Early planetesimals were dominated by rocky chondrules, study shows

The study, published in Nature Astronomy, argues that during the Solar System's first million years, aerodynamic forces caused larger chondrules to be preferentially gathered into forming planetesimals, while finer, ice-rich dust was largely excluded. By examining sulfur concentrations and iron oxidation states in iron meteorites from the outer Solar System, the authors estimated matrix material at only 8% to 17% of the original composition.

These findings explain why ancient chondrules are rare in the meteorite record, as many were incorporated into bodies that later melted, erasing their physical signatures. The research highlights that early planetesimals were not assembled from a uniform dust cloud but from a compositionally sorted mixture. The work was led by Damanveer Grewal and involved input from Yale University researchers. The results refine models of how volatile-poor and volatile-rich materials were distributed in the nascent Solar System.