System. Previous studies have revealed that moderately heavy and trace element isotope anomalies (e.g., Ti, Sr, Mo, and Nd) in CAIs record large nucleosynthetic isotope variations compared to bulk meteorites. Calcium is a major element in CAIs that has six stable isotopes with multiple nucleosynthetic origins. As such, Ca isotopes in CAIs have been an important target of isotopic analysis since the 1970s. However, the Ca isotope compositions of CAIs measured by previous-generation mass spectrometers are less precise than recent isotopic data of heavy elements, which complicates their direct comparisons. Obtaining high-precision Ca isotopic data provides a stronger link between CAI-formation processes from nebular gas and the origin of their source materials.