The search for extraterrestrial life has not yet been particularly successful, unless, of course, you believe in the alien origin of Zhanna Aguzarova. But perhaps we are just looking in the wrong place, said a group of scientists from the Institute of Astronomy at Cambridge University, led by Nikku Madhusudhan.
Since we have only one sample – our own planet Earth, we are trying to find life on objects similar to it. First of all, scientists paid attention to rocky rocky planets, about the same size as the Earth, which were in the habitable zone of their star. That is, the conditions on the surface – the temperature and density of the atmosphere – must ensure the existence of water in liquid form. In total, scientists have already discovered about 4500 exoplanets, but they all bear little resemblance to our Earth.
But probably, with the search for aliens, the situation is the same as with the “only true Marxist-Leninist teaching” – if you focus on one thing, then nothing good will come of it. Scientists from Cambridge have identified a new class of exoplanets, they do not look like terrestrial planets, but can become a haven for some life forms.
To imagine this cradle of life, you have to pretty much strain your imagination. Because such worlds do not exist in our solar system, it is something in between the ice giant Neptune, a gas dwarf and the terrestrial planets. The surface of such planets is covered with an ocean of liquid water, and the dense atmosphere is saturated with hydrogen. Nikku Madhusudkhan and his colleagues called the exoplanets Hycean, a term derived from a combination of the words hydrogen and ocean. It would be problematic to relax on the shore of such an ocean even in a chemical protection suit, earlier such planets were considered unfit for life. As the Kapotnya district in Moscow used to be.
However, scientists from Cambridge, after a thorough study of one of these planets, codenamed K2-18b, came to the conclusion that everything is not so bad. This exoplanet orbits a red dwarf located 124 light-years from the solar system. The year on K2-18b lasts only 33 days (during this time it makes a full revolution around its star). It is the first exoplanet with a liquid water ocean in the habitable zone, and a large amount of water vapor (20 to 50 percent) has been detected in its atmosphere. And where there is water, there is life – at least, this is how we imagine it today.
“We believe that habitable planets may be much larger than previously thought,” says Nikku Madhusudhan. – The radius of the “hydrogen oceans” can be 2.6 the radius of the Earth, and the mass – 10 Earth masses (approximately these are the parameters of K2-18b). In this case, the pressure at the ocean surface will still be acceptable for living microorganisms. At the same time, the boundaries of the habitable zone are expanding significantly. An exoplanet of the Hycean class can be so close to its star that the temperature of the atmosphere can reach 200 degrees Celsius. And the far border of the “Goldilocks zone” can be moved as far as possible, since a comfortable temperature will be maintained due to the greenhouse effect.
By the way, among the 4500 discovered exoplanets, the worlds of the Hycean type prevail. Previously, they were not given much attention, since they were looking for a twin of our Earth, but now it is more reasonable to focus on the “hydrogen oceans”, scientists say. The fact is that large planets with a dense atmosphere and high temperatures are an excellent target for observation. Under these conditions, using spectral analysis, it is easier to detect biomarkers that can be signs of life. Ozone, oxygen and methane are considered to be such markers in the atmosphere. However, in oxygen-deprived atmospheres, the presence of biological activity can be signaled by organic compounds such as dimethyl sulfide and methyl chloride.
Of course, the chance to meet planets like the Hycean Diva Plavalaguna (remember such an opera singer from The Fifth Element) or some other highly evolved creature is most likely excluded, but various bacteria and microbes may well thrive.
Scientists suggest that detailed observations can be carried out using the newest James Webb telescope, which is going to be launched in November this year. The 11 most promising exoplanets from the category of “hydrogen oceans” have already been selected as candidates, and among them is the same K2-18b.
