Origins of Chiral Life in Interstellar Molecular Clouds

Abstract

The exploring of galactic chemical composition across the the Milky Way, and specifically across the solar neighborhood, provides insights into the chemical evolution of the universe. Since the formation of the first stars some hundred million years after the big bang (BB), heavier elements are synthesized in different stellar production processes at the expense of lighter elements. When the relative abundances of the life-forming elements evaluated for the Last Universal Common Ancestor (LUCA) are compared with the solar neighborhood stellar abundances, a striking similarity occurs. In this study, we tested the hypothesis that in some particular regions and at some particular time, the abundance curve of the first living matter and the universe coincided. Indeed, the best agreement between the two curves was obtained for (4 ± 1)× 109 yr after the BB, indicating the time of the origin of life. All organisms evolved on the Earth independently of place and time are leading to the LUCA and involve chiral molecules such as L amino acids and D sugars in fundamental life processes. The growing evidence from carbonaceous meteorites analysis shows an excess of L-type amino acids and D-type sugars, suggesting that the increase in L-type or D-type molecular chirality is the process that takes place in planetary and stellar forming systems, thus the life emerging from interstellar molecular clouds (IMCs) had to be chiral. Here we propose the spin-polarized proton–proton scattering as a potential physical process that takes place in IMCs environments and could lead to enrichment of L-type amino acids and D-type sugars.

Possible Role of Metal-Ions in the Chemistry of Prochirality and the Origin of Chirality in the Interstellar Medium

“…There are two ways via which enantioenrichment may occur in the ISM. The first way could be through the asymmetry induced in elastic proton–proton scattering. − Through this process, one enantiomer could be selectively destroyed. The other way of enantioenrichment is similar to what is done in terrestrial asymmetric synthesis, via the use of “chiral auxiliaries” .…”