A comic about how scientists will explore Mars in the fight against cosmic radiation.
It examines several avenues for future research to protect astronauts from radiation, including drug therapy, genetic engineering and hibernation technology. The authors also note that radiation and aging kill the body in similar ways, and suggest that ways to combat one may also work against the other. An article with a fighting motto in the title: Viva la radioresistance! ("Long Live Radiation Resistance!") was published in the magazine Oncotarget.
“The renaissance of space exploration will likely lead to the first human missions to Mars and deep space. But to survive in conditions of increased cosmic radiation, people will have to become more resistant to external factors. In this article, we propose a methodology for achieving enhanced radioresistance, stress resistance, and aging resistance. While working on the strategy, we brought together leading scientists from Russia, as well as from NASA, the European Space Agency, the Canadian Radiation Center and more than 25 other centers around the world. On Earth, radioresistance technologies will also be useful, especially if “ side effect“There will be healthy longevity,” comments Alexander Zhavoronkov, associate professor at MIPT.
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We will make sure that radiation does not prevent humanity from conquering space and colonizing Mars. Thanks to scientists, we will fly to the Red Planet and have a disco and barbecue there .
Space versus man
"IN cosmic scale our planet is just a small ship, well protected from cosmic radiation. The Earth's magnetic field deflects solar and galactic charged particles, thereby significantly reducing the level of radiation on the planet's surface. During long-distance space flights and colonization of planets with very weak magnetic fields (for example, Mars), there will be no such protection, and astronauts and colonists will be constantly exposed to streams of charged particles with enormous energy. In fact, the space future of humanity depends on how we overcome this problem,” shares the head of the department of experimental radiobiology and radiation medicine of the Federal Medical Biophysical Center named after A. I. Burnazyan, professor of the Russian Academy of Sciences, employee of the laboratory for the development of innovative medicines MIPT Andreyan Osipov.
Man is defenseless against the dangers of space: solar radiation, galactic cosmic rays, magnetic fields, the radioactive environment of Mars, the Earth's radiation belt, microgravity (weightlessness).
Humanity has seriously set its sights on colonizing Mars - SpaceX promises to deliver humans to the Red Planet as early as 2024, but some significant problems have still not been resolved. Thus, one of the main health hazards for astronauts is cosmic radiation. Ionizing radiation damages biological molecules, particularly DNA, leading to various violations: nervous system, of cardio-vascular system and, mainly, to cancer. Scientists propose to join forces and, using the latest advances in biotechnology, increase human radioresistance so that he can conquer the vastness of deep space and colonize other planets.
Human defense
The body has ways to protect itself from DNA damage and repair it. Our DNA is constantly exposed to natural radiation, as well as active forms oxygen (ROS), which are formed during normal cellular respiration. But when DNA is repaired, especially in cases of severe damage, errors can occur. The accumulation of DNA damage is considered one of the main causes of aging, so radiation and aging are similar enemies of humanity. However, cells can adapt to radiation. It has been shown that a small dose of radiation can not only do no harm, but also prepare cells to face higher doses. Currently, international radiation protection standards do not take this into account. Recent research suggests that there is a certain radiation threshold, below which the principle “hard in training, easy in battle” applies. The authors of the article believe that it is necessary to study the mechanisms of radio adaptability in order to take them into service.
Ways to increase radioresistance: 1) gene therapy, multiplex genetic engineering, experimental evolution; 2) biobanking, regenerative technologies, tissue and organ engineering, induced cell renewal, cell therapy; 3) radioprotectors, geroprotectors, antioxidants; 4) hibernation; 5) deuterated organic components; 6) medical selection of radioresistant people.
Head of the Laboratory of Genetics of Life Span and Aging at MIPT, Corresponding Member of the Russian Academy of Sciences, Doctor biological sciences Alexey Moskalev explains: “Our long-term studies of the effects of low doses of ionizing radiation on the lifespan of model animals have shown that small damaging effects can stimulate the cells’ and body’s own defense systems (DNA repair, heat shock proteins, removal of non-viable cells, innate immunity). However, in space, humans will encounter a larger and more dangerous range of radiation doses. We have accumulated a large database of geroprotectors. The knowledge gained suggests that many of them function according to the activation mechanism reserve capabilities, increasing stress resistance. It is likely that such stimulation will help future colonizers of outer space.”
Astronaut Engineering
Moreover, radioresistance differs among people: some are more resistant to radiation, others less. Medical selection of radioresistant individuals involves taking cell samples from potential candidates and comprehensively analyzing the radioadaptivity of these cells. Those who are most resistant to radiation will fly into space. In addition, it is possible to conduct genome-wide studies of people living in areas with high level background radiation or those who encounter him by profession. Genomic differences in people who are less susceptible to cancer and other radiation-related diseases can in the future be isolated and “instilled” into astronauts using modern methods genetic engineering, such as genome editing.
There are several options for which genes need to be introduced to increase radioresistance. First, antioxidant genes will help protect cells from reactive oxygen species produced by radiation. Several experimental groups have already successfully tried to reduce sensitivity to radiation using such transgenes. However, this method will not save you from direct exposure to radiation, only from indirect exposure.
You can introduce genes for proteins responsible for DNA repair. Such experiments have already been carried out - some genes really helped, and some led to increased genomic instability, so this area awaits new research.
A more promising method is the use of radioprotective transgenes. Many organisms (such as tardigrades) have high degree radioresistance, and if we find out what genes and molecular mechanisms are behind it, they can be translated into humans using gene therapy. To kill 50% of tardigrades, you need a radiation dose 1000 times greater than lethal for humans. Recently, a protein was discovered that is believed to be one of the factors for such endurance - the so-called damage suppressor Dsup. In an experiment with a human cell line, it turned out that the introduction of the Dsup gene reduces damage by 40%. This makes the gene a promising candidate for protecting humans from radiation.
Fighter's First Aid Kit
Medicines that increase radiation protection organism are called “radioprotectors”. To date, there is only one FDA-approved radioprotector. But the main signaling pathways in cells that are involved in the processes of senile pathologies are also involved in responses to radiation. Based on this, geroprotectors - drugs that reduce the rate of aging and extend life expectancy - can also serve as radioprotectors. According to the Geroprotectors.org and DrugAge databases, there are more than 400 potential geroprotectors. The authors believe that it will be useful to consider existing medications for the presence of gero- and radioprotective properties.
Since ionizing radiation also acts through reactive oxygen species, redox absorbers, or, more simply put, antioxidants such as glutathione, NAD and its precursor NMN, can help cope with radiation. The latter appear to play an important role in the response to DNA damage and are therefore of great interest from the point of view of protection against radiation and aging.
Hypernation in hibernation
Soon after the launch of the first space flights, the leading designer of the Soviet space program, Sergei Korolev, began developing an ambitious project for a manned flight to Mars. His idea was to put the crew into a state of hibernation during long space travel. During hibernation, all processes in the body slow down. Experiments with animals show that in this state, resistance to extreme factors increases: lower temperatures, lethal doses of radiation, overloads, and so on. In the USSR, the Mars project was closed after the death of Sergei Korolev. And currently the European space agency is working on the Aurora project for flights to Mars and the Moon, which considers the option of hibernating astronauts. ESA believes that hibernation will provide greater safety during long-duration automated flights. If we talk about the future colonization of space, then it is easier to transport and protect from radiation a bank of cryopreserved germ cells, rather than a population of “ready” people. But this will clearly not be in the near future, and perhaps by that time radio protection methods will be developed enough so that people are not afraid of space.
Heavy artillery
All organic compounds contain carbon-hydrogen bonds (C-H). However, it is possible to synthesize compounds that contain deuterium, a heavier analogue of hydrogen, instead of hydrogen. Due to its greater mass, bonds with deuterium are more difficult to break. However, the body is designed to work with hydrogen, so if too much hydrogen is replaced with deuterium, it can lead to bad consequences. It has been shown in various organisms that the addition of deuterated water increases lifespan and has anti-cancer effects, but more than 20% deuterated water in the diet begins to have toxic effects. The authors of the article believe that preclinical trials should be conducted and a safety threshold should be sought.
An interesting alternative is to replace not hydrogen, but carbon with a heavier analogue. 13 C is only 8% heavier than 12 C, while deuterium is 100% heavier than hydrogen - such changes will be less critical for the body. However, this method will not protect against N-H gap And O-H communication, which hold DNA bases together. In addition, the production of 13 C is currently very expensive. However, if production costs can be reduced, carbon replacement could provide additional human protection from cosmic radiation.
“The problem of radiation safety of participants space missions belongs to the class very much complex problems, which cannot be solved within one scientific center or even an entire country. It is for this reason that we decided to bring together specialists from leading centers in Russia and around the world in order to learn and consolidate their vision of ways to solve this problem. In particular, among the Russian authors of the article there are scientists from the FMBC named after. A.I. Burnazyan, Institute of Biomedical Problems of the Russian Academy of Sciences, MIPT and other world-famous institutions. During the work on the project, many of its participants met each other for the first time and now plan to continue the joint research they had begun,” concludes project coordinator Ivan Ozerov, radiobiologist, head of the group for the analysis of cellular signaling pathways at the Skolkovo startup Insilico.
Designer Elena Khavina, MIPT press service
As already mentioned, as soon as the Americans began their space program, their scientist James Van Allen accomplished enough important discovery. First American artificial satellite, which they launched into orbit, was much smaller than the Soviet one, but Van Allen thought of attaching a Geiger counter to it. Thus, what was expressed at the end of the 19th century was officially confirmed. The outstanding scientist Nikola Tesla hypothesized that the Earth is surrounded by a belt of intense radiation.
Photograph of Earth by astronaut William Anders
during the Apollo 8 mission (NASA archives)
Tesla, however, was considered a great eccentric, and academic science- even crazy, so his hypotheses about the giant generated by the Sun electric charge have been shelved for a long time, and the term “ sunny wind"brought nothing but smiles. But thanks to Van Allen, Tesla's theories were revived. At the instigation of Van Allen and a number of other researchers, it was established that radiation belts in space begin at 800 km above the Earth's surface and extend up to 24,000 km. Since the radiation level there is more or less constant, the incoming radiation should be approximately equal to the outgoing radiation. Otherwise, it would either accumulate until it “baked” the Earth, as in an oven, or it would dry up. On this occasion, Van Allen wrote: “Radiation belts can be compared to a leaky vessel, which is constantly replenished from the Sun and flows into the atmosphere. A large portion of solar particles overflows the vessel and splashes out, especially in the polar zones, leading to auroras, magnetic storms and other similar phenomena."
Radiation from the Van Allen belts depends on the solar wind. In addition, they appear to focus or concentrate this radiation within themselves. But since they can only concentrate in themselves what came directly from the Sun, one more question remains open: how much radiation is in the rest of the cosmos?
Orbits of atmospheric particles in the exosphere(dic.academic.ru)
The Moon does not have Van Allen belts. She also has no protective atmosphere. It is open to all solar winds. If a strong solar flare had occurred during the lunar expedition, a colossal flow of radiation would have incinerated both the capsules and the astronauts on the part of the lunar surface where they spent their day. This radiation is not just dangerous - it is deadly!
In 1963, Soviet scientists told renowned British astronomer Bernard Lovell that they did not know of a way to protect astronauts from the deadly effects of cosmic radiation. This meant that even the much thicker metal shells of the Russian devices could not cope with the radiation. How could the thinnest (almost like foil) metal used in American capsules protect astronauts? NASA knew this was impossible. The space monkeys died less than 10 days after returning, but NASA never told us the real reason their death.
Monkey astronaut (RGANT archive)
Most people, even those knowledgeable in space, are not aware of the existence of deadly radiation permeating its expanses. Oddly enough (or perhaps just for reasons that can be guessed), in the American “Illustrated Encyclopedia of Space Technology” the phrase “cosmic radiation” does not appear even once. And in general, American researchers (especially those associated with NASA) avoid this topic a mile away.
Meanwhile, Lovell, after talking with Russian colleagues who were well aware of cosmic radiation, sent the information he had to NASA administrator Hugh Dryden, but he ignored it.
One of the astronauts who allegedly visited the Moon, Collins, mentioned cosmic radiation only twice in his book:
"At least the moon was far beyond earth belts Van Allen, which foreshadowed a good dose of radiation for those who were there, and a fatal dose for those who lingered.”
“Thus, the Van Allen radiation belts surrounding the Earth and the possibility of solar flares require understanding and preparation to avoid exposing the crew to increased doses of radiation.”
So what does “understand and prepare” mean? Does this mean that beyond the Van Allen belts, the rest of space is free of radiation? Or did NASA have a secret strategy for sheltering from solar flares after adopting final decision about the expedition?
NASA claimed that it could simply predict solar flares, and therefore sent astronauts to the Moon when flares were not expected and the radiation danger to them was minimal.
While Armstrong and Aldrin were doing work in outer space
on the surface of the moon, Michael Collins
placed in orbit (NASA archive)
However, other experts say: “It is only possible to predict the approximate date of future maximum radiation and its density.”
The Soviet cosmonaut Leonov nevertheless went into outer space in 1966 - however, in a super-heavy lead suit. But after just three years American astronauts jumped on the surface of the Moon, and not at all in super-heavy spacesuits, but rather quite the opposite! Maybe over the years, experts from NASA have managed to find some kind of ultra-light material that reliably protects against radiation?
However, researchers suddenly find out that at least Apollo 10, Apollo 11 and Apollo 12 set off precisely during those periods when the number of sunspots and the corresponding solar activity was approaching its maximum. Generally accepted theoretical maximum of 20th solar cycle lasted from December 1968 to December 1969. During this period, the Apollo 8, Apollo 9, Apollo 10, Apollo 11, and Apollo 12 missions supposedly moved beyond the protection zone of the Van Allen belts and entered cislunar space.
Further study of monthly graphs showed that single solar flares are a random phenomenon, occurring spontaneously over an 11-year cycle. It also happens that in the “low” period of the cycle it happens a large number of outbreaks in a short period of time, and during the “high” period - a very small number. But what is important is that it is very strong flares can occur at any time during the cycle.
During the Apollo era, American astronauts spent total almost 90 days. Since radiation from unpredictable solar flares reaches the Earth or Moon in less than 15 minutes, the only way to protect against it would be to use lead containers. But if the rocket power was enough to lift such excess weight, then why was it necessary to go into space in tiny capsules (literally 0.1 mm of aluminum) at a pressure of 0.34 atmospheres?
This despite the fact that even thin layer The protective coating, called “mylar,” according to the Apollo 11 crew, turned out to be so heavy that it had to be urgently removed from the lunar module!
It seems that NASA selected special guys for lunar expeditions, albeit adjusted for circumstances, cast not from steel, but from lead. The American researcher of the problem, Ralph Rene, was not too lazy to calculate how often each of the supposedly completed lunar expeditions should have been affected by solar activity.
By the way, one of the authoritative employees of NASA (distinguished physicist, by the way) Bill Modlin, in his work “Prospects for Interstellar Travel,” frankly reported: “Solar flares can emit GeV protons in the same energy range as most cosmic particles, but much more intense . The increase in their energy with increased radiation poses a particular danger, since GeV protons penetrate several meters of material... Solar (or stellar) flares with the emission of protons are a periodically occurring very serious danger in interplanetary space, which provides a radiation dose of hundreds of thousands of roentgens in a few hours at the distance from the Sun to the Earth. This dose is lethal and millions of times higher than permissible. Death can occur after 500 roentgens in a short period of time.”
Yes, the brave American guys then had to shine worse than the fourth Chernobyl power unit. " Space particles dangerous, they come from all directions and require at least two meters of dense screen around any living organisms.” But the space capsules that NASA demonstrates to this day were just over 4 m in diameter. With the thickness of the walls recommended by Modlin, the astronauts, even without any equipment, would not have fit into them, not to mention the fact that there would not have been enough fuel to lift such capsules. But, obviously, neither the leadership of NASA nor the astronauts they sent to the Moon read their colleague’s books and, being blissfully unaware, overcame all the thorns on the road to the stars.
However, maybe NASA actually developed some kind of ultra-reliable spacesuits for them, using (obviously, very classified) ultra-light material that protects against radiation? But why wasn’t it used anywhere else, as they say, in for peaceful purposes? Well, okay, they didn’t want to help the USSR with Chernobyl: after all, perestroika had not yet begun. But, for example, in 1979 in the same USA at the Three Mile Island nuclear power plant there was a major accident reactor unit, which led to a meltdown of the reactor core. So why didn’t the American liquidators use space suits based on the much-advertised NASA technology, costing no less than $7 million, to eliminate this delayed-action nuclear mine on their territory?..
Since their appearance on Earth, all organisms have existed, developed and evolved under constant exposure to radiation. Radiation is the same natural phenomenon as wind, tides, rain, etc.
Natural background radiation (NBR) was present on Earth at all stages of its formation. It was there long before life and then the biosphere appeared. Radioactivity and the accompanying ionizing radiation were a factor that influenced the current state of the biosphere, the evolution of the Earth, life on Earth and the elemental composition solar system. Any organism is exposed to the radiation background characteristic of a given area. Until the 1940s it was caused by two factors: the decay of radionuclides natural origin, located both in the habitat of a given organism, and in the organism itself, and by cosmic rays.
Sources of natural (natural) radiation are space and natural radionuclides contained in natural form and concentrations in all objects of the biosphere: soil, water, air, minerals, living organisms, etc. Any of the objects around us and we ourselves are radioactive in the absolute sense of the word.
The world's population receives the main dose of radiation from natural sources radiation. Most of them are such that it is absolutely impossible to avoid exposure to radiation from them. Throughout the history of the Earth different types radiation penetrates the earth's surface from space and comes from radioactive substances located in earth's crust. A person is exposed to radiation in two ways. Radioactive substances can be outside the body and irradiate it from the outside (in this case we talk about external irradiation) or they can end up in the air that a person breathes, in food or water and get inside the body (this method of irradiation is called internal).
Any inhabitant of the Earth is exposed to radiation from natural sources of radiation. This depends, in part, on where people live. Radiation levels in some places on the globe, especially where radioactive rocks occur, are significantly higher than average, and in other places they are lower. Earthly sources radiations are collectively responsible for most of the exposure that humans are exposed to through natural radiation. On average, they provide more than 5/6 of the annual effective equivalent dose received by the population, mainly due to internal exposure. The rest is contributed by cosmic rays, mainly through external irradiation.
The natural radiation background is formed by cosmic radiation (16%) and radiation created by radionuclides scattered in nature contained in the earth's crust, ground air, soil, water, plants, food, in animal and human organisms (84%). Technogenic background radiation is associated mainly with processing and transportation rocks, burning coal, oil, gas and other fossil fuels, as well as nuclear weapons testing and nuclear energy.
There is a natural background radiation integral factor environment, which has a significant impact on human life. Natural background radiation varies widely in different regions of the Earth. The equivalent dose in the human body is on average 2 mSv = 0.2 rem. Evolutionary development shows that in conditions natural background are provided optimal conditions for the life of humans, animals and plants. Therefore, when assessing the hazard caused by ionizing radiation, it is essential to know the nature and levels of exposure from various sources.
Since radionuclides, like any atoms, form certain compounds in nature and, in accordance with their chemical properties are part of certain minerals, the distribution of natural radionuclides in the earth’s crust is uneven. Cosmic radiation, as mentioned above, also depends on a number of factors and can differ several times. Thus, the natural background radiation is different in different places on the globe. This is related to the convention of the concept of “normal radiation background”: with altitude above sea level, the background increases due to cosmic radiation, in places where granites or thorium-rich sands come to the surface, the background radiation is also higher, and so on. Therefore, we can only talk about the average natural radiation background for a given area, territory, country, etc.
The average effective dose received by a resident of our planet from natural sources per year is 2.4 mSv .
Approximately 1/3 of this dose is formed due to external radiation (approximately equally from space and from radionuclides) and 2/3 is due to internal radiation, that is, natural radionuclides located inside our body. The average human specific activity is about 150 Bq/kg. Natural background radiation (external exposure) at sea level averages about 0.09 μSv/h. This corresponds to approximately 10 µR/h.
Cosmic radiation is a stream of ionizing particles that falls to Earth from outer space. The composition of cosmic radiation includes:
Cosmic radiation consists of three components that differ in origin:
1) radiation from particles captured magnetic field Earth;
2) galactic cosmic radiation;
3) corpuscular radiation Sun.
Radiation of charged particles captured by the Earth's magnetic field - at a distance of 1.2-8 earth radii there are so-called radiation belts containing protons with an energy of 1-500 MeV (mostly 50 MeV), electrons with an energy of about 0.1-0.4 MeV and a small amount of alpha particles.
Compound. Galactic cosmic rays are composed primarily of protons (79%) and alpha particles (20%), reflecting the abundance of hydrogen and helium in the Universe. Among the heavy ions highest value have iron ions due to their relatively high intensity and large atomic number.
Origin. The sources of galactic cosmic rays are stellar flares, supernova explosions, pulsar acceleration, explosions of galactic nuclei, etc.
Lifetime. The lifetime of particles in cosmic radiation is about 200 million years. Confinement of particles occurs due to the magnetic field of interstellar space.
Interaction with the atmosphere . Entering the atmosphere, cosmic rays interact with atoms of nitrogen, oxygen and argon. Particles collide with electrons more often than with nuclei, but high-energy particles lose little energy. In collisions with nuclei, particles are almost always eliminated from the flow, so the weakening of primary radiation is almost entirely due to nuclear reactions.
When protons collide with nuclei, neutrons and protons are knocked out of the nuclei, and nuclear fission reactions occur. The resulting secondary particles have significant energy and themselves induce the same nuclear reactions, i.e., a whole cascade of reactions is formed, a so-called broad atmospheric shower is formed. One primary particle high energy can generate a shower involving ten successive generations of reactions in which millions of particles are born.
New nuclei and nucleons, which make up the nuclear-active component of radiation, are formed mainly in the upper layers of the atmosphere. In its lower part, the flow of nuclei and protons is significantly weakened due to nuclear collisions and further ionization losses. At sea level it generates only a few percent of the dose rate.
Cosmogenic radionuclides
As a result of nuclear reactions occurring under the influence of cosmic rays in the atmosphere and partly in the lithosphere, radioactive nuclei. Of these, the greatest contribution to dose creation is made by (β-emitters: 3 H (T 1/2 = 12.35 years), 14 C (T 1/2 = 5730 years), 22 Na (T 1/2 = 2.6 years) - entering the human body with food. As follows from the data presented, the largest contribution to radiation is made by carbon-14. An adult consumes ~ 95 kg of carbon per year with food.
Solar radiation, consisting of electromagnetic radiation up to the X-ray range, protons and alpha particles;
The listed types of radiation are primary; they almost completely disappear at an altitude of about 20 km due to interaction with top layers atmosphere. In this case, secondary cosmic radiation is formed, which reaches the surface of the Earth and affects the biosphere (including humans). Secondary radiation includes neutrons, protons, mesons, electrons and photons.
The intensity of cosmic radiation depends on a number of factors:
Changes in the flux of galactic radiation,
Geographical latitude,
Altitudes above sea level.
Depending on the altitude, the intensity of cosmic radiation increases sharply.
Radionuclides of the earth's crust.
Long-lived (with a half-life of billions of years) isotopes that did not have time to decay during the existence of our planet are scattered in the earth's crust. They probably formed simultaneously with the formation of the planets of the Solar System (relatively short-lived isotopes decayed completely). These isotopes are called natural radioactive substances, which means those that were formed and are constantly being re-formed without human intervention. As they decay, they form intermediate, also radioactive, isotopes.
External sources radiation are more than 60 natural radionuclides found in the Earth's biosphere. Naturally occurring radioactive elements are found in relatively small quantity in all shells and core of the Earth. Special meaning for humans have radioactive elements of the biosphere, i.e. that part of the Earth's shell (litho-, hydro- and atmosphere) where microorganisms, plants, animals and humans are located.
For billions of years, there was a constant process of radioactive decay of unstable atomic nuclei. As a result of this, the total radioactivity of the Earth's substance and rocks gradually decreased. Relatively short-lived isotopes decayed completely. Mainly elements with half-lives measured in billions of years have been preserved, as well as relatively short-lived secondary products of radioactive decay, forming successive chains of transformations, the so-called families radioactive elements. In the earth's crust, natural radionuclides can be more or less evenly dispersed or concentrated in the form of deposits.
Natural (natural) radionuclides can be divided into three groups:
Radionuclides belonging to radioactive families (series),
Other (not belonging to radioactive families) radionuclides that became part of the earth's crust during the formation of the planet,
Radionuclides formed under the influence of cosmic radiation.
During the formation of the Earth, radionuclides, along with stable nuclides, also became part of its crust. Most of These radionuclides belong to the so-called radioactive families (series). Each series represents a chain of successive radioactive transformations, when the nucleus formed during the decay of the parent nucleus also, in turn, decays, again generating an unstable nucleus, etc. The beginning of such a chain is a radionuclide that is not formed from another radionuclide, but is contained in the earth's crust and biosphere from the moment of their birth. This radionuclide is called the ancestor and the entire family (series) is named after it. In total, there are three ancestors in nature - uranium-235, uranium-238 and thorium-232, and, accordingly, three radioactive series - two uranium and thorium. All series end with stable isotopes of lead.
Thorium has the longest half-life (14 billion years), so it has been preserved almost completely since the accretion of the Earth. Uranium-238 decayed to a large extent, the vast majority of uranium-235 decayed, and the isotope neptunium-232 decayed entirely. For this reason, there is a lot of thorium in the earth's crust (almost 20 times more than uranium), and uranium-235 is 140 times less than uranium-238. Since the ancestor of the fourth family (neptunium) has completely disintegrated since the accretion of the Earth, it is almost absent from rocks. Neptunium has been found in trace amounts in uranium ores. But its origin is secondary and is due to the bombardment of uranium-238 nuclei by cosmic ray neutrons. Neptunium is now produced using artificial nuclear reactions. For an ecologist it is of no interest.
About 0.0003% (according to various sources 0.00025-0.0004%) of the earth's crust is uranium. That is, one cubic meter of the most ordinary soil contains an average of 5 grams of uranium. There are places where this amount is thousands of times greater - these are uranium deposits. In cubic meter sea water contains about 1.5 mg of uranium. This natural chemical element is represented by two isotopes -238U and 235U, each of which is the ancestor of its own radioactive series. The vast majority of natural uranium (99.3%) is uranium-238. This radionuclide is very stable, the probability of its decay (namely, alpha decay) is very small. This probability is characterized by a half-life of 4.5 billion years. That is, since the formation of our planet, its quantity has decreased by half. From this, in turn, it follows that the background radiation on our planet used to be higher. Chains of radioactive transformations that generate natural radionuclides of the uranium series:
The radioactive series includes both long-lived radionuclides (that is, radionuclides with long period half-life) and short-lived, but all radionuclides of the series exist in nature, even those that decay quickly. This is due to the fact that over time, an equilibrium has been established (the so-called “secular equilibrium”) - the decay rate of each radionuclide is equal to the rate of its formation.
There are natural radionuclides that entered the earth's crust during the formation of the planet and that do not belong to the uranium or thorium series. First of all, it is potassium-40. The content of 40 K in the earth's crust is about 0.00027% (mass), half-life is 1.3 billion years. The daughter nuclide, calcium-40, is stable. Potassium-40 in significant amount is part of plants and living organisms and makes a significant contribution to the total dose of internal radiation to humans.
Natural potassium contains three isotopes: potassium-39, potassium-40 and potassium-41, of which only potassium-40 is radioactive. The quantitative ratio of these three isotopes in nature looks like this: 93.08%, 0.012% and 6.91%.
Potassium-40 breaks down in two ways. About 88% of its atoms experience beta radiation and become calcium-40 atoms. The remaining 12% of atoms, experiencing K-capture, turn into argon-40 atoms. The potassium-argon method of determination is based on this property of potassium-40 absolute age rocks and minerals.
The third group of natural radionuclides consists of cosmogenic radionuclides. These radionuclides are formed under the influence of cosmic radiation from stable nuclides as a result of nuclear reactions. These include tritium, beryllium-7, carbon-14, sodium-22. For example, nuclear reactions of the formation of tritium and carbon-14 from nitrogen under the influence of cosmic neutrons:
Special place Carbon ranks among natural radioisotopes. Natural carbon is made up of two stable isotopes, among which carbon-12 predominates (98.89%). The rest is almost entirely carbon-13 (1.11%).
In addition to the stable isotopes of carbon, five more radioactive ones are known. Four of them (carbon-10, carbon-11, carbon-15 and carbon-16) have very short half-lives (seconds and fractions of a second). A fifth radioisotope, carbon-14, has a half-life of 5,730 years.
In nature, the concentration of carbon-14 is extremely low. For example, in modern plants there is one atom of this isotope for every 10 9 atoms of carbon-12 and carbon-13. However, with the advent atomic weapons and nuclear technology, carbon-14 is obtained artificially through interaction slow neutrons with atmospheric nitrogen, so its amount is constantly growing.
There is some convention regarding what background is considered “normal”. Thus, with the “planetary average” annual effective dose per person being 2.4 mSv, in many countries this value is 7-9 mSv/year. That is, from time immemorial, millions of people have lived under conditions of natural dose loads that are several times higher than the statistical average. Medical research and demographic statistics show that this does not affect their lives in any way, does not have any negative influence on their health and the health of their offspring.
Speaking about the conventionality of the concept of “normal” natural background, we can also point out a number of places on the planet where the level of natural radiation exceeds the statistical average not only several times, but also tens of times (table); tens and hundreds of thousands of inhabitants are exposed to this effect. And this is also the norm, this also does not affect their health in any way. Moreover, many areas with increased background radiation have been places of mass tourism (sea coasts) and recognized resorts (Caucasian coasts) for centuries. Mineral water, Karlovy Vary, etc.).
One of the main negative biological factors in outer space, along with weightlessness, is radiation. But if the situation with weightlessness is different bodies The solar system (for example, on the Moon or Mars) will be better than on the ISS, but with radiation things are more complicated.
According to its origin, cosmic radiation is of two types. It consists of galactic cosmic rays (GCRs) and heavy positively charged protons emanating from the Sun. These two types of radiation interact with each other. During solar activity the intensity of galactic rays decreases, and vice versa. Our planet is protected from the solar wind by a magnetic field. Despite this, some charged particles reach the atmosphere. The result is a phenomenon known as Polar Lights. High-energy GCRs are almost not delayed by the magnetosphere, but they do not reach the Earth's surface in dangerous quantities due to its dense atmosphere. The ISS orbit is higher dense layers atmosphere, however inside radiation belts Earth. Because of this, the level of cosmic radiation at the station is much higher than on Earth, but significantly lower than in outer space. According to their own protective properties The Earth's atmosphere is approximately equivalent to an 80 cm layer of lead.
The only reliable source of data on the radiation dose that can be received during long-duration spaceflight and on the surface of Mars is the RAD instrument on research station Mars Science Laboratory, better known as Curiosity. To understand how accurate the data it collects is, let's first look at the ISS.
In September 2013, the journal Science published an article on the results of the RAD tool. On a comparative graph built by the Laboratory jet propulsion NASA (organization not associated with experiments conducted on the ISS, but works with the RAD instrument Curiosity rover), it is indicated that during six months of stay on the near-Earth space station a person receives a radiation dose of approximately 80 mSv (millisievert). But the Oxford University publication from 2006 (ISBN 978-0-19-513725-5) states that an astronaut on the ISS receives an average of 1 mSv per day, i.e. the six-month dose should be 180 mSv. As a result, we see a huge scatter in estimates of the level of radiation in the long-studied low Earth orbit.
The main solar cycles have a period of 11 years, and since the GCR and solar wind are interconnected, for statistically reliable observations it is necessary to study radiation data at different parts of the solar cycle. Unfortunately, as stated above, all of the data we have on radiation in outer space was collected in the first eight months of 2012 by MSL on its way to Mars. Information about radiation on the surface of the planet was accumulated by him over the subsequent years. This does not mean that the data is incorrect. You just need to understand that they can only reflect the characteristics of a limited period of time.
The latest data from the RAD tool was published in 2014. According to scientists from NASA's Jet Propulsion Laboratory, during a six-month stay on the surface of Mars, a person will receive an average radiation dose of about 120 mSv. This figure is halfway between the lower and upper estimates of the radiation dose on the ISS. During the flight to Mars, if it also takes six months, the radiation dose will be 350 mSv, i.e. 2-4.5 times more than on the ISS. During its flight, MSL experienced five solar flares of moderate power. We do not know for sure what radiation dose astronauts will receive on the Moon, since no experiments were conducted that specifically studied cosmic radiation during the Apollo program. Its effects have only been studied in conjunction with the effects of other negative phenomena, such as the influence of lunar dust. However, it can be assumed that the dose will be higher than on Mars, since the Moon is not protected even by a weak atmosphere, but lower than in outer space, since a person on the Moon will be irradiated only “from above” and “from the sides” , but not from under your feet./
In conclusion, it can be noted that radiation is a problem that will definitely require a solution in the event of colonization of the Solar System. However, it is widely believed that the radiation situation outside the Earth’s magnetosphere does not allow long-term space flights, is simply not true. For a flight to Mars, it will be necessary to install a protective coating either on the entire residential module of the space flight complex, or on a separate, especially protected “storm” compartment, in which astronauts can wait out proton showers. This does not mean that developers will have to use complex anti-radiation systems. To significantly reduce the level of radiation, a thermal insulation coating, which is used on lander vehicles, is sufficient. spaceships to protect against overheating when braking in the Earth's atmosphere.
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