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Constraints on Conditions in the Solar Nebula from the Laboratory Study of Presolar Grains

Constraints on Conditions in the Solar Nebula from the Laboratory Study of Presolar Grains. Gary R. Huss Hawai’i Institute of Geophysics and Planetology University of Hawai’i at Manoa. Silicon Carbide. Hibonite (CaAl 12 O 19 ). Young stellar systems in Orion.

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Constraints on Conditions in the Solar Nebula from the Laboratory Study of Presolar Grains

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  1. Constraints on Conditions in the Solar Nebula from the Laboratory Study of Presolar Grains Gary R. Huss Hawai’i Institute of Geophysics and Planetology University of Hawai’i at Manoa Silicon Carbide Hibonite (CaAl12O19)

  2. Young stellar systems in Orion

  3. Chondritic Meteorites preserve material from the Solar Nebula

  4. Types of Presolar Grains

  5. CI Chondrites: Representative Samples of Molecular Cloud? • Chemical composition matches Sun • High abundances of presolar grains • Severely altered on parent body

  6. Fraction of Primitive Chondritic Material Directly Traceable to Molecular Cloud *Plus unknown amount of interstellar organic compounds.

  7. Constraints on Presolar Carbon in CI from Diamond Abundance • Hard lower limit: ISM carbon is 20% diamond (Allamandola et al., 1993) • Reasonable LL: ISM carbon is 4-5% diamond • Upper limit: major fraction of MC organic material destroyed; other elements unfractionated

  8. How much of CI chondrites came directly from molecular cloud material? • Bulk composition implies little chemical fraction-ation and little addition of fractionated material • Evidence for small addition of high-T material (≤5%) • High abundances of most presolar grains • High percentage of carbon may be presolar • Large fraction may have been destroyed • High percentage of other elements also presolar • Complete evaporation and recondensation destroys presolar grains • ~90% of CI material from molecular cloud.

  9. Presolar Materials as Tracers of Nebular and Parent Body Processing

  10. Effects of Metamorphism on Abundances of Presolar Materials • Abundances of all types decrease with increasing metamorphic grade • Rate of decrease related to chemical and thermal resistance of materials • All started with the same mixture

  11. LL Chondrites • Lithophile elements more refractory than Na are unfractionated • Volatile elements depleted • Refractory presolar components unfractionated • Thermally sensitive presolar components depleted

  12. CO Chondrites • Elements more refractory than Au unfractionated (except for addition of CAIs) • Volatile elements depleted • Presolar components fractionated • Resistant components enriched relative to CI

  13. CR Chondrites • Elements more refractory than Cr unfractionated • Volatile elements depleted • Presolar components more steeply fractionated • Resistant components enriched relative to CI

  14. Crystalline Silicates: Astronomical Observations • Crystalline silicates are rare in the interstellar medium. • Crystalline silicates are more abundant in protostellar disks. • Abundance of crystalline silicates higher near protostar. • Crystalline silicates form in protostellar disks.

  15. Matrix of ALHA 77307 From Brearley 1993, GCA 57, 1521

  16. Molecular cloud material survives in chondrites • Its survival depends on structure and composition • Presolar grains are keys to understanding early solar system processes

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