The Tarda Meteorite: A Window into the Formation of D-type Asteroids

• Published in: The Astrophysical Journal Letters
• Main Authors: Marrocchi, Yves, Avice, Guillaume, Barrat, Jean-Alix
• Other Authors: Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: asteroids; Trans-Neptunian objects; carbonaceous chondrites; isotopic abundances; [SDU]Sciences of the Universe [physics]; Tagish; Tagish Lake
• Online Access: https://hal.archives-ouvertes.fr/hal-03368940; https://hal.archives-ouvertes.fr/hal-03368940/document; https://hal.archives-ouvertes.fr/hal-03368940/file/Marrocchi-modified.pdf; https://doi.org/10.3847/2041-8213/abfaa3

International audience Dynamic models of solar system evolution suggest that D-type asteroids formed beyond Saturn's 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 16 O-rich chondrules and chondrule fragments, high C/H ratios, and enrichments in deuterium, 15 N, and 13 C. By combining our results with literature data on carbonaceous chondrites related to C-type asteroids, we show that the outer solar system at that time was characterized by large-scale 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.