A planet for experimentation: how scientists use Earth to search for alien life

Today, the search for alien life is limited only by the technological capabilities of mankind. On

closest to Earth Mars recently went probeInSight, the landing of which NASA broadcast live. Astrobiologists are not only interested in the Red Planet in the Solar System. The circle of potentially "inhabited" celestial bodies includes Venus, the satellite of Jupiter Europe, Enceladus and Titan, revolving around Saturn - they may contain living microorganisms or traces of life that once existed.

Conditions on these distant neighbors of the Earth are calledextreme. Venusian temperature does not allow to explore the hot surface of the planet, which is heated to 470 ° C, and the inaccessibility of Europe, Enceladus and Titan becomes an even greater obstacle for scientists: the nearest launch of the probe to Europe is scheduled for 2025, and the issue of similar projects for other satellites has not yet been resolved at all.

InSight probe on the surface of Mars. Image: NASA

Heavy Duty Space Telescopes Discoveredhumanity planets that exist outside the solar system. The famous Kepler was replaced by the improved exoplanetary telescope SPECULOOS, which will receive detailed images of the surfaces of the nearest exoplanets and smaller exosatellites. Astronomical objects of this type are also found outside our galaxy - scientists from the University of Oklahoma used microlensing to detect exoplanet clusters at a distance of 3.8 billion light years.

Exoplanets - planets revolving around other luminaries, exceptThe sun Today, scientists are aware of the existence of approximately 100 billion of such exoplanets in the Milky Way galaxy, and up to 20 billion of them may be similar to Earth.

Despite the huge amount of potentiallyinhabited planets, the task of finding extraterrestrial life is not facilitated. A team of astronomers at Washington State University led by Dirk Schulze-Makuch has developed a special classification scheme for exoplanets designed to facilitate cataloging - the Planetary Living Index Index (PHI) formula, which takes into account the hardness of the planet's surface, its possible atmosphere, energy source and chemical composition of the environment. The problem is that scientists cannot obtain data on the atmosphere of an exoplanet or exosatellite, the presence or absence of liquid water and, finally, possible organic elements on or under the object's surface.

However, astronomers are positive andhypothesize the forthcoming sensations of a cosmic scale. Such a certainty is the result of research not of the cosmos, but of the Earth. On the home planet of people already have the necessary conditions to imitate unfriendly external environments.

Destroy the life once appeared on the planet, it is difficult. The requirements for maintaining the simplest forms are simple: water, a constant source of energy, and being in a belt of planetary habitat.

The main interest of scientists is addressed to the archaea domain, towhich include living organisms extremophiles. This species is able to survive at extremely low and high temperatures, in alkaline and acidic environments. Such bacteria live, for example, in the subglacial lake “Vostok”, where pressure and temperature are comparable with similar indicators in the ocean of Europe.

Do extremophiles survive in space - openquestion, but the presence of water on astronomical bodies is encouraging scientists. In the next five years, scientists will not acquire precious samples of ice or soil from potentially inhabited worlds, therefore, experiments on the detection of microorganisms continue where the Earth is easily confused with the alien world.

Jets and stratostats for Venus

Scientists have proven that bacteria are capable of flying oreven soar, for example, in the second layer of the Earth’s atmosphere - the stratosphere. If a person finds himself in such a space, it is unlikely he will be able to live for a long time - a cold and dry environment rises 10-50 km from the surface of the Earth. Temperatures of –56 ° C and jet winds at a speed of 160 km / h make the stratosphere unsuitable for life. Breathing also does not work: ozone harbors the entire earthly world from ultraviolet from space, but above the ozone layer, at a distance of 32 km from the surface of the planet, there is already no corresponding protection. It seems that even extremophiles have nothing to do in the Earth's stratosphere.

Biologists say the opposite. Studies of microorganisms in the upper atmosphere have been conducted since the 30s, and earlier they required much more financial and human resources. Pilot Charles Lindberg rose into the sky over the Atlantic to take atmospheric samples - during such "sorties" the aviator's wife drove the monoplane. Airplanes are well suited for the upper atmosphere, but they cannot climb higher - into the stratosphere and mesosphere. Less dense flows simply do not hold apparatus.

In the 70s, the technology of studying the stratosphere wasimproved. They began to launch balloons and rockets into the sky — they literally “took swabs” of the air envelope, then returning them to Earth. Early results were not reliable: the instruments were not sterilized. Modern scientists face the task of confirming and clarifying data from the 20th century.

David Smith, astrobiologist from NASA, exploresstratosphere and upper atmosphere. Data on the environment is collected using a Gulfstream III jet capable of rising to the height of the stratosphere. The cascade sampler passes air through thin shock plates with microscopic holes. The principle of this method resembles a sieve: dust and microorganisms settle on the plates and are delivered down to Earth.

Smith himself believes that microorganisms cannotgrow or multiply at the height of the stratosphere: too cold and dry. But this environment is well suited for “conservation”: organisms survive 10–50 km from Earth. Staying in one place, traveling in streams of rarefied air, reaching the troposphere, microorganisms “wait” for a return to the comfortable environment of the planet.

You can explore the upper layers of the atmosphere without a jet. Stratostat - a special device of the type of aerostat capable of raising a person to the height of the stratosphere.

The first stratostat was designed by the SwissAuguste Picard to study cosmic rays. The scientist made the first flight on a new device in 1931, but for almost 100 years of its history, the device has not yet left the research toolkit.

Scientists from the University of Sheffield have discoveredmicroorganisms brought to Earth from the stratosphere. In 2013, a team of researchers launched a special balloon at an altitude of 27 km, and right at the time when Perseid meteor shower rained over the Earth.

The size of the particles brought by the stratosphericso large that their detection at the height of the stratosphere came as a surprise. The fact that they were brought from the Earth is almost impossible: over the past three years, there have not been such strong volcanic eruptions. Biologist Milton Wainwright believes that the hypothesis of an alien origin of these microorganisms is quite possible.

Theory of Panspermia - the hypothesis of the emergence of earthly life. Explains the appearance of life on Earth thanks to a certain comet that brought the first microorganisms to the planet.

The results obtained by the Wainwright team couldchange ideas about life - it continues to arrive on Earth from outer space. The results of isotope fractionation did not confirm encouraging conclusions: the ratio of isotopes of microorganisms turned out to be the same as that of terrestrial samples. Nevertheless, this experience proves that bacteria survive in the stratosphere.

Venusian atmosphere

On a wave of universal space rush in the 60sscience popularist and astronomer Karl Sagan suggested that the upper atmosphere of Venus could hide the residual microorganisms that once existed on the cool surface of the planet. Today, the bacteria will not survive on the surface, constantly burning hot because of the Venusian greenhouse effect - the temperature reaches 465 ° С, and the atmospheric pressure is 92 times more than the Earth one.

But terrestrial experiments in the stratosphere helpsubstantiate the hypothesis of the existence of life on Venus. But in the clouds. A recent study published in the journal Astrobiology reports that the temperature, pressure and chemical composition of the atmosphere 48 km from the surface of the planet are suitable for the survival of huge colonies of alien bacteria.

The temperature in the stratosphere of Venus reaches 60 ° C - hot, but acceptable for life. The pressure stops at 775 mm Hg. Art.

The chemical composition of the upper layers of Venusmore acidic than the earth's: sulfuric acid, carbon dioxide and water droplets. For extremophiles like the earth, even such conditions do not seem fatal. If life on Earth has proved something, it is that it survives in the most sudden places - in boiling springs and under the ice of permafrost. Rakesh Mogul, co-author of the article on life on Venus, states: "On Earth, life can thrive in extremely acidic conditions, it can feed on carbon dioxide or produce sulfuric acid on its own." Therefore, the conjecture about the alien origin of microbes registered on Earth does not seem fiction.

Pictures of Venus show dark spots in the atmospherethe planets. They change shape, size and position, but do not disappear completely. Modern analyzes show that the spots are made of points that correspond to terrestrial bacteria in size. The spectra of light absorbed by the particles of Venus are also similar to the spectra of the same terrestrial bacteria.

Underwater research

Benefit in the study of alien life bringnot only the Antarctic subglacial lakes, but also the glacial reservoirs of Chile. In the Andes, on the lakes of Laguna Negra and Lo Encasado, scientists are testing microorganism detection devices. In the Andean waters there are few nutrients, and the sun penetrates water through ultraviolet rays. These lakes are real cemeteries, because traces of once-living microorganisms settle on the bottom as biomolecules. A recent study published in the journal Astrobiology tells how micro-stations will help detect bacteria on Mars or Titan.

High mountain lakes of the Andes carry researchers tothe past of Mars, where it is believed that lakes with liquid water were subjected to the same exposure to UV radiation. So, Martian bacteria could adapt to the rays just like Chilean microorganisms.

To obtain biomolecules use LDChip -450-biosensor chip detecting proteins or DNA of ancient or modern life. This is the main part of the device Signs of Life Detector (SOLID), collecting up to 2 g of soil and ice. They are examined for biomaterials. The tool is convenient because you can decipher the results in the field.

In the sediments from the bottom, sulfate-reducing bacteria, archaeans that form methane, and exopolymer substances, products of gamma proteobacteria, were found.

Professor Don Cowan, Microbial Researcherecology from the University of Pretoria in South Africa, said: "All research results can help identify the same elements in astrobiological samples from Mars, which will be evidence of alien life." The wider the biomarker library becomes, the higher the accuracy of alien specimen research. The universal results are determined: how bacteria are stored, how they react to radiation and the environment. New information is used to improve tests that discover life.