Who has not dreamed of flying into space, even knowing what cosmic radiation is? At least fly to the orbit of the Earth or to the Moon, or even better - further away, to some kind of Orion. In fact, the human body is very little adapted to such travel. Even when flying into orbit, astronauts face many dangers that threaten their health and sometimes life. Everyone watched the cult TV series Star Trek. One of the wonderful characters there gave a very accurate description of such a phenomenon as cosmic radiation. "These are dangers and diseases in darkness and silence," said Leonard McCoy, aka Bones, aka Bonesaw. It is very difficult to be more precise. Cosmic radiation on a journey will make a person tired, weak, sick, suffering from depression.
Feelings in flight
The human body is not adapted to life in an airless space, since evolution did not include such abilities in its arsenal. Books have been written about this, this issue is being studied in detail by medicine, and centers have been set up all over the world to study the problems of medicine in space, under extreme conditions, at high altitudes. Of course, it's funny to watch the astronaut smiling on the screen, around which various objects float in the air. In fact, his expedition is much more serious and fraught with consequences than it seems to a simple inhabitant from Earth, and here it is not only cosmic radiation that creates trouble.
At the request of journalists, astronauts, engineers, scientists, who experienced everything that happens to a person in space, spoke about the sequence of various new sensations in an artificially created environment alien to the body. Literally ten seconds after the start of the flight, an unprepared person loses consciousness, because the acceleration of the spacecraft increases, separating it from the launch complex. A person does not yet feel cosmic rays as strongly as in outer space - radiation is absorbed by the atmosphere of our planet.
Major Trouble
But there are also enough overloads: a person becomes four times heavier than his own weight, he is literally pressed into the chair, it is even difficult to move his arm. Everyone has seen these special chairs, for example, in the Soyuz spacecraft. But not everyone understood why the astronaut had such a strange posture. However, it is necessary because overload sends almost all the blood in the body down to the legs, and the brain is left without blood supply, which is why fainting occurs. But the chair invented in the Soviet Union helps to avoid at least this trouble: a posture with raised legs makes the blood supply oxygen to all parts of the brain.
Ten minutes after the start of the flight, the lack of gravity will make a person almost lose his sense of balance, orientation and coordination in space, a person may not even track moving objects. He is nauseated and vomits. The same can be caused by cosmic rays - the radiation here is already much stronger, and if a plasma ejection occurs on the sun, the threat to the life of astronauts in orbit is real, even passengers of airliners can suffer in flight at high altitude. Vision changes, edema and changes in the retina occur, the eyeball is deformed. A person becomes weak and cannot perform the tasks that are in front of him.
Riddles
However, from time to time, people also feel high cosmic radiation on Earth; for this, they do not have to surf the cosmic expanses at all. Our planet is constantly bombarded by rays of cosmic origin, and scientists suggest that our atmosphere does not always provide sufficient protection. There are many theories that endow these energy particles with such a force that it significantly limits the chances of planets for the emergence of life on them. In many ways, the nature of these cosmic rays is still an unsolvable mystery for our scientists.
Subatomic charged particles in space move almost at the speed of light, they have already been registered repeatedly on satellites, and even on these nuclei of chemical elements, protons, electrons, photons and neutrinos. Also, the presence of cosmic radiation particles - heavy and superheavy - in the attack is not excluded. If it were possible to detect them, a whole series of contradictions in cosmological and astronomical observations would be resolved.
Atmosphere
What protects us from cosmic radiation? Only our atmosphere. Cosmic rays that threaten the death of all living things collide in it and generate streams of other particles - harmless, including muons, much heavier relatives of electrons. A potential danger still exists, since some particles reach the surface of the Earth and penetrate many tens of meters into its bowels. The level of radiation that any planet receives indicates its suitability or unsuitability for life. The high that cosmic rays carry with them is much higher than the radiation from its own star, because the energy of protons and photons, for example, of our Sun, is lower.
And with a high life is impossible. On Earth, this dose is controlled by the strength of the planet's magnetic field and the thickness of the atmosphere, which significantly reduce the danger of cosmic radiation. For example, there could well be life on Mars, but the atmosphere there is negligible, there is no own magnetic field, which means there is no protection from cosmic rays that permeate the entire cosmos. The level of radiation on Mars is huge. And the influence of cosmic radiation on the planet's biosphere is such that all life on it dies.
What's more important?
We are lucky, we have both the thickness of the atmosphere that envelops the Earth, and our own sufficiently powerful magnetic field that absorbs harmful particles that have reached the earth's crust. I wonder whose protection for the planet works more actively - the atmosphere or the magnetic field? Researchers are experimenting by creating models of the planets with or without a magnetic field. And the magnetic field itself differs in these models of planets in strength. Previously, scientists were sure that it was the main protection against cosmic radiation, since they control its level on the surface. However, it was found that the amount of exposure determines to a greater extent the thickness of the atmosphere that covers the planet.
If the Earth's magnetic field is "turned off", the radiation dose will only double. This is a lot, but even for us it will be reflected quite inconspicuously. And if you leave the magnetic field and remove the atmosphere to one tenth of its total amount, then the dose will increase fatally - by two orders of magnitude. Terrible cosmic radiation will kill everything and everyone on Earth. Our Sun is a yellow dwarf star, it is around them that the planets are considered the main contenders for habitability. These are relatively dim stars, there are many of them, about eighty percent of the total number of stars in our Universe.
Space and evolution
Theorists have calculated that such planets orbiting yellow dwarfs, which are in habitable zones, have much weaker magnetic fields. This is especially true of the so-called super-Earths - large rocky planets with a mass ten times larger than our Earth. Astrobiologists were sure that the weak magnetic fields significantly reduced the chances of habitability. And now new discoveries suggest that this is not as big a problem as people used to think. The main thing would be the atmosphere.
Scientists are comprehensively studying the effect of increasing radiation on existing living organisms - animals, as well as on various plants. Radiation-related research consists of exposing them to varying degrees of radiation, from small to extreme, and then determining whether they survive and how differently they will feel if they survive. Microorganisms, which are affected by gradually increasing radiation, may show us how evolution took place on Earth. It was cosmic rays, their high radiation that once made the future man get off the palm tree and start exploring space. And never again will humanity return to the trees.
Space Radiation 2017
At the beginning of September 2017, our entire planet was greatly alarmed. The sun suddenly ejected tons of solar matter after the merger of two large groups of dark spots. And this ejection was accompanied by class X flares, which forced the planet's magnetic field to work literally for wear and tear. A large magnetic storm followed, causing illness in many people, as well as exceptionally rare, almost unprecedented natural phenomena on Earth. For example, powerful pictures of northern lights were recorded near Moscow and in Novosibirsk, which had never been in these latitudes. However, the beauty of such phenomena did not obscure the consequences of a deadly solar flare that penetrated the planet with cosmic radiation, which turned out to be truly dangerous.
Its power was close to the maximum, X-9.3, where the letter is the class (extremely large flash), and the number is the flash strength (out of ten possible). Along with this release, there was a threat of failure of space communication systems and all equipment located on the astronauts were forced to wait out this stream of terrible cosmic radiation carried by cosmic rays in a special shelter. The quality of communication during these two days deteriorated significantly both in Europe and in America, exactly where the flow of charged particles from space was directed. About a day before the moment when the particles reached the surface of the Earth, a warning about cosmic radiation was issued, which sounded on all continents and in every country.
The power of the sun
The energy emitted by our luminary into the surrounding outer space is truly enormous. Within a few minutes, many billions of megatons fly into space, if you count in TNT equivalent. Mankind will be able to produce so much energy at modern rates only in a million years. Only a fifth of all the energy emitted by the Sun per second. And this is our little and not too hot dwarf! If you just imagine how much destructive energy is produced by other sources of cosmic radiation, next to which our Sun will seem like an almost invisible grain of sand, your head will spin. What a blessing that we have a good magnetic field and a great atmosphere that do not let us die!
Humans are exposed to this danger every day because the radiation in space never dries up. It is from there that most of the radiation comes to us - from black holes and from clusters of stars. It is capable of killing at a high dose of radiation, and at a low dose it can turn us into mutants. However, we must also remember that evolution on Earth took place thanks to such flows, radiation changed the structure of DNA to the state that we observe today. If you sort out this "medicine", that is, if the radiation emitted by the stars exceeds the permissible levels, the processes will be irreversible. After all, if creatures mutate, they will not return to their original state, there is no reverse effect here. Therefore, we will never see those living organisms that were present in a newborn life on Earth. Any organism is trying to adapt to changes in the environment. Either it dies, or it adapts. But there is no turning back.
ISS and solar flare
When the Sun sent us its hello with a stream of charged particles, the ISS was just passing between the Earth and the star. The high-energy protons released during the explosion created an absolutely undesirable radiation background within the station. These particles pierce through absolutely any spacecraft. However, this radiation spared space technology, since the impact was powerful, but too short to disable it. However, the crew hid all this time in a special shelter, because the human body is much more vulnerable than modern technology. The outbreak was not one, they went in a whole series, but it all began on September 4, 2017, in order to shake the cosmos with an extreme ejection on September 6. Over the past twelve years, a stronger flow on Earth has not yet been observed. The plasma cloud that was thrown out by the Sun overtook the Earth much earlier than planned, which means that the speed and power of the stream exceeded the expected one and a half times. Accordingly, the impact on the Earth was much stronger than expected. For twelve hours, the cloud was ahead of all the calculations of our scientists, and accordingly, the planet's magnetic field was more disturbed.
The power of the magnetic storm turned out to be four out of five possible, that is, ten times more than expected. In Canada, auroras were also observed even in the middle latitudes, as in Russia. Planetary character magnetic storm happened on Earth. You can imagine what was going on in space! Radiation is the most significant danger of all existing there. Protection from it is needed immediately, as soon as the spacecraft leaves the upper atmosphere and leaves magnetic fields far below. Streams of uncharged and charged particles - radiation - constantly permeate space. The same conditions await us on any planet in the solar system: there is no magnetic field and atmosphere on our planets.
Types of radiation
In space, ionizing radiation is considered the most dangerous. These are gamma radiation and X-rays of the Sun, these are particles flying after chromospheric solar flares, these are extragalactic, galactic and solar cosmic rays, solar wind, protons and electrons of the radiation belts, alpha particles and neutrons. There is also non-ionizing radiation - this is ultraviolet and infrared radiation from the Sun, this is electromagnetic radiation and visible light. There is no great danger in them. We are protected by the atmosphere, and the astronaut is protected by the spacesuit and ship's skin.
Ionizing radiation delivers irreparable troubles. This is a harmful effect on all life processes that occur in the human body. When a high-energy particle or photon passes through a substance in its path, they form a pair of charged particles - an ion as a result of interaction with this substance. This affects even non-living matter, and the living reacts most violently, since the organization of highly specialized cells requires renewal, and this process, as long as the organism is alive, occurs dynamically. And the higher the level of evolutionary development of the organism, the more irreversible is the radiation damage.
Radiation protection
Scientists are looking for such funds in various fields of modern science, including pharmacology. So far, no drug has been effective, and people who have been exposed to radiation continue to die. Experiments are carried out on animals both on earth and in space. The only thing that became clear is that any drug should be taken by a person before the start of irradiation, and not after.
And given that all such drugs are toxic, we can assume that the fight against the effects of radiation has not yet led to a single victory. Even if pharmacological agents are taken on time, they only provide protection against gamma radiation and X-rays, but do not protect against ionizing radiation from protons, alpha particles and fast neutrons.
All organisms from the moment of their appearance on Earth have existed, developed and evolved under the constant influence of radiation. Radiation is the same natural phenomenon as wind, ebbs and flows, rain, etc.
The natural radiation background (NRF) was present on the Earth at all stages of its formation. It was long before life appeared, and then the biosphere. Radioactivity and the ionizing radiation accompanying it were a factor that influenced the current state of the biosphere, the evolution of the Earth, life on Earth, and the elemental composition of the solar system. Any organism is exposed to the radiation background characteristic of the area. Until the 1940s it was due to two factors: the decay of radionuclides of natural origin, located both in the habitat of a given organism and in the organism itself, and cosmic rays.
Sources of natural (natural) radiation are space and natural radionuclides contained in natural form and concentration in all objects of the biosphere: soil, water, air, minerals, living organisms, etc. Any of the objects around us and ourselves in the absolute sense words are radioactive.
The world's population receives the main dose of radiation from natural sources of radiation. Most of them are such that it is absolutely impossible to avoid radiation from them. Throughout the history of the Earth's existence, various types of radiation penetrate to the earth's surface from space and come from radioactive substances located in the 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 they talk about external radiation) or they can be 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. It depends, in part, on where people live. The level of radiation in some places on the globe, especially where radioactive rocks occur, is much higher than average, and in other places it is lower. Terrestrial sources of radiation together are responsible for most of the exposure to which a person is exposed due to 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, surface air, soil, water, plants, food products, in animal and human organisms (84%). The technogenic radiation background is mainly associated with the processing and movement of rocks, the combustion of coal, oil, gas and other fossil fuels, as well as with nuclear weapons testing and nuclear energy.
The natural radiation background is an integral environmental factor that has a significant impact on human life. The natural radiation background 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 under conditions of natural background, optimal conditions are provided for the life of humans, animals, and plants. Therefore, when assessing the hazard due to 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 by several times. Thus, the natural radiation background in different places of the globe is different. This is related to the conditionality of the concept of “normal radiation background”: with height above sea level, the background increases due to cosmic radiation, in places where granites or thorium-rich sands come to the surface, the radiation background 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 value of the effective dose received by an inhabitant 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 are due to internal exposure, that is, natural radionuclides located inside our body. The average specific activity of a person is about 150 Bq/kg. Natural background radiation (external exposure) at sea level averages about 0.09 µSv/h. This corresponds to about 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 of particles captured by the Earth's magnetic field;
2) galactic cosmic radiation;
3) corpuscular radiation of the Sun.
Radiation of charged particles captured by the Earth's magnetic field - at a distance of 1.2-8 Earth radii are the so-called radiation belts containing protons with an energy of 1-500 MeV (mainly 50 MeV), electrons with an energy of about 0.1-0.4 MeV and a small amount of alpha particles.
Compound. Galactic cosmic rays consist mainly of protons (79%) and α-particles (20%), which reflects the prevalence of hydrogen and helium in the Universe. Of the heavy ions, iron ions are of the greatest importance 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. Particles are held by the magnetic field of interstellar space.
Interaction with the atmosphere . Entering the atmosphere, cosmic rays interact with nitrogen, oxygen and argon atoms. Collisions of particles with electrons occur more often than with nuclei, but high-energy particles lose little energy. In collisions with nuclei, particles almost always leave the flow, so the attenuation of the 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 take place. 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 extensive air shower is formed. One high-energy primary particle can give rise to a shower that includes ten successive generations of reactions in which millions of particles are born.
New nuclei and nucleons, which make up the nuclear-active component of the radiation, are formed mainly in the upper layers of the atmosphere. In its lower part, the flux of nuclei and protons is significantly weakened due to nuclear collisions and further - ionization losses. At sea level, it forms only a few percent of the dose rate.
Cosmogenic radionuclides
As a result of nuclear reactions under the influence of cosmic rays in the atmosphere and partially in the lithosphere, radioactive nuclei are formed. Of these, the greatest contribution to the creation of the dose 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 above data, carbon-14 makes the largest contribution to exposure. 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 a height of about 20 km due to interaction with the upper layers of the atmosphere. In this case, secondary cosmic radiation is formed, which reaches the Earth's surface and affects the biosphere (including humans). The composition of the secondary radiation includes neutrons, protons, mesons, electrons and photons.
The intensity of cosmic radiation depends on a number of factors:
Changes in the flow of galactic radiation,
sun activity,
geographic latitude,
Heights above sea level.
Depending on the height, the intensity of cosmic radiation increases sharply.
Radionuclides of the earth's crust.
Long-lived (with a half-life of billions of years) isotopes are scattered in the earth's crust, which did not have time to decay during the existence of our planet. They were formed, probably, 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 re-formed without human intervention. Decaying, they form intermediate, also radioactive, isotopes.
External sources of radiation are more than 60 natural radionuclides located in the Earth's biosphere. Natural radioactive elements are contained in relatively small amounts in all shells and the core of the Earth. Of particular importance for humans are the 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 has been a constant process of radioactive decay of unstable nuclei of atoms. As a result, the total radioactivity of the Earth's matter, rocks gradually decreased. Relatively short-lived isotopes decayed completely. Preserved are mainly elements with a half-life measured in billions of years, as well as relatively short-lived secondary products of radioactive decay, resulting in successive chains of transformations, the so-called families of 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 included in the earth's crust during the formation of the planet,
Radionuclides formed under the action of cosmic radiation.
During the formation of the Earth, along with stable nuclides, radionuclides also entered into the composition of its crust. Most of these radionuclides belong to the so-called radioactive families (series). Each row is 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 since their birth. This radionuclide is called the ancestor and the whole family (series) is named after him. 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 rows 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 entire isotope of neptunium-232 decayed. 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 in rocks. Neptunium is 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. Now neptunium is obtained using artificial nuclear reactions. For the ecologist it is of no interest.
About 0.0003% (according to various sources 0.00025-0.0004%) of the mass of the earth's crust is uranium. That is, one cubic meter of the most common soil contains an average of 5 grams of uranium. There are places where this amount is thousands of times greater - these are uranium deposits. A cubic meter of 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 number has halved. From this, in turn, it follows that the radiation background 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 a long half-life) and short-lived ones, but all radionuclides of the series exist in nature, even those that quickly decay. This is due to the fact that over time an equilibrium has been established (the so-called "secular equilibrium") - the rate of decay of each radionuclide is equal to the rate of its formation.
There are natural radionuclides that entered the composition of the earth's crust during the formation of the planet and which do not belong to the uranium or thorium series. The first is potassium-40. The content of 40 K in the earth's crust is about 0.00027% (mass), the half-life is 1.3 billion years. The daughter nuclide, calcium-40, is stable. Potassium-40 is found in significant amounts in plants and living organisms, making a significant contribution to the total internal dose of human exposure.
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 turn into calcium-40 atoms. The remaining 12% of the atoms, experiencing K-capture, turn into argon-40 atoms. The potassium-argon method for determining the absolute age of rocks and minerals is based on this property of potassium-40.
The third group of natural radionuclides are cosmogenic radionuclides. These radionuclides are formed by cosmic radiation from stable nuclides as a result of nuclear reactions. These include tritium, beryllium-7, carbon-14, sodium-22. For example, the nuclear reactions of the formation of tritium and carbon-14 from nitrogen under the action of cosmic neutrons:
Carbon occupies a special place among natural radioisotopes. Natural carbon consists of two stable isotopes, among which carbon-12 predominates (98.89%). The rest is almost entirely accounted for by the carbon-13 isotope (1.11%).
In addition to 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). The fifth radioisotope, carbon-14, has a half-life of 5730 years.
In nature, the concentration of carbon-14 is extremely low. For example, in modern plants, one atom of this isotope accounts for 10 9 carbon-12 and carbon-13 atoms. However, with the advent of atomic weapons and nuclear technology, carbon-14 is obtained artificially by the interaction of slow neutrons with atmospheric nitrogen, so its amount is constantly growing.
There is some convention regarding the point of view of what background is considered "normal". Thus, with an "average planetary" annual effective dose per person of 2.4 mSv in many countries, this value is 7-9 mSv / year. That is, from time immemorial, millions of people live in conditions of natural dose loads, which are several times higher than the average. Medical studies and demographic statistics show that this does not affect their lives in any way, does not have any negative impact on their health and the health of their offspring.
Speaking about the conditionality of the concept of “normal” natural background, one can also indicate a number of places on the planet where the level of natural radiation exceeds the average not only at 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, it also does not affect their health in any way. Moreover, many areas with a high radiation background have been places of mass tourism (sea coasts) and recognized resorts (Caucasian Mineralnye Vody, Karlovy Vary, etc.) for centuries.
Space is radioactive. It is simply impossible to hide from radiation. Imagine that you are standing in the middle of a sandstorm, and a whirlpool of small pebbles is constantly circling around you, which will hurt your skin. This is what cosmic radiation looks like. And this radiation does a lot of harm. But the problem is that, unlike pebbles and pieces of earth, ionizing radiation does not bounce off human flesh. It goes through her like a cannonball through a building. And this radiation does a lot of harm.
Last week, scientists at the University of Rochester Medical Center published the results of a study indicating that long-term exposure to galactic radiation, which astronauts traveling to Mars may be exposed to, can increase the risk of Alzheimer's disease.
Reading the media reports about this study, I started to get curious. We've been sending people into space for over half a century. We have the opportunity to follow a whole generation of astronauts - as these people grow old and die. And we are constantly monitoring the health of those who fly into space today. Scientific work, such as that carried out at the University of Rochester, is carried out on laboratory animals such as mice and rats. They are designed to help us prepare for the future. But what do we know about the past? Has radiation affected people who have already been in space? How does it affect those in orbit at the moment?
There is one key difference between the astronauts of today and the astronauts of the future. The difference is the Earth itself.
Galactic cosmic radiation, sometimes called cosmic radiation, is precisely what causes the greatest concern among researchers. It is made up of particles and bits of atoms that could have come from the formation of a supernova. Most of this radiation, about 90%, consists of protons stripped from hydrogen atoms. These particles fly through the galaxy at almost the speed of light.
And then they strike at the Earth. Our planet has a couple of defense mechanisms that shelter us from the effects of cosmic radiation. First, the Earth's magnetic field repels some particles and completely blocks some. Particles that overcome this barrier begin to collide with atoms in our atmosphere.
If you throw a large Lego tower down the stairs, it will shatter into small pieces that will fly away from it on each new step. Approximately the same thing happens in our atmosphere and with galactic radiation. Particles collide with atoms and fall apart to form new particles. These new particles hit something again and fall apart again. With every step they lose energy. The particles slow down and gradually weaken. By the time they "stop" on the surface of the Earth, they no longer have the powerful store of galactic energy that they had before. This radiation is much less dangerous. A small piece from Lego hits much weaker than a tower assembled from them.
For all the astronauts we sent into space, Earth's protective barriers helped a lot, at least in part. Francis Cucinotta told me about this. He is the scientific director of NASA's program to study the effects of radiation on humans. This is just the guy who can tell you how harmful radiation is to astronauts. According to him, with the exception of the Apollo flights to the Moon, a person is present in space within the limits of the Earth's magnetic field. The International Space Station, for example, is above the atmosphere, but still deep in the first layer of defense. Our astronauts are not fully exposed to cosmic radiation.
In addition, under such influence they are quite a short time. The longest flight into space lasted a little over a year. And this is important, because the damage from radiation has a cumulative effect. You risk much less when you spend six months on the ISS than when you go (so far in theory) on a multi-year trip to Mars.
But what's interesting and rather disturbing, Cucinotta told me, is that even with all these defense mechanisms, we're seeing how the radiation is affecting astronauts.
A very unpleasant thing is cataracts - changes in the lens of the eye, causing it to become cloudy. Because less light enters the eye through a cloudy lens, people with cataracts can see worse. In 2001, Cucinotta and colleagues reviewed data from an ongoing study of astronaut health and came to the following conclusion. Astronauts who were exposed to a higher dose of radiation (because they had made more flights into space or because of the nature of their missions*) were more likely to develop cataracts than those who had a lower radiation dose.
There is probably also an increased risk of cancer, although it is difficult to quantify and accurately analyze such a risk. The fact is that we do not have data from epidemiologists about what type of radiation astronauts are exposed to. We know the number of cancer cases after the atomic bombing of Hiroshima and Nagasaki, but this radiation is not comparable to galactic radiation. In particular, Cucinotta is most concerned about VHF ions - highly atomic high-energy particles.
These are very heavy particles and they move very fast. On the surface of the Earth, we do not experience their effects. They are weeded out, slowed down and broken into pieces by the defense mechanisms of our planet. However, VHF ions can cause more harm and more varied harm than radiation with which radiologists are familiar. We know this because scientists compare blood samples from astronauts before and after space travel.
Cucinotta calls this a pre-flight check. Scientists take a blood sample from an astronaut before launching into orbit. When an astronaut is in space, scientists divide the blood they take and expose it to varying degrees of gamma radiation. It's like the harmful radiation that we sometimes encounter on Earth. Then, when the astronaut returns, they compare these gamma-rayed blood samples with what actually happened to him in space. “We see two to three times the difference in different astronauts,” Cucinotta told me.
Such a concept as solar radiation became known quite a long time ago. As numerous studies have shown, it is far from always guilty of increasing the level of air ionization.
This article is intended for persons over 18 years of age.
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Cosmic radiation: truth or myth?
Cosmic rays are radiation that appears during the explosion of a supernova, and also as a result of thermonuclear reactions on the Sun. The different nature of the origin of the rays also affects their main characteristics. Cosmic rays that penetrate from space outside our solar system can be conditionally divided into two types - galactic and intergalactic. The latter species remains the least studied, since the concentration of primary radiation in it is minimal. That is, intergalactic radiation is of no particular importance, since it is completely neutralized in our atmosphere.
Unfortunately, just as little can be said about the rays that came to us from our galaxy called the Milky Way. Despite the fact that its size exceeds 10,000 light years, any changes in the radiation field at one end of the galaxy will immediately come back to haunt the other.
The danger of radiation from space
Direct cosmic radiation is detrimental to a living organism, so its influence is extremely dangerous for humans. Fortunately, our Earth is reliably protected from these space aliens by a dense dome from the atmosphere. It serves as an excellent protection for all life on earth, as it neutralizes direct cosmic radiation. But not completely. When it collides with air, it breaks up into smaller particles of ionizing radiation, each of which enters into an individual reaction with its atoms. Thus, high-energy radiation from space weakens and forms secondary radiation. At the same time, it loses its lethality - the level of radiation becomes approximately the same as in x-rays. But you should not be afraid - this radiation completely disappears during the passage through the Earth's atmosphere. Whatever the sources of cosmic rays, and what power they would not have, the danger to a person who is on the surface of our planet is minimal. It can bring tangible harm only to astronauts. They are exposed to direct cosmic radiation, as they have no natural protection in the form of an atmosphere.
The energy released by cosmic rays primarily affects the Earth's magnetic field. Charged ionizing particles literally bombard it and cause the most beautiful atmospheric phenomenon -. But that's not all - radioactive particles, in view of their nature, are capable of causing malfunctions in the operation of various electronics. And if in the last century this did not cause much discomfort, then in our time it is a very serious problem, since the most important aspects of modern life are tied to electrics.
People are also susceptible to these visitors from space, although the mechanism of cosmic rays is very specific. Ionized particles (that is, secondary radiation) affect the Earth's magnetic field, thereby causing storms in the atmosphere. Everyone knows that the human body consists of water, which is very susceptible to magnetic vibrations. Thus, cosmic radiation affects the cardiovascular system, and causes poor health in weather-dependent people. This, of course, is unpleasant, but by no means fatal.
What protects the Earth from solar radiation?
The sun is a star, in the depths of which various thermonuclear reactions constantly take place, which are accompanied by strong energy emissions. These charged particles are called the solar wind and have a strong effect on our Earth, or rather on its magnetic field. It is with him that ionized particles interact, which form the basis of the solar wind.
According to the latest research by scientists from all over the world, the plasma shell of our planet plays a special role in neutralizing the solar wind. This happens as follows: solar radiation collides with the Earth's magnetic field and is scattered. When there is too much of it, the plasma shell takes the blow, and an interaction process occurs that is similar to a short circuit. The result of such a struggle may be cracks in the protective shield. But nature has foreseen this too - streams of cold plasma rise from the surface of the Earth and rush to places of weakened protection. Thus, the magnetic field of our planet reflects a blow from space.
But it is worth stating the fact that solar radiation, unlike cosmic radiation, still falls on the Earth. At the same time, you should not worry in vain, because in fact this is the energy of the Sun, which should fall on the surface of our planet in a scattered state. Thus, it heats the surface of the Earth and helps to develop life on it. So, it is worth clearly distinguishing between different types of radiation, because some of them not only do not have a negative impact, but are also necessary for the normal functioning of living organisms.
However, not all substances on Earth are equally susceptible to solar radiation. There are surfaces that absorb it more than others. These are, as a rule, underlying surfaces with a minimum level of albedo (the ability to reflect solar radiation) - these are earth, forest, sand.
Thus, the temperature on the Earth's surface, as well as the length of daylight hours, directly depends on how much solar radiation the atmosphere absorbs. I would like to say that the main amount of energy still reaches the surface of our planet, because the air shell of the Earth serves as an obstacle only for infrared rays. But UV rays are only partially neutralized, which leads to some problems with the skin in humans and animals.
The effect of solar radiation on the human body
When exposed to the rays of the infrared spectrum of solar radiation, the thermal effect is clearly manifested. It contributes to the expansion of blood vessels, stimulation of the cardiovascular system, activates skin respiration. As a result, the main systems of the body relax, the production of endorphins (hormones of happiness), which have an analgesic and anti-inflammatory effect, increases. Heat also affects metabolic processes, activating metabolism.
The light emission of solar radiation has a significant photochemical effect, which activates important processes in tissues. This type of solar radiation allows a person to use one of the most important systems of touch in the external world - vision. It is to these quanta that we should be grateful for the fact that we see everything in colors.
Important Influencing Factors
Infrared solar radiation also stimulates brain activity and is responsible for human mental health. It is also important that this particular type of solar energy affects our biological rhythms, that is, the phases of activity and sleep.
Without light particles, many vital processes would be at risk, which is fraught with the development of various diseases, including insomnia and depression. Also, with minimal contact with light solar radiation, the working capacity of a person is significantly reduced, and most processes in the body slow down.
UV radiation is quite useful for our body, as it also triggers immunological processes, that is, it stimulates the body's defenses. It is also necessary for the production of porphyrite - an analogue of plant chlorophyll in our skin. However, an excess of UV rays can cause burns, so it is very important to know how to properly protect yourself from this during the period of maximum solar activity.
As you can see, the benefits of solar radiation for our body are undeniable. Many people are very worried about whether food absorbs this type of radiation and whether it is dangerous to eat contaminated foods. I repeat - solar energy has nothing to do with cosmic or atomic radiation, which means that you should not be afraid of it. Yes, and it would be pointless to avoid it ... No one has yet been looking for a way to escape from the Sun.
07.12.2016
The Curiosity rover has a RAD instrument on board to determine the intensity of radioactive exposure. During its flight to Mars, Curiosity measured the radiation background, and today scientists who work with NASA spoke about these results. Since the rover flew in a capsule, and the radiation sensor was located inside, these measurements practically correspond to the radiation background that will be present in a manned spacecraft.The RAD instrument consists of three solid silicon wafers that act as a detector. Additionally, it has a cesium iodide crystal, which is used as a scintillator. The RAD is set to look at the zenith during landing and capture the field at 65 degrees.
In fact, this is a radiation telescope that captures ionizing radiation and charged particles in a wide range.
The equivalent dose of absorbed radiation exposure is 2 times greater than the dose of the ISS.
A six-month flight to Mars is roughly equivalent to one year spent in near-Earth orbit. Given that the total duration of the expedition should be about 500 days, the outlook is not optimistic.
For a person, the accumulated radiation of 1 Sievert increases the risk of cancer by 5%. NASA allows its astronauts to accumulate no more than 3% risk, or 0.6 Sievert, over their careers.
The life expectancy of astronauts is lower than the average in their countries. At least a quarter of deaths are due to cancer.
Of the 112 Russian cosmonauts who flew, 28 are no longer with us. Five people died: Yuri Gagarin - on a fighter, Vladimir Komarov, Georgy Dobrovolsky, Vladislav Volkov and Viktor Patsaev - when returning from orbit to Earth. Vasily Lazarev died from poisoning with low-quality alcohol.
Of the 22 other conquerors of the stellar ocean, for nine the cause of death was oncology. Anatoly Levchenko (47), Yuri Artyukhin (68), Lev Demin (72), Vladimir Vasyutin (50), Gennady Strekalov (64), Gennady Sarafanov (63), Konstantin Feoktistov (83), Vitaly Sevastyanov (75) died of cancer ). The official cause of death of another cosmonaut who died of cancer has not been disclosed. For flights outside the Earth, the healthiest, strongest are selected.
So, nine deaths from cancer out of 22 cosmonauts make up 40.9%. Now let's turn to similar statistics for the country as a whole. Last year, 1,768,500 Russians left this world (Rosstat data). At the same time, 173.2 thousand died from external causes (transport accidents, alcohol poisoning, suicides, murders). It remains 1 million 595 thousand 300. How many citizens have been ruined by oncology? Answer: 265.1 thousand people. Or 16.6%. Compare: 40.9 and 16.6%. It turns out that ordinary citizens die of cancer 2.5 times less often than astronauts.
There is no similar information for the US astronaut corps. But even fragmentary data testify: oncology also mows down American stargazers. Here is an incomplete list of victims of a terrible disease: John Swigert Jr. - bone marrow cancer, Donald Slayton - brain cancer, Charles Wich - brain cancer, David Walker - cancer, Alan Shepard - leukemia, George Lowe - colon cancer, Ronald Paris - brain tumor brain.
During one flight to the Earth's orbit, each crew member receives such exposure as if he had been examined 150–400 times in an X-ray room.
Taking into account the fact that the daily dose on the ISS is up to 1 mSv (annual allowable dose for a person on earth), the maximum period of astronauts' stay in orbit is limited to approximately 600 days for their entire career.
On Mars itself, the radiation should be about two times lower than in space, due to the atmosphere and dust suspension in it, i.e., correspond to the level of the ISS, but exact indicators have not yet been published. The RAD indicators during the days of dust storms will be interesting - let's find out how good the Martian dust is a good radiation screen.
Now the record for being in near-Earth orbit belongs to 55-year-old Sergey Krikalev - he has 803 days on his account. But he scored them intermittently - in total he made 6 flights from 1988 to 2005.
Radiation in space arises mainly from two sources: from the Sun during flares and coronal ejections, and from cosmic rays that occur during supernova explosions or other high-energy events in our and other galaxies.
In the illustration: the interaction of the solar "wind" and the Earth's magnetosphere.
Cosmic rays make up the bulk of the radiation in interplanetary travel. They account for a radiation share of 1.8 mSv per day. Only three percent of the exposure is accumulated by Curiosity from the Sun. This is also due to the fact that the flight took place in a relatively quiet time. Flashes increase the total dose, and it approaches 2 mSv per day.
The peaks are due to solar flares.
Current technical means are more effective against solar radiation, which has low energy. For example, it is possible to equip a protective capsule where astronauts can hide during solar flares. However, even 30 cm aluminum walls will not protect against interstellar cosmic rays. Lead would probably help better, but this will significantly increase the mass of the ship, which means the cost of launching and accelerating it.
It may be necessary to assemble an interplanetary spacecraft in orbit around the Earth - to hang heavy lead plates to protect against radiation. Or use the Moon for assembly, where the weight of the spacecraft will be lower.
The most effective means of minimizing exposure should be new types of engines that will significantly reduce the time of flight to Mars and back. NASA is currently working on solar electric propulsion and nuclear thermal propulsion. The first one can in theory accelerate up to 20 times faster than modern chemical engines, but acceleration will be very long due to low thrust. An apparatus with such an engine is supposed to be sent to tow an asteroid, which NASA wants to capture and transfer to lunar orbit for subsequent visits by astronauts.
The most promising and encouraging developments in electric jet engines are being carried out under the VASIMR project. But to travel to Mars, solar panels will not be enough - you need a reactor.
A nuclear heat engine develops a specific impulse about three times higher than modern types of rockets. Its essence is simple: the reactor heats the working gas (assumed hydrogen) to high temperatures without the use of an oxidizing agent, which is required for chemical rockets. In this case, the heating temperature limit is determined only by the material from which the engine itself is made.
But such simplicity also causes difficulties - traction is very difficult to control. NASA is trying to solve this problem, but does not consider the development of NRE a priority.
The use of a nuclear reactor is still promising in that part of the energy could be used to generate an electromagnetic field, which would additionally protect pilots from both cosmic radiation and radiation from their own reactor. The same technology would make profitable the extraction of water on the Moon or asteroids, that is, it would additionally stimulate the commercial use of space.
Although now this is nothing more than theoretical reasoning, it is possible that such a scheme will become the key to a new level of exploration of the solar system.
Additional requirements for space and military microcircuits.
First of all - increased requirements for reliability (both the crystal itself and the case), resistance to vibration and overloads, humidity, temperature range - much wider, because military equipment should work in -40C, and when heated to 100C .
Then - resistance to the damaging factors of a nuclear explosion - EMP, a large instantaneous dose of gamma / neutron radiation. Normal operation at the time of the explosion may not be possible, but at least the device should not be irreversibly damaged.
And finally - if the microchip is for space - the stability of parameters as the total dose of radiation slowly accumulates and survival after a meeting with heavy charged particles of cosmic radiation.
How does radiation affect microcircuits?
In "pieces of particles" cosmic radiation consists of 90% protons (i.e. hydrogen ions), 7% helium nuclei (alpha particles), ~1% heavier atoms and ~1% electrons. Well, the stars (including the Sun), the nuclei of galaxies, the Milky Way - abundantly illuminate everything not only with visible light, but also with X-ray and gamma radiation. During solar flares, the radiation from the sun increases by 1000-1000000 times, which can be a serious problem (both for people of the future and current spacecraft outside the earth's magnetosphere).
There are no neutrons in cosmic radiation for the obvious reason - free neutrons have a half-life of 611 seconds, and turn into protons. Even from the sun, a neutron cannot fly, except perhaps at a very relativistic speed. A small number of neutrons arrive from the earth, but these are trifles.
Around the earth there are 2 belts of charged particles - the so-called radiation: at an altitude of ~ 4000 km from protons, and at an altitude of ~ 17000 km from electrons. Particles there move in closed orbits, captured by the earth's magnetic field. There is also the Brazilian magnetic anomaly - where the internal radiation belt comes closer to the earth, up to a height of 200 km.
Electrons, gamma and x-rays.
When gamma and X-ray radiation (including the secondary one, obtained due to the collision of electrons with the body of the device) passes through the microcircuit, a charge begins to gradually accumulate in the gate dielectric of the transistors, and accordingly, the parameters of the transistors begin to slowly change - the threshold voltage of the transistors and the leakage current. An ordinary civilian digital microcircuit can stop working normally after 5000 rad (however, a person can stop working after 500-1000 rad).
In addition, gamma and x-ray radiation makes all pn junctions inside the microcircuit work like small "solar batteries" - and if in space there is usually insufficient radiation to greatly affect the operation of the microcircuit, during a nuclear explosion, the flow of gamma and x-ray radiation may already be enough to disrupt the operation of the microcircuit due to the photoelectric effect.
In a low orbit of 300-500 km (where people fly), the annual dose can be 100 rad or less, respectively, even in 10 years, the accumulated dose will be tolerated by civilian microcircuits. But in high orbits >1000km, the annual dose can be 10000-20000 rad, and ordinary microcircuits will gain a lethal dose in a matter of months.
Heavy charged particles (HPC) - protons, alpha particles and high-energy ions
This is the biggest problem of space electronics - TGCH have such high energy that they “pierce” the microcircuit through (together with the satellite body), and leave behind a “loop” of charge. At best, this can lead to a software error (0 becomes 1 or vice versa - single-event upset, SEU), at worst - lead to thyristor latchup (single-event latchup, SEL). In a latched chip, the power is shorted to ground, the current can go very high, and lead to the combustion of the chip. If you have time to turn off the power and connect it before burning, then everything will work as usual.
Perhaps this was exactly what happened with Phobos-Grunt - according to the official version, non-radiation-resistant imported memory chips failed already on the second orbit, and this is possible only because of the HTS (according to the total accumulated radiation dose in low orbit, a civilian chip could work for a long time).
It is the latching that limits the use of conventional terrestrial microcircuits in space with all sorts of software tricks to increase reliability.
What happens if you protect the spacecraft with lead?
With galactic cosmic rays, particles with an energy of 3 * 1020 eV sometimes arrive at us, i.e. 300000000 TeV. In human-understandable units, this is about 50J, i.e. in one elementary particle the energy is like that of a bullet of a small-caliber sports pistol.
When such a particle collides, for example, with a lead atom of radiation protection, it simply tears it to shreds. The shards will also have gigantic energy, and will also tear apart everything in their path. Ultimately - the thicker the protection of heavy elements - the more fragments and secondary radiation we will receive. Lead can greatly attenuate only relatively mild radiation from terrestrial nuclear reactors.
High-energy gamma radiation has a similar effect - it is also capable of tearing heavy atoms to shreds due to a photonuclear reaction.
The ongoing processes can be considered using the example of an x-ray tube.
Electrons from the cathode fly towards the heavy metal anode, and upon collision with it, X-rays are generated due to bremsstrahlung.
When an electron from cosmic radiation arrives at our ship, our radiation protection will turn into a natural X-ray tube, next to our delicate microcircuits and even more delicate living organisms.
Because of all these problems, radiation shielding from heavy elements, as on earth, is not used in space. They use protection mostly consisting of aluminum, hydrogen (from various polyethylenes, etc.), since it can only be broken into subatomic particles - and this is much more difficult, and such protection generates less secondary radiation.
But in any case, there is no protection from TGCH, moreover - the more protection - the more secondary radiation from high-energy particles, the optimal thickness is about 2-3 mm of aluminum. The most difficult thing is the combination of hydrogen protection, and slightly heavier elements (the so-called Graded-Z) - but this is not much better than pure "hydrogen" protection. In general, cosmic radiation can be attenuated by about 10 times, and that's it.
