A link between meteoritic organic compounds and the homochirality of life?

Current theories suggest that portions of interstellar compounds should eventually be incorporated into the comets, "asteroids" and planets of new planetary systems. Astronomical observations point to processes such as the formation of comet and asteroid belts, familiar to our solar system, as likely occurring in many star systems. As with comets and asteroids, the formation of organic compounds around new-formed stars might be a common process. The only laboratory items available for the study of a wide range of primordial organic-chemical processes are carbonaceous meteorites.

Among the most interesting features (and relevant to origin of life studies) of carbonaceous meteorites are the enantiomer excesses possessed by some of their organic compounds. While the majority of indigenous meteoritic compounds are racemic, i.e., their D/L enantiomer ratios are 50:50, some of the more unusual amino acids contain slightly more of one enantiomer - usually the L. In addition, initial analyses of some meteoritic sugar derivatives (sugar acids) revealed significant enantiomer excesses of the D enantiomers.

A question of relevance from such studies is: did extraterrestrial sources aid in the beginning of life's homochirality? This presentation will include the results of recent analyses of enantiomer ratios of meteoritic compounds as well attempts at laboratory re-creation of such excesses.

If the forces that acted on organic compounds (and/or their precursors) in the early Solar System are common, then specific laboratory experiments may indicate whether enantiomer excesses in organic compounds are available for the origin of life in a multitude of planetary systems.

Speaker: George Cooper, NASA Ames