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Glycine and other amino acids form in dense interstellar clouds well before turning into new stars and planets, suggests a new study by researchers at Queen Mary University of London and the Leiden Observatory.
An artist’s impression of glycine along with interstellar dark clouds in the laboratory. Image credit: Harold Linnartz.
The unraveling of the formation and distribution of complex organic molecules in space is the key to our understanding of the initial conditions for the emergence of life on Earth.
Glycine, the simplest amino acid, methylamine, the precursor of the amine, and other organic compounds were recently detected in the coma of comets as Wild 2 by NASA’s Stardust mission and 67P / Churyumov-Gerasimenko by ESA’s Rosetta mission.
There is strong evidence that comets are the most primitive planetary bodies in our solar system and that the organic molecules in their ices have an interstellar origin.
How and when such complex molecules are formed along the process of star and planet formation remains under debate.
In a new study, Dr Sergio Ioppolo of Queen Mary University of London and colleagues show that it is possible for glycine to form on the surface of frozen dust grains, in the absence of energy, through “dark chemistry.”
“Dark chemistry refers to chemistry without the need for energy radiation,” said Dr. Ioppolo.
“In the laboratory we were able to simulate the conditions in dark interstellar clouds where the cold dust particles are covered by thin layers of ice and then processed by the atoms that cause the fragmentation of the precursor species and the recombination of reactive intermediates.”
Dr. Ioppolo and co-authors first showed that methylamine, the precursor of glycine, could form.
Then, using a unique ultra high vacuum configuration, equipped with a series of atomic beam lines and accurate diagnostic tools, the researchers 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 team 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 co-author Professor Herma Cuppen, a scientist at Radboud University.
“The important conclusion of this work is that molecules that are considered to be building blocks of life are already formed at a stage that is well before the formation of stars and planets begins,” said senior author Dr. Harold Linnartz. , Director of the astrophysics laboratory 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 ice before inclusion in the comets and planetesimals that make up the material from which in definitive the planets are made. “
“Once formed, glycine can also become a precursor to other complex organic molecules,” said 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.”
The findings appear this week in the journal Nature Astronomy.
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S. Ioppolo et al. A non-energetic mechanism for the formation of glycine in the interstellar medium. Nat Astron, published online November 16, 2020; doi: 10.1038 / s41550-020-01249-0
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