COORDINATED ANALYSES OF PRESOLAR GRAINS IN THE ALLAN HILLS 77307 AND QUEEN ELIZABETH RANGE 99177 METEORITES

Journal Article · Tue Aug 10 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/719/1/166· OSTI ID:21455020

Nguyen, Ann N; Nittler, Larry R; Alexander, Conel M. O'D. ^[1]; Stadermann, Frank J ^[2]

---

1. Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015 (United States)
2. Laboratory for Space Sciences and the Physics Department, Washington University, One Brookings Drive, St. Louis, MO 63130 (United States)

We report the identification of presolar silicates ({approx}177 ppm), presolar oxides ({approx}11 ppm), and one presolar SiO{sub 2} grain in the Allan Hills (ALHA) 77307 chondrite. Three grains having Si-isotopic compositions similar to SiC X and Z grains were also identified, though the mineral phases are unconfirmed. Similar abundances of presolar silicates ({approx}152 ppm) and oxides ({approx}8 ppm) were also uncovered in the primitive CR chondrite Queen Elizabeth Range (QUE) 99177, along with 13 presolar SiC grains and one presolar silicon nitride. The O-isotopic compositions of the presolar silicates and oxides indicate that most of the grains condensed in low-mass red giant and asymptotic giant branch stars. Interestingly, unlike presolar oxides, few presolar silicate grains have isotopic compositions pointing to low-metallicity, low-mass stars (Group 3). The {sup 18}O-rich (Group 4) silicates, along with the few Group 3 silicates that were identified, likely have origins in supernova outflows. This is supported by their O- and Si-isotopic compositions. Elemental compositions for 74 presolar silicate grains were determined by scanning Auger spectroscopy. Most of the grains have non-stoichiometric elemental compositions inconsistent with pyroxene or olivine, the phases commonly used to fit astronomical spectra, and have comparable Mg and Fe contents. Non-equilibrium condensation and/or secondary alteration could produce the high Fe contents. Transmission electron microscopic analysis of three silicate grains also reveals non-stoichiometric compositions, attributable to non-equilibrium or multistep condensation, and very fine scale elemental heterogeneity, possibly due to subsequent annealing. The mineralogies of presolar silicates identified in meteorites thus far seem to differ from those in interplanetary dust particles.

• OSTI ID: 21455020
• Journal Information: Astrophysical Journal, Vol. 719, Issue 1; Other Information: DOI: 10.1088/0004-637X/719/1/166; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
CHONDRITES
INTERSTELLAR GRAINS
INTERSTELLAR SPACE
ISOTOPE RATIO
NUCLEAR REACTIONS
NUCLEOSYNTHESIS
OLIVINE
OXYGEN 18
SILICA
SILICATES
SILICON CARBIDES
SILICON NITRIDES
SILICON OXIDES
SPECTROSCOPY
STELLAR WINDS
STOICHIOMETRY
SUPERNOVAE
TRANSMISSION ELECTRON MICROSCOPY
BINARY STARS
CARBIDES
CARBON COMPOUNDS
CHALCOGENIDES
DIMENSIONLESS NUMBERS
ELECTRON MICROSCOPY
ERUPTIVE VARIABLE STARS
EVEN-EVEN NUCLEI
ISOTOPES
LIGHT NUCLEI
METEORITES
MICROSCOPY
MINERALS
NITRIDES
NITROGEN COMPOUNDS
NUCLEI
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PARTICLES
PNICTIDES
SILICATE MINERALS
SILICON COMPOUNDS
SPACE
STABLE ISOTOPES
STARS
STELLAR ACTIVITY
STONE METEORITES
SYNTHESIS
VARIABLE STARS