The atmosphere is the gas envelope of the planet, moving together with the planet in world space as a whole. Almost all the planets of our solar system have their own atmospheres, but only the earth's atmosphere is capable of supporting life. In the atmospheres of the planets there are aerosol particles: solid dust particles raised from the solid surface of the planet, liquid or solid particles resulting from the condensation of atmospheric gases, meteoric dust. Let us consider in detail the composition and features of the atmospheres of the planets of the solar system.
Mercury. There are traces of the atmosphere on this planet: helium, argon, oxygen, carbon and xenon are recorded. The pressure of the atmosphere on the surface of Mercury is extremely small: it is two-trillionth of the Earth's normal atmospheric pressure. With such a rarefied atmosphere, the formation of winds and clouds is impossible in it, it does not protect the planet from the heat of the Sun and cosmic radiation.
Venus. In 1761, Mikhail Lomonosov, observing the passage of Venus across the disk of the Sun, noticed a thin iridescent rim that surrounded the planet. This is how the atmosphere of Venus was discovered. This atmosphere is extremely powerful: the pressure at the surface was 90 times greater than at the surface of the Earth. The atmosphere of Venus is 96.5% carbon dioxide. Nitrogen accounts for no more than 3%. In addition, impurities of inert gases (first of all, argon) were found. The greenhouse effect in Venus's atmosphere is raising the temperature by 400 degrees!
The sky on Venus has a bright yellow-green hue. The foggy haze extends to an altitude of about 50 km. Further, up to an altitude of 70 km, there are clouds of small drops of sulfuric acid. It is believed to be formed from sulfur dioxide from volcanoes. The speed of rotation at the level of the upper boundary of the clouds is different than above the surface of the planet itself. This means that over the equator of Venus at an altitude of 60-70 km, a hurricane wind constantly blows at a speed of 100-300 m / s in the direction of the planet's motion. The uppermost layers of Venus's atmosphere are composed almost entirely of hydrogen.
The atmosphere of Venus extends to an altitude of 5500 km. In accordance with the rotation of Venus from east to west in the same direction, the rotation of the atmosphere occurs. According to the temperature profile, the atmosphere of Venus is divided into two regions: the troposphere and the thermosphere. On the surface, the temperature is + 460 ° C, it changes little day and night. Towards the upper border of the troposphere, the temperature drops to -93 ° C.
Mars. The sky of this planet is not black, as it was supposed, but pink. It turned out that the dust hanging in the air absorbs 40% of the incoming sunlight, creating a color effect. The atmosphere of Mars is 95% carbon dioxide. About 4% is accounted for by nitrogen and argon. Oxygen and water vapor in the Martian atmosphere is less than 1%. The average atmospheric pressure at the surface level is 15,000 times less than on Venus, and 160 times less than at the Earth's surface. The greenhouse effect raises the average surface temperature by 9 ° C.
Mars is characterized by sharp temperature fluctuations: during the day the temperature can reach + 27 ° С, but by the morning up to -50 ° С. This is due to the fact that the rarefied atmosphere of Mars is not able to retain heat. One of the manifestations of the temperature difference is very strong winds, the speed of which reaches 100 m / s. On Mars, there are clouds of a wide variety of shapes and types: cirrus, wavy.
A. Mikhailov, prof.
Science and Life // Illustrations
Lunar landscape.
Melting of the polar spot on Mars.
Orbits of Mars and Earth.
Lowell's map of Mars.
Kühl's model of Mars.
Drawing of Mars by Antoniadi.
Considering the question of the existence of life on other planets, we will only talk about the planets of our solar system, since we do not know anything about the presence of other suns, which are stars, of their own planetary systems, similar to ours. According to modern views on the origin of the solar system, one can even assume that the formation of planets orbiting a central star is a case, the probability of which is negligible, and that therefore the vast majority of stars do not have their own planetary systems.
Further, it is necessary to make a reservation that we involuntarily consider the question of life on planets from our, earthly point of view, assuming that this life manifests itself in the same forms as on Earth, that is, assuming life processes and the general structure of organisms similar to those on earth. In this case, for the development of life on the surface of any planet, certain physicochemical conditions must exist, the temperature must not be too high or too low, water and oxygen must be available, while the basis of organic matter must be carbon compounds.
Atmospheres of the planets
The presence of the atmosphere at the planets is determined by the tension of the force of gravity on their surface. Large planets have sufficient gravitational force to keep a gaseous shell around them. Indeed, gas molecules are in constant rapid motion, the speed of which is determined by the chemical nature of this gas and the temperature.
Light gases - hydrogen and helium - have the highest velocity; as the temperature rises, the speed increases. Under normal conditions, that is, a temperature of 0 ° and atmospheric pressure, the average velocity of a hydrogen molecule is 1840 m / sec, and oxygen is 460 m / sec. But under the influence of mutual collisions, individual molecules acquire speeds several times higher than the indicated average numbers. If a hydrogen molecule appears in the upper layers of the earth's atmosphere at a speed exceeding 11 km / s, then such a molecule will fly away from the earth into interplanetary space, since the force of gravity will be insufficient to hold it.
The smaller the planet, the less massive it is, the less this limiting or, as they say, critical speed. For Earth, the critical speed is 11 km / sec, for Mercury it is only 3.6 km / sec, for Mars 5 km / sec, for Jupiter, the largest and most massive of all planets, 60 km / sec. It follows from this that Mercury, and even more so even smaller bodies, like satellites of planets (including our Moon) and all small planets (asteroids), cannot keep the atmospheric envelope near their surface with their weak attraction. Mars is able, albeit with difficulty, to hold an atmosphere much thinner than that of Earth, while Jupiter, Saturn, Uranus and Neptune are gravitationally strong enough to hold powerful atmospheres containing light gases like ammonia and methane, and possibly free hydrogen as well.
The absence of an atmosphere inevitably entails the absence of water in a liquid state. In an airless space, water evaporation is much more vigorous than at atmospheric pressure; therefore, the water quickly turns into steam, which is a very light basin, subject to the same fate as other gases in the atmosphere, that is, it leaves the planet's surface more or less quickly.
It is clear that on a planet devoid of atmosphere and water, conditions for the development of life are completely unfavorable, and we cannot expect either plant or animal life on such a planet. All minor planets, satellites of planets, and from major planets - Mercury fall under this category. Let's say a little more about the two bodies of this category, namely the Moon and Mercury.
Moon and Mercury
For these bodies, the absence of an atmosphere was established not only by the above considerations, but also by direct observations. When the Moon moves across the sky, making its way around the Earth, it often covers the stars with itself. The disappearance of a star behind the disk of the Moon can be observed already in a small tube, and it always happens quite instantly. If the lunar paradise were surrounded by at least a rare atmosphere, then, before completely disappearing, the star would shine through this atmosphere for some time, and the apparent brightness of the star would gradually decrease, in addition, due to the refraction of light, the star would seem displaced from its place ... All these phenomena are completely absent when the stars are covered by the Moon.
Lunar landscapes, observed through telescopes, are striking in the sharpness and contrast of their illumination. There is no penumbra on the moon. Deep black shadows are found near bright, sunlit places. This happens because, due to the absence of an atmosphere, there is no blue daytime sky on the moon, which with its light would soften the shadows; the sky is always black there. There is no twilight on the moon, and after sunset, a dark night immediately sets in.
Mercury is much farther from us than the Moon. Therefore, we cannot observe such details as on the Moon. We do not know the type of its landscape. The coverage of stars by Mercury, due to its apparent smallness, is extremely rare, and there is no indication that such coverage has ever been observed. But there are passages of Mercury in front of the disk of the Sun, when we observe that this planet in the form of a tiny black point slowly creeps along the bright solar surface. In this case, the edge of Mercury is sharply outlined, and those phenomena that were seen when Venus passed in front of the Sun were not observed in Mercury. But it is still possible that small traces of the atmosphere of Mercury were preserved, but this atmosphere has a completely insignificant density compared to the earth.
On the Moon and Mercury, temperature conditions are completely unfavorable for life. The moon rotates on its axis extremely slowly, due to which day and night continue on it for fourteen days. The heat of the sun's rays is not tempered by the air shell, and as a result, during the day on the moon, the surface temperature rises to 120 °, that is, above the boiling point of water. During the long night, the temperature drops to 150 ° below zero.
During the lunar eclipse, it was observed that, within just a little over an hour, the temperature dropped from 70 ° C to 80 ° C, and after the end of the eclipse, almost in an equally short period of time, returned to its original value. This observation points to the extremely low thermal conductivity of the rocks that form the lunar surface. Solar heat does not penetrate deep, but remains in the thinnest upper layer.
One must think that the surface of the Moon is covered with light and loose volcanic tuffs, maybe even ash. Already at a depth of one meter the contrasts of heat and cold are smoothed out only so that it is likely that an average temperature prevails there, which does not differ much from the average temperature of the earth's surface, that is, it is several degrees above zero. Some germs of living matter may have survived there, but their fate, of course, is unenviable.
On Mercury, the difference in temperature conditions is even sharper. This planet is always turned to the Sun on one side. In the daytime hemisphere of Mercury, the temperature reaches 400 °, that is, it is above the melting point of lead. And on the night hemisphere, frost should reach the temperature of liquid air, and if there was an atmosphere on Mercury, then on the night side it should have turned into liquid, and maybe even freeze. Only on the border between the daytime and nighttime hemispheres within a narrow zone can there be temperature conditions that are at least somewhat favorable for life. However, there is no need to think about the possibility of a developed organic life there. Further, in the presence of traces of the atmosphere, free oxygen could not be retained in it, since at the temperature of the daytime hemisphere oxygen vigorously combines with most chemical elements.
So, with regard to the possibility of life on the Moon, the prospects are rather unfavorable.
Venus
Unlike Mercury, Venus has certain signs of a thick atmosphere. When Venus passes between the Sun and the Earth, it is surrounded by a light ring - this is its atmosphere, which is illuminated by the Sun in transmission. Such transits of Venus in front of the solar disk are very rare: the last transit took place in 18S2, the next next one will occur in 2004.However, almost every year, Venus passes, though not through the solar disk itself, but rather close to it, and then it is visible in the shape of a very narrow sickle, like the moon just after the new moon. According to the laws of perspective, the sunlit crescent of Venus should have formed an arc of exactly 180 °, but in reality there is a longer bright arc, which occurs due to the reflection and bending of the sun's rays in the atmosphere of Venus. In other words, there is twilight on Venus, which increases the length of the day and partially illuminates its night hemisphere.
The composition of the atmosphere of Venus is still poorly understood. In 1932, with the help of spectral analysis, the presence of a large amount of carbon dioxide was detected in it, corresponding to a layer 3 km thick under standard conditions (i.e., at 0 ° and 760 mm of pressure).
The surface of Venus always appears to us to be dazzling white and without noticeable permanent spots or outlines. It is believed that in the atmosphere of Venus there is always a thick layer of white clouds, completely covering the solid surface of the planet.
The composition of these clouds is unknown, but most likely they are water vapor. We do not see what is under them, but it is clear that the clouds should temper the heat of the sun's rays, which on Venus, which is closer to the Sun than the Earth, would otherwise be excessively strong.
Temperature measurements gave about 50-60 ° C for the daytime hemisphere, and 20 ° C for the nighttime. Such contrasts are explained by the slow rotation of Venus about the axis. Although the exact period of its rotation is unknown due to the absence of noticeable spots on the planet's surface, it seems that a day on Venus lasts no less than our 15 days.
What are the odds of life on Venus?
In this respect, scientists differ in their opinions. Some believe that all the oxygen in its atmosphere is chemically bound and exists only in the composition of carbon dioxide. Since this gas has low thermal conductivity, then the temperature near the surface of Venus should be quite high, perhaps even close to the boiling point of water. This could explain the presence of a large amount of water vapor in the upper layers of its atmosphere.
Note that the above results of determining the temperature of Venus refer to the outer surface of the cloud cover, i.e. to a fairly high height above its hard surface. In any case, one must think that the conditions on Venus resemble a greenhouse or a greenhouse, but probably with an even much higher temperature.
Mars
The planet Mars is of the greatest interest from the point of view of the question of the existence of life. In many ways, it is similar to Earth. From the spots that are clearly visible on its surface, it has been established that Mars rotates about its axis, making one revolution at 24 hours and 37 m. Therefore, there is a change of day and night on it of almost the same duration as on Earth.
The axis of rotation of Mars makes an angle of 66 ° with the plane of its orbit, almost exactly the same as that of the Earth. Thanks to this tilt of the axis, the seasons on Earth change. Obviously, there is a similar change on Mars, but only every season on it is almost twice as long as ours. The reason for this is that Mars, being on average one and a half times farther from the Sun than the Earth, makes its revolution around the Sun in almost two Earth years, more precisely in 689 days.
The most distinct detail on the surface of Mars, noticeable when looking at it through a telescope, is a white spot, which coincides in position with one of its poles. The spot is best seen at the south pole of Mars, because during the periods of its closest proximity to the Earth, Mars is tilted towards the Sun and the Earth with its southern hemisphere. It is noticed that with the onset of winter in the corresponding hemisphere of Mars, the white spot begins to increase, and in summer it decreases. There were even cases (for example, in 1894) when the polar spot almost completely disappeared in autumn. One may think that it is snow or ice, which is deposited in winter by a thin cover near the poles of the planet. That this cover is very thin follows from the indicated observation of the disappearance of the white spot.
Due to the remoteness of Mars from the Sun, its temperature is relatively low. Summers are very cold there, but nevertheless it happens that the polar snows completely melt. The long duration of summer does not sufficiently compensate for the lack of heat. It follows that there is little snow, perhaps only a few centimeters, it is even possible that the white polar spots are not snow, but frost.
This circumstance is in full agreement with the fact that, according to all data, there is little moisture on Mars, little water. Seas and large bodies of water were not found on it. Clouds are very rarely observed in its atmosphere. The very orange color of the planet's surface, thanks to which Mars appears to the naked eye as a red star (hence its name for the ancient Roman god of war), by most "observers" is explained by the fact that the surface of Mars is a waterless sandy desert colored with iron oxides.
Mars moves around the Sun along a noticeably elongated ellipse. Due to this, its distance from the Sun changes over a fairly wide range - from 206 to 249 million km. When the Earth is on the same side of the Sun as Mars, the so-called oppositions of Mars occur (because Mars at this time is in the side of the sky opposite to the Sun). During oppositions, Mars is observed in the night sky under favorable conditions. Confrontations alternate on average after 780 days, or after two years and two months.
However, not in every confrontation Mars approaches the Earth at its shortest distance. For this, it is necessary that the opposition coincides with the time of the closest approach of Mars to the Sun, which happens only every seventh or eighth opposition, that is, after about fifteen years. Such oppositions are called great oppositions; they took place in 1877, 1892, 1909 and 1924. The next great confrontation will be in 1939 T. It is to these dates that the main observations of Mars and related discoveries are timed. Mars was closest to Earth during the opposition of 1924, but even then its distance from us was 55 million km. Mars is never closer to Earth.
"Channels" on Mars
In 1877, the Italian astronomer Schiaparelli, making observations in a relatively modest telescope, but under the transparent sky of Italy, discovered on the surface of Mars, in addition to dark spots, albeit incorrectly called seas, a whole network of narrow straight lines or stripes, which he called the straits (in Italian canale). Hence, the word "channel" began to be used in other languages to designate these mysterious formations.
Schiaparelli, as a result of his many years of observations, compiled a detailed map of the surface of Mars, on which hundreds of channels are drawn, connecting between the dogs> dark spots of the "seas". Later, the American astronomer Lowell, who even built a special observatory for observing Mars in Arizona, discovered channels in the dark spaces of the "seas". He found that both the "seas" and the canals change their visibility depending on the seasons: in the summer they become darker, sometimes taking on a gray-greenish tint, in winter they turn pale and brownish. Lowell's maps are even more detailed than Schiaparelli's, with many channels plotted on them, forming a complex but fairly regular geometric network.
To explain the phenomena observed on Mars, Lowell developed a theory that became widespread, mainly among astronomy enthusiasts. This theory boils down to the following.
Lowell's orange surface, like most other observers, is mistaken for a sandy wasteland. He considers the dark spots of the "seas" to be areas covered with vegetation - fields and forests. He considers the canals to be an irrigation network laid by intelligent beings living on the surface of the planet. However, the channels themselves are not visible to us from the Earth, since their width is far from sufficient for this. To be visible from Earth, the channels must be at least ten kilometers wide. Therefore, Lowell believes that we see only a wide strip of vegetation that unfolds its green leaves when the channel itself, which runs in the middle of this strip, is filled with spring water flowing in from the poles, where it is formed from the melting of polar snows.
However, little by little, doubts began to arise about the reality of such straight-line channels. The most indicative was the fact that the observers, armed with the most powerful modern telescopes, did not see any channels, but only observed an unusually rich picture of various details and shades on the surface of Mars, which, however, were devoid of regular geometric outlines. Only observers using medium-power tools saw and sketched the canals. Hence, a strong suspicion arose that the channels represent only an optical illusion (optical illusion) that occurs with extreme eye strain. Many works and various experiments have been carried out to clarify this circumstance.
The most convincing are the results obtained by the German physicist and physiologist Kühl. He arranged a special model depicting Mars. Against a dark background, Kuehl pasted a circle he had cut out of an ordinary newspaper, on which were placed several gray spots, resembling in their outlines the "seas" on Mars. If we look at such a model up close, then it is clear what it is - you can read the newspaper text and no illusion is created. But if you move further away, then with the right lighting, straight thin stripes begin to appear, going from one dark spot to another and, moreover, not coinciding with the lines of the printed text.
Kuehl studied this phenomenon in detail.
He showed that the three presence of many small details and shades, gradually turning into one another, when the eye cannot catch them "about all the details, there is a desire to combine these details with simpler geometric schemes, as a result of which the illusion of straight stripes appears where there is no correct outline. An outstanding contemporary observer, Antoniadi, who is also a good artist, paints Mars as spotty, with a mass of irregular details, but without any rectilinear channels.
You might think that this question is best solved by three photography help. The photographic plate cannot be fooled: it should, it would seem, show what actually exists on Mars. Unfortunately, this is not so. Photography, which has given so much in relation to stars and nebulae, gives less in relation to the surface of planets than the eye of the observer sees with the same instrument. This is explained by the fact that the image of Mars, obtained even with the largest and long-focal instruments, is very small on the plate - only up to 2 mm in diameter. Of course, such an image cannot make out large details. There is a defect from which modern photography enthusiasts, who shoot with Leica-type devices, suffer so much, namely, the graininess of the image appears, which obscures all the small details.
Life on Mars
However, photographs of Mars, taken through different light filters, clearly proved the existence of an atmosphere on Mars, although much more rare than on Earth. Sometimes in the evening in this atmosphere light points are noticed, which are probably cumulus clouds. But in general, the cloudiness on Mars is negligible, which is quite consistent with the small amount of water on it.
Nearly all Mars observers nowadays agree that the dark spots of the "seas" do indeed represent areas covered with plants. In this respect, Lowell's theory is confirmed. However, until relatively recently, there was one obstacle. The question was complicated by the temperature conditions on the surface of Mars.
Since Mars is one and a half times farther from the Sun than the Earth, it receives two and a quarter times less heat. The question of to what temperature such an insignificant amount of heat can warm its surface depends on the structure of the atmosphere of Mars, which is a "fur coat" of unknown thickness and composition.
Recently it was possible to determine the temperature of the surface of Mars by direct measurements. It turned out that in the equatorial regions at noon the temperature rises to 15-25 ° C, but in the evening a strong cold snap sets in, and the night, apparently, is accompanied by constant hard frosts.
Conditions on Mars are similar to those observed in our high mountains: thin air and transparency, significant heating by direct sunlight, cold in the shade and severe night frosts. The conditions are undoubtedly very harsh, but it can be assumed that the plants have acclimatized, adapted to them, as well as to the lack of moisture.
So, the existence of plant life on Mars can be considered almost proven, but we cannot say anything definite about animals, and even more intelligent ones.
As for the other planets of the solar system - Jupiter, Saturn, Uranus and Neptune, it is difficult to assume the possibility of life on them for the following reasons: firstly, the low temperature due to the distance from the Sun and, secondly, the poisonous gases recently discovered in their atmospheres - ammonia and methane. If these planets have a solid surface, then it is hidden somewhere at great depths, but we see only the upper layers of their extremely powerful atmospheres.
Even less likely is life on the planet farthest from the Sun - the recently discovered Pluto, about the physical conditions of which we still do not know anything.
So, of all the planets in our solar system (except for the Earth), one can suspect the existence of life on Venus and consider the existence of life on Mars almost proven. But, of course, this all refers to the present time. Over time, with the evolution of the planets, conditions can change dramatically. We will not talk about this due to lack of data.
The atmosphere of the planets and their satellites - its density and composition are determined by the diameter and mass of the planets, the distance from the Sun, the peculiarities of their formation and development. The farther the planet is from the Sun, the more volatile components were and are now in its composition; the less the planet's mass, the less its ability to hold these volatiles, etc. Probably, the terrestrial planets have long lost their primary atmosphere. The closest planet to the Sun, Mercury, with its relatively low mass (unable to hold molecules with an atomic weight of less than 40 in a gravitational field) and high surface temperature, has practically no atmosphere (CO 2 = 2000 atm-cm). There is a certain atmospheric corona, consisting of inert gases - argon, neon and helium. Apparently, argon and helium are radiogenic and constantly enter the atmosphere due to a kind of "emanation" of the rocks that make up Mercury, and, possibly, endogenous processes. The presence of neon is a mystery. It is difficult to assume that so much neon could have been present in the original substance of Mercury that it could still stand out from the bowels of this planet, especially since no solid evidence of plutonic activity has been found on this planet.
Venus has the warmest and most powerful atmosphere of all terrestrial planets. The planet's atmosphere is 97% CO 2, it contains 0 2, N 2 and H 2 0. The temperature at the surface reaches 747 + 20 K, the pressure (8.83 + 0.15) 10 6 Pa. The atmosphere of Venus is most likely the result of its inner activity. AP Vinogradov believed that the entire CO 2 of the Venusian atmosphere is due to the degassing of all carbonates at a high temperature of its surface. Apparently, this is not entirely true, for it is not clear how, then, these carbonates could have formed? It is unlikely that the temperature of the surface of Venus was significantly lower in the past, it is unlikely that there was once a hydrosphere on its surface, and, therefore, carbonates could not form. It was believed that all the water by Venus was lost due to the dissociation of its molecules in the atmosphere into hydrogen and oxygen, followed by the dissipation of hydrogen into space. Oxygen, on the other hand, entered into chemical reactions with carbonaceous matter, which led to the enrichment of the atmosphere with carbon dioxide. Perhaps this was so, but then we should assume on Venus the presence of plutonism, which ensures the supply of more and more portions of matter from its depths to the zone of reaction with oxygen, i.e. to the surface, which seems to be confirmed by the data obtained as a result research "Venus-13" and "Venus-14".
On Mars there is a small atmosphere, the pressure of which at the base, depending on the conditions, is in the range (2.9-8.8) 10 2 Pa. In the area of the V-King-1 station landing, the atmospheric pressure was 7.6-10 2 Pa. The mass of the Martian atmosphere in the northern hemisphere is somewhat greater than in the southern. Small amounts of water vapor and traces of ozone were found in the atmosphere. The temperature of the surface of Mars changes depending on latitude and reaches 140-150 K at the boundary of the polar caps. The temperature on the surface of the equatorial regions can be 300 K during the day, and at night it drops to 180 K. The maximum cooling occurs in the high latitudes of Mars during the long polar night. When the temperature drops to 145 K, atmospheric carbon dioxide begins to condense, but before that, water vapor freezes out of the atmosphere. The polar caps of Mars are probably composed of a lower layer of water ice, which is covered with solid carbon dioxide on top.
The atmospheres of the major planets Jupiter, Saturn and Uranus are composed of hydrogen, helium, methane; Jupiter's atmosphere is the most powerful of the other outer planets. Based on the analysis of the photo- and IR spectra, various models of light reflection in the atmospheres of the outer planets, in addition to the predominant H 2, CH 4, H 3 and He, components such as C 2 H 2, C 2 H 6, PH 3 were also found; the possibility of the presence of more complex organic substances is not excluded. The ratio H / He is about 10, that is, close to the solar one, the ratio of hydrogen isotopes D / H, for example, for Jupiter is 2 x 10 ~ 5, which is close to the interstellar ratio of 1.4 x 10 ~ 5. Based on the above, we can conclude that the matter of the outer planets does not undergo nuclear transformations and since the formation of the solar system, light gases have not been removed from the atmosphere of the outer planets. The phenomenon of the presence of atmospheres in the satellites of the outer planets is also very noteworthy. Even such moons of Jupiter as Io and Europa, with masses close to the mass of the Moon, nevertheless have an atmosphere, and Io's satellite, in particular, is surrounded by a sodium cloud. The atmospheres of Io and Titan have a reddish tint, and it has been established that this coloration is caused by different compounds.
The atmosphere of the Earth is very different from the atmospheres of other planets in the solar system. Having a nitrogen-oxygen base, the earth's atmosphere creates conditions for life, which, due to certain circumstances, cannot exist on other planets.
Instructions
Venus is the closest planet to the sun, which has an atmosphere, and such a high density that Mikhail Lomonosov asserted its existence in 1761. The presence of an atmosphere in Venus is such an obvious fact that until the twentieth century, mankind was under the influence of the illusion that Earth and Venus are twin planets, and life is also possible on Venus.
Space exploration has shown that everything is far from rosy. The atmosphere of Venus is ninety-five percent carbon dioxide, and does not release heat from the Sun outside, creating a greenhouse effect. Because of this, the temperature on the surface of Venus is 500 degrees Celsius, and the likelihood of life on it is negligible.
Mars has an atmosphere similar in composition to Venus, also consisting mainly of carbon dioxide, but with admixtures of nitrogen, argon, oxygen and water vapor, albeit in very small quantities. Despite the acceptable surface temperature of Mars at certain times of the day, it is impossible to breathe such an atmosphere.
In defense of proponents of ideas about life on other planets, it is worth noting that planetary scientists, having studied the chemical composition of the rocks of Mars, in 2013 declared that 4 billion years ago the red planet had the same amount of oxygen as the Earth.
The giant planets do not have a solid surface, and their atmosphere is similar in composition to that of the sun. Jupiter's atmosphere, for example, is mostly hydrogen and helium with small amounts of methane, hydrogen sulfide, ammonia, and water believed to be found in the inner layers of this vast planet.
Saturn's atmosphere is very similar to that of Jupiter, and is also, for the most part, composed of hydrogen and helium, albeit in slightly different proportions. The density of such an atmosphere is unusually high, and we can speak with a high degree of certainty only about its upper layers, in which clouds of frozen ammonia float, and the wind speed sometimes reaches one and a half thousand kilometers per hour.
Uranus, like the rest of the giant planets, has an atmosphere composed of hydrogen and helium. During the research carried out with the Voyager spacecraft, an interesting feature of this planet was discovered: the atmosphere of Uranus is not heated by any internal sources of the planet, and receives all its energy only from the Sun. This is why Uranus has the coldest atmosphere in the entire solar system.
Neptune has a gaseous atmosphere, but its blue color suggests that it contains an unknown substance that gives the atmosphere of hydrogen and helium such a hue. Theories about the absorption of the red color of the atmosphere by methane have not yet received their full confirmation.
What can be the connection between the presence of the atmosphere on the planet and the duration of its revolution around the axis? It would seem no. And yet, using the example of the planet closest to the Sun, Mercury, we are convinced that in some cases such a connection exists.
By the force of gravity, on its surface, Mercury could hold an atmosphere of the same composition as that of the earth, although not as dense.
The speed required to completely overcome the attraction of Mercury on its surface is 4900 m / s, and the fastest molecules of our atmosphere do not reach this speed at low temperatures). And yet, Mercury is devoid of an atmosphere. The reason is that it moves around the Sun like the motion of the Moon around the Earth, that is, it always faces the central luminary with the same side. The orbital traversal time (88 days) is equal to the revolution time around the axis. Therefore, on one side of Mercury, the one that always faces the Sun, the day continuously lasts and there is an eternal summer; on the other side, turned away from the Sun, there is a continuous night and eternal winter.
With such extraordinary climatic conditions, what should happen to the planet's atmosphere? Obviously, in the night half, under the influence of the terrible cold, the atmosphere will thicken into liquid and freeze. Due to a sharp drop in atmospheric pressure, the gas shell of the daytime side of the planet rushes there and hardens in turn. As a result, the entire atmosphere should collect in solid form on the night side of the planet, or rather, in that part of it where the Sun does not look at all. Thus, the absence of an atmosphere on Mercury is an inevitable consequence of physical laws.
For the same reasons that the existence of an atmosphere on Mercury is unacceptable, we must also reject the guess, which is often expressed, that there is an atmosphere on the invisible side of the Moon. It is safe to say that if there is no atmosphere on one side of the moon, then it cannot be on the opposite). Wells' science fiction novel The First Men on the Moon is at odds with the truth on this point. The novelist admits that there is air on the Moon, which, during a continuous 14-day night, manages to thicken and freeze, and with the onset of day it again turns into a gaseous state, forming an atmosphere. Nothing of the kind, however, can happen. “If,” wrote prof. O.D. Khvolson, - on the dark side of the Moon the air solidifies, then almost all the air should go from the light side to the dark and freeze there as well. Under the influence of sunlight, solid air should turn into gas, which will immediately pass to the dark side and solidify there ... Continuous distillation of air should take place, and nowhere and never can it achieve any noticeable elasticity. "
It has even been established that there is a lot of carbon dioxide in the atmosphere, or rather, in the stratosphere of Venus - ten thousand times more than in the earth's atmosphere.