What might alien beings look like? The publication Gizmodo addressed this question to astrobiologists looking for living organisms in space. "Lenta.ru" tells what the experts answered.
According to Seth Shostak, an astronomer at the Search for Extraterrestrial Intelligence (SETI) Institute, the most unrealistic forms of alien intelligent life are created by the imagination of the authors of science fiction films. So, the Daleks from the sci-fi series Doctor Who are similar, in the words of the scientist, to "industrial vacuum cleaners", and this has nothing to do with reality. Somewhere in the universe there may be organisms whose intelligence is comparable to that of a human, but Shostak is sure that aliens are more like insects.
Astronomer and physicist Caitlin Ahrens of the University of Arkansas believes that alien creatures can be found on planets orbiting large enough stars and located in the "Goldilocks zone" (habitable zone) - an area around a star where water in liquid form.
However, there is a possibility that life could have arisen in worlds farther from the parent stars. For example, Jupiter's moon Europa and Saturn's moon Enceladus are outside the Goldilocks zone, but they most likely have liquid water under a thick ice crust. Although the sun's rays - the main source of energy for all life on Earth - do not penetrate the oceans, hydrothermal vents similar to "black smokers" are possible at the bottom.
Far away. Photo: Nelo Hotsuma / Rockwall / Wikimedia
They carry highly mineralized waters to the oceans, which is a suitable habitat for chemosynthetic bacteria, which receive energy from redox reactions. Their vital activity supports the existence of other, more complex organisms, such as snails, crabs, worms, sea sponges.
Ahrens added that alien beings may not fit into modern ideas about life. On Earth, organisms are composed primarily of hydrocarbons, while in other worlds they can be made of sulfur, silicon, or other elements. They can be of any shape or size and may not be intelligent.
Douglas Vakoh, president of the METI (Messaging to Extra-Terrestrial Intelligence) International program, specializing in the search for extraterrestrial signals sent by other civilizations, believes that evolution on other planets is not the same as on Earth. The development of life and the emergence of new species depend on random events, but this does not mean that the emergence of forms resembling terrestrial ones is impossible.
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Geysers of Enceladus. Photo: Public Domain / Wikimedia
“Sharks and dolphins are similar, although they are very distant relatives: sharks are fish, dolphins are mammals. One should not be surprised at the similar convergence of body shape when we face life in other worlds,”says the scientist.
Moreover, various combinations of even similar details can give many creatures that are strikingly different from organisms on Earth. Therefore, Vakoch does not think that a person will ever meet brothers in mind like him.
The researcher also does not exclude that the oceans on the satellites in the solar system are inhabited. Space probes could detect life there in two ways: take samples of the water thrown into space by giant geysers, or drill a many kilometers of ice shell. However, the water on Enceladus is too cold for creatures larger than a microbe to live there.
Tardigrade. Image: Schokraie E, Warnken U, Hotz-Wagenblatt A, Grohme MA, Hengherr S / Wikimedia
Another moon of Saturn, Titan, with a dense atmosphere and liquid carbon seas on the surface, may also be inhabited by primitive life forms. The problem is that there is no water on this celestial body, so the metabolism there must be completely different.
Europa's advantage is that its subglacial ocean interacts with the mineral-rich mantle of the moon. Another factor is the generation of energy in its depths that can support life. Part of this energy is formed during the decay of radioactive elements, part - under the influence of tidal forces arising from the rotation of the satellite around Jupiter. All this is sufficient for the existence of organisms like tardigrades. These creatures can survive in low temperatures and high pressure, but, unlike their terrestrial counterparts, they must withstand extreme conditions for a long time. Wakoch calls such organisms "steroid-on tardigrades."
The scientist believes that real aliens are not like "gray humanoids", as they are represented by UFO fans and fans of science fiction. For another form of intelligent life to resemble a human, a whole series of coincidences is necessary. Anthropogenesis on Earth included the formation of key niches in the African savannas. The vertical position of the body of ancient people allowed them to notice predators lurking in the tall grass. Otherwise, the brain in the upper body is a very dubious advantage. Therefore, alien intelligent beings can be of any shape and have tentacles instead of arms.
NASA astrobiologist Rocco Manicelli also believes that only primitive single-celled life is possible on Enceladus. But liquid water and energy are not the only prerequisites for the development of organisms. You need reduced carbon, nitrogen, phosphorus in sufficient concentrations so that they react with each other and form biological polymers.
Alexander Enikeev