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Scientists have discovered that the most energetic light rays in the universe, known as gamma rays, may have played a key role in the rise of life on Earth, a finding that provides clues to one of science’s biggest mysteries. , reports a new study.
In a one-of-a-kind experiment, the researchers demonstrated that compounds called amino acids, which are the building blocks of life, can be forged by gamma-ray bursts inside space rocks due to the decay of radioactive elements. The results point to a possible origin of the amino acids that ended up spreading across the Earth billions of years ago, enriching our planet with the ingredients necessary for life.
The question of how life came to be has inspired countless myths across time and cultures, and has also become one of science’s most persistent problems. Scientists have long suspected that some of the ingredients for life were delivered to Earth by space rocks spewing from its surface more than four billion years ago. However, it is not clear what types of amino acids might have existed within these ancient meteorites, or how they might have formed.
Now, scientists led by Yoko Kebukawa, an astrobiologist at Yokohama National University, have experimentally shown that formaldehyde and ammonia, common compounds in space rocks, can be transformed into amino acids when exposed to gamma rays, a finding that points to to “a new prebiotic amino acid”. acid-forming pathway that contributes to the origin of life.” according to a published study in ACS Central Sciences.
“To the best of our knowledge, it is the first time that amino acids [have been produced] of formaldehyde and ammonia using gamma rays,” Kebukawa said in an email to Motherboard, adding that his team was “surprised by the results.”
“We expected some amino acids to be produced, but the results were much better than expected, with quality and quantity,” he continued. “Several amino acids were produced by gamma rays and their amount was significant.”
Kebukawa and his colleagues had previously shown that ammonia and formaldehyde could be transformed into amino acids and organic molecules in the presence of liquid water and heat. Ammonia, formaldehyde, and water are present in carbonaceous chondrites, an ancient group of space rocks, leading scientists to believe that these meteorites played an important role in making Earth habitable. However, the heat source that catalyzed the reactions that produce the amino acids remains unclear.
In the new study, Kebukawa’s team explored the possibility that gamma rays created by the decay of radioactive atoms, such as aluminum isotopes, may have been the cauldron that cooked these primordial biomolecules. To do this, the researchers exposed tubes of dissolved ammonia and formaldehyde to gamma rays emitted by the decay of cobalt isotopes.
The experiment created a panoply of compounds that are useful to living things, including alanine, glycine, and various beta amino acids. Furthermore, the team estimated that it would take less than 100,000 years for some amino acids to reach the abundance observed in a rock such as the Murchison meteorite, a carbonaceous chondrite that landed in Australia in 1969. This short period of time suggests that amino acids are likely common in carbonaceous chondrites in the early solar system, reinforcing the idea that these rocks helped pave the way for life on Earth, and perhaps on other planets.
“Amino acids can be produced non-biologically in various space environments,” Kebukawa explained. “Among them, the processes of the meteorite parent body are the final stage of organic evolution in space before being delivered to Earth. Amino acids produced in the bodies of meteorites would be delivered directly to ancient Earth as meteorites and could become the building blocks of life.”
“Just like on Earth, these amino acids could reach ancient Mars, where the climate was temperate and there were oceans,” he added. “In addition, gamma-ray-produced amino acids possibly occurred on subsurface ocean worlds on icy moons like Enceladus” within “a few million years after the formation of the solar system” before radioactive gamma-ray sources ran out. .
The researchers hope to build on these findings by exploring whether gamma rays could produce other types of organic compounds that were important to the emergence of life. While there are still far more questions than answers when it comes to the origins of life, the new study opens a tantalizing window into the energetic reactions that briefly heated space rocks billions of years ago, potentially turning them into seeds that would eventually flourish. in the vibrant biosphere. we inhabit today.