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ABSTRACT:
Only a very small fraction of the organic compounds in nature are found in planets or comets and other condensed objects. By far the larger quantity, more than 99.9% by mass, reside in the enormous molecular clouds in interstellar space of the Milky Way and other galaxies. Abiotic organic chemistry, as observed in molecular clouds, offers a glimpse of the chemical evolution preceding the onset of life on our own planet, and allows us to evaluate the possibility that – during the evolution from a molecular cloud to a planetary system – complex organic molecules are formed, transformed and preserved until they are incorporated into comets and meteorites. The analyses of such cosmic debris show that some of the amino acids present an excess of the L-conformation enantiomer in straightforward similarity with terrestrial biomolecular homochirality. This coincidence is too striking to be fortuitous; it points out that products of routine cosmic chemistry contributed to the early Earth organic pool and facilitated prebiotic molecular evolution.
Among the many scenarios put forward to explain the origin of chiral homogeneity, one involves the asymmetric photolysis of amino acids present in space, triggered by circularly polarized ultraviolet radiation.
Here we propose that amino acids formed in the cavities of interstellar dust aggregates are
exposed to asymmetric photolysis induced by an effective ultraviolet circularly polarization generated in situ.