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At least one prebiotic molecule, an ingredient for building life, can form in the harsh environment of interstellar space, away from stars and planets, new research shows.
It was thought that the simplest amino acid glycine, without which life could not exist, required the irradiation of stars to form. But new laboratory experiments show that it can form through what is known as “dark chemistry,” which occurs without energetic radiation.
Glycine has been detected in some interesting places. It appears to be discovered in a meteorite and Venus’s atmosphere.
Of particular interest is its presence in the atmosphere of comet 67P / Churyumov-Gerasimenko, suggesting that the molecule could form independently of the Sun or planets.
But laboratory experiments and models had suggested that glycine forms when interstellar ice is immersed in radiation – ultraviolet, cosmic, thermal, X-rays – in the later stages of star formation.
At sufficiently high energies, the radiation can destroy amino acids, so a team of astronomers led by astrochemist Sergio Ioppolo of Queen Mary University of London in the UK decided to see if there were alternative training paths.
And they found one.
“In the laboratory,” said Ioppolo, “we were able to simulate the conditions in interstellar dark clouds in which cold dust particles are covered by thin layers of ice and then processed by the atoms that cause the precursor species to fragment and form. recombination of reactive intermediates “.
Research began with methylamine, a precursor to the amine of glycine.
Although we have no evidence of the presence of glycine in the interstellar medium, astronomers have found methylamine and methylamine has also been detected on comet 67P / CG. In an independent series of experiments, researchers have shown that methylamine can form non-energetically under interstellar conditions.
Next, the researchers used methylamine-enriched ice to determine whether glycine can form under similar conditions.
They deposited it as a gas in an ultra high vacuum system called SURFRESIDE2, designed specifically to study surface reactions in interstellar space. The system was cooled to an interstellar temperature of 13 Kelvin (-260 degrees Celsius or -436 degrees Fahrenheit) to allow ice to form.
The chemical reactions in the ice actually led to the formation of glycine, the researchers found. And that ice was essential to the process.
Subsequently, they used astrochemical models to validate their results. They extrapolated their experimental results, obtained in a single day’s time, to the millions of years that cosmic processes can extend. And they found that glycine should be able to form in interstellar space, in small but significant quantities, with sufficient time.
These molecules are not likely to develop much further towards life in the freezing vacuum of space.
What the research means is that glycine and methylamine can form in space before star formation (and, subsequently, planet formation) begins. Which, in turn, means that there is potentially a lot of prebiotic molecular material out there, trapped in ice, which then accumulates on meteorites, comets, planetesimals and eventually planets.
“Once formed, glycine can also become a precursor to other complex organic molecules,” Ioppolo said.
“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 research was published in Nature Astronomy.
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