The Cosmochemical Record of Carbonaceous Meteorites: An Evolutionary Story

Sandra Pizzarello

Department of Chemistry & Biochemistry, Arizona State University, Tempe, AZ 85287–1604. USA. pizzar@asu.edu.

Received October 24, 2009
Accepted December 18, 2009

Abstract

This account traces a lecture given to El Colegio Nacional last March during a Conference "On the origin of life on the Earth" organized to celebrate Darwin's Bicentennial. It reports on the extraterrestrial organic materials found in carbon–containing meteorites, their composition, likely origin and possible prebiotic contribution to early terrestrial environments. Overall, this abiotic chemistry displays structures as diverse as kerogen–like macromolecules and simpler soluble compounds, such as amino acids, amines and polyols, and show an isotopic composition that verifies their extraterrestrial origin and lineage to cosmochemical synthetic regimes. Some meteoritic compounds have identical counterpart in the biosphere and encourage the proposal that their exogenous delivery to the early Earth might have fostered molecular evolution. Particularly suggestive in this regard are the unique L–asymmetry of a number of amino acids in some meteorites as well as the rich and almost exclusively water–soluble compositions discovered for other meteorite types.

Key words: Cosmochemical, Life, Earth, Abiotic Chemistry, Macromolecules.

Resumen

Esta reseña resume una conferencia impartida en marzo pasado en El Colegio Nacional en el Simposio "Sobre el origen de la vida en la Tierra" organizado para la celebración del Bicentenario del nacimiento de Darwin. Se informa sobre los materiales orgánicos extraterrestres encontrados en meteoritos que contienen carbono, su composición, origen probable y su posible contribución prebiótica al ambiente terrestre incial. Esta química abiótica incluye estructuras diversas, tales como macromoléculas querogénicas y compuestos solubles simples, como amino ácidos, aminas y polioles, y muestran una composición isotópica que confirma su origen extraterrestre y su linaje sintético cosmoquímico. Algunos compuestos meteoríticos tienen contrapartes idénticas en la biósfera y apoyan la propuesta referente a que su envío exógeno a la Tierra primitiva podría haber favorecido la evolución molecular. Particularmente sugerente en este aspecto es la asimetría L exclusiva como su rica y casi exclusiva composición soluble en agua también descubierta en otros tipos de meteoritos.

Palabras clave: Cosmoquímica, vida, Tierra, química abiótica, macromoléculas.

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Acknowledgements

I am grateful to Professor Eusebio Juaristi, Guillermo Delgado–Lamas and Antonio Lazcano for their invitation and the opportunity to visit the Colegio Nacional. I also thank an anonymous referee for a very helpful review. These studies were supported through the years by grants from the Exobiology, Cosmochemistry and Origins of the Solar System programs of the US National Aeronautic and Space Administration.

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