title: Pristine extraterrestrial material with unprecedented nitrogen isotopic variation.
abstract: Pristine meteoritic materials carry light element isotopic fractionations that constrain physiochemical conditions during solar system formation. Here we report the discovery of a unique xenolith in the metal-rich chondrite Isheyevo. Its fine-grained, highly pristine mineralogy has similarity with interplanetary dust particles (IDPs), but the volume of the xenolith is more than 30,000 times that of a typical IDP. Furthermore, an extreme continuum of N isotopic variation is present in this xenolith: from very light N isotopic composition (delta(15)N(AIR) = -310 +/- 20 per thousand), similar to that inferred for the solar nebula, to the heaviest ratios measured in any solar system material (delta(15)N(AIR) = 4,900 +/- 300 per thousand). At the same time, its hydrogen and carbon isotopic compositions exhibit very little variation. This object poses serious challenges for existing models for the origin of light element isotopic anomalies.
authors.affiliation: Laboratoire de Minéralogie et Cosmochimie du Muséum, Muséum National d'Histoire Naturelle, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7202, 75005 Paris, France. briani@mnhn.fr
authors.forename: Giacomo
authors.initials: G
authors.lastname: Briani
authors.forename: Matthieu
authors.initials: M
authors.lastname: Gounelle
authors.forename: Yves
authors.initials: Y
authors.lastname: Marrocchi
authors.forename: Smail
authors.initials: S
authors.lastname: Mostefaoui
authors.forename: Hugues
authors.initials: H
authors.lastname: Leroux
authors.forename: Eric
authors.initials: E
authors.lastname: Quirico
authors.forename: Anders
authors.initials: A
authors.lastname: Meibom
mesh_terms: D019443:Cosmic Dust; D005118:Extraterrestrial Environment; D006358:Hot Temperature; D058085:Iron Compounds / Q000737:chemistry; D017616:Magnesium Compounds / Q000737:chemistry; D019110:Meteoroids; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008903:Minerals / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry / Q000648:ultrastructure; D009587:Nitrogen Isotopes / Q000737:chemistry; D010316:Particle Size; D052638:Particulate Matter / Q000737:chemistry; D017640:Silicates / Q000737:chemistry; D016082:Solar System; D013052:Spectrometry, X-Ray Emission
chemical_list: D019443:Cosmic Dust; D058085:Iron Compounds; D017616:Magnesium Compounds; D008903:Minerals; D009587:Nitrogen Isotopes; D052638:Particulate Matter; D017640:Silicates; C092478:pyroxene; C034475:olivine