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

Today, the search for alien life is limited only by humanity's technological capabilities.

Mars, the closest to Earth, recently departed the InSight probe, the landing of which NASA broadcast live.Astrobiologists are not only interested in the Red Planet in the Solar System.Venus, Jupiter's moon Europa, Enceladus and Titan, orbiting Saturn, can bebe 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.

ExoplanetsPlanets orbiting stars other than the Sunabout 100 billion such exoplanets in the Milky Way galaxy, and up to 20 billion of them could beto be like the 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.

Nevertheless, astronomers are positive and put forward hypotheses about imminent sensations on a cosmic scale.Such confidence is the result not of space exploration, but of the Earth.On the home planet of humans, there are already the necessary conditions for imitation of 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 to the archaeal domain, which includes living organisms extremophiles.This species is able to survive in 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 to those in the ocean of Europa.

Whether extremophiles survive in space is an open question, but the presence of water on astronomical bodies is encouragingIn the next five years, scientists will not acquire precious samples of ice or soil from potentially habitable worlds, so experiments to detect microorganisms continue where Earth is easily confused with an 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.

Studies of microorganisms in the upper atmosphere have been conducted since the 1930s, and earlier they required much more money and human resources.Pilot Charles Lindbergh took to the skies over the Atlantic to take atmospheric samples - during such "sorties" the monoplane was flown by the aviator's wife.Airplanes are well suited to the upper atmosphere, but they can't go higher, into the stratosphere and mesosphere.Less dense streams simply do not hold the devices.

In the 70s, technologies for studying the stratosphere wereimproved. Balloons and rockets began to be launched into the sky - they literally “took strokes” of the air shell, then returned them to Earth. Early results were not reliable: the devices were not sterilized. Modern scientists are faced with the task of confirming and clarifying the data of the 20th century.

David Smith, an astrobiologist at NASA, exploresstratosphere and upper atmosphere. Environmental data is collected using a Gulfstream III jet capable of reaching stratosphere altitudes. The cascade sampler forces air through thin impact plates with microscopic holes. The principle of this method resembles a sieve: dust and microorganisms settle on the plates and are delivered down to the Earth.

Smith himself believes that microorganisms cannotgrow or reproduce at stratosphere altitude: too cold and dry. But this environment is well suited for “preservation”: organisms survive 10–50 km from the Earth. Staying in one place, traveling in currents of rarefied air, reaching the troposphere, microorganisms “wait” to 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 stratospheric balloon was designed by a SwissAuguste Piccard for the study of cosmic rays. The scientist made the first flight on the new device in 1931, but in almost 100 years of its history the device has still not left the research toolbox.

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 stratospheric balloon turned out to beso large that their discovery at stratosphere heights was a surprise. It is almost impossible that they were brought from Earth: such strong volcanic eruptions have not occurred in the last three years. Biologist Milton Wainwright believes that the hypothesis of the alien origin of these microorganisms is quite possible.

Theory of Panspermia- hypothesis of the origin 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

In the wake of the general space fever in the 60sScience popularizer and astronomer Carl Sagan suggested that Venus's upper atmosphere might hide residual microorganisms that once existed on the planet's cool surface. Today, bacteria will not survive on a surface that is constantly hot due to the Venusian greenhouse effect - temperatures reach 465 ° C, and atmospheric pressure is 92 times higher than Earth's.

But terrestrial experiments in the stratosphere helpsubstantiate the hypothesis about 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 reaches60 ° C- hot, but livable. The pressure stops at 775 mmHg. Art.

At the same time, the chemical composition of the upper layers of Venusmore acidic than the earth: sulfuric acid, carbon dioxide and drops of water. For extremophiles like those on Earth, even such conditions will not seem lethal. If life on Earth has proven anything, it is that it survives in the most unexpected places - in boiling springs and under the ice of permafrost. Rakesh Mogul, co-author of the paper on life on Venus, states: “On Earth, life can thrive in extremely acidic conditions, can feed on carbon dioxide or produce sulfuric acid on its own.” Therefore, the guess about the alien origin of microbes that have settled on Earth does not seem fantastic.

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

Benefits in the study of alien lifenot only Antarctic subglacial lakes, but also glacial reservoirs of Chile. In the Andes, on the lakes Laguna Negra and Lo Encasado, scientists are testing devices for detecting microorganisms. Andean waters have few nutrients, and the sun penetrates the water bodies with ultraviolet rays. These lakes are real cemeteries, because traces of once living microorganisms settle at the bottom as biomolecules. A recent study published in the journal Astrobiology reveals how microfossils could 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, LDChip is used -a biosensor chip with 450 antibodies that detects proteins or DNA from ancient or modern life. This is the main part of the Signs of Life Detector (SOLID) device, which collects up to 2 g of soil and ice. They are being examined for biomaterials. The tool is convenient because the results can be deciphered in the field.

In sediments from the bottom, sulfate-reducing bacteria, methane-producing archaea, and exopolymer substances—products of gammaproteobacteria—were found.

Professor Don Cowan, microbial researcherin ecology from the University of Pretoria in South Africa, says: “All of the research results could help identify the same elements in astrobiological samples from Mars, which would provide evidence of alien life.” The wider the library of biomarkers becomes, the higher the accuracy of studies of alien samples. Universal results are determined: how bacteria are preserved, how they react to radiation and the environment. The new information is being used to improve tests that detect life.