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Isótopos de bario en el meteorito Allende: evidencia en contra de un elemento súper pesado extinto
Science (New York, N.Y.)
|December 2, 1983
Resumen
El meteorito de Allende contiene xenón con proporciones isotópicas inusuales, identificado como xenón de fisión de condrita carbonácea (CCF). Este xenón y su portador de carbono son probablemente antiguas reliquias de la nucleosíntesis estelar, no de la fisión de elementos superpesados.
Área de la Ciencia:
- Cosmoquímica es la cosmoquímica.
- La astrofísica nuclear es una astrofísica nuclear.
- La meteorología es meteorítica.
Sus antecedentes:
- El meteorito de Allende, una condrita carbonácea, contiene granos presolares.
- El xenón isotópicamente anómalo, denominado xenón de fisión de condrita carbonácea (CCF), se ha detectado en muestras de meteoritos.
- El origen del xenón CCF es objeto de debate, con hipótesis que incluyen la fisión in situ de elementos superpesados extintos o orígenes presolares.
Objetivo del estudio:
- Para investigar el origen del xenón-131 isotópicamente anómalo al xenón-136 (xenón CCF) encontrado en el meteorito de Allende.
- Para probar la hipótesis de que el xenón CCF resultó de la fisión in situ de un elemento súper pesado extinto.
- Para determinar si el xenón CCF y su portador son reliquias presolares.
Principales métodos:
- Análisis de las fracciones de carbono y cromita del meteorito de Allende.
- Medición de las abundancias isotópicas de xenón (Xe-131 a Xe-136).
- Medición de la abundancia isotópica de bario (Ba-130 a Ba-138) en las mismas fracciones.
Principales resultados:
- Las fracciones que contienen xenón CCF (hasta 5 x 10^11 átomos/g) no mostraron anomalías isotópicas detectables en el bario-130 hasta el bario-138.
- La ausencia de anomalías de bario descarta la fisión in situ de un elemento superpesado como fuente del xenón CCF.
Conclusiones:
- El xenón CCF y su portador carbonoso son probablemente reliquias presolares, originadas en la nucleosíntesis estelar.
- Este hallazgo apoya la interpretación del xenón CCF como evidencia de procesos que ocurrieron antes de la formación del sistema solar.
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