Extraterrestrial life

The emergence of life on Earth provides obvious prerequisites for the assumption that the same conditions could exist on other planets. One can definitely speak only about the evolution of life, which resembles the earth ^[6] .

Soviet astronomer Joseph Shklovsky cautiously suggested that favorable conditions for the emergence of life exist on planets orbiting near cold and fairly stable single stars of spectral class G, K, M (close in their properties to the Sun ). The number of such stars in our galaxy can be estimated as 10 ^{9 [7]} .

The discovery of the planets of other star systems also indirectly indicates the presence of places in the universe that are favorable for the emergence of life in the " inhabited zone ". The possibilities of modern astronomy do not allow us to estimate the living conditions on such planets, but if in the future technical capabilities allow us to determine, say, the presence of oxygen in the atmosphere, this will be important evidence in favor of proof of the existence of life outside the Earth.

The presence on Earth of life forms that can maintain the ability to reproduce after being in extreme conditions (withstand high temperature, pressure, adverse environment) suggests that life can be born and survive under conditions far from terrestrial.

A possible proof of the existence of life outside the Earth is not only of purely theoretical significance. One of the common theories that explain the origin of life on Earth is panspermia . We should not forget that life outside the Earth at the moment is nothing more than a scientific hypothesis. Many scientists are very skeptical of both the ability to detect extraterrestrial life in the foreseeable future, and the ability to recognize it, even if humans are lucky to encounter it ^[8] .

If our galaxy alone has billions of planets and millions of billions of planets in the Universe, then, of course, the question of whether other civilizations can exist there or not will become more and more relevant.

- Academician V. A. Hambartsumyan ^[9]

In past centuries, the presence of life on the planets of the solar system was considered highly probable. This was especially associated with the discovery by astronomy of the seasons (seasons), possible seas and land, and so on. channels on Mars . There were even abstract assumptions about the existence of selenites , Martians , etc. Some scholars ^{[ who? ]} at the beginning of the 20th century, the presence of Martian vegetation was considered proven, and the Venusian - possible.

Since the second half of the 20th century, scientists have been conducting a focused search for extraterrestrial life inside the solar system and beyond, especially with the help of automatic interplanetary stations (AMS) and space telescopes . Research data from meteorites , the upper layers of the Earth’s atmosphere and data collected in space programs allow some scientists to argue that the simplest forms of life can exist on other planets of the solar system. Moreover, according to modern scientific ideas, the probability of detecting highly organized life on all planets of the solar system, except for Mars and some satellites of Jupiter and Saturn , is extremely small.

Astrobiologists continue to search for at least elementary forms ( bacteria , protozoa ) on Mars, Venus. Some satellites of the gas giants Jupiter and Saturn with subsurface oceans, water ice, and the atmosphere ( Europe , Callisto , Ganymede , Enceladus , and Titan ) are also considered promising for search ^[10] .

Studies of Mars with the help of orbital and descent AMS so far have only allowed us to state the favorable factors that contribute to life. Signs of water were discovered on the surface of the planet. This, as well as the presence of methane in the atmosphere and climatic conditions of the planet indicate that, in principle , simple microorganisms can be detected on Mars ^{[11] [12]} . Within the framework of the Viking AMC program, direct searches were made for traces of life on the surface of Mars, which did not give a positive result, as were the subsequent programs of the Phoenix , Spirit , Opportunity , Curiosity lander and rovers. The programs of landing AMS / Mars rovers ExoMars and AMS of soil return Mars Sample Return Mission are focused on further searches.

The possible presence of living creatures on the surface of Venus was announced in January 2012 by Leonid Ksanfomaliti, chief scientific researcher at the Space Research Institute of the Russian Academy of Sciences . When studying photographs transmitted by the Soviet AMS in the 1970s and 1980s, he discovered certain objects that appear and disappear in a series of successive shots (see: Life on Venus ).

In 2010, a group of scientists from NASA announced on the basis of data received from the Cassini AMS about the detection of indirect signs of the vital activity of primitive organisms on the Saturn satellite Titan (see: Life on Titan ). The search for life on the spot on the moons of Jupiter is supposed in promising AMS programs with descent vehicles, cryobots , hydrobots of the Laplace-P type , etc.

The search for life forms outside the solar system is organized in the direction of detecting possible traces of the activity of intelligent beings . So, since 1971, the SETI project has been working, in which scientists are trying to detect the activity of extraterrestrial civilizations in the radio range . The SETI project has a public distribution in the form of the SETI @ home crowdsourcing program.

After the appearance of a crowdsourcing Internet resource for exploring the WikiSky Universe close to SETI, the search for UFOs and other manifestations of extraterrestrial intelligence in space became available not only to astronomers and participants of the SETI project and SETI @ home program, but also to a wider masses.

The discoveries of exoplanets , which became especially numerous with the advent of specialized space telescopes such as Kepler , including the crowdsourcing project Planet Hunters to search for such planets in its database, also became promising in terms of searching for extraterrestrial life and civilizations on exoplanets located in the inhabited zone . After 2020, NASA plans to launch the ATLAST space telescope, capable of detecting indirect signs of vital activity on exoplanets in the habitable zone. The presence of life on the planet will be indirectly confirmed in case of detection of " biosignatures " (for example, molecular oxygen, ozone, water and methane) in the atmosphere spectrum of earth-like exoplanets.

Some hypotheses suggest that pulsars are a kind of super-powerful “beacons” ( Joseph Shklovsky’s hypothesis), and quasars are possible pulses of the photonic engines of starships of extraterrestrial civilizations moving away from the observer (this was supposed to explain the huge speed of the quasar calculated from its redshift , the photon engine and would have a sublight speed, which removed the paradox about the huge distance of the quasar from the observer).

There are also theoretical assumptions about the possibility of using extraterrestrial civilizations, in addition to starships, O'Neill colonies , Dyson spheres and other astroengineering structures that can be detected by observational astronomy , including Hubble , Wise, and other telescopes. In 2015, The results of observations of the space telescope for the search for Kepler exoplanets by a number of researchers suggested the existence of the Dyson sphere or other astroengineering structures in the star system KIC 8462852 of the constellation Cygnus .

• Water in liquid form can be one of the signs of life, as it is a convenient habitat, it is believed that life on Earth originated in water. Seen on Europe , Enceladus .

• Presence of organic compounds or substances characteristic of life (e.g. certain carbon isotopes ):
  • Glycine ^[13] ;
  • Ammonia , methane ^{[14] [15]} are substances with a short “period of life” in the atmosphere of planets. Two possible reasons for the presence of these substances in the atmosphere of planets: life or volcanism . For example, the presence of these substances in the Martian atmosphere indirectly indicates the possibility of the existence of modern life on Mars, since volcanism has not been noticed on this planet for a long time.
• Abnormal infrared radiation ^[16] .
• Meaningful radio messages will be a sign of intelligent life (see SETI @ home ).
• The signs of a technologically developed life will be constructions of a cosmic scale; as a result of space exploration, they have not been discovered and their usefulness for a civilization of this level is disputed.

To establish the presence of these indicators are used: a telescope to enhance the light flux, a spectrograph to analyze its spectrum .

In the study of carbon-containing (carbonaceous) meteorites , substances are found in their composition, which in terrestrial conditions are waste products.

In the study of stone meteorites, the so-called “Organized elements” - microscopic (5-50 microns) “unicellular” formations, often having distinct double walls, pores, spikes, and so on.

To date, it has not been proven that these fossils belong to the remains of any forms of extraterrestrial life. But, on the other hand, these entities have such a high degree of organization that it is customary to associate with life.

A feature of “organized elements” is also their abundance: approximately 1800 “organized elements” fall per 1 g of carbonaceous meteorite material ^[17] .

In August 1996, an article was published in the journal Science on the study of the meteorite ALH 84001 , found in Antarctica in 1984. Isotopic dating showed that a meteorite arose 4-4.5 billion years ago, and 15 million years ago was thrown into interplanetary space; 13 thousand years ago, a meteorite fell to Earth. Studying a meteorite using an electron microscope , scientists discovered microscopic fossils resembling bacterial colonies, consisting of individual parts measuring approximately 100 nm. Traces of substances formed during the decomposition of microorganisms were also found. The work was mixed by the scientific community. Critics noted that the size of the found formations is 100-1000 times smaller than typical terrestrial bacteria, and their volume is too small to accommodate DNA and RNA molecules in it. In subsequent studies, traces of terrestrial bio-pollution were found in the samples. In general, the arguments for the fact that the formations are fossils of bacteria do not look convincing enough.

Extraterrestrial life is one of the important attributes and also actors in the works of many authors. Mention of the existence of life outside the Earth dates back to ancient ( Lucian ) and medieval literature ( Giordano Bruno ). The modern sci-fi tradition of encountering alien life is laid down by the works of Joseph Roni Sr. (Xypehuzy) and Herbert Wells ( War of the Worlds ). The problem of searching and researching extraterrestrial life is raised by such famous authors as Robert Sheckley (for example, the story “Leech”), Clifford Saymak (“ Everything Alive ”), Kir Bulychev (“Half Life”, “ Village ”), Ivan Efremov (“ Heart of the Snake” ”,“ Andromeda Nebula ”) and many others.

Themes related to extraterrestrial life are diverse. These are attempts to recognize the difficult to distinguish line between intelligent and unreasonable life ( Strugatsky brothers “ Noon, XXII Century ”, Vasily Golovachev “ Relic ”). Collision with an inorganic life form (" Country of crimson clouds "). Out of control mechanisms themselves become kind of alive and begin to evolve ( Stanislav Lem “ Invincible ”).

In addition to the widespread disclosure of science fiction in literary and cinematographic works, the possible emergence of extraterrestrial life in the Earth’s biosphere, paleocontacts and modern alien visits and personal contacts with them also appear in the studies of ufology enthusiasts, as well as in some conspiracy theories .

• Xenobiology
• Carbon chauvinism
• Extraterrestrial civilization

• John Willis All these worlds are yours. The Scientific Search for Extraterrestrial Life = Willis Jon. All These Worlds Are Yours: The Scientific Search for Alien Life. - Alpina Publisher, 2018 .-- 286 p. - ISBN 978-5-91671-849-2 .

• Leonid Popov. Astronomers have provided habitat ratings for planets and moons (neopr.) . Membrana (November 24, 2011). Date of treatment November 26, 2011. Archived February 22, 2012.