An important building block of life can form long before the stars

Comets are the most pristine material in our solar system and reflect the molecular composition present when our solar system is formed. The recognition of glycine in the coma of comet 67P / Churyumov-Gerasimenko and the samples returned to Earth by the Stardust mission proposes that amino acids, such as glycine, are formed long before stars. However, until recently, it was believed that the development of glycine required energy, placing clear limits on the environment in which it tends to form.

In the new study, an international team of astrophysicists and astrochemical modellers mostly based at the Laboratory for Astrophysics at the Leiden Observatory in the Netherlands suggests that glycine, and most likely other amino acids, form in dense interstellar clouds well before that they turn into new stars. and planets. Glycine can form on the surface of frozen dust grains, in the absence of energy, through “dark chemistry”.

Dr Sergio Ioppolo, of Queen Mary University of London and lead author of the paper, said: “Dark chemistry refers to chemistry without the need for energy radiation. In the laboratory, we were able to simulate the conditions in dark interstellar clouds in which thin layers of ice cover cold dust particles and subsequently processed by impacting the atoms causing the fragmentation of the precursor species and the recombination of reactive intermediates. “

Scientists initially indicated that methylamine, the precursor species of glycine detected in the coma state of comet 67P, could form. Then, using a unique ultra-high vacuum configuration, equipped with a series of atomic light lines and accurate diagnostic tools, they claimed that glycine could also form and that the presence of water ice was essential in this process.

Further investigations using astrochemical models confirmed the experimental results. It allowed the researchers to extrapolate the obtained data on a typical laboratory time scale of just one day under interstellar conditions, spanning millions of years.

Professor Herma Cuppen of Radboud University, Nijmegen, responsible for some of the modeling studies within the paper, said: “From this, we find that low but substantial amounts of glycine can be formed in space over time.”

Harold Linnartz, Director of the Astrophysics Laboratory at the Leiden Observatory, said: “The important conclusion of this work is that the molecules considered constitutive elements of life are already formed in a phase that is well before the start of the formation of stars and planets. Such an early formation of glycine in the evolution of star-forming regions implies that this amino acid can be formed more ubiquitously in space and is conserved in most of the ice prior to inclusion in the comets and planetesimals that make up the material from which eventually you find the planets. done.”

Doctor Ioppolo said, “Once formed, glycine can also become a precursor to other complex organic molecules. Following the same mechanism, in principle, other functional groups can be added to the glycine backbone, resulting in other amino acids, such as alanine and serine, in dark clouds in space. Eventually, this enriched organic molecular inventory is included in celestial bodies, such as comets, and delivered to young planets, as has happened to our Earth and many other planets. “

Journal Search:

1. Ioppolo, S., Fedoseev, G., Chuang, KJ. et al. “A non-energetic mechanism for the formation of glycine in the interstellar medium”. Nat Astron (2020). DOI: 10.1038 / s41550-020-01249-0.