Proteins from Cosmic Ice express
In the black depths of space, on the surfaces of tiny icy dust grains, a quiet construction is underway. There, where temperatures drop to near absolute zero and harsh radiation abounds, the ordinary amino acid glycine, the simplest protein building block, links up with itself. The product is a dipeptide: a short chain of two units, already resembling a protein.
Such dust grains, coated with ice made of water and simple molecules, are true cosmic laboratories. In the experiment, a frozen film of glycine played their role. It was bombarded with protons (simulating cosmic rays) at a temperature of about minus 260 °C. And the birth of glycylglycine was recorded. No liquid water — only ice and radiation.
Original abstract
as written by the authors arXiv:2607.26814
The origin of the molecular building blocks of life is a central question in science. A few $$\alpha$$-amino acids such as glycine, the simplest proteinogenic amino acid, have been detected in meteorites and comets, indicating an extraterrestrial origin for some prebiotic molecules. However, the formation of peptides, short chains of $$\alpha$$-amino acids linked by peptide bonds, under astrophysical conditions has remained unresolved. Here we show that the building blocks of proteins can form in interstellar ice analogues exposed to ionising radiation, without the presence of liquid water. Using isotopically labelled glycine irradiated with protons at cryogenic temperatures, we detect the formation of glycylglycine, the simplest dipeptide, along with deuterated and non-deuterated water as by-products. Peptide bond formation is confirmed by infrared spectroscopy and high-resolution mass spectrometry, which also reveal the production of other complex organic species. These findings demonstrate a non-aqueous route to peptide formation under space-like conditions and suggest that such molecules could form in the cold interstellar medium and be incorporated into forming planetary systems. Our results challenge aqueous-centric models of early biochemical evolution and broaden potential settings for the origins of life.
Glycylglycine is not just a laboratory curiosity. It is the shortest peptide bond in nature, and it already possesses some protein-like properties, such as the ability to carry copper ions in the blood.
In Carl Sagan's novel Contact, a signal from space contained blueprints for a machine, but the very idea that complex chemistry could arise in the interstellar medium resonates with this discovery.