Where and how to look for extraterrestrial life? Astronomers have discovered thousands of exoplanets and several thousand more candidates for this status. What’s next? What to look for when searching for signs of extraterrestrial life? This question is answered a new study by scientists from Cambridge University, which was published in the journal Science Advances.
Not only the location in the habitable zone, but the amount of impact on the planet of ultraviolet radiation from its home star is a key indicator that will indicate the possibility of development of life, the researchers said. In their work, the researchers analyzed the data of several exoplanets and identified a group of candidates potentially suitable for abiogenesis.
“Life as we know it, requires diversity of molecular structures that perform functions inside the cell. We are talking about DNA, RNA, proteins, cell membranes, composed of elementary components (lipids, nucleotides and amino acids). The question of whether, where and how did these components for a long time remained a mystery to us. However, the latest research finally began to shed light on how these components could occur on the surface of the young Earth,” explains astrophysicist Paul Rimmer from the University of Cambridge.
“For example, the effects of UV light on hydrogen cyanide (hydrocyanic acid, a chemical compound widely present in nature) dissolved in water with the addition of negatively charged ions (anions), for example, bisulfites, leads to the appearance of monosaccharides”.
Under the right conditions hydrogen cyanide contained in abundance in protoplanetary disks, in combination with the negatively charged ions can create large concentrations of various elemental components necessary for the emergence of life. Beyond this, however, requires a sufficient amount of ultraviolet radiation, since otherwise the output will be a simple inert matter, scientists say.
In 2015 in the laboratory of Biophysics repeat the scenario of the origin of life on Earth, affecting chemicals UV lamps. In the experiment, the participants received a lipid, amino acids and nucleotides — are important components of living cells. Rimmer and his team used the study results 2015 for their work.
“First, we measured the number of emitted UV photons. Then I saw that pretty quickly from the hydrogen cyanide formed “building blocks” for RNA,” says Paul Rimmer.
Next, the researchers compared the amounts of UV radiation in the laboratory with the amount of UV radiation of stars. In the course of this work the scientists came to the conclusion that the stars are approximately the same temperature as the Sun, emit enough ultraviolet light to form on the surface of exoplanets “bricks” of RNA molecules.
The colder the star, the less they create UV radiation, which triggers the process of abiogenesis. At the same time, scientists note that if the planet is too close to the star, the flare, reminiscent of the sun, would be fatal for life. In addition, an excess of high-energy radiation can destroy essential molecules. So, too active UV light ionize the atmospheric gases, taking up electrons. In the result the planets gradually lose their atmospheres. To avoid this, the atmosphere such space bodies should be completely similar to earth.
The objects of study were a group of stars discovered by the telescope “Kepler”. To check the researchers chose only rocky planet (that is, the size is not much bigger than our Earth) located in the so-called habitable zones of their stars, not too hot and cold to sustain water in liquid form on the surface. After studying the data, the researchers came to the conclusion that the most suitable for exoplanets are planets like Kepler-452b. The latter is located in the constellation of Cygnus at a distance of 1402 light years from the Solar system.
The scientists said in any exoplanets it is best to search for life
Nikolai Khizhnyak