Searching, listening and smelling

"Within a decade, we will find compelling evidence of life beyond Earth," Ellen Stofan, the agency's science director, said at NASA's Habitable Worlds in Space Conference in April 2015. She added that irrefutable and defining facts about the existence of extraterrestrial life will be collected within 20-30 years.

“We know where to look and how to look,” Stofan said. "And since we are on the right track, there is no reason to doubt that we will find what we are looking for." What exactly was meant by a celestial body, representatives of the agency did not specify. Their claims indicate that it could be, for example, Mars, another object in the solar system, or some kind of exoplanet, although in the latter case it is difficult to assume that conclusive evidence will be obtained in just one generation. Definitely The discoveries of recent years and months show one thing: water - and in a liquid state, which is considered a necessary condition for the formation and maintenance of living organisms - is abundant in the solar system.

"By 2040, we will have discovered extraterrestrial life," echoed NASA's Seth Szostak of the SETI Institute in his numerous media statements. However, we are not talking about contact with an alien civilization - in recent years, we have been fascinated by new discoveries of precisely the prerequisites for the existence of life, such as liquid water resources in the bodies of the solar system, traces of reservoirs and streams. on Mars or the presence of Earth-like planets in the life zones of stars. So we hear about the conditions conducive to life, and about traces, most often chemical. The difference between the present and what happened a few decades ago is that now the footprints, signs and conditions of life are not exceptional almost anywhere, even on Venus or in the bowels of Saturn's distant moons.

The number of tools and methods used to discover such specific clues is growing. We are improving the methods of observation, listening and detection in various wavelengths. There has been a lot of talk lately about looking for chemical traces, signatures of life even around very distant stars. This is our "sniff".

Excellent Chinese canopy

Our instruments are larger and more sensitive. In September 2016, the giant was put into operation. Chinese radio telescope FASTwhose task will be to search for signs of life on other planets. Scientists all over the world place great hopes on his work. "It will be able to observe faster and farther than ever before in the history of extraterrestrial exploration," said Douglas Vakoch, chairman METI International, an organization dedicated to the search for alien forms of intelligence. FAST field of view will be twice as large as Arecibo telescope in Puerto Rico, which has been at the forefront for the past 53 years.

The FAST canopy (spherical telescope with five hundred meters aperture) has a diameter of 500 m. It consists of 4450 triangular aluminum panels. It occupies an area comparable to thirty football fields. To work, he needs complete silence within a radius of 5 km, therefore, almost 10 people from the surrounding area were relocated. people. The radio telescope is located in a natural pool among the beautiful scenery of green karst formations in the southern province of Guizhou.

However, before FAST can properly monitor for extraterrestrial life, it must first be properly calibrated. Therefore, the first two years of his work will be devoted mainly to preliminary research and regulation.

Millionaire and physicist

One of the most famous recent projects to search for intelligent life in space is a project of British and American scientists, supported by Russian billionaire Yuri Milner. The businessman and physicist has spent $100 million on research that is expected to last at least ten years. “In one day, we will collect as much data as other similar programs have collected in a year,” says Milner. Physicist Stephen Hawking, who is involved in the project, says the search makes sense now that so many extrasolar planets have been discovered. “There are so many worlds and organic molecules in space that it seems that life can exist there,” he commented. The project will be called the largest scientific study to date looking for signs of intelligent life beyond Earth. Led by a team of scientists from the University of California, Berkeley, it will have broad access to two of the most powerful telescopes in the world: green bank in West Virginia and Telescope parks in New South Wales, Australia.

We can recognize an advanced civilization from afar by:

• the presence of gases, especially air pollutants, chlorofluorocarbons, carbon dioxide, methane, ammonia;
• lights and reflections of light from objects built by civilization;
• heat dissipation;
• intense radiation releases;
• mysterious objects - for example, large stations and moving ships;
• the existence of structures whose formation cannot be explained by reference to natural causes.

Milner introduced another initiative called. He promised to pay $1 million. awards to whoever creates a special digital message to send into space that best represents humanity and the Earth. And the ideas of the Milner-Hawking duo do not end there. Recently, the media reported on a project that involves sending a laser-guided nanoprobe to a star system that reaches speeds of ... one-fifth the speed of light!

space chemistry

Nothing is more comforting to those looking for life in outer space than the discovery of well-known "familiar" chemicals in the outer reaches of space. Even clouds of water vapor "Hanging" in outer space. A few years ago, such a cloud was discovered around the quasar PG 0052+251. According to modern knowledge, this is the largest known reservoir of water in space. Precise calculations show that if all this water vapor were to condense, there would be 140 trillion times more water than the water in all of the Earth's oceans. The mass of the "reservoir of water" found among the stars is 100 XNUMX. times the mass of the sun. Just because somewhere there is water does not mean that there is life there. In order for it to flourish, many different conditions must be met.

Recently, we hear quite often about astronomical "finds" of organic substances in remote corners of space. In 2012, for example, scientists discovered at a distance of about XNUMX light years from us hydroxylaminewhich is made up of nitrogen, oxygen and hydrogen atoms and, when combined with other molecules, is theoretically capable of forming the structures of life on other planets.

Organic compounds in a protoplanetary disk orbiting the star MWC 480.

Methylcyanide (SN₃CN) я cyanoacetylene (HC₃N) that were in the protoplanetary disk orbiting the star MWC 480, discovered in 2015 by researchers at the American Harvard-Smithsonian Center for Astrophysics (CfA), is another clue that there may be chemistry in space with a chance for biochemistry. Why is this relationship such an important discovery? They were present in our solar system at the time when life was being formed on Earth, and without them, our world would probably not look the way it does today. The star MWC 480 itself is twice the mass of our star and is about 455 light-years from the Sun, which is not much compared to the distances found in space.

Recently, in June 2016, researchers from a team that includes, among others, Brett McGuire of the NRAO Observatory and Professor Brandon Carroll of the California Institute of Technology noticed traces of complex organic molecules belonging to the so-called chiral molecules. Chirality is manifested in the fact that the original molecule and its mirror reflection are not identical and, like all other chiral objects, cannot be combined by translation and rotation in space. Chirality is characteristic of many natural compounds - sugars, proteins, etc. So far, we have not seen any of them, except for the Earth.

These discoveries do not mean that life originates in space. However, they suggest that at least some of the particles needed for its birth may be formed there, and then travel to the planets along with meteorites and other objects.

Colors of life

Deserved Kepler space telescope contributed to the discovery of more than a hundred terrestrial planets and has thousands of exoplanet candidates. As of 2017, NASA plans to use another space telescope, Kepler's successor. Transiting Exoplanet Exploration Satellite, TESS. Its task will be to search for extrasolar planets in transit (ie, passing through parent stars). By sending it into a high elliptical orbit around the Earth, you can scan the entire sky for planets orbiting bright stars in our immediate vicinity. The mission is likely to last two years, during which about half a million stars will be explored. Thanks to this, scientists expect to discover several hundred planets similar to Earth. Further new tools such as eg. James Webb Space Telescope (James Webb Space Telescope) should follow and dig into the discoveries already made, probe the atmosphere and look for chemical clues that could later lead to the discovery of life.

Project Transiting Exoplanet Survey Satellite - Visualization

However, as far as we know approximately what the so-called biosignatures of life (for example, the presence of oxygen and methane in the atmospheres) are, it is not known which of these chemical signals from a distance of tens and hundreds of light years finally decide the matter. Scientists agree that the presence of oxygen and methane at the same time is a strong prerequisite for life, since there are no known non-living processes that would produce both gases at the same time. However, as it turns out, such signatures can be destroyed by exo-satellites, possibly orbiting exoplanets (as they do around most planets in the solar system). For if the atmosphere of the Moon contains methane, and the planets contain oxygen, then our instruments (at the present stage of their development) can combine them into one oxygen-methane signature without noticing the exomoon.

Maybe we should look not for chemical traces, but for color? Many astrobiologists believe that halobacteria were among the first inhabitants of our planet. These microbes absorbed the green spectrum of radiation and converted it into energy. On the other hand, they reflected violet radiation, due to which our planet, when viewed from space, had just that color.

To absorb green light, halobacteria used retinal, i.e. visual purple, which can be found in the eyes of vertebrates. However, over time, exploiting bacteria began to dominate on our planet. chlorophyllwhich absorbs violet light and reflects green light. That's why the earth looks the way it does. Astrologers speculate that in other planetary systems, halobacteria may continue to grow, so they speculate search for life on purple planets.

Objects of this color are likely to be seen by the aforementioned James Webb telescope, which is scheduled to launch in 2018. Such objects, however, can be observed, provided that they are not too far from the solar system, and the central star of the planetary system is small enough not to interfere with other signals.

Other primordial organisms on an Earth-like exoplanet, in all likelihood, plants and algae. Since this means the characteristic color of the surface, both earth and water, one should look for certain colors that signal life. New generation telescopes should detect the light reflected by exoplanets, which will reveal their colors. For example, in the case of observing the Earth from space, you can see a large dose of radiation. near infrared radiationwhich is derived from chlorophyll in vegetation. Such signals, received in the vicinity of a star surrounded by exoplanets, would indicate that "there" could also be something growing. Green would suggest it even more strongly. A planet covered in primitive lichens would be in shadow bile.

Scientists determine the composition of exoplanet atmospheres based on the aforementioned transit. This method makes it possible to study the chemical composition of the planet's atmosphere. Light passing through the upper atmosphere changes its spectrum - the analysis of this phenomenon provides information about the elements present there.

Researchers from University College London and the University of New South Wales published in 2014 in the journal Proceedings of the National Academy of Sciences a description of a new, more accurate method for analyzing the occurrence of methane, the simplest of organic gases, the presence of which is generally recognized as a sign of potential life. Unfortunately, modern models describing the behavior of methane are far from perfect, so the amount of methane in the atmosphere of distant planets is usually underestimated. Using state-of-the-art supercomputers provided by the DiRAC () project and the University of Cambridge, about 10 billion spectral lines have been modeled, which can be associated with the absorption of radiation by methane molecules at temperatures up to 1220 ° C. The list of new lines, about 2 times longer than the previous ones, will allow a better study of the methane content in a very wide temperature range.

Methane signals the possibility of life, while another much more expensive gas oxygen - it turns out that there is no guarantee of the existence of life. This gas on Earth comes mainly from photosynthetic plants and algae. Oxygen is one of the main signs of life. However, according to scientists, it may be a mistake to interpret the presence of oxygen as equivalent to the presence of living organisms.

Recent studies have identified two cases where the detection of oxygen in the atmosphere of a distant planet could give a false indication of the presence of life. In both of them, oxygen was produced as a result of non-abiotic products. In one of the scenarios we analyzed, ultraviolet light from a star smaller than the Sun could damage carbon dioxide in an exoplanet's atmosphere, releasing oxygen molecules from it. Computer simulations have shown that the decay of CO₂ gives not only₂, but also a large amount of carbon monoxide (CO). If this gas is strongly detected in addition to oxygen in the exoplanet's atmosphere, it could indicate a false alarm. Another scenario concerns low-mass stars. The light they emit contributes to the formation of short-lived O molecules.₄. Their discovery next to O₂ it should also spark an alarm for astronomers.

Looking for methane and other traces

The main mode of transit says little about the planet itself. It can be used to determine its size and distance from the star. A method of measuring radial velocity can help determine its mass. The combination of the two methods makes it possible to calculate the density. But is it possible to examine the exoplanet more closely? It turns out it is. NASA already knows how to better view planets like Kepler-7 b, for which the Kepler and Spitzer telescopes have been used to map atmospheric clouds. It turned out that this planet is too hot for life forms as we know it, with temperatures ranging from 816 to 982 °C. However, the very fact of such a detailed description of it is a big step forward, given that we are talking about a world that is a hundred light years away from us.

Adaptive optics, which is used in astronomy to eliminate disturbances caused by atmospheric vibrations, will also come in handy. Its use is to control the telescope with a computer in order to avoid local deformation of the mirror (of the order of several micrometers), which corrects errors in the resulting image. yes it works Gemini Planet Scanner (GPI) located in Chile. The tool was first launched in November 2013. GPI uses infrared detectors, which are powerful enough to detect the light spectrum of dark and distant objects such as exoplanets. Thanks to this, it will be possible to learn more about their composition. The planet was chosen as one of the first observation targets. In this case, the GPI works like a solar coronagraph, meaning it dims the disk of a distant star to show the brightness of a nearby planet.

The key to observing "signs of life" is the light from a star orbiting the planet. Exoplanets, passing through the atmosphere, leave a specific trace that can be measured from the Earth by spectroscopic methods, i.e. analysis of radiation emitted, absorbed or scattered by a physical object. A similar approach can be used to study the surfaces of exoplanets. However, there is one condition. Surfaces must sufficiently absorb or scatter light. Evaporating planets, meaning planets whose outer layers float around in a large dust cloud, are good candidates.

As it turns out, we can already recognize elements like cloudiness of the planet. The existence of a dense cloud cover around the exoplanets GJ 436b and GJ 1214b was established based on a spectroscopic analysis of the light from the parent stars. Both planets belong to the category of so-called super-Earths. GJ 436b is located 36 light years from Earth in the constellation Leo. GJ 1214b is in the constellation Ophiuchus, 40 light years away.

The European Space Agency (ESA) is currently working on a satellite whose task will be to accurately characterize and study the structure of already known exoplanets (CHEOPS). The launch of this mission is scheduled for 2017. NASA, in turn, wants to send the already mentioned TESS satellite into space in the same year. In February 2014, the European Space Agency approved the mission PLATO, associated with sending a telescope into space designed to search for Earth-like planets. According to the current plan, in 2024 he should start searching for rocky objects with water content. These observations should also help in the search for the exomoon, in much the same way that Kepler's data were used.

The European ESA developed the program several years ago. Darwin. NASA had a similar "planetary crawler". TPF (). The aim of both projects was to study Earth-sized planets for the presence of gases in the atmosphere that signal favorable conditions for life. Both included bold ideas for a network of space telescopes collaborating in the search for Earth-like exoplanets. Ten years ago, technologies were not yet sufficiently developed, and programs were closed, but not everything was in vain. Enriched by the experience of NASA and ESA, they are currently working together on the Webb Space Telescope mentioned above. Thanks to its large 6,5-meter mirror, it will be possible to study the atmospheres of large planets. This will allow astronomers to detect chemical traces of oxygen and methane. This will be specific information about the atmospheres of exoplanets - the next step in refining knowledge about these distant worlds.

Various teams are working at NASA to develop new research alternatives in this area. One of these lesser known and still in its early stages is the . It will be about how to shade the light of a star with something like an umbrella, so that you can observe the planets on its outskirts. By analyzing the wavelengths, it will be possible to determine the components of their atmospheres. NASA will evaluate the project this year or next and decide if the mission is worth it. If it starts, then in 2022.

Civilizations on the periphery of galaxies?

Finding traces of life means more modest aspirations than the search for entire extraterrestrial civilizations. Many researchers, including Stephen Hawking, do not advise the latter - because of the potential threats to humanity. In serious circles, there is usually no mention of any alien civilizations, space brothers or intelligent beings. However, if we want to look for advanced aliens, some researchers also have ideas on how to increase the chances of finding them.

For example. Astrophysicist Rosanna Di Stefano of Harvard University says advanced civilizations live in densely packed globular clusters on the outskirts of the Milky Way. The researcher presented her theory at the annual meeting of the American Astronomical Society in Kissimmee, Florida, in early 2016. Di Stefano justifies this rather controversial hypothesis by the fact that at the edge of our galaxy there are about 150 old and stable spherical clusters that provide good ground for the development of any civilization. Closely spaced stars can mean many closely spaced planetary systems. So many stars clustered into balls is good ground for successful leaps from one place to another while maintaining an advanced society. The proximity of stars in clusters could be useful in sustaining life, Di Stefano said.