Isotopic imprints of late molecular cloud infall in the outer Solar SystemOPEN ACCESS

10/07/2026 17:09 · by karmaka · in accretion, carbonaceous chondrite, CI, CL, CM, CO, CR, CT, CV, CY, planets/planetesimals, ungrouped

Elishevah van Kooten, Sebastian Sjørring Lodal, Isaac Onyett, Lasse Rasmus Pohlmann, Jean Bollard, Courtney Rundhaug, Martin Schiller & Martin Bizzarro

Nature Astronomy, Published: 10 July 2026

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We spotted the following typos in the text. When “NWA 1256” (a Ureilite) or “NWA 12561” (an H5) are mentioned (in the Method passage and in table 1) NWA 12563 (CM2-an) or NWA 12651 (CM) must be meant (karmaka, 10 July 2026)

Former preprint (4 June 2026): PDF (OPEN ACCESS)

“Understanding the physicochemical evolution of the outer protoplanetary disk is critical, as it governed the distribution and delivery of key volatiles—such as water and organic compounds—to the inner, initially hot and volatile-poor terrestrial planet-forming region. These materials are essential for establishing potentially habitable environments and directly influence the emergence of life on rocky planets. Here we extend beyond the traditional building blocks of the outer disk, the carbonaceous chondrite groups, and examine their ungrouped counterparts—the anomalous chondrites—to constrain a coherent model of disk evolution using Si, Mg, Fe and Cr nucleosynthetic isotope systematics. Our results reveal that the outer disk was replenished via addition of isotopically distinct molecular cloud material that contributed a substantial fraction of mass (>30%) to the building blocks of the gas giant accretion region. This late-infalling material did not contribute to the main accretion phase of the terrestrial planets that have evolved their volatile budget solely from Ivuna-type planetesimals such as Ryugu and Bennu, which, in our model, were formed at the inward-migrating water ice line. The accretion of these icy planetesimals in the inner disk fundamentally revises our view of Solar System evolution, dissolving the canonical dichotomy between non-carbonaceous and carbonaceous reservoirs and identifying a unified pathway for the delivery of volatile-rich material to the terrestrial planet region.”