Researchers report evidence of internal melting and partial differentiation of a carbonaceous meteorite source body, showing that such primitive bodies began to differentiate into core, mantle, and crust structures in the early Solar System. Although isotopic and paleomagnetic data suggest that carbonaceous chondrite planetesimals differentiated, meteoritic evidence of the onset of such differentiation, beginning with internal melting, have not been found. Jérôme Aléon and colleagues examined the petrology of a meteoritic fragment of a basaltic rock, suggesting melted material, enclosed in a chondrite. Isotopic composition of the basaltic rock, called a trachybasalt due to its composition enriched in iron and alkaline elements, was consistent with a model of a melting carbonaceous chondrite, further enriched in sodium due to fluid-assisted metamorphism at depth. The texture of the crystals in the trachybasalt was consistent with the rapid cooling that would occur if magma ascended through chondritic material. The trachybasalt represents early magmatic processes in a carbonaceous asteroid. According to the authors, the results show a link between the relatively undifferentiated icy cometary bodies and the highly differentiated iron meteorite source bodies, which are linked together by isotopic signatures.
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Article #19-19550: "Alkali magmatism on a carbonaceous chondrite planetesimal," by Jérôme Aléon et al.
MEDIA CONTACT: Jérôme Aléon, National Museum of Natural History, Paris, FRANCE; e-mail: jerome.aleon@mnhn.fr
Proceedings of the National Academy of Sciences