The «Test» experiment, in which astronauts collect fine sediment from various surfaces outside the International Space Station, has been going on for almost 15 years. On Earth, scientists study the samples delivered to find out whether there are microorganisms on the surface of the ISS that have retained their viability and how they got there. Elena Shubralova, chief specialist at TsNIIMash, spoke about this, as well as how far life can exist from Earth, how microorganisms affect the durability of man-made space structures, and the fact that life may not have been brought to our planet from space, but rather that the Earth is spreading life into outer space, in an interview with special correspondent Denis Kaiyran.
– Why is the «Test» experiment being carried out on the outer surface of the ISS?
– The knowledge that humans have today does not allow us to think about life that originated on Earth and is concentrated only in the biosphere of our planet. The main question that we are trying to answer with the «Test» experiment is whether there is a boundary to the Earth's biosphere. To do this, it was important to get an idea of whether microorganisms remain viable in the conditions of open space, as well as how chemically aggressive the environment can be, whether microorganisms can travel in space, what settles on the surface of the ISS and how it can affect the station's materials.
The practice of operating orbital stations for 50 years has shown that microorganisms survive perfectly well inside their hermetically sealed volume. In domestic and foreign experiments on the outer surface of the ISS, microorganisms placed in special devices in open space also retain viability. However, the exposed biological objects are protected there, which does not correspond to the impact of the full range of factors of open space and, in particular, the aggressive influence of the near-object environment.
The outer surface of the ISS modules and its structural elements is almost 8.5 thousand square meters and is an ideal experimental base, accessible for studying the entire composition of finely dispersed matter deposited on its surface, including bacteria and fungal spores viable in the aggressive environment of the near-object space. Since 2010, as part of the «Test» experiment, samples of cosmic dust in its natural state from the outer surface of the Russian segment of the ISS have been regularly delivered to Earth.
The experiment is being conducted by the leading organizations of the Roscosmos State Corporation, TsNIIMash and the Rocket and Space Corporation (RSC) Energia, with the participation of the Institute of Medical and Biological Problems (IMBP) of the Russian Academy of Sciences, the Gamaleya National Research Center of Epidemiology and Microbiology, the RUDN Medical Institute, the Educational, Scientific and Production Complex of MIPT, the Joint Institute for High Temperatures (JIHT) of the Russian Academy of Sciences, and the All-Russian Research Institute of Physical, Technical and Radiotechnical Measurements (VNIIFTRI).
– The space experiment «Test» is more than 10 years old. Why is it taking so long to conduct it on the ISS?
– During the sessions, 39 samples were collected on various modules, from various surfaces and materials, thermal control screens, screen-vacuum thermal insulation, portholes, in areas facing the Earth and away from the Earth, on side surfaces, different in illumination and incident flow. The work is big, it takes a lot of time, and a spacewalk lasts six to seven hours and there are only two to three of them per year.
– What types of analysis are carried out on the obtained materials? What do they do with the samples on Earth?
– «Test» makes it possible to conduct biological and chemical analyses on one delivered material. The experimental device is implemented as a hermetic block with two blind cavities, into which cylindrical samplers with tampons treated with a preservative are screwed. The samples are hermetically sealed in a vacuum outside the spacecraft in sterile containers and delivered to Earth for laboratory studies of the chemical composition of the sediment and the presence of viable spores of microorganisms in it.
Specialists from various branches of science with the appropriate methods in the field of microbiology, molecular biology, physics and cosmochemistry, materials science are involved in laboratory analyses of the samples received.
– What percentage of the total amount of material studied is made up of “live” bacteria and fungi?
– Viable microbial spores were detected already in the first sampling session in 2010. As a result of microbiological analysis, viable microbial spores were detected in 50% of samples, molecular (genetic) analysis confirmed the presence of DNA and its fragments in 75% of samples. Fragments of Mycobacteria DNA of heterotrophic marine bacterioplankton living in the Barents Sea, DNA of the extremophilic bacterium Delftia, DNA of bacteria living in the soil of Madagascar and various water bodies, DNA of plant genomes, DNA of archaea and DNA of fungi Erythrobasidium and Cystobasidium, Bjerkandera were identified, DNA of the bacterium Acidovorax sp, previously isolated from sea water, was identified.
The presence on the surface of the ISS of representatives of typical terrestrial and marine genera of bacteria proved the presence of ascending transport of bacterial DNA from the troposphere to the ionosphere through the mechanism of turbulent electrothermodiffusion, capturing aerosol particles with the ascending branch of the global electric circuit, that is, the transfer of aerosol matter from the troposphere to the heights of the ionosphere.
Moreover, we found not only DNA, but also viable bacteria. They did not show DNA changes that would be expected given the proton flux density, helium nuclei and heavy charged particles, as well as the intensity and spectrum of UV radiation. Moreover, traces of metabolic activity of these microorganisms were detected.
The data obtained indicate that in the upper part of the ionosphere (400 kilometers), living organisms are not random inhabitants, but form a permanent community, previously attributed only to the aerobiosphere at altitudes of up to 70 kilometers.
– Is it possible to understand how long the viability of microflora on the surface of the pressurized housing is preserved?
– Naturally, the question arose about the duration of the viability of spores detected on the surface of the ISS, in the conditions of open space. A device was developed for exposing probes contaminated with detected microorganisms on the outer surface of the ISS.
In 2017, four Test-Exhibit devices with probes contaminated with the substances found on the outer surface of the ISS were placed in areas with different illumination and orientation relative to the velocity vector on the outer surface of the Pirs and Poisk modules. A comparative analysis of the results of exposure for one and almost two years made it possible to establish a trend towards a decrease in the number of bacteria and fungi. During the first year, the number of colony-forming units (CFU) decreased by three orders of magnitude, and during the second year, by two orders of magnitude compared to the first year. The proven preservation of the viability of microorganism spores for two years indicates the presence of a biochemically active environment on the surface of the ISS and the possibility of transporting microorganisms in outer space.
In 2025, two more devices will be delivered after 3.5 years in outer space (exposure began in June 2021).
– At what altitude from the Earth’s surface can living organisms exist? Can life survive on the surface of the Moon and in the vastness of deep space?
— The absence of mutational changes in the exposed bio-objects proves their resistance to the conditions of outer space. They not only survive, but also maintain an active metabolism, allowing them to repair mutations caused by cosmic rays, ultraviolet radiation, X-rays and the aggressive environment around the object.
In orbital vacuum conditions, when the ISS is periodically in shaded and sunny areas, dehydration of microorganisms that have landed on its surface occurs. This is similar to the method of lyophilization (or sublimation drying) of microorganisms for storage in collections, which has been widely and long used by microbiologists, and may be one of the factors for their long-term survival in space.
In addition, the exposure of collection samples in outer space as part of the «Test» experiment showed that lyophilized microorganisms are not killed by UV radiation and radiation. The postulate of sterilization of spacecraft by cosmic rays in outer space conditions is not confirmed. A hypothesis of «inverse panspermia» arises: the Earth can spread life into outer space.
– Are there microorganisms on the surface of the station that got there not from Earth, but from space?
– Microorganisms on the outer surface of the ISS can be of both terrestrial and extraterrestrial origin. This is an open system, during extravehicular work we can bring microorganisms and chemical elements to the station, as well as take something out into space during airlocking and work. Then it can be «inadvertently» delivered to Earth with returned cargo and astronauts.
The ISS crosses meteoroid streams of one or more of the 36 comet tails on each orbit. According to calculations by the Mission Control Center (MCC) of TsNIIMash, the ISS is in the area protected by the Earth for only 92.8 days per year, or 25.4% of the total time. Therefore, material for studying cometary matter can be obtained from the outer surface of the station.
It should be taken into account that particles of the 36 meteoroid streams can both bring and carry microorganisms from near-Earth space (NES) into interplanetary space.
– In addition to microorganisms, do scientists find comet dust, parts of micrometeorites and other elements of space «travelers»?
– Chemical analysis is also performed on particles on the surfaces of exposure devices and swabs contaminated with microorganism spores. The results allowed us to determine 65 elements in the samples, including radioactive isotopes. The presence of elements that are a constant component of meteoroids in their characteristic ratios of nickel to iron and cobalt to nickel indicates the presence of finely dispersed sediment of meteoroid matter on the surface of the ISS.
It is known that 0.05% of the mass of the entire Galaxy is made up of microscopic dust particles. Comet tail particles may contain molecules and particles of the interstellar medium adsorbed by them, from which information can be obtained about the chemical composition and structure of the interstellar matter. The surface of the ISS retains traces of the impact of micrometeoroids and comet tail particles.
Studies of two tissue bundles that had been on the outer surface of the ISS for almost nine years confirmed the aggressiveness of the external environment. Using a microscope, it was possible to see traces of tissue destruction and particles «put on» the fibers of the fabric.
In addition, when analyzing the fabric, the rare earth element holmium, which has paramagnetic properties, was found in significant concentrations. This lanthanide is found in a dispersed state on Earth. Its unexpectedly high content can only be due to dust from interplanetary space getting onto the surface of the ISS. Among space objects with an abnormally high holmium content, Przybylski's star stands out.
The «Test» experiment established for the first time the presence of traces of volcanic gases on the surface of a space object. Their marker was particles of the rare metal rhenium and radioisotope elements repeatedly detected during chemical analysis of fine sediment from the surface of the ISS. This is consistent with the almost constant detection of volcanic gas components in sediment samples on the surface of the ISS: sulfur, fluorine, chlorine, including radioactive isotopes of potassium, cesium, uranium, as in the gases of the fumarole fields of the Kudryavy volcano on Iturup Island. Their presence at an altitude of 400 kilometers above the Earth is a de facto confirmation of the Global Electric Circuit.
The main role in their delivery to such a height is played by thunderstorm activity during the development of typhoons and volcanic eruptions, as well as the possible formation of jets and sprites (lightning in reverse), connecting the stratosphere and ionosphere, on the «crest» of which a rapid injection of aerodisperse particles into the ionosphere is possible with a change in the phase state «aerosol-cosmosol».
It is interesting to note that viable spores of the fungus Mucor, previously found in the greenhouse of the ISS Zvezda service module, were found in a tissue bundle that had been on the outer surface of the ISS for 10 years. This species is known to be able to maintain the viability of its spores in extreme conditions and even in nuclear reactors. This is determined by the dense shell formed on the spores in such conditions and the decrease in the intensity of metabolic processes in the cytoplasm.
– Is it planned to conduct the «Test» experiment on the Russian Orbital Station (ROS)? What changes will be made, and what results do you expect, given the station's new orbit?
– Such easy-to-use devices as the Test and Exposure Device should be included in the standard equipment of the Russian Orbital Station (ROS), and sampling operations in various places of the station should be regular. This will allow us to assess the impact of changes in the inclination and altitude of the station's orbit on the permissible service life of orbital platforms, since this also depends on changes in physical environmental factors. In particular, on UV radiation, temperature changes, radiation, aggressive chemical environment, atomic oxygen, elements with high electron affinity (sulfur, fluorine, chlorine), radioactive elements (uranium, thorium, radium, cesium), chemical elements reaching the surface of the station, volcanic gases, cosmic dust and streams of micrometeoroid rains.
The importance of conducting research is determined by the inclination of the ROS, the movement of the station over dynamically changing polar (Arctic and Antarctic) zones of sharp warming. This is a long-term research task. Regular monitoring of the dynamics of fine sediment on the surface of the ROS will reveal dangerous aspects of changes in the Earth's exosphere. Space debris, expeditionary vehicles and multi-thousand orbital groups together define new dangerous aspects of the Earth's exosphere that must be monitored.