2025-10-01 イェール大学
Web要約 の発言：
＜関連情報＞
- https://news.yale.edu/2025/10/01/patchwork-planets-piecing-together-early-solar-system
- https://www.science.org/doi/10.1126/sciadv.adw1668
長期にわたる核形成と衝突による破壊が太陽系外縁部の初期の微惑星を形成した Protracted core formation and impact disruptions shaped the earliest outer Solar System planetesimals
Damanveer S. Grewal, Zhongtian Zhang, Varun Manilal, Thomas S. Kruijer, […] , and Sarah T. Stewart
Science Advances Published:1 Oct 2025
DOI:https://doi.org/10.1126/sciadv.adw1668
Abstract
The distinct compositions of metallic cores from noncarbonaceous (NC) and carbonaceous (CC) iron meteorite parent bodies (IMPBs) reflect differences in accretion and differentiation histories of earliest inner and outer Solar System planetesimals. Compared to NC IMPBs, CC IMPBs have smaller, sulfur (S)–poor, highly siderophile element (HSE)–enriched cores and younger core formation ages. However, the origins of these differences remain debated. Using equilibrium partitioning models between the S-poor solid and the S-rich liquid metal, we argue that HSE enrichment in IID, IIF, IIIF, and IVB cores resulted from a multistage evolutionary sequence: (i) segregation of S-rich, HSE-depleted protocores during initial planetesimal heating; (ii) collisional disruption before S-poor metal segregation; (iii) reaccretion of mantle fragments into daughter planetesimals; and (iv) further 26Al-driven heating producing HSE-enriched, S-poor cores. We suggest that iron meteorites from these CC IMPBs originate from such second-generation cores. Accounting for “missing” S-rich protocores helps reconcile several NC-CC IMPB differences and highlights the role of early collisional processing in shaping planetesimal chemical evolution.
