As the "dissemination lecturer" from the once cult film "Carnival Night" said, "whether there is life on Mars, whether there is life on Mars - this is unknown to science." 66 years ago, when Eldar Ryazanov was filming his famous tape, the Synclite of Academicians would not have given any other answer. And what does today's science claim, and not only about the Red Planet? Putting the question squarely, are there other abodes of life in the Universe?
Let us first of all remember that our evolutionary tree is literally littered with points of contact with other living beings who have passed on to us some of their hereditary information. Human DNA contains a great variety of fragments inherited from bacteria and viruses. In theory, we can assume that among them there are also parts of the genomes of extraterrestrial organisms. Moreover, the possibility of such transportation has already been proven. In our collections, there are at least thirty meteorites ejected from the surface of Mars. It is possible that in the past, in this way, Martian microorganisms could have entered the Earth, which not only survived, but also left a genetic memory about themselves in terrestrial organisms.
Harsh school
Nowadays, different types of extremophile bacteria are known that do not die at high temperatures and pressures, do not need oxygen, and generally reproduce safely in conditions that were not so long ago considered absolutely unsuitable for life. For example, ten years ago in southern Africa, in rocks deep under the soil layer, microorganisms were discovered that use molecular hydrogen as an energy source. Colonies of these bacteria are completely isolated from any contact with the earth's surface for at least 200 million years. In light of this discovery, being able to survive space travel inside a meteorite doesn't seem unthinkable.
The likelihood of borrowing extraterrestrial genetic information is very small, but still nonzero. If ever it is confirmed, it will be possible to assume that in a certain sense the human species arose through symbiosis with alien life, which originated not on our planet, and perhaps not even in the solar system. Then it turns out that the reception of information from extraterrestrial senders has already taken place - only at the genetic level.
Signal from space
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Our cosmic non-singularity would be proved much more radically if we received signals from space that could be deciphered or at least recognized as artificially created events, and not just natural processes. Of course, they can only be transmitted across interstellar distances, since there is no intelligent life outside of the Earth in the solar system. But for this it is necessary that at least one civilization, which is at a comparable stage of technological development, should not arise too far from us. I do not want to dogmatically assert that this is generally impossible. However, from the point of view of our ideas about the pace and complexity of biological and social evolution and today's knowledge about the intragalactic surroundings of the Sun, the existence of even one such civilization seems extremely unlikely. And it is hardly necessary to specifically specify that we have never received any signals from extraterrestrial civilizations. I won't talk about flying saucers and other fabrications, this is from the realm of fantasy and superstition, not science.
Other stars
Of course, interstellar contact isn't the only way to demonstrate the existence of extraterrestrial life. No matter how the chances of the emergence of advanced civilizations in the depths of space are estimated, there is no doubt that the likelihood of the emergence of at least primitive living organisms will be much higher. Moreover, subsequent space expeditions will allow to unambiguously answer the question of whether there is (or at least was) life on Mars. The same applies to the search for life on the satellites of the giant planets Jupiter and Saturn, although this is a matter of the more distant future. Extrasolar planets (exoplanets) are a different matter, because not only do we not plan to send there at least automatic probes, but we also do not have the technologies that would allow us to hope for the feasibility of such flights.
And yet the matter is not hopeless. We are already collecting information about the atmospheres of these planets, and in the future we will be able to receive information about their surfaces. There are signs by which one can suspect the presence of life on a particular celestial body. For example, 2 billion years ago, the oxygen content in the earth's atmosphere increased sharply due to the vital activity of photosynthetic bacteria. If a planet with an oxygen atmosphere is found, it could be considered a candidate for inhabited world status. These suspicions will be strengthened if there are noticeable amounts of carbon dioxide and methane in its air basin. There are other chemical markers that also indicate the possibility of biological processes. Finding them is an important part of exoplanet research.
Culture shock
Now let's say that we have more or less convincingly proven the existence of primitive life on Mars or even outside the solar system. It is interesting to think about how humanity will react to such a discovery. There are different points of view, but it seems to me that no culture shock will follow, the impact will be minimal. Such a discovery will hardly surprise anyone, since we are already accustomed to thinking that sooner or later it will happen. Something like this had already happened when the first extrasolar planets were discovered. This information was received with great interest, but without exaltation, since it was long expected. Similarly, the general public expects scientists to discover extraterrestrial life.
But the opposite situation can lead to more serious consequences. If for several decades astronomers and astrobiologists do not find a single even potentially habitable planet, society will probably experience great disappointment. Such an outcome could indeed be a culture shock. Humanity will feel its universal loneliness, and who knows what its reaction will be. However, let's not guess.
Michael Mumma, Director of NASA's Goddard Astrobiology Center, and Senior Researcher in the Solar System Research Unit at NASA's Goddard Space Flight Research Center.
Interviewed by: Alexey Levin, Oleg Makarov, Dmitry Mamontov