Stanford University scientists came to the conclusion that cosmic rays have played an important role in the development of life on Earth. According to the study, published in the Astrophysical journal, high-energy particles bombarding the planet’s atmosphere could affect the chirality of biological molecules — the property by which some molecules are mirror copies of other molecules of the same substance. As a result of DNA, RNA and amino acids become more stable.
Molecules that have the same chemical composition, but are mirror copies of each other, are called enantiomers. For example, amino acids are mostly L-, sugar-and D-enantiomers. In this case only one molecule of sugar with the wrong configuration when embedded in the DNA can disrupt the helical structure of double chain. The fact that in living organisms, almost all molecules of one type have the same chirality (that is, are homochiral), but not the other, the scientists explained fundamental physical interactions, however, the exact cause still remains an unsolved mystery.
According to the authors of the new work, the choice of molecules with a specific configuration dependent on the polarization of the radiation, in which mutations in the same connection was faster than their mirror copies. High-energy particles in cosmic rays have collided with nitrogen and oxygen in the upper atmosphere of the Earth, causing a stream of muons that reach the surface. At the same time, the nucleic acid involved in prebiotic evolution (i.e., before the appearance of the first living organisms), took the right-hand and left-hand helical configuration. Muons forced right DNA and RNA to mutate and hence evolve faster, making them more stable and suitable for living organisms.
Muons are unstable particles that exist for just two millionths of a second, but since they move at a speed close to the speed of light, they manage to penetrate to a depth of 700 meters below the Earth’s surface. They also have a magnetic polarization, i.e. the muons, on average, have the same magnetic orientation. When the muons finally decay, they produce electrons with the same magnetic polarization.
The researchers suggest that it is because of this mechanism, the chirality, in General, the same for all biological molecules in the Universe. That is, the carbohydrates in the composition of DNA are right-hand drive configuration like on Earth and on other planets.
