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La evidencia del isótopo de osmio para un portador del proceso s en las condritas primitivas
A D Brandon1, M Humayun, I S Puchtel
1NASA Johnson Space Center, Mail Stop KR, Houston, TX 77058, USA. alan.d.brandon1@jsc.nasa.gov
Science (New York, N.Y.)
|August 20, 2005
Resumen
Las anomalías del isótopo de osmio en las condritas revelan un portador insoluble (Os(i)) de sitios nucleosintéticos específicos. El metamorfismo destruyó este portador, lo que lleva a la homogeneidad isotópica en los meteoritos procesados.
Área de la Ciencia:
- Cosmoquímica es la cosmoquímica.
- Geoquímica de isótopos La geoquímica de isótopos es la química de los isótopos.
- Ciencias planetarias Ciencias planetarias.
Sus antecedentes:
- Las condritas, meteoritos primitivos, conservan los primeros materiales del sistema solar.
- Los isótopos de osmio (Os) proporcionan información sobre la nucleosíntesis estelar y la formación de meteoritos.
- Los granos presolares son portadores de firmas isotópicas extraterrestres.
Objetivo del estudio:
- Para investigar el origen y el portador de las anomalías del isótopo de osmio en meteoritos primitivos.
- Para determinar el impacto de los procesos metamórficos en la composición isotópica del osmio.
- Para restringir las condiciones de s-proceso nucleosíntesis responsable de Os presolar.
Principales métodos:
- Extracción química de osmio de las condritas en masa desequilibradas y metamorfoseadas.
- Medición de alta precisión de los isótopos de osmio.
- Comparación de composiciones isotópicas para identificar portadores presolares y efectos metamórficos.
Principales resultados:
- El osmio en las condritas desequilibradas exhibe anomalías isotópicas atribuidas a un portador insoluble del proceso s (Os(i)).
- El metamorfismo destruyó efectivamente el portador de Os, lo que resultó en la homogeneización isotópica del osmio en las condritas metamorfoseadas.
- La composición isotópica de Os(i) sugiere la formación en sitios de proceso s con densidades de neutrones más altas que las condiciones promedio del sistema solar.
Conclusiones:
- El portador Os (i) representa un componente presolar distinto originado en entornos estelares específicos.
- El metamorfismo jugó un papel crucial en el procesamiento y la homogeneización de los materiales presolares en la nebulosa solar temprana.
- Las anomalías del isótopo de osmio sirven como marcadores sensibles para comprender la nucleosíntesis y la evolución de los meteoritos.
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