title: Hydrogen isotope fractionation in methane plasma.
abstract: The hydrogen isotope ratio (D/H) is commonly used to reconstruct the chemical processes at the origin of water and organic compounds in the early solar system. On the one hand, the large enrichments in deuterium of the insoluble organic matter (IOM) isolated from the carbonaceous meteorites are interpreted as a heritage of the interstellar medium or resulting from ion-molecule reactions taking place in the diffuse part of the protosolar nebula. On the other hand, the molecular structure of this IOM suggests that organic radicals have played a central role in a gas-phase organosynthesis. So as to reproduce this type of chemistry between organic radicals, experiments based on a microwave plasma of CH4have been performed. They yielded a black organic residue in which ion microprobe analyses revealed hydrogen isotopic anomalies at a submicrometric spatial resolution. They likely reflect differences in the D/H ratios between the various CHxradicals whose polymerization is at the origin of the IOM. These isotopic heterogeneities, usually referred to as hot and cold spots, are commensurable with those observed in meteorite IOM. As a consequence, the appearance of organic radicals in the ionized regions of the disk surrounding the Sun during its formation may have triggered the formation of organic compounds.
authors.affiliation: Institut de Minéralogie, Physique des Matériaux et Cosmochimie, UMR 7590, Muséum National d'Histoire Naturelle, 75231 Paris Cedex 05, France; robert@mnhn.fr.
authors.forename: François
authors.initials: F
authors.lastname: Robert
authors.affiliation: Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols, UMR CNRS 7619, Université Pierre et Marie Curie, 75252 Paris Cedex 05, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Derenne
authors.affiliation: Laboratoire des Sciences des Procédés et des Matériaux, CNRS-UPR 3407, Université Paris 13, Sorbonne Paris Cité, 93430 Villetaneuse, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Lombardi
authors.affiliation: Laboratoire des Sciences des Procédés et des Matériaux, CNRS-UPR 3407, Université Paris 13, Sorbonne Paris Cité, 93430 Villetaneuse, France.
authors.forename: Khaled
authors.initials: K
authors.lastname: Hassouni
authors.affiliation: Laboratoire des Sciences des Procédés et des Matériaux, CNRS-UPR 3407, Université Paris 13, Sorbonne Paris Cité, 93430 Villetaneuse, France.
authors.forename: Armelle
authors.initials: A
authors.lastname: Michau
authors.affiliation: Laboratoire de Chimie Théorique, Université Pierre et Marie Curie, 75252 Paris, France.
authors.forename: Peter
authors.initials: P
authors.lastname: Reinhardt
authors.affiliation: Institut de Minéralogie, Physique des Matériaux et Cosmochimie, UMR 7590, Muséum National d'Histoire Naturelle, 75231 Paris Cedex 05, France.
authors.forename: Rémi
authors.initials: R
authors.lastname: Duhamel
authors.affiliation: Institut de Minéralogie, Physique des Matériaux et Cosmochimie, UMR 7590, Muséum National d'Histoire Naturelle, 75231 Paris Cedex 05, France.
authors.forename: Adriana
authors.initials: A
authors.lastname: Gonzalez
authors.affiliation: Institut de Minéralogie, Physique des Matériaux et Cosmochimie, UMR 7590, Muséum National d'Histoire Naturelle, 75231 Paris Cedex 05, France.|Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols, UMR CNRS 7619, Université Pierre et Marie Curie, 75252 Paris Cedex 05, France.
authors.forename: Kasia
authors.initials: K
authors.lastname: Biron
keywords: cosmochemistry; hydrogen isotopes; insoluble organic matter; meteorites; methane plasma