Calcium–aluminium-rich inclusions (CAIs) are one of the first solids to have condensed in the solar nebula, while presolar grains formed in various evolved stellar environments. It is generally accepted that CAIs formed close to the Sun at temperatures above 1,500 K, where presolar grains could not survive, and were then transported to other regions of the nebula where the accretion of planetesimals took place. In this context, a commonly held view is that presolar grains are found solely in the fine-grained rims surrounding chondrules and in the low-temperature fine-grained matrix that binds the various meteoritic components together. Here we demonstrate, on the basis of noble gas isotopic signatures, that presolar SiC grains were incorporated into fine-grained CAIs in the Allende carbonaceous chondrite at the time of their formation, and have survived parent-body processing. This finding provides new clues on the conditions in the nascent Solar System at the condensation of the first solids.

富含钙铝的包裹体 (CAI) 是最早在太阳星云中凝聚的固体之一，而太阳前颗粒则是在各种演化的恒星环境中形成的。人们普遍认为，CAI 在 1,500 K 以上的温度下靠近太阳形成，前太阳颗粒无法存活，然后被运送到星云的其他区域，在那里发生了小行星的吸积。在这种情况下，一个普遍持有的观点是，太阳前晶粒仅存在于球粒周围的细粒边缘和将各种陨石成分结合在一起的低温细粒基质中。在这里，我们证明，基于惰性气体同位素特征，前太阳 SiC 晶粒在阿连德碳质球粒陨石形成时被掺入细粒 CAI 中，并且在母体加工过程中幸存下来。这一发现为新生的太阳系中第一个固体凝结的条件提供了新的线索。