Homogeneous Distribution of ~(26)Al in the Solar System from the Mg Isotopic Composition of Chondrules

摘要

The timing of the formation of the first solids in the solar system remains poorly constrained. Micrometer-scale, high-precision magnesium (Mg) isotopic analyses demonstrate that Earth, refractory inclusions, and chondrules from primitive meteorites formed from a reservoir in which short-lived aluminum-26 (~(26)Al) and Mg isotopes were homogeneously distributed at +10%. This level of homogeneity validates the use of ~(26)Al as a precise chronometer for early solar system events. High-precision chondrule ~(26)Al isochrons show that several distinct chondrule melting events took place from ～1.2 million years (My) to ～4 My after the first solids condensed from the solar nebula, with peaks between ～1.5 and ～3 My, and that chondrule precursors formed as early as 0.87_(-0.16)~(+0.19) My after.