Building blocks of life found in the comet by NASA researchers

Scientists have shown that glycine, an important building block of life, can form under the harsh conditions that govern chemistry in space, indicating that the molecule can form in dense interstellar clouds well before they transform into new stars and planets. The study, published in the journal Nature Astronomy, detected glycine in comet 67P / Churyumov-Gerasimenko and in samples returned to Earth by NASA’s Stardust mission which was the first to return extraterrestrial material outside the moon’s orbit to Earth. .

According to researchers, including those from Queen Mary University of London in the United Kingdom, 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.

While until recently scientists thought that the formation of amino acids such as glycine required energy, placing clear constraints on the environment in which it can form, current findings suggest that these protein blocks can form long before stars.

Researchers have shown that it is possible for glycine to form on the surface of the icy dust grains of comets, in the absence of energy, through “dark chemistry”.

“Dark chemistry refers to chemistry without the need for energy radiation,” explained Sergio Ioppolo, lead author of the study at Queen Mary University of London.

The results contradicted previous studies that suggested ultraviolet (UV) radiation was needed to produce this molecule.

“In the laboratory, we were able to simulate the conditions in dark interstellar clouds where cold dust particles are covered with thin layers of ice and then processed by atoms that cause the precursor species to fragment and reactive intermediates to recombine,” he said. Ioppolo.

The researchers first showed that methylamine, the precursor molecule 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, the scientists confirmed that glycine could also be formed and that the presence of water ice was essential in this process. .

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

“From this we find that low but substantial amounts of glycine can form in space over time,” said Herma Cuppen, co-author of the study at Radboud University in the Netherlands.

Based on the results, scientists believe that molecules considered to be building blocks of life are already formed at a stage that is well before the formation of stars and planets begins.

“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 prior to inclusion in comets and planetesimals that make up the material from which the end the planets are made, “said Harold Linnartz, Director of the Laboratory for Astrophysics at the Leiden Observatory in the Netherlands.

“Once formed, glycine can also become a precursor to other complex organic molecules,” explained Ioppolo.

They said other functional groups can be added to the glycine backbone, resulting in the formation of other amino acid molecules, 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 has happened to our Earth and many other planets,” Ioppolo said.