Researchers find new method to simulate primordial impacts of comets and asteroids on planets
How did life on Earth begin? Science still does not have a definitive answer to this question. However, research in Astrobiology (a field that studies the origins, early evolution, distribution and future of life on planets in connection with the astronomical environment) has revealed that celestial bodies, such as comets, asteroids and meteoroids, may contain an essential component for the formation of proteins in living organisms, the amino acid glycine. This indicates the possibility that these bodies were responsible for bringing energy and molecules fundamental to the formation of the chemical reactions that started life on the planet to the primitive earth. “Primitive Earth” is the expression used to name the planet in its first billion years, when the Solar System was still being formed.
To simulate the impact of a meteorite on planet Earth, its consequences on the chemical structure of glycine and whether or not proteins would be generated – a result that would corroborate the hypothesis described above – two researchers from the Faculty of Applied Sciences at Unicamp (FCA) devised a small-scale experiment in partnership with colleagues from Kyushu University (Japan). Augusto Luchessi, coordinator of the Biotechnology Laboratory (BioTech), and Ricardo Floriano, from Materials Laboratory (LabMat), subjected a small amount of the amino acid to a very high pressure and torsion method (HPT, in English, High-Pressure Torsion), innovative technique that had not yet been used in impact simulations. The results of the work, supported by the São Paulo Research Foundation (Fapesp), were recently published in an article in the journal Scientific Reports, from the Nature group.
According to Astrobiology specialist Douglas Galante, previous studies used static pressure in equilibrium, that is, just compression, dissociated from rotation. According to the researcher at the National Center for Research in Energy and Materials (CNPEM), the experiment carried out at FCA inaugurates a more efficient and realistic way of conducting simulations of the impact of celestial bodies on planets: “With this method, we are opening up an entire area of experiments on the effects of meteor and comet impacts”.
Luchessi and Floriano observed a unique result: glycine did not generate a protein under the conditions tested, but exploded with such force that it damaged part of the equipment used in the simulation, being partially decomposed into ethanol and other by-products not yet identified. According to scientific literature in the area, ethanol has already been found in comets. What was not known was that it could originate from the decomposition of glycine, as demonstrated in the experiment. “The result was something new, as we are normally concerned with the reverse reaction, the formation of glycine, not with its degradation and its by-products. The data can explain the presence of ethanol in some environments in the astrophysical environment”, says Galante.
FCA researchers intend to expand the investigations, testing other conditions, for example, mixing metals or minerals with the amino acid to simulate compositions similar to those of meteorites that collided on Earth and, with this, generate organic molecules and even proteins. “The glycine sample we used was a type of compact button-shaped powder, similar to table salt. After the explosion, it turned into a very hard material”, says Floriano. “I had never seen this with metals or ceramics, materials that are very hard when compared to organic ones. It was very interesting to observe the reaction with an organic material. The mass used for the glycine sample was too small to release enough energy to explode and damage the matrices of the HPT machine,” he added.
According to Luchessi, it is possible that the byproducts generated by the glycine explosion are highly reactive molecules containing nitrogen, a fundamental component of all amino acids present in nature, as well as the different nucleotides that make up DNA and RNA molecules. “Many questions can now be asked from this experiment – these are new frontiers of study. We are dealing with astrobiology, and the explanations for the origin of life on Earth, from a scientific and academic point of view, are still open. I consider that we have contributed two pieces of the puzzle,” he said.
Impacts made planet habitable
Normally, we associate impact events with mass extinction processes, as happened with the extinction of dinosaurs and other species, but Galante warns: science has shown that collisions between celestial bodies were vital for the origin of life on Earth and in other planets. “It was asteroid impacts that brought a large part of the volatile elements to Earth, such as gases present in the atmosphere and water in the oceans.” According to him, the impacts are also responsible for the variety of complex organic molecules, which probably combined with others that were forming on the planet itself, creating the conditions necessary for the beginning of prebiotic chemistry and the origin of life. Possibly, it was collisions with asteroids that provided the energy for several of these reactions, either by creating hydrothermal regions around the impact crater that increase the habitability of the region, or through the shock itself, as the experiment seeks to show. “In the first few hundred million years of the Solar System, when there were still many remnants of planetary formation wandering between the planets' orbits, impacts were much more frequent, and therefore they must have been important environmental forces that shaped our planet and contributed for making it habitable as it is today”, says the researcher.
