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Title: Identification of Isotopically Primitive Interplanetary Dust Particles: A NanoSIMS Isotopic Imaging Study

Abstract

We have carried out a comprehensive survey of the isotopic compositions (H, B, C, N, O,S) of a suite of interplanetary dust particles (IDPs), including both cluster and individual particles. Isotopic imaging with the NanoSIMS shows the presence of numerous discrete hotspots that are strongly enriched in 15N, including the largest 15N enrichments ({approx}1300 ?) observed in IDPs to date. A number of the IDPs also contain larger regions with more modest enrichments in 15N, leading to average bulk N isotopic compositions that are 15N-enriched in these IDPs. Although C isotopic compositions are normal in most of the IDPs, two 15N-rich hotspots have correlated 13C anomalies. CN?/C? ratios suggest that most of the 15N-rich hotspots are associated with relatively N-poor carbonaceous matter, although specific carriers have not been determined. H isotopic distributions are similar to those of N: D anomalies are present both as distinct very D-rich hotspots and as larger regions with more modest enrichments. Nevertheless, H and N isotopic anomalies are not directly correlated, consistent with results from previous studies. Oxygen isotopic imaging shows the presence of abundant presolar silicate grains in the IDPs. The O isotopic compositions of the grains are similar to those found in presolarmore » oxide and silicate grains from primitive meteorites. Most of the silicate grains in the IDPs have isotopic ratios consistent with meteoritic Group 1 oxide grains, indicating origins in oxygen-rich red giant and asymptotic giant branch stars, but several presolar silicates exhibit the 17O and 18O enrichments of Group 4 oxide grains, whose origin is less well understood. Based on their N isotopic compositions, the IDPs studied here can be divided into two groups. One group is characterized as being ''isotopically primitive'' and consists of those IDPs that have anomalous bulk N isotopic compositions. These particles typically also contain numerous 15N-rich hotspots, occasional C isotopic anomalies, and abundant presolar silicate grains. In contrast, the other ''isotopically normal'' IDPs have normal bulk N isotopic compositions and, although some contain 15N-rich hotspots, none exhibit C isotopic anomalies and none contain presolar silicate or oxide grains. Thus, isotopically interesting IDPs can be identified and selected on the basis of their N isotopic compositions for further study. However, this distinction does not extend to H isotopic compositions. Although both H and N anomalies 2 are frequently attributed to the survival of molecular cloud material in IDPs and, thus, should be more common in IDPs with anomalous bulk N compositions, D anomalies are as common in normal IDPs as they are in those characterized as isotopically primitive, based on their N isotopes. This may be due to different effects of secondary processing on the isotopic systems involved.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
882100
Report Number(s):
PNNL-SA-46541
Journal ID: ISSN 0016-7037; GCACAK; 11393; KP1303000; TRN: US200613%%593
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geochimica et Cosmochimica Acta; Journal Volume: 70; Journal Issue: 9
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CLOUDS; DUSTS; METEORITES; ORIGIN; OXIDES; OXYGEN; PROCESSING; SILICATES; STARS; Environmental Molecular Sciences Laboratory

Citation Formats

Floss, Christine, Stadermann, Frank J., Bradley, John P., Dai, Zurong, Bajt, Sasa, Giles, Graham, and Lea, Alan S.. Identification of Isotopically Primitive Interplanetary Dust Particles: A NanoSIMS Isotopic Imaging Study. United States: N. p., 2006. Web. doi:10.1016/j.gca.2006.01.023.
Floss, Christine, Stadermann, Frank J., Bradley, John P., Dai, Zurong, Bajt, Sasa, Giles, Graham, & Lea, Alan S.. Identification of Isotopically Primitive Interplanetary Dust Particles: A NanoSIMS Isotopic Imaging Study. United States. doi:10.1016/j.gca.2006.01.023.
Floss, Christine, Stadermann, Frank J., Bradley, John P., Dai, Zurong, Bajt, Sasa, Giles, Graham, and Lea, Alan S.. Mon . "Identification of Isotopically Primitive Interplanetary Dust Particles: A NanoSIMS Isotopic Imaging Study". United States. doi:10.1016/j.gca.2006.01.023.
@article{osti_882100,
title = {Identification of Isotopically Primitive Interplanetary Dust Particles: A NanoSIMS Isotopic Imaging Study},
author = {Floss, Christine and Stadermann, Frank J. and Bradley, John P. and Dai, Zurong and Bajt, Sasa and Giles, Graham and Lea, Alan S.},
abstractNote = {We have carried out a comprehensive survey of the isotopic compositions (H, B, C, N, O,S) of a suite of interplanetary dust particles (IDPs), including both cluster and individual particles. Isotopic imaging with the NanoSIMS shows the presence of numerous discrete hotspots that are strongly enriched in 15N, including the largest 15N enrichments ({approx}1300 ?) observed in IDPs to date. A number of the IDPs also contain larger regions with more modest enrichments in 15N, leading to average bulk N isotopic compositions that are 15N-enriched in these IDPs. Although C isotopic compositions are normal in most of the IDPs, two 15N-rich hotspots have correlated 13C anomalies. CN?/C? ratios suggest that most of the 15N-rich hotspots are associated with relatively N-poor carbonaceous matter, although specific carriers have not been determined. H isotopic distributions are similar to those of N: D anomalies are present both as distinct very D-rich hotspots and as larger regions with more modest enrichments. Nevertheless, H and N isotopic anomalies are not directly correlated, consistent with results from previous studies. Oxygen isotopic imaging shows the presence of abundant presolar silicate grains in the IDPs. The O isotopic compositions of the grains are similar to those found in presolar oxide and silicate grains from primitive meteorites. Most of the silicate grains in the IDPs have isotopic ratios consistent with meteoritic Group 1 oxide grains, indicating origins in oxygen-rich red giant and asymptotic giant branch stars, but several presolar silicates exhibit the 17O and 18O enrichments of Group 4 oxide grains, whose origin is less well understood. Based on their N isotopic compositions, the IDPs studied here can be divided into two groups. One group is characterized as being ''isotopically primitive'' and consists of those IDPs that have anomalous bulk N isotopic compositions. These particles typically also contain numerous 15N-rich hotspots, occasional C isotopic anomalies, and abundant presolar silicate grains. In contrast, the other ''isotopically normal'' IDPs have normal bulk N isotopic compositions and, although some contain 15N-rich hotspots, none exhibit C isotopic anomalies and none contain presolar silicate or oxide grains. Thus, isotopically interesting IDPs can be identified and selected on the basis of their N isotopic compositions for further study. However, this distinction does not extend to H isotopic compositions. Although both H and N anomalies 2 are frequently attributed to the survival of molecular cloud material in IDPs and, thus, should be more common in IDPs with anomalous bulk N compositions, D anomalies are as common in normal IDPs as they are in those characterized as isotopically primitive, based on their N isotopes. This may be due to different effects of secondary processing on the isotopic systems involved.},
doi = {10.1016/j.gca.2006.01.023},
journal = {Geochimica et Cosmochimica Acta},
number = 9,
volume = 70,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2006},
month = {Mon May 01 00:00:00 EDT 2006}
}