The building blocks of life can form long before the stars

An international team of scientists has shown that glycine, the simplest amino acid and an important building block of life, can form under the harsh conditions that govern chemistry in space.

The results, published in Nature Astronomy, suggest that glycine, and most likely other amino acids, form in dense interstellar clouds well before transforming into new stars and planets.

Comets are the most pristine material in our solar system and reflect the molecular composition present at the time our sun and planets were about to form. Detection of glycine in the comet of comet 67P / Churyumov-Gerasimenko and in samples returned to Earth by the Stardust mission suggests that amino acids, such as glycine, are formed long before stars. However, until recently, the formation of glycine was thought to require energy, placing clear constraints on the environment in which it can form.

In the new study, the international team of astrophysicists and astrochemical modellers, mostly based at the Laboratory for Astrophysics at the Leiden Observatory in the Netherlands, demonstrated that it is possible for glycine to form on the surface of frozen dust grains. in the absence of energy, through “dark chemistry”. The results contradict previous studies that have suggested that UV radiation was needed to produce this molecule.

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 energetic radiation. In the laboratory we were able to simulate conditions in dark interstellar clouds. where the cold dust particles are covered by thin layers of ice and subsequently processed by the atoms that cause the fragmentation of the precursor species and the recombination of the reactive intermediates “.

Scientists first showed that methylamine, the precursor species for glycine that was detected in the coma of comet 67P, could form. Then, using a unique ultra-high vacuum configuration, equipped with a series of atomic beam lines and accurate diagnostic tools, they were able to confirm 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 and allowed the researchers to extrapolate the data obtained on a typical laboratory time scale of only one day under interstellar conditions, spanning millions of years. ‘From this we find that low but substantial amounts of glycine can be formed in space over time,’ said Professor Herma Cuppen of Radboud University, Nijmegen, who was responsible for some of the modeling studies within the paper.

“The important conclusion of this work is that the molecules that are considered building blocks of life are already formed at a stage that is well before the formation of stars and planets begins,” said Harold Linnartz, Director of the Laboratory of Astrophysics. at the Leiden Observatory. “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 the finally the planets are made. “

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