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Pruebas de isótopos de magnesio de que la pérdida de vapor por acreción da forma a las composiciones planetarias
Remco C Hin1, Christopher D Coath1, Philip J Carter2
1School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK.
Nature
|September 30, 2017
Resumen
Los cuerpos planetarios muestran isótopos de magnesio más pesados que los meteoritos primitivos. Esta diferencia probablemente surgió de la pérdida de vapor durante la acreción planetesimal, no de procesos nebulosos o de núcleo.
Área de la Ciencia:
- Ciencias planetarias
- Cosmoquímica
- Geoquímica de los isótopos
Sus antecedentes:
- Los planetas diferenciados son químicamente distintos de los meteoritos condríticos primitivos.
- El origen de las depleciones volátiles en los planetas (acreción vs fraccionamiento nebular) sigue siendo objeto de debate.
- Las composiciones isotópicas ofrecen información sobre los procesos de formación planetaria.
Objetivo del estudio:
- Para investigar el origen de las fracciones químicas en los cuerpos planetarios.
- Para determinar si las depleciones volátiles se deben a procesos de acreción o nebulosas.
- Para analizar las composiciones de isótopos de magnesio en cuerpos diferenciados.
Principales métodos:
- Desarrolló un método analítico mejorado para reducir las inexactitudes de medición.
- Las composiciones de isótopos de magnesio medidos en cuerpos planetarios diferenciados y meteoritos condríticos.
- Fraccionamiento isotópico modelado durante las etapas de formación planetaria.
Principales resultados:
- Todos los cuerpos diferenciados estudiados exhiben composiciones de isótopos de magnesio más pesados en comparación con los meteoritos condríticos.
- La fraccionamiento durante la condensación de la nebulosa solar, la formación de núcleos o la diferenciación de silicatos no explica las variaciones de isótopos de magnesio observadas.
- La fraccionamiento isotópico a través del escape de vapor durante la acreción planetesimal proporciona una explicación viable.
Conclusiones:
- Las variaciones de isótopos de magnesio en los planetas se explican mejor por la pérdida significativa de vapor durante la acreción.
- Este mecanismo, que implica fraccionamiento de vapor líquido y escape, también afecta a los isótopos de silicio y hierro.
- Aproximadamente el 40% de la pérdida de vapor de los planetesimales durante el crecimiento representa las composiciones elementales e isotópicas observadas.
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