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Coordinated mineralogical and isotopic analyses of a cosmic symplectite discovered in a comet 81P/Wild 2 sample
Author(s) -
Nguyen Ann N.,
Berger Eve L.,
NakamuraMessenger Keiko,
Messenger Scott,
Keller Lindsay P.
Publication year - 2017
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.12905
Subject(s) - parent body , troilite , pyroxene , comet , olivine , geochemistry , albite , geology , formation and evolution of the solar system , meteorite , chondrite , mineral , mineralogy , chalcedony , carbonaceous chondrite , chemistry , astrobiology , physics , quartz , paleontology , organic chemistry , calcite
We have discovered in a Stardust mission terminal particle a unique mineralogical assemblage of symplectically intergrown pentlandite ((Fe,Ni) 9 S 8 ) and nanocrystalline maghemite (γ‐Fe 2 O 3 ). Mineralogically similar cosmic symplectites (COS) have only been found in the primitive carbonaceous chondrite Acfer 094 and are believed to have formed by aqueous alteration. The O and S isotopic compositions of the Wild 2 COS are indistinguishable from terrestrial values. The metal and sulfide precursors were thus oxidized by an isotopically equilibrated aqueous reservoir either inside the snow line, in the Wild 2 comet, or in a larger Kuiper Belt object. Close association of the Stardust COS with a Kool mineral assemblage (kosmochloric Ca‐rich pyroxene, FeO‐rich olivine, and albite) that likely originated in the solar nebula suggests the COS precursors also had a nebular origin and were transported from the inner solar system to the comet‐forming region after they were altered.

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