  Life as we know it is homochiral, but the origins of biological homochirality
on early Earth remain elusive. Shallow closed-basin lakes are a plausible
prebiotic environment on early Earth, and most are expected to have significant
sedimentary magnetite deposits. We hypothesize that UV (200-300nm) irradiation
of magnetite deposits could generate hydrated spin-polarized electrons
sufficient to induce chirally selective prebiotic chemistry. Such electrons are
potent reducing agents that drive reduction reactions where the spin
polarization direction can alter enantioselectively the reaction kinetics. Our
estimate of this chiral bias is based on the strong effective spin-orbit
coupling observed in the chiral-induced spin selectivity (CISS) effect, as
applied to energy differences in reduction reactions for different isomers. In
the original CISS experiments, spin selective electron transmission through a
monolayer of dsDNA molecules is observed at room temperature - indicating a
strong coupling between molecular chirality and electron spin. We propose that
the chiral symmetry breaking due to the CISS effect, when applied to reduction
chemistry, can induce enantioselective synthesis on the prebiotic Earth and
thus facilitate the homochiral assembly of life's building blocks.
