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The Tarda meteorite : A window into the formation of D-type asteroids

Marrocchi, Y. ; Avice, G. ; Barrat, J.A., Astrophysical J. Letters

The Tarda meteorite : A window into the formation of D-type asteroids

Marrocchi, Y. ; Avice, G. ; Barrat, J.A.

The Astrophysical Journal Letters, 2021, 913:L9

Abstract :

Dynamic models of solar system evolution suggest that D-type asteroids formed beyond Saturnʼs orbit and represent invaluable witnesses of the prevailing conditions in the outer solar system. Here, we report a comprehensive petrographic and isotopic characterization of the carbonaceous chondrite Tarda, a recent fall recovered in the Moroccan Sahara. We show that Tarda shares strong similarities with the D-type-derived chondrite Tagish Lake, implying that Tarda represents a rare sample of D-type asteroids. Both Tarda and Tagish Lake are characterized by the presence of rare 16O-rich chondrules and chondrule fragments, high C/H ratios, and enrichments in deuterium, 15N, and 13C. By combining our results with literature data on carbonaceous chondrites related to C-type asteroids, we show that the outer solar system 4.56 Gy ago was characterized by largescale oxygen isotopic homogeneities in (i) the water–ice grains accreted by asteroids and (ii) the gas controlling the formation of FeO-poor chondrules. Conversely, the zone in which D-type asteroids accreted was significantly enriched in deuterium relative to the formation regions of C-type asteroids, features likely inherited from unprocessed, D-rich, molecular-cloud materials.

Voir en ligne : https://doi.org/10.3847/2041-8213/abfaa3




publié jeudi 20 mai 2021