MULTIPLE ORIGINS OF NITROGEN ISOTOPIC ANOMALIES IN METEORITES AND COMETS

Journal Article · Wed Oct 20 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/722/2/1342· OSTI ID:21471311

Aleon, Jerome ^[1]

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1. Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, CSNSM-CNRS-IN2 P3, Bat 104, Orsay Campus 91405 (France)

Isotopic fractionation and mixing calculations compared with coupled hydrogen and nitrogen isotopic composition of organic molecules from primitive chondrites, interplanetary dust particles (IDPs), and comets C/1995 O1 (Hale-Bopp) and 81P/Wild2 reveal that meteoritic and cometary organic matter contains three different isotopic components of different origins. (1) A major component of carbonaceous chondrites, IDPs, and comets Hale-Bopp and Wild2 shows correlated H and N isotopic compositions attributable to isotope exchange between an organic matter of solar composition and a reservoir formed by ion-molecule reactions at T < 25 K under conditions where competing reactions are strongly inhibited, possibly in the final evolutionary stages of the presolar cloud core, or more likely in the coldest outer regions of the solar protoplanetary disk. (2) In carbonaceous chondrites, IDPs, and comet Wild2, this component is mixed with a {sup 15}N-rich component having identical {sup 15}N and D enrichments relative to the protosolar gas. Temperatures > 100 K deduced from the low D/H ratio and an anti-correlation between the abundance of this component and meteoritic age indicate a late origin in the solar protoplanetary disk. N{sub 2} self-shielding and the non-thermal nucleosynthesis of {sup 15}N upon irradiation are possible but unlikely sources of this component, and a chemical origin is preferred. (3) An interstellar component with highly fractionated hydrogen isotopes and unfractionated nitrogen isotopes is present in ordinary chondrites. A dominantly solar origin of D and {sup 15}N excesses in primitive solar system bodies shows that isotopic anomalies do not necessarily fingerprint an interstellar origin and implies that only a very small fraction of volatile interstellar matter survived the events of solar system formation.

• OSTI ID: 21471311
• Journal Information: Astrophysical Journal, Vol. 722, Issue 2; Other Information: DOI: 10.1088/0004-637X/722/2/1342; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
CHONDRITES
COMETS
FRACTIONATION
HYDROGEN
HYDROGEN ISOTOPES
ION-MOLECULE COLLISIONS
ISOTOPE RATIO
ISOTOPIC EXCHANGE
METEOROIDS
NITROGEN 15
NUCLEOSYNTHESIS
PROTOPLANETS
SOLAR SYSTEM
COLLISIONS
DIMENSIONLESS NUMBERS
ELEMENTS
ION COLLISIONS
ISOTOPES
LIGHT NUCLEI
METEORITES
MOLECULE COLLISIONS
NITROGEN ISOTOPES
NONMETALS
NUCLEI
ODD-EVEN NUCLEI
SEPARATION PROCESSES
STABLE ISOTOPES
STONE METEORITES
SYNTHESIS