How studies of life in extreme conditions help us understand what forms of living organisms we will encounter in space and on other planets.
One evening in November 1938, the regular news broadcast on American radio was interrupted by an "emergency message": aliens had been discovered in New Jersey. Panic voices of eyewitnesses told about aggressive invaders. Shots rang out in the background, signaling that everything was very serious. The news, alas, turned out to be fake - it was just a radio show "War of the Worlds" by H. G. Wells. But not all listeners understood this.
Even decades later, the public's reaction to this "special message" remains a matter of controversy. Some claimed that thousands of people fled into the streets in panic. Others said they did not notice the intense social unrest and unrest. Be that as it may, it became clear to everyone: if someday aliens are really discovered, people will hardly be happy about this event.
But what if the first aliens were not armed to the teeth, intelligent and ruthless creatures, but tiny microorganisms, the likeness of which we can meet on our planet? What will this discovery bring us and how can it change our understanding of life?
The chances of finding microbial colonies outside of Earth are much higher than the chances of finding the Martians in Wells' fantasy. In fact, scientists can make the first discovery of alien life within 20 years - this is the period that NASA representatives are now calling. It will be a landmark event in the long history of human space exploration. But only a few will really pay attention to it. And in a few decades, such news may become routine, just as news about the discovery of new exoplanets at the beginning of our century has become routine.
Michael Varnum, a psychologist at the University of Arizona, conducted several studies to find out how people would react to the news of the discovery of unknown microbes outside the Earth. It turned out that people are even more positive about alien microbes than artificial organisms created by humans in scientific laboratories. In 2017, astrophysicist Rene Heller conducted his own experiment, asking volunteers to help him decode a fake alien signal. Hundreds of people responded to his message. As Heller happily realized, today such discoveries generate more interest than horror in people.
At the moment, we have not yet discovered anything living on other planets: astrobiology remains a science without an object. But the study of various organisms on the good old Earth can already tell us a lot about what to expect from the life that we will meet in space. Over the past hundred years, the discoveries of biologists have significantly changed our understanding of the concept of living things. Now we know that life is much more complex and diverse than it seemed to us before.
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This is not Mars, this is the Atacama Desert in Chile, the conditions in which are indeed very similar to those of Mars.
Deserts, space, ocean
The idea that life can exist on other planets was expressed by Democritus. Its next apologist was the Italian magician and reformer Giordano Bruno. This idea was truly entrenched in the Age of Enlightenment, and since then has experienced only one short period of decline. At the beginning of the 20th century, many were convinced that there was an advanced civilization on Mars that had built a gigantic network of canals for irrigating fields. The channels were clearly visible through a telescope, and they were seen by completely different people from different parts of the planet. In reality, "Martian irrigation" turned out to be an optical illusion. Despite this, the hypothesis of the existence of life on Mars and other planets of the solar system today seems even more plausible than before.
In 2015, biologists from Arizona and Berlin Technical Universities examined soil samples from the Chilean Atacama Desert, one of the driest places on the planet. In many ways, it resembles the surface of Mars. It turned out that even in such an inhospitable climate, various types of bacteria can survive and reproduce. During a long drought, they fall into suspended animation, and then, being near the water, immediately come to life. In hibernation, these bacteria can survive for hundreds or even thousands of years. The oceans left the surface of Mars about 2.5 million years ago. But in the bowels of the planet, there may still be colonies of bacteria that will wait for their researchers.
In the late 1970s, a real revolution in biology was made by the discovery of thermophilic bacteria, which do not need sunlight and can inhabit the depths of the ocean, creating entire underwater ecosystems. These bacteria live near geothermal springs, where water is in close contact with the mantle. The temperature in such springs can reach 350 ° C. Extremophile bacteria, unlike most other species, receive their energy not from the sun, but from metals dissolved in water. These bacteria feed on worms and molluscs, and those, in turn, are eaten by larger predators. The discovery surprised even the scientists themselves.
Holger Jannasch, oceanologist, participant of the first studies of thermophilic bacteria:
We were stunned by the thought that solar energy, which is so important for the existence of life on our planet, could be replaced by earthly energy. […] This is a completely new concept and, in my opinion, one of the main biological discoveries of the 20th century.
Hydrothermal vents, home to unusual species of bacteria
We may well find underwater ecosystems similar to the terrestrial one on the moons of Saturn and Jupiter - Europa and Enceladus. There, too, there are oceans of salt water and significant geothermal activity. Enceladus' water is similar to Lake Mono in California. There is a lot of salt and soda in this lake, and therefore there are no fish - but unusual bacteria live in it, which have adapted well to concentrations of arsenic that are deadly for other organisms. Similar bacteria probably live on Enceladus.
In 2015, the American space station Cassini-Huygens flew past Enceladus - straight through water plumes that rise several kilometers above the frozen surface of the satellite. In this water, scientists have managed to find hydrogen molecules. This means that under the ice of Enceladus, geological processes are taking place - just like on Earth. Consequently, the microorganisms of Enceladus (if they exist) can receive energy from carbon dioxide dissolved in water. This is the very reaction that lies at the base of the entire tree of life on Earth.
Several flights to Europe and Enceladus are planned for the 2030s. It is these celestial bodies, not counting Mars, that today are the main target for astrobiologists. Most likely, this is where we first find alien life. But first, you still need to get to her. It is not yet known how thick the ice sheets of Europa and Enceladus are - maybe only a few kilometers, or maybe several tens. Will bacteria and multicellular organisms be able to survive in such extreme conditions?
Back in the middle of the 20th century, Soviet scientists suggested that vast lakes of fresh water could be hidden under the ice of Antarctica. Ice in the interior of the continent turns into water - partly due to the enormous pressure of the ice masses, and partly due to the same geothermal activity. The existence of Lake Vostok, which got its name in honor of the Soviet station, was confirmed by radar in the 1960s and 1970s. In 2012, Russian researchers drilled a well to a depth of 3,769 meters, reached the water and took samples for analysis. In March 2013, scientists announced the discovery of a new type of bacteria in the samples, the DNA of which is only 86% identical with organisms known to science. Then this data was refuted, but traces of several unusual bacteria in the lake were still found.
Research in Antarctica is ongoing. A real breakthrough is worth waiting for when scientists get to the deeper layers of the lake - to the sources of geothermal activity, which saturate the water with minerals and are located at a depth of about 5 thousand meters.
Russian research station "Vostok", under which, at a depth of almost 4,000 meters, there is a large lake with fresh water.
If bacteria can live in the lakes of Antarctica - under enormous pressure and low temperature, “without light, without organic carbon dissolved in water, with highly diluted ions of basic substances, long-term isolation from surface biota for at least 14 million years and, probably, with excess of dissolved oxygen”- then they can live on other planets, which we previously considered unsuitable for life.
However, it is quite possible that alien life will not be built on earthly models. Titan's liquid lakes can be home to methanogens - organisms that use not water, but methane as a solvent. Planets with higher atmospheric temperatures can inhabit organisms built on a molecule of silicon, rather than carbon, as is customary on Earth. For many years, scientists have been debating whether viruses can be considered living organisms. The correct answer depends on which definition of life we use. If space exploration continues, this concept will be revised more than once.
When writing this article, materials from the book by astronomer John Willis were used “All these worlds are yours. Scientific searches for extraterrestrial life ", which is published by the publishing house" Alpina Publisher "in March this year.
Oleg Matfatov