Where to look for life and how to recognize it
When we look for life in space, we hear the Fermi paradox alternating with the Drake equation. Both talk about intelligent life forms. But what if alien life is not intelligent? After all, that doesn't make it any less scientifically interesting. Or maybe he does not want to communicate with us at all - or is he hiding or going beyond what we can even imagine?
Both Fermi's paradox (“Where are they ?!” - since the probability of life in space is not small) and Drake equation, estimating the number of advanced technical civilizations, it is a bit of a mouse. At present, specific issues such as the number of terrestrial planets in the so-called zone of life around the stars.
According to the Planetary Habitability Laboratory in Arecibo, Puerto Rico, To date, more than fifty potentially habitable worlds have been discovered. Except that we don't know if they're habitable in every way, and in many cases they're just too remote for us to gather the information we need with the methods we know. However, given that we've only looked at a small part of the Milky Way so far, it seems like we already know a lot. However, the paucity of information still frustrates us.
Where to look
One of these potentially friendly worlds is almost 24 light years away and lies within constellation scorpio, exoplanet Gliese 667 Cc orbiting red dwarf. With a mass 3,7 times that of Earth and an average surface temperature well above 0°C, if the planet had a suitable atmosphere, it would be a good place to look for life. It's true that Gliese 667 Cc probably doesn't rotate on its axis like the Earth does - one side of it always faces the Sun and the other is in shadow, but a possible thick atmosphere could transfer enough heat to the shadow side as well maintain a stable temperature at the border of light and shadow.
According to scientists, it is possible to live on such objects revolving around red dwarfs, the most common types of stars in our Galaxy, but you just need to make slightly different assumptions about their evolution than the Earth, which we will write about later.
Another chosen planet, Kepler 186f (1), is five hundred light years away. It appears to be only 10% more massive than Earth and about as cold as Mars. Since we have already confirmed the existence of water ice on Mars and know that its temperature is not too cold to prevent the survival of the toughest bacteria known on Earth, this world may turn out to be one of the most promising for our requirements.
Another strong candidate Kepler 442b, located more than 1100 light years from Earth, is located in the constellation Lyra. However, both it and the above-mentioned Gliese 667 Cc lose points from strong solar winds, much more powerful than those emitted by our own sun. Of course, this does not mean the exclusion of the existence of life there, but additional conditions would have to be met, for example, the action of a protective magnetic field.
One of astronomers' new Earth-like finds is a planet about 41 light-years away, marked as LHS 1140b. At 1,4 times the size of Earth and twice as dense, it is located in the home region of the home star system.
“This is the best thing I've seen in the last decade,” Jason Dittmann of the Harvard-Smithsonian Center for Astrophysics says enthusiastically in a press release about the discovery. “Future observations could detect a potentially habitable atmosphere for the first time. We plan to look for water there, and eventually molecular oxygen.”
There is even an entire star system that plays an almost stellar role in the category of potentially viable terrestrial exoplanets. This is TRAPPIST-1 in the constellation of Aquarius, 39 light years away. Observations have shown the existence of at least seven minor planets orbiting the central star. Three of them are located in a residential area.
“This is an amazing planetary system. Not only because we found so many planets in it, but also because they are all remarkably similar in size to Earth, ”says Mikael Gillon from the University of Liege in Belgium, who conducted the study of the system in 2016, in a press release. Two of these planets TRAPPIST-1b Oraz TRAPPIST-1stake a closer look under a magnifying glass. They turned out to be rocky objects like the Earth, making them even more suitable candidates for life.
TRAPPIST-1 it is a red dwarf, a star other than the Sun, and many analogies may fail us. What if we were looking for a key similarity to our parent star? Then a star revolves in the constellation Cygnus, very similar to the Sun. It is 60% larger than Earth, but it remains to be determined whether it is a rocky planet and whether it has liquid water.
“This planet has spent 6 billion years in its star's home zone. It is much longer than the Earth,” commented John Jenkins of NASA’s Ames Research Center in an official press release. "It means more chances for life to arise, especially if all the necessary ingredients and conditions exist there."
Indeed, quite recently, in 2017, in the Astronomical Journal, researchers announced the discovery first atmosphere around a planet the size of Earth. With the help of the telescope of the Southern European Observatory in Chile, scientists observed how during the transit it changed part of the light of its host star. This world known as GJ 1132b (2), it is 1,4 times the size of our planet and is 39 light years away.
2. Artistic visualization of the atmosphere around exoplanet GJ 1132b.
Observations suggest that the "super-Earth" is covered with a thick layer of gases, water vapor or methane, or a mixture of both. The star around which GJ 1132b orbits is much smaller, colder and darker than our Sun. However, it seems unlikely that this object is habitable - its surface temperature is 370°C.
How to search
The only scientifically proven model that can help us in our search for life on other planets (3) is the Earth's biosphere. We can make a huge list of the diverse ecosystems our planet has to offer.including: hydrothermal vents deep on the sea floor, Antarctic ice caves, volcanic pools, cold methane spills from the sea floor, caves full of sulfuric acid, mines and many other places or phenomena ranging from the stratosphere to the mantle. Everything we know about life in such extreme conditions on our planet greatly expands the field of space research.
3. Artistic vision of an exoplanet
Scholars sometimes refer to the Earth as Fr. biosphere type 1. Our planet shows many signs of life on its surface, mostly from energy. At the same time, it exists on Earth itself. biosphere type 2much more camouflaged. Its examples in space include planets such as present-day Mars and the gas giant's icy moons, among many other objects.
Recently launched Transit satellite for exoplanet exploration (TESS) to continue working, that is, to discover and indicate interesting points in the Universe. We hope that more detailed studies of the discovered exoplanets will be carried out. James Webb Space Telescope, operating in the infrared range - if it eventually goes into orbit. In the field of conceptual work, there are already other missions - Habitable exoplanet observatory (HabEx), multi-range Large UV Optical Infrared Inspector (LUVUAR) or Origins Space Telescope infrared (OST), aimed at providing much more data on exoplanet atmospheres and components, with a focus on search biosignatures of life.
4. Variety of traces of the existence of life
The last is astrobiology. Biosignatures are substances, objects or phenomena resulting from the existence and activity of living beings. (4). Typically, missions look for terrestrial biosignatures, such as certain atmospheric gases and particles, as well as surface images of ecosystems. However, according to experts from the National Academy of Sciences, Engineering and Medicine (NASEM), collaborating with NASA, it is necessary to move away from this geocentrism.
- notes prof. Barbara Lollar.
The generic tag can be sahara. A new study suggests that the sugar molecule and the DNA component 2-deoxyribose may exist in distant corners of the universe. A team of NASA astrophysicists managed to create it in laboratory conditions that mimic interstellar space. In a publication in Nature Communications, the scientists show that the chemical could be widely distributed throughout the universe.
In 2016, another group of researchers in France made a similar discovery regarding ribose, an RNA sugar used by the body to make proteins and thought to be a possible precursor to DNA in early life on Earth. Complex sugars add to the growing list of organic compounds found on meteorites and produced in a laboratory that mimic space. These include amino acids, the building blocks of proteins, nitrogenous bases, the basic units of the genetic code, and a class of molecules that life uses to build membranes around cells.
The early Earth was likely showered with such materials by meteoroids and comets impacting its surface. Sugar derivatives can evolve into sugars used in DNA and RNA in the presence of water, opening up new possibilities for studying the chemistry of early life.
"For more than two decades, we've wondered if the chemistry we find in space could create the compounds needed for life," writes Scott Sandford of NASA's Ames Laboratory of Astrophysics and Astrochemistry, co-author of the study. “The universe is an organic chemist. It has large vessels and a lot of time, and the result is a lot of organic material, some of which remains useful for life.
Currently, there is no simple tool for detecting life. Until a camera captures a growing bacterial culture on a Martian rock or plankton swimming under the ice of Enceladus, scientists must use a suite of tools and data to look for biosignatures or signs of life.
5. CO2-enriched laboratory atmosphere subjected to plasma discharges
On the other hand, it is worth checking some methods and biosignatures. Scholars have traditionally recognized, for example, presence of oxygen in the atmosphere planet as a sure sign that life may be present on it. However, a new Johns Hopkins University study published in December 2018 in ACS Earth and Space Chemistry recommends reconsidering similar views.
The research team conducted simulation experiments in a laboratory chamber designed by Sarah Hirst (5). The scientists tested nine different gas mixtures that could be predicted in the exoplanetary atmosphere, such as super-Earth and minineptunium, the most common types of planets. Milky Way. They exposed the mixtures to one of two types of energy, similar to that which causes chemical reactions in the planet's atmosphere. They found many scenarios that produced both oxygen and organic molecules that could build sugars and amino acids.
However, there was no close correlation between oxygen and the components of life. So it seems that oxygen can successfully produce abiotic processes, and at the same time, vice versa - a planet on which there is no detectable level of oxygen is able to accept life, which actually happened even on ... Earth, before cyanobacteria began to massively produce oxygen .
Projected observatories, including space ones, could take care of planet spectrum analysis looking for the aforementioned biosignatures. Light reflected from vegetation, especially on older, warmer planets, can be a powerful signal of life, new research from scientists at Cornell University shows.
Plants absorb visible light, using photosynthesis to turn it into energy, but not absorbing the green part of the spectrum, which is why we see it as green. Mostly infrared light is also reflected, but we can no longer see it. The reflected infrared light creates a sharp peak in the spectrum graph, known as the "red edge" of vegetables. It is still not entirely clear why plants reflect infrared light, although some research suggests that this is done to avoid heat damage.
So it is possible that the discovery of a red edge of vegetation on other planets would serve as proof of the existence of life there. Astrobiology paper authors Jack O'Malley-James and Lisa Kaltenegger of Cornell University have described how the red edge of vegetation may have changed over the course of Earth's history (6). Ground vegetation such as mosses first appeared on Earth between 725 and 500 million years ago. Modern flowering plants and trees appeared about 130 million years ago. Different types of vegetation reflect infrared light slightly differently, with different peaks and wavelengths. Early mosses are the weakest spotlights compared to modern plants. In general, the vegetation signal in the spectrum gradually increases over time.
6. Reflected light from the Earth depending on the type of vegetation cover
Another study, published in the journal Science Advances in January 2018 by the team of David Catling, an atmospheric chemist at the University of Washington in Seattle, takes a deep look at our planet's history to develop a new recipe for detecting single-celled life in distant objects in the near future. . Of the four billion years of Earth's history, the first two can be described as a "slimy world" ruled by methane-based microorganismsfor whom oxygen was not a life-giving gas, but a deadly poison. The emergence of cyanobacteria, i.e. photosynthetic green cyanobacteria derived from chlorophyll, determined the next two billion years, displacing "methanogenic" microorganisms into nooks and crannies where oxygen could not get, i.e. caves, earthquakes, etc. Cyanobacteria gradually turned our green planet, filling the atmosphere with oxygen and creating the basis for the modern known world.
Not entirely new are claims that the first life on Earth could have been purple, so hypothetical alien life on exoplanets could also be purple.
Microbiologist Shiladitya Dassarma of the University of Maryland School of Medicine and graduate student Edward Schwiterman of the University of California, Riverside are the authors of a study on the subject, published in October 2018 in the International Journal of Astrobiology. Not only Dassarma and Schwiterman, but also many other astrobiologists believe that one of the first inhabitants of our planet were halobacteria. These microbes absorbed the green spectrum of radiation and converted it into energy. They reflected the violet radiation that made our planet look like this when viewed from space.
To absorb green light, the halobacteria used the retina, the visual violet color found in the eyes of vertebrates. Only over time, bacteria began to dominate our planet, using chlorophyll, which absorbs violet light and reflects green light. That's why the earth looks the way it does. However, astrobiologists suspect that halobacteria may evolve further in other planetary systems, so they suggest the existence of life on purple planets (7).
Biosignatures are one thing. However, scientists are still looking for ways to detect technosignatures as well, i.e. signs of the existence of advanced life and technical civilization.
NASA announced in 2018 that it was intensifying its search for alien life using just such “technological signatures,” which, as the agency writes on its website, “are signs or signals that allow us to conclude the existence of technological life somewhere in the universe.” . The most famous technique that can be found is radio signals. However, we also know many others, even traces of the construction and operation of hypothetical megastructures, such as the so-called Dyson spheres (eight). Their list was compiled during a workshop hosted by NASA in November 8 (see box opposite).
— a UC Santa Barbara student project — uses a suite of telescopes aimed at the nearby Andromeda galaxy, as well as other galaxies, including our own, to detect technosignatures. Young explorers are looking for a civilization similar to ours or higher than ours, trying to signal its presence with an optical beam similar to lasers or masers.
Traditional searches—for example, with SETI's radio telescopes—have two limitations. First, it is assumed that intelligent aliens (if any) are trying to talk to us directly. Secondly, we will recognize these messages if we find them.
Recent advances in (AI) open up exciting opportunities to re-examine all collected data for subtle inconsistencies that have so far been overlooked. This idea is at the heart of the new SETI strategy. scan for anomalieswhich are not necessarily communication signals, but rather by-products of a high-tech civilization. The goal is to develop a comprehensive and intelligent "abnormal engine"capable of determining which data values and connection patterns are unusual.
Technosignature
Based on the November 28, 2018 NASA workshop report, we can distinguish several types of technosignatures.
Communications
"Messages in a bottle" and alien artifacts. We sent these messages ourselves aboard Pioneer and Voyager. These are both physical objects and their accompanying radiation.
Artificial Intelligence. As we learn to use AI for our own benefit, we increase our ability to recognize potential alien AI signals. Interestingly, there is also a possibility that a link will be established between the earth system with artificial intelligence and the space-based form of artificial intelligence in the near future. The use of AI in the search for alien technosignatures, as well as assistance in big data analysis and pattern recognition, looks promising, although it is not at all certain that AI will be free from perceptual biases typical of humans.
Atmospheric
One of the most obvious artificial ways of changing the observed features of the Earth by mankind is atmospheric pollution. So whether these are artificial atmospheric elements created as unwanted by-products of industry or a deliberate form of geoengineering, detecting the presence of life from such relationships can be one of the most powerful and unambiguous technosignatures.
Structural
Artificial megastructures. They do not have to be Dyson spheres directly surrounding the parent star. They can also be structures smaller than continents, such as highly reflective or highly absorbing photovoltaic structures (power generators) located above the surface or in circumplanetary space above clouds.
Heat islands. Their existence is based on the assumption that sufficiently developed civilizations are actively handling waste heat.
artificial lighting. As observation techniques develop, artificial light sources should be found on the night side of exoplanets.
On a planetary scale
Dissipation of energy. For biosignatures, models of the energy released by life processes on exoplanets have been developed. Where there is evidence of the presence of any technology, the creation of such models based on our own civilization is possible, although it may be unreliable.
Climate stability or instability. Strong technosignatures can be associated both with stability, when there are no preconditions for it, or with instability.
Geoengineering. Scientists believe that an advanced civilization may want to create conditions similar to those it knows on its home globe, on its expanding planets. One of the possible technosignatures could be, for example, the discovery of several planets in one system with a suspiciously similar climate.
How to recognize life?
Modern cultural studies, i.e. literary and cinematic, ideas about the appearance of Aliens mainly came from only one person - Herbert George Wells. As far back as the nineteenth century, in an article entitled "The Million Man of the Year," he foresaw that a million years later, in 1895, in his novel The Time Machine, he created the concept of the future evolution of man. The prototype of the aliens was presented by the writer in The War of the Worlds (1898), developing his concept of Selenite on the pages of the novel The First Men in the Moon (1901).
However, many astrobiologists believe that most of the life we will ever find off Earth will be unicellular organisms. They infer this from the harshness of most of the worlds we have so far found in so-called habitats, and the fact that life on Earth existed in a unicellular state for about 3 billion years before evolving into multicellular forms.
The galaxy may indeed be teeming with life, but probably mostly in micro sizes.
In the fall of 2017, scientists from the University of Oxford in the UK published an article "Darwin's Aliens" in the International Journal of Astrobiology. In it, they argued that all possible alien life forms are subject to the same fundamental laws of natural selection as we are.
“In our own galaxy alone, there are potentially hundreds of thousands of habitable planets,” says Sam Levin of the Oxford Department of Zoology. "But we have only one true example of life, on the basis of which we can make our visions and predictions - the one from Earth."
Levin and his team say it's great for predicting what life might be like on other planets. evolution theory. He must certainly develop gradually in order to become stronger over time in the face of various challenges.
“Without natural selection, life will not acquire the functions it needs to survive, such as metabolism, the ability to move or have sense organs,” the article says. “It will not be able to adapt to its environment, evolving in the process into something complex, noticeable and interesting.”
Wherever this happens, life will always be faced with the same problems - from finding a way to efficiently use the sun's heat to the need to manipulate objects in its environment.
The Oxford researchers say there have been serious attempts in the past to extrapolate our own world and human knowledge of chemistry, geology and physics to supposed alien life.
Levin says. -.
Oxford researchers have gone so far as to create several hypothetical examples of their own. extraterrestrial life forms (9)
9 Visualized Aliens From Oxford University
Levin explains. -
Most of the theoretically habitable planets known to us today revolve around red dwarfs. They are blocked by the tides, that is, one side is constantly facing a warm star, and the other side is facing outer space.
says prof. Graziella Caprelli from the University of South Australia.
Based on this theory, Australian artists have created fascinating images of hypothetical creatures inhabiting a world orbiting a red dwarf (10).
10. Visualization of a hypothetical creature on a planet orbiting a red dwarf.
The ideas and assumptions described that life will be based on carbon or silicon, common in the universe, and on the universal principles of evolution, may, however, come into conflict with our anthropocentrism and prejudiced inability to recognize the “other”. It was interestingly described by Stanislav Lem in his "Fiasco", whose characters look at Aliens, but only after some time they realize that they are Aliens. To demonstrate the human weakness in recognizing something surprising and simply "foreign", Spanish scientists recently conducted an experiment inspired by a famous 1999 psychological study.
Recall that in the original version, the scientists asked the participants to complete a task while watching a scene in which there was something surprising — like a man dressed as a gorilla — a task (like counting the number of passes in a basketball game). . It turned out that the vast majority of observers interested in their activities ... did not notice the gorilla.
This time, researchers from the University of Cadiz asked 137 participants to scan aerial photographs of interplanetary images and find structures built by intelligent beings that seem unnatural. In one picture, the researchers included a small photograph of a man disguised as a gorilla. Only 45 out of 137 participants, or 32,8% of the participants, noticed the gorilla, although it was an "alien" that they clearly saw in front of their eyes.
Yet, while representing and identifying the Stranger remains such a difficult task for us humans, the belief that "They're Here" is as old as civilization and culture.
More than 2500 years ago, the philosopher Anaxagoras believed that life exists on many worlds thanks to the "seeds" that scattered it throughout the cosmos. About a hundred years later, Epicurus noticed that the Earth might be just one of many inhabited worlds, and five centuries after him, another Greek thinker, Plutarch, suggested that the Moon might have been inhabited by extraterrestrials.
As you can see, the idea of extraterrestrial life is not a modern fad. Today, however, we already have both interesting places to look, as well as increasingly interesting search techniques, and a growing willingness to find something completely different from what we already know.
However, there is a small detail.
Even if we manage to find undeniable traces of life somewhere, wouldn't it make us feel better at not being able to quickly get to this place?
Ideal living conditions
Planet in ecosphere/ecozone/habitable zone,
that is, in a region around the star that is similar in shape to a spherical layer. Within such an area, physical and chemical conditions may exist that ensure the emergence, maintenance and development of living organisms. The existence of liquid water is considered the most important. The ideal conditions around the star are also known as the "Goldilocks Zone" - from a well-known children's fairy tale in the Anglo-Saxon world.
Adequate mass of the planet. A state of something similar to the amount of energy. The mass can't be too big, because strong gravity doesn't suit you. Too little, however, will not maintain the atmosphere, the existence of which, from our point of view, is a necessary condition for life.
Atmosphere + greenhouse effect. These are other elements that take into account our current outlook on life. The atmosphere heats up as the atmospheric gases interact with the star's radiation. For life as we know it, the storage of thermal energy in the atmosphere is of great importance. Worse, if the greenhouse effect is too strong. To be "just right", you need the conditions of the "Goldilocks" zone.
A magnetic field. It protects the planet from the hard ionizing radiation of the nearest star.
