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According to a new study that recreates the formation of molecules in the laboratory, phosphates, essential ingredients in DNA-based life forms, can come from space. Phosphates seeded to life would then have returned to Earth thanks to the asteroids and comets that affected the planet billions of years ago.
Phosphate compounds may have arrived on Earth delivered by comets, such as Comet 67P / Churyumov-Gerasimenko. Credit: ESA / Rosetta / NAVCAM.
Without phosphates or diphosporic acid, living beings would not be able to synthesize DNA. These are the main components of chromosomes, filiform structures in which the DNA is packaged. Phosphorus is also part of the adenosine triphosphate (ATP), which stores energy in the cell and feeds the cellular processes. Bones and teeth are also made of phosphorus.
A long-standing debate among scientists is whether these chemical compounds were forged on Earth or elsewhere in the universe, which led to a displacement on cosmic bodies that collided with our planet.
Although the debate seems impossible to resolve, researchers from the University of Hawaii at Manatoa have now brought convincing evidence of the possibility of generating phosphates in space.
For their experiment, the researchers worked with the chemical phosphine, which is derived from phosphorus and can be found in the atmospheres of planets such as Jupiter or Saturn, but also those of comets such as the famous 67P / Churyumov-Gerasimenko explored by the Rosetta Spacecraft in 2016.
First, the team recreated ice-grains – typical of interstellar space – in a vacuum chamber where the temperature was only 5 degrees Kelvin above absolute zero (-450 ° F / – 267.7 ° C). Then they added water, carbon dioxide and – very carefully because it is highly toxic – phosphine. Finally, the researchers fired ionizing radiation – the type of cosmic radiation – causing chemical reactions that formed phosphoric acid and diphosphoric acid.
"On Earth, phosphine is deadly to living things," said Andrew Turner, lead author of the study in Nature Communications, in a report. "But in the interstellar medium, exotic phosphine chemistry can promote rare chemical reaction pathways to initiate the formation of biorixed molecules such as oxoacids of phosphorus, which could eventually trigger the molecular evolution of life as we do. know.
In deep space, it is reasonable to assume that such nanoparticles are embedded in large objects such as asteroids and comets, which would eventually arrive on Earth.
"Since comets at least partially contain the remains of the protoplanetary disk material that formed our solar system, these compounds could go back to the interstellar medium wherever a sufficient amount of phosphine in interstellar ice is available," said Cornelia Meinert of the University of Nice. .
The results appeared in the newspaper Nature Communications.
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