A non-energetic mechanism for glycine formation in the interstellar medium

TL;DR

This study demonstrates that glycine, a key amino acid, can form in cold interstellar ices through non-energetic surface reactions, suggesting prebiotic molecules originate earlier in star formation than previously thought.

Contribution

It provides the first laboratory evidence of glycine formation via radical addition in cold interstellar conditions without energetic irradiation, supported by astrochemical models.

Findings

Glycine forms in cold dense interstellar ices without UV or cosmic ray energy input.

Solid methylamine is confirmed as an important side product.

Glycine formation occurs at an earlier star-formation stage than previously believed.

Abstract

The detection of the amino acid glycine and its amine precursor methylamine on the comet 67P/Churyumov-Gerasimenko by the Rosetta mission provides strong evidence for a cosmic origin of prebiotics on Earth. How and when such complex organic molecules form along the process of star- and planet-formation remains debated. We report the first laboratory detection of glycine formed in the solid phase through atom and radical-radical addition surface reactions under cold dense interstellar cloud conditions. Our experiments, supported by astrochemical models, suggest that glycine forms without the need for energetic irradiation, such as UV photons and cosmic rays, in interstellar water-rich ices, where it remains preserved, in a much earlier star-formation stage than previously assumed. We also confirm that solid methylamine is an important side-reaction product. A prestellar formation of glycine on ice grains provides the basis for a complex and ubiquitous prebiotic chemistry in space enriching the chemical content of planet-forming material.