Study Reveals Early Solar System Formed from Chondrules, Not Ice

Chondrules are small, millimeter-sized beads of rock formed by intense heat. The study indicates that if the first solid bodies had a recipe, it would emphasize chondrules while including only a small amount of matrix, which contains water ice and organic molecules.

To reconstruct the initial mixture of materials, researchers examined iron meteorites from parent bodies that had melted entirely, destroying the chondrules contained within. This analysis allowed them to work backward to deduce the original composition of these bodies.

Damanveer Grewal, the study's lead author and an assistant professor at Yale, noted the significance of chondrules as crucial building blocks for planets. The chemical analysis revealed that the original matrix content in these early planetesimals was likely between 8% and 17%, lower than any known primitive meteorites.

Using two distinct chemical tracers linked to the matrix—sulfur concentration and the oxidation state of iron—the researchers determined that these planetesimals were indeed matrix-poor. Their findings suggest that the earliest solid bodies were constructed from 83% to 92% chondrules, indicating a selective assembly process.

Grewal explained that the study provides insights into why older chondrules are rare in the meteorite record; they were incorporated into early bodies that eventually melted, leaving behind only chemical evidence of their prior existence. This research offers a deeper understanding of the formative processes that led to the creation of rocky planets in the solar system.

Reference: "Planetesimal compositions governed by aerodynamic sorting from the onset of Solar System formation" by Damanveer S. Grewal, Zhongtian Zhang, and Joanna Drążkowska, published in Nature Astronomy.