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Entrega cometaria de moléculas orgánicas a la Tierra primitiva
C F Chyba1, P J Thomas, L Brookshaw
1Laboratory for Planetary Studies, Cornell University, Ithaca, NY 14853, USA.
Science (New York, N.Y.)
|July 27, 1990
Resumen
La Tierra primitiva puede haber recibido moléculas orgánicas prebióticas de impactos de asteroides y cometas. Las primeras atmósferas densas permitieron la entrega intacta de moléculas orgánicas, cruciales para los orígenes de la vida.
Área de la Ciencia:
- Astrobiología Astrobiología.
- Ciencias planetarias Ciencias planetarias.
- La geoquímica es la geoquímica.
Sus antecedentes:
- Especulación sobre la acreción de la Tierra de moléculas orgánicas prebióticas de impactos de asteroides y cometas durante el bombardeo pesado (hace 4.5 a 3.8 mil millones de años).
- Comprensión previa de la entrada atmosférica y los efectos del impacto en la supervivencia de las moléculas orgánicas.
Objetivo del estudio:
- Para investigar la supervivencia y la entrega de moléculas orgánicas prebióticas de cometas y asteroides a la Tierra temprana.
- Para determinar las condiciones bajo las cuales las moléculas orgánicas podrían ser entregadas intactas.
Principales métodos:
- Modelado de las interacciones atmosféricas cometa-asteroide, incluido el frenado aéreo y la pirólisis por impacto.
- Análisis de las tasas de supervivencia de las moléculas orgánicas a diferentes velocidades de impacto y densidades atmosféricas.
- Cálculo de las tasas de acreción de moléculas orgánicas en la Tierra primitiva.
Principales resultados:
- Las moléculas orgánicas no sobreviven a impactos que excedan aproximadamente 10 km/s.
- El frenado aéreo en atmósferas de 1 bar es insuficiente para ralentizar pequeños cometas/asteroides por debajo de esta velocidad crítica.
- Las primeras atmósferas plausibles densas (10 bares de CO2) permitieron la entrega orgánica comética intacta a tasas de 10^6-10^7 kg/año hace 4.500 millones de años.
Conclusiones:
- Las primeras atmósferas densas fueron cruciales para la entrega de moléculas orgánicas prebióticas intactas de impactos extraterrestres.
- La tasa de acreción de moléculas orgánicas disminuyó con el tiempo con una vida media de aproximadamente 10^8 años.
- Este mecanismo de entrega proporciona una fuente significativa de material orgánico para los orígenes de la vida en la Tierra.
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