Sanderson, Hannah; Courville, S. W.; Harrison, C. S.; Rider-Stokes, B. G.; Davies, F. A. & Suttle, M. D. [Vis alle 7 forfattere av denne artikkelen] (2026). Insights into the size and number of CM chondrite parent bodies from thermal modelling and links to asteroids. Journal of the Geological Society. ISSN 0016-7649. 183(5). doi: 10.1144/jgs2026-033. Fulltekst i vitenarkiv Vis sammendrag
CM chondrites are some of the most abundant meteorites and record evidence of aqueous alteration, thermal metamorphism and impacts on their parent bodies. Determining the size and number of CM chondrite parent bodies could shed light on the evolution of hydrated asteroids and how common CM-like material was in the early Solar System. Here, we combine thermal evolution modelling with the peak temperature distribution in the CM chondrite catalogue to constrain the parent body's early thermal history. Additionally, we perform UV-Vis-NIR spectral comparisons to asteroids to understand the parent body's later collisional evolution. The timing of aqueous alteration and the number of heated CM chondrites is consistent with 50 km, low temperature, aqueously altered parent body(ies) thermally metamorphosed by impacts. Spectra link the CM chondrites to hydrated, low density asteroids and combined with dynamical matches limits the radii of surviving parent body(ies) to < 150 km. Thermal modelling cannot determine the number of parent bodies, but the number of asteroids that are spectral or dynamical matches to CM chondrites supports that there were multiple parent bodies. Overall, our results suggest that one or more 50–100 km radius planetesimals that accreted 3.5–4 Myrs after CAI formation could have produced the CM chondrites.
Bryson, James F.J.; Sanderson, Hannah R.; Nimmo, Francis; Sridhar, Sanjana; Brennecka, Gregory A. & Marrocchi, Yves [Vis alle 7 forfattere av denne artikkelen] (2026). A collective trigger for widespread planetesimal formation revealed by accretion ages. Earth and Planetary Science Letters. ISSN 0012-821X. 681. doi: 10.1016/j.epsl.2026.119936. Fulltekst i vitenarkiv Vis sammendrag
The formation of planetesimals was an integral part of the cascading series of processes that built the terrestrial planets. To illuminate planetesimal formation, here we develop a refined thermal evolution model to calculate the formation ages of meteorite parent planetesimals. This model includes chemical reactions and phase changes during heating, as well as natural variations in the proportions of the constituent phases of these planetesimals. We find that the parent bodies of non-carbonaceous (NC) and carbonaceous (CC) iron meteorites start forming at very similar times ( ∼ 0.95 Myr after calcium-aluminium-rich inclusion [CAI] formation) and occupy overlapping time windows. NC and CC chondrite parent bodies formed later during non-overlapping periods. We combine these ages with proportions of isotopic end-members we recover from mixing models to construct records of motion throughout the protoplanetary disk. These records argue that NC and CC material traversed the barrier in the disk after  ∼ 0.95 Myr after CAI formation. The onset of this motion coincided with planetesimal formation, indicating that the phenomenon that drove motion also triggered planetesimal formation. We argue that this feature also served as the semi-permeable barrier in the disk. Although its identity is uncertain, the effects this phenomenon had on the timing of planetesimal formation and motion through the disk can now serve as constraints on models of disk evolution. Models that reproduce these effects would elucidate the nature and implications of this phenomenon, which is key to unlocking a holistic model of terrestrial planet building.

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Publisert 4. nov. 2025 12:00 - Sist endret 20. mars 2026 12:31