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Análisis de activación de neutrones de una partícula devuelta desde el asteroide Itokawawa
M Ebihara1, S Sekimoto, N Shirai
1Department of Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan. ebihara-mitsuru@tmu.ac.jp
Science (New York, N.Y.)
|August 27, 2011
Resumen
El análisis de un grano de la nave espacial Hayabusa revela un origen extraterrestre y una composición primitiva. Su composición química es similar a la de las condritas, aunque con menores niveles de iridio en sus componentes metálicos.
Área de la Ciencia:
- Cosmoquímica es la cosmoquímica.
- Ciencias planetarias Ciencias planetarias.
- Astrogeología y Astrogeología.
Sus antecedentes:
- Las muestras del asteroide Itokawa fueron devueltas a la Tierra por la misión Hayabusa.
- Comprender la composición de las muestras de asteroides proporciona información sobre los primeros materiales del sistema solar.
- El análisis de activación de neutrones es una técnica sensible para determinar la composición elemental.
Objetivo del estudio:
- Para determinar la composición química y el origen de un grano de asteroide Itokawa devuelto.
- Para comparar las características químicas de la muestra de Itokawa con las clases conocidas de meteoritos.
- Para investigar las implicaciones de la composición de la muestra para los procesos de condensación nebular.
Principales métodos:
- Se analizó un solo grano de ~ 3 microgramos de la muestra de Itokawa de la misión Hayabusa.
- El análisis de activación de neutrones se empleó para determinar la composición elemental del grano.
- Se calcularon y compararon las relaciones elementales clave (por ejemplo, Fe/Sc, Ni/Co, Ir/Ni, Ir/Co).
Principales resultados:
- El grano está compuesto principalmente de olivino, con menor plagioclasa, troilita y metal.
- La muestra de Itokawa exhibe características químicas (razones Fe/Sc, Ni/Co) similares a las de las condritas, lo que confirma un origen extraterrestre y una composición primitiva.
- El metal en la muestra de Itokawa muestra proporciones de iridio/níquel e iridio/cobalto aproximadamente cinco veces más bajas que las condritas carbonáceas CI, similares a los metales condritos ordinarios.
Conclusiones:
- El grano de Itokawa es extraterrestre y tiene una composición química primitiva.
- El agotamiento del iridio en el metal de la muestra de Itokawa sugiere que se condensó de un entorno nebuloso donde los elementos siderófilos refractarios ya estaban segregados.
- Este hallazgo contribuye a comprender la evolución química de la nebulosa solar y la formación de planetesimales.
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