UNITED STATES (VOP TODAY NEWS) — Proxima Centauri and the planets from the TRAPPIST-1 system can be habitable, despite the high level of ultraviolet radiation on their surface, since even harsher conditions prevailed on the early Earth, which did not prevent the emergence of life.
This is written by American planetologists in the journal MNRAS.
“Considering that life on Earth actually exists from the moment of its formation, we have shown that ultraviolet radiation will not be the main obstacle to the appearance of microbes and on planets in red dwarfs. Neighboring worlds are still the most interesting corners of space for the search for extraterrestrial life,” – said Lisa Kaltenegger from the Carl Sagan Institute in Ithaca (USA).
Over the past three years, scientists have found several planets that claim, if not the title of “Earth twin”, then its “sisters” or “cousins”. The first planet was found near our nearest star, Proxima Centauri, and the other three were found in the TRAPPIST-1 star system in the constellation Aquarius, which is inhabited at once by seven earth-like planets.
All of these planets are united by the fact that they are small in size, are in the “zone of life” – in an orbit where water can exist in a liquid form, and rotate around red dwarfs.
The last point is both a plus and a minus – red dwarfs live for a very long time, which leaves much time for the birth of life, but some of them have a very restless character in their youth and produce many flashes.
Both of these star features, as many paleontologists now believe, should have made Proxima b and the worlds from the TRAPPIST-1 system absolutely lifeless, as they should receive tens or even hundreds of times more ultraviolet radiation than the Earth today.
Kaltenegger and her colleagues checked if this is true.
To do this, they created accurate computer models of these worlds, taking into account the interaction of the atmosphere with UV rays and cosmic radiation. They compared the results of these calculations with what happened on Earth about four billion years ago.
A key feature of these calculations, as noted by paleontologists themselves, was that they took into account the differences in the strength of the different types of radiation on DNA and other cell components, as well as the atmosphere of the planets. For example, ultraviolet with a wavelength of 360 nanometers affects life about a thousand times weaker than hard radiation with a higher vibration frequency, and does not lead to the formation of ozone.
Scientists conducted similar calculations for another planet – the Earth itself, in the state in which it was about four million years ago. Then she did not have a protective ozone layer that prevents the penetration of ultraviolet radiation to the surface, as well as a strong magnetic field that protects it from flares and exposure to cosmic rays.
When scientists compared these calculations, the most “lifeless” planet was not Proxima B or her “cousin” from other star systems, but the newborn Earth. It turned out that she received significantly more ultraviolet radiation, and her atmosphere was much more aggressive towards life than all known earth-like planets in red dwarfs.
For example, the ultraviolet level at its surface was about an order of magnitude higher than that of Proxima b, and two orders of magnitude higher than on TRAPPIST-1e with all reasonable combinations of composition, density and other properties of their atmosphere.
This, however, did not prevent the existence of the first primitive microbes on the surface of the Earth, whose traces of existence were recently found in Australia. As scientists assume, they could avoid the action of ultraviolet radiation, dwelling at sufficiently great depths or using various pigments and fluorescent proteins that absorb UV rays.
Accordingly, nothing should interfere with the emergence of similar defense systems in aliens living on Proxima b or other more prosperous planets in red dwarfs. Therefore, as Kaltenegger concludes, one should not exclude such worlds from the search for “brothers of reason”.
This article is written and prepared by our foreign editors writing for VOP from different countries around the world – edited and published by VOP staff in our newsroom.
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