Toward a better understanding of the origins of life on earth

Certain chemical molecules are known as chiral molecules, i.e. they can occur in two forms (or enantiomers): one form is referred to as “right” and the other as “left.” Each of these two forms exhibits different properties. Upon being produced synthetically in a laboratory, the formation of chiral substances generates a mixture, half of which contains one of these two forms.

The molecules that formed the basis for life such as the sugars comprising our genetic material, or amino acids (which are the building blocks of proteins) are chiral molecules. However, in living organisms, these molecules occur in only one of the aforementioned two forms, a phenomenon known as the homochirality of living organisms.

There are currently two theories concerning the origin of this particularity. The first, known as the biotic theory, holds that life emerged from a mixture of the two forms, and that asymmetry appeared only incrementally over the course of evolution. The second theory, known as the abiotic theory, holds that the imbalance between chemical forms was engendered in space, and that the molecules that formed the basis for life were brought to the earth by meteorites.

Investigating the comet’s core

The goal of the CHIRGEN project was to investigate these theories. Coordinated by Professor Uwe Meierhenrich, co-investigator of the COSAC instrument, the project involves three French teams (from Institut d’astrophysique spatiale (IAS), Institut de Chimie de Nice (ICN), and Synchrotron Soleil) and two Mexican teams (from the Autonomous University of the State of Morelos, and the Autonomous National University of Mexico). Having produced, in the lab, interstellar ice analogues, the French partners of the Chirgen project irradiated this ice in order to replicate the conditions in space, so as to be able to determine whether an imbalance between the chemical forms in the ice would occur. In a second phase, the Mexican partners will carry out autocatalysis experiments in order to determine whether or not this imbalance increases. These results, along with the findings gathered by Philae, will go a long way toward deepening our understanding of the origin of genetic code asymmetry – a crucial step toward understanding the origin of life.

Find out more: