The search for life beyond Earth. The most promising exoplanets have been identified
Researchers from the University of Cambridge and the Medical Research Council Laboratory of Molecular Biology (MRC LMB) have discovered that the chances of developing aoj life on the surface of a rocky planet such as Earth are linked to the type and intensity of light, whichore emitted by the parent star.
In a study published in „Science Advances” They argue that a key factor responsible for the development of theoj life, may be the amount of ultraviolet (UV) light coming from the parent star. Ultraviolet light powers a series of chemical reactions thatore produce the bricks of life.
On this basis, the researchers identified a group of extrasolar planets thatore could have developed life in a similar wayob, as probably occurred on Earth. UV radiation reaching this group of planets from the parent star is sufficient to allow these chemical reactions to take place. These planets are also found in the so-called. ecosphere – wok zoneoł stars where conditions are suitable for keeping liquid water on the surface.
– Life as we know it requires rotive molecular structures, whichore full roThe different functions in the comorki. These include DNA, RNA, proteins and cell membranesorkowe, whichore composed of a relatively simple building block – lipidow, nucleotideow and amino acidow. For a long time it was a mystery where these bricks of life came from, but recently this has been clarified – said Paul Rimmer of the University of Cambridge, head of theow author of the publication. – For example, UV rays incident on cyanideor in water, together with a negatively charged ion, such as sulfuric acid, leads to sugarsow – explained Rimmer.
Under the right conditions, hydrogen cyanideor, whichory in large quantities is found in protoplanetary disks can form high concentrations of many bricks of life. But for that, enough UV light is needed. This was demonstrated by experiments conducted in 2015. By emitting ultraviolet radiation on hydrogen cyanide, scientists have led to the formation of lipidow, amino acidow and nucleotideow, with ktorych all are components of living comorek. When they did not provide enough UV light, this reaction did not occur.
The research was led by Professor John Sutherland of the MRC LMB. In a paper published in 2015 in „Nature Chemistry”, he concluded that cyanide, although a poison, was in fact a key ingredient in the primordial soup from which theorej comes all life on Earth. In this hypothesis, carbon from meteoritesoin striking the young Earth interacted with nitrogen in the atmosphere, forming hydrogen cyanideor, whichory fell to the surface, where it reacted with other elements using UV light.
Rimmer and his teamoł they used this as the basis of their research. Porownali the amount of UV light used in the 2015 experiment to the light emitted by stars, wokoł ktorciated by the known exoplanets found in the ecosphere.
– This allowed us to pick out the best places to look for extraterrestrial life. This brings us somewhat closer to answering the question of whether we are alone in the universe? – assessed Rimmer.
Both groups of scientistsow have joined forces and conducted a series of experimentsoin the lab to measure how quickly bricks of life can form under UV rays. – Chemical processes also occur in the dark, but they are much slower – admitted Didier Queloz of the Cavendish Laboratory.
The same experiment conducted in the dark with hydrogen cyanide and sulfuric acid yielded an inert compound, whichowhich could not be used to build the basic elements of theoin life. An experiment conducted with UV light produced the necessary bricks of life.
In the next step, scientists analyzed the amount of UV rays emitted by rotive stars and have calculated the amount of these rays available to every known exoplanet. This gave a picture of where such chemical reactions could be activated. Researchers called it the zone of abiogenesis.
In the course of their work, the scientists observed that the ecosphere and the abiogenesis zone do not always coincide. On Earth, we are in an ideal place in orbit wokoł the right kind of star. The researchers also discovered that it was the stars, whichore have the same temperature as our Sun, produce the right amount of UV light. Cooler stars do not produce enough UV light to activate the processes mentioned earlier – unless there are frequent flares on themoin the sun, although these, as we now know, may be roalso disastrous for life.
Amongod known exoplanets, whichore reside in the abiogenesis zone, there are several planets detected by the Kepler Space Telescope. It m.in. Kepler exoplanet 452b, whichora was named „Earth’s cousin”, However, it is too far away from us to be studied with the technology currently available to us. Ross 128b, on the other hand, may be a barren world, although it has so far been considered an extremely promising place to search for life.
– Unfortunately, we don’t know how likely life is to have originated, as we only know one example, so it is worth looking for extraterrestrial life in places that most resemble our planet. There is an important roThe difference between what is necessary and what is sufficient. Bricks of life are necessary, but may be insufficient. Perhaps they can occur for billions of years and nothing will happen. Nevertheless, it is worth looking at places where the necessary conditions exist – emphasized Rimmer.
According to the latest estimatesoThere are as many as 700 million in the observable Universeoin the trillionoin rocky planets. – Conditions conducive to the origin of life are not everything. We still do not know how likely life is to arise, even given the favorable circumstances. If it’s really unlikely, we may be alone, but if not, we may have company – Sutherland said.