Life's Chirality From Prebiotic Environments

TL;DR

This paper reviews how environmental factors could have led to life's homochirality through symmetry breaking, with implications for detecting extraterrestrial life’s chirality.

Contribution

It synthesizes recent research on environmental influences causing chiral symmetry breaking, proposing scenarios for the origin of biological homochirality and its implications for astrobiology.

Findings

Environmental disturbances can induce chiral excess without autocatalysis.

Chiral-selective reaction rates influenced by environment can produce homochirality.

Extraterrestrial life is likely to exhibit racemic stereochemistry on average.

Abstract

A key open question in the study of life is the origin of biomolecular homochirality: almost every life-form on Earth has exclusively levorotary amino acids and dextrorotary sugars. Will the same handedness be preferred if life is found elsewhere? We review some of the pertinent literature and discuss recent results suggesting that life's homochirality resulted from sequential chiral symmetry breaking triggered by environmental events. In one scenario, autocatalytic prebiotic reactions undergo stochastic fluctuations due to environmental disturbances. In another, chiral-selective polymerization reaction rates influenced by environmental effects lead to substantial chiral excess even in the absence of autocatalysis. Applying these arguments to other potentially life-bearing platforms has implications to the search for extraterrestrial life: we predict that a statistically representative sampling of extraterrestrial stereochemistry will be racemic (chirally neutral) on average.