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Samario-146 en el sistema solar temprano: evidencia de neodimio en el meteorito de Allende
Science (New York, N.Y.)
|December 2, 1983
Resumen
Los investigadores encontraron enriquecimientos significativos de isótopos de neodimio en un meteorito, probablemente de la desintegración del samario. Esto sugiere una mayor abundancia inicial de samario-146 en el sistema solar temprano, potencialmente útil para la datación.
Área de la Ciencia:
- Cosmoquímica es la cosmoquímica.
- La geoquímica de los isótopos es la geoquímica de los isótopos.
- Ciencias planetarias Ciencias planetarias.
Sus antecedentes:
- Los meteoritos, como las condritas, son restos del sistema solar primitivo, proporcionando información sobre su formación y evolución.
- Las anomalías isotópicas en los meteoritos pueden indicar la presencia de isótopos radiactivos de corta duración en el sistema solar temprano.
- El samario-146 (vida media de 108 millones de años) es un isótopo ahora extinto relevante para la nucleosíntesis y la cronología del sistema solar temprano.
Objetivo del estudio:
- Para investigar el origen de los grandes enriquecimientos isotópicos de neodimio-142 y neodimio-143 observados en una fracción carbono-cromita del meteorito de Allende.
- Determinar la abundancia inicial del extinto samario-146 en el sistema solar primitivo.
- Evaluar el potencial del sistema isotópico samario-neodimio como cronómetro para los primeros eventos del sistema solar.
Principales métodos:
- Análisis de una fracción carbono-cromita de la condrita C3V de Allende.
- La medición de los enriquecimientos de isótopos de neodimio (neodimio-142 y neodimio-143).
- Modelado del enriquecimiento isotópico considerando la desintegración alfa del samario-146 y el samario-147, y los efectos de retroceso nuclear.
Principales resultados:
- Se observaron enriquecimientos isotópicos significativos de neodimio-142 (0,47%) y neodimio-143 (36%) en la muestra analizada.
- Atribuyó estos enriquecimientos a la desintegración alfa del extinto samario-146 y del de larga vida samario-147.
- Demostró que el retroceso nuclear magnificaba el enriquecimiento isotópico en las películas de carbono circundantes.
- Se proporcionó una estimación mejorada para la abundancia inicial de samario-146: (146) Sm/(144) Sm = (4.5 ± 0.5) x 10−3.3.
- Esta abundancia es más alta de lo predicho por algunos modelos de nucleosíntesis.
Conclusiones:
- Las anomalías isotópicas del neodimio observadas son consistentes con la formación a través de la desintegración del samario, significativamente mejorada por el retroceso nuclear.
- La abundancia inicial estimada de samario-146 es más alta de lo modelado anteriormente, lo que afecta nuestra comprensión de la nucleosíntesis temprana del sistema solar.
- El par isotópico samario-neodimio tiene potencial como un valioso cronómetro para la datación de eventos en el sistema solar temprano.
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