Which planet has virtually no atmosphere? Are the planets habitable? When it gets hot

The planets belonging to the terrestrial group - Mercury, Venus, Earth, Mars, Pluto - have small sizes and masses, the average density of these planets is several times higher than the density of water; they rotate slowly around their axes; they have few satellites (Mercury and Venus have none at all, Mars has two, Earth has one).

The similarity of the terrestrial planets does not exclude some differences. For example, Venus, unlike other planets, rotates in the direction opposite to its movement around the Sun, and is 243 times slower than the Earth.. The period of rotation of Mercury (i.e., the year of this planet) is only 1/3 longer than the period of its rotation around axes.
The angles of inclination of the axes to the planes of their orbits for the Earth and Mars are approximately the same, but completely different for Mercury and Venus. Consequently, Mars has the same seasons as the Earth, although they are almost twice as long as on Earth.

It is possible to include distant Pluto, the smallest of the 9 planets, among the terrestrial planets. The average diameter of Pluto is about 2260 km. The diameter of Charon, the moon of Pluto, is only half the size. Therefore, it is possible that the Pluto-Charon system, like the Earth-Moon system, is a “double planet”.

Similarities and differences are also found in the atmospheres of the terrestrial planets. Unlike Mercury, which, like the Moon, is practically devoid of an atmosphere, Venus and Mars have one. Venus has a very dense atmosphere, mainly consisting of carbon dioxide and sulfur compounds. The atmosphere of Mars, on the contrary, is extremely rarefied and also poor in oxygen and nitrogen. The pressure at the surface of Venus is almost 100 times greater, and at Mars almost 150 times less than at the surface of the Earth.

The temperature at the surface of Venus is very high (about 500°C) and remains almost the same all the time. The high surface temperature of Venus is due to the greenhouse effect. The thick, dense atmosphere allows the rays of the Sun to pass through, but blocks infrared thermal radiation coming from the heated surface. Gas in the atmospheres of the terrestrial planets is in continuous motion. Often during dust storms that last for several months, huge amounts of dust rise into the atmosphere of Mars. Hurricane winds have been recorded in the atmosphere of Venus at altitudes where the cloud layer is located (from 50 to 70 km above the surface of the planet), but near the surface of this planet the wind speed reaches only a few meters per second.

Terrestrial planets, like the Earth and the Moon, have rocky surfaces. The surface of Mercury, replete with craters, is very similar to the Moon. There are fewer “seas” there than on the Moon, and they are small. As on the Moon, most craters were formed by meteorite impacts. Where there are few craters, we see relatively young areas of the surface.

A rocky desert and many individual stones are visible in the first photo-television panoramas transmitted from the surface of Venus by automatic stations of the Venus series. Ground-based radar observations discovered many shallow craters on this planet, the diameters of which range from 30 to 700 km. In general, this planet turned out to be the smoothest of all the terrestrial planets, although it also has large mountain ranges and extensive hills, twice the size of terrestrial Tibet.

Almost 2/3 of the Earth's surface is occupied by oceans, but there is no water on the surface of Venus and Mercury.

The surface of Mars is also replete with craters. There are especially many of them in the southern hemisphere of the planet. The dark areas that occupy a significant part of the planet's surface are called seas. The diameters of some seas exceed 2000 km. Hills resembling the earth's continents, which are light fields of orange-red color, are called continents. Like Venus, there are huge volcanic cones. The height of the largest of them - Olympus - exceeds 25 km, the diameter of the crater is 90 km. The base diameter of this giant cone-shaped mountain is more than 500 km. The fact that millions of years ago powerful volcanic eruptions occurred on Mars and surface layers were displaced is evidenced by the remains of lava flows, huge surface faults (one of them - Mariner - stretches for 4000 km), numerous gorges and canyons

4.6 billion years ago, condensations began to form in our Galaxy from clouds of stellar matter. As the gases became more dense and condensed, they heated up, radiating heat. As density and temperature increased, nuclear reactions began, converting hydrogen into helium. Thus, a very powerful source of energy arose - the Sun.

Simultaneously with the increase in temperature and volume of the Sun, as a result of the combination of fragments of interstellar dust in a plane perpendicular to the axis of rotation of the Star, planets and their satellites were created. The formation of the Solar System was completed about 4 billion years ago.

At the moment, the Solar System has eight planets. These are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Nepton. Pluto is a dwarf planet and the largest known object in the Kuiper Belt (which is a large belt of debris similar to the asteroid belt). After its discovery in 1930, it was considered the ninth planet. This changed in 2006 with the adoption of a formal definition of planet.

On the planet closest to the Sun, Mercury, it never rains. This is due to the fact that the planet’s atmosphere is so rarefied that it is simply impossible to detect. And where will the rain come from if the daytime temperature on the surface of the planet sometimes reaches 430º Celsius? Yeah, I wouldn't want to be there :)

But on Venus there is constant acid rain, since the clouds above this planet do not consist of life-giving water, but of deadly sulfuric acid. True, since the temperature on the surface of the third planet reaches 480º Celsius, drops of acid evaporate before they reach the planet. The sky above Venus is pierced by large and terrible lightning, but there is more light and roar from them than rain.

On Mars, according to scientists, a long time ago the natural conditions were the same as on Earth. Billions of years ago, the atmosphere above the planet was much denser, and it is possible that heavy rainfall filled these rivers. But now there is a very thin atmosphere above the planet, and photographs transmitted by reconnaissance satellites indicate that the surface of the planet resembles the deserts of the southwestern United States or the Dry Valleys in Antarctica. When winter hits parts of Mars, thin clouds containing carbon dioxide appear above the red planet and frost covers dead rocks. Early in the morning there are such thick fogs in the valleys that it seems as if it is about to rain, but such expectations are in vain.

By the way, the air temperature during the day on Mrsa is 20º Celsius. True, at night it can drop to - 140 :(

Jupiter is the largest of the planets and is a giant ball of gas! This ball is almost entirely composed of helium and hydrogen, but it is possible that deep inside the planet there is a small solid core shrouded in an ocean of liquid hydrogen. However, Jupiter is surrounded on all sides by colored bands of clouds. Some of these clouds even consist of water, but, as a rule, the vast majority of them are formed by frozen crystals of ammonia. From time to time, powerful hurricanes and storms fly over the planet, bringing with them snowfalls and rains of ammonia. This is where to hold the Magic Flower.

During a strong solar storm, the Earth loses about 100 tons of atmosphere.

Space Weather Facts

Solar flares can sometimes heat the solar surface to temperatures of 80 million F, which is hotter than the sun's core!

The fastest coronal mass ejection recorded was on August 4, 1972, and it traveled from the Sun to Earth in 14.6 hours - a speed of about 10 million kilometers per hour or 2,778 km/sec.

On April 8, 1947, the largest sunspot in recent history was recorded, with a maximum size exceeding 330 times the area of the Earth.

The most powerful solar flare in the last 500 years occurred on September 2, 1859 and was discovered by two astronomers who were lucky enough to look at the sun at the right time!

Between May 10 and May 12, 1999, the solar wind pressure virtually disappeared, causing the Earth's magnetosphere to expand more than 100 times in volume!

Typical coronal mass ejections can be millions of kilometers in size, but the mass is equivalent to a small mountain!

Some sunspots are so cool that water vapor can form at a temperature of 1550 C.

The most powerful auroras can generate more than 1 trillion watts, which is comparable to an average earthquake.

On March 13, 1989, in Quebec (Canada), as a result of a major geomagnetic storm, a major power failure occurred, causing a power outage for 6 hours. Damage to Canada's economy amounted to $6 billion

During intense solar flares, astronauts may see bright, flashing streaks of light from the impact of high-energy particles on the eyeballs.

The biggest challenge for astronauts traveling to Mars will be coping with solar storms and radiation.

Space weather forecasting costs just $5 million a year, but saves more than $500 billion in annual revenue from the satellite and electrical industries.

During the last solar cycle, $2 billion worth of satellite technology was damaged or destroyed.

A repeat of the Carrington event, like the one in 1859, could cost $30 billion a day for the US power grid and up to $70 billion for the satellite industry.

On August 4, 1972, a solar flare was so strong that, according to some estimates, an astronaut would have received a lethal dose of radiation during flight.

During the Maunder Minimum (1645-1715), accompanied by the onset of the Little Ice Age, the 11-year sunspot cycle was not detected.

In one second, the sun converts 4 million tons of matter into clean energy.

The Sun's core is almost as dense as lead and has a temperature of 15 million degrees C.

During a strong solar storm, the Earth loses about 100 tons of atmosphere.

Rare earth magnetic toys can have a magnetic field 5 times stronger than the magnetic field of sunspots.

One of the striking features of the Solar System is the diversity of planetary atmospheres. Earth and Venus are similar in size and mass, but Venus's surface is 460°C hot under an ocean of carbon dioxide that presses down on the surface like a kilometer-long layer of water.

Callisto and Titan are large satellites of Jupiter and Saturn, respectively; they are almost the same size, but Titan has an extensive nitrogen atmosphere , much larger than that of the Earth, and Callisto is practically devoid of atmosphere.

Where do such extremes come from? If we knew this, we could explain why the Earth is full of life, while other planets near it appear lifeless. By understanding how atmospheres evolve, we could determine which planets outside the solar system might be habitable.

The planet acquires gas cover in different ways. It can spew steam from its depths, it can capture volatile substances from comets and asteroids upon collision with them, or its gravity can attract gases from interplanetary space. In addition, planetary scientists come to the conclusion that the loss of gas plays as important a role as its acquisition.

Even the earth's atmosphere, which looks unshakable, gradually flows into outer space.

The rate of leakage is currently very small: about 3 kg of hydrogen and 50 g of helium (the two lightest gases) per second; but even such a trickle can become significant over a geological period, and the rate of loss may once have been much higher. As Benjamin Franklin wrote, “A small leak can sink a big ship.”
Current atmospheres of terrestrial planets and satellites of giant planets reminiscent of the ruins of medieval castles - these are the remnants of former luxury that have become a victim of robbery and dilapidation .
The atmospheres of even smaller bodies are like ruined forts - defenseless and easily vulnerable.

By recognizing the importance of atmospheric leakage, we are changing our understanding of the future of the solar system.
For decades, scientists have tried to understand why Mars is so thin.
atmosphere, but now we are surprised that he even retained
some kind of atmosphere.
Is the difference between Titan and Callisto due to the fact that Callisto lost its atmosphere before air appeared on Titan? Was Titan's atmosphere once denser than it is today? How did Venus retain nitrogen and carbon dioxide but lose all water?
Did a hydrogen leak contribute to the origin of life on Earth? Will our planet ever turn into a second Venus?

When it gets hot

If
The rocket has reached its second escape velocity, then it is moving so fast that it is able to overcome the gravity of the planet. The same can be said of atoms and molecules, although they usually achieve escape velocity without having a specific target.
During thermal evaporation, gases become so hot that they cannot be contained.
In non-thermal processes, atoms and molecules are ejected as a result of chemical reactions or the interaction of charged particles. Finally, when colliding with asteroids and comets, entire pieces of the atmosphere are torn off.

The most common process of these three is thermal evaporation. All bodies in the solar system are heated by sunlight. They get rid of this heat in two ways: by emitting infrared radiation and by evaporating the substance. In long-lived objects, such as the Earth, the first process dominates, and, for example, in comets, the second process dominates. If the balance between heating and cooling is upset, even a large body the size of Earth can heat up quite quickly, and at the same time its atmosphere, which usually contains a small fraction of the mass of the planet, can evaporate quite quickly.
Our solar system is filled with bodies devoid of air, apparently mainly due to thermal evaporation. A body becomes airless if solar heating exceeds a certain threshold, depending on the body's gravitational force.
Thermal evaporation occurs in two ways.
The first is called Jeans evaporation in honor of the English astrophysicist James Jeans, who described this phenomenon at the beginning of the 20th century.
In this case, the air from the upper layer of the atmosphere literally evaporates atom by atom, molecule by molecule. In lower layers, mutual collisions hold particles together, but above a level called the exobase (at Earth's 500 km above the surface), the air is so thin that gas particles almost never collide. Above the exobase, nothing can stop an atom or molecule that has sufficient speed to fly into space.

Hydrogen, as the lightest gas, overcomes the planet's gravity more easily than others. But first he must get to the exobase, and on Earth this is a long process.
Molecules containing hydrogen usually do not rise above the lower atmosphere: water vapor (H2O) condenses and falls down as rain, and methane (CH4) oxidizes and turns into carbon dioxide (CO2). Some water and methane molecules reach the stratosphere and break down, releasing hydrogen, which slowly diffuses upward until it reaches the exobase. Some hydrogen escapes, as evidenced by ultraviolet images showing a halo of hydrogen atoms around our planet.

The temperature at the height of the Earth's exobase fluctuates around 1000 K, which corresponds to an average speed of hydrogen atoms of about 5 km/s.
This is less than the second escape velocity for the Earth at this altitude (10.8 km/s); but the velocities of the atoms around the mean are widely distributed, so some hydrogen atoms have a chance to overcome the planet's gravity. The leakage of particles from the high-speed “tail” in their velocity distribution explains from 10 to 40% of the Earth’s loss of hydrogen. The evaporation of Jeans partly explains the lack of an atmosphere on the Moon: gases emerging from under the surface of the Moon easily evaporate into space.

The second path of thermal evaporation is more effective. While during Jeans evaporation the gas escapes molecule by molecule, the heated gas can escape entirely. The upper layers of the atmosphere can absorb ultraviolet radiation from the Sun, heat up and, expanding, push air upward.
As the air rises, it accelerates, overcomes the speed of sound and reaches escape velocity. This form of thermal evaporation is called
hydrodynamic outflow, or planetary wind (by analogy with the solar wind - a stream of charged particles ejected by the Sun into space).

Basic provisions

Many
The gases that make up the atmosphere of the Earth and other planets slowly flow into space. Hot gases, especially light gases, evaporate, chemical
reactions and collisions of particles lead to the ejection of atoms and molecules, and
comets and asteroids sometimes tear off large chunks of the atmosphere.
The leak explains many of the mysteries of the solar system. For example, Mars is red because its water vapor has split into hydrogen and oxygen; hydrogen flew into space, and oxygen oxidized (covered with rust) the soil.
A similar process on Venus led to the appearance of a dense atmosphere from
carbon dioxide. Surprisingly, Venus's mighty atmosphere is the result of a gas leak.

David Catling and Kevin Zahnle
Magazine "In the World of Science"

The Earth is losing its atmosphere! Are we at risk of oxygen starvation?

Researchers were amazed by a recent discovery: it turned out that our planet is losing its atmosphere faster than Venus and Mars due to the fact that it has a much larger and more powerful magnetic field.

This may mean that the Earth's magnetic field is not as good a protective shield as previously thought. Scientists were confident that it was thanks to the action of the Earth's magnetic field that the atmosphere was well protected from the harmful effects of the Sun. But it turned out that the Earth’s magnetosphere contributes to the thinning of the Earth’s atmosphere due to the accelerated loss of oxygen.

According to Christopher Russell, a professor of geophysics and a specialist in space physics at the University of California, scientists are accustomed to believing that humanity is extremely lucky with its earthly “residence”: the Earth’s remarkable magnetic field, they say, perfectly protects us from solar “attacks” - cosmic rays, solar flares Sun and solar wind. Now it turns out that the earth’s magnetic field is not only a protector, but also an enemy.

A group of specialists led by Russell came to this conclusion while working together at the Conference of Comparative Planetology.

A. Mikhailov, prof.

Science and life // Illustrations

Lunar landscape.

Melting polar spot on Mars.

Orbits of Mars and Earth.

Lowell's map of Mars.

Kühl's model of Mars.

Drawing of Mars by Antoniadi.

When considering the question of the existence of life on other planets, we will talk only about the planets of our solar system, since we know nothing about the presence of other suns, such as stars, of their own planetary systems similar to ours. According to modern views on the origin of the solar system, one can even believe that the formation of planets orbiting a central star is an event whose probability is negligible, and that therefore the vast majority of stars do not have their own planetary systems.

Next, we need to make a reservation that we inevitably 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 are similar to those on earth. In this case, for the development of life on the surface of a planet, certain physical and chemical conditions must exist, the temperature must not be too high and not too low, the presence of water and oxygen must be present, and the basis of organic matter must be carbon compounds.

Planetary atmospheres

The presence of atmospheres on planets is determined by the tension 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 temperature.

Light gases - hydrogen and helium - have the highest speed; As the temperature increases, the speed increases. Under normal conditions, i.e., a temperature of 0° and atmospheric pressure, the average speed of a hydrogen molecule is 1840 m/sec, and that of oxygen is 460 m/sec. But under the influence of mutual collisions, individual molecules acquire speeds several times greater 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/sec, then such a molecule will fly away from the Earth into interplanetary space, since the force of Earth’s gravity will be insufficient to hold it.

The smaller the planet, the less massive it is, the lower 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 that Mercury, and even more so even smaller bodies, like the satellites of the planets (including our Moon) and all small planets (asteroids), cannot retain the atmospheric shell at their surface with their weak attraction. Mars is able, albeit with difficulty, to retain an atmosphere much thinner than that of the Earth, while Jupiter, Saturn, Uranus and Neptune, their gravity is strong enough to retain powerful atmospheres containing light gases such as ammonia and methane, and possibly also free hydrogen.

The absence of an atmosphere inevitably entails the absence of liquid water. In airless space, the evaporation of water occurs much more energetically than at atmospheric pressure; therefore, water quickly turns into steam, which is a very light basin, subject to the same fate as other atmospheric gases, that is, it more or less quickly leaves the surface of the planet.

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 of the 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. As the Moon moves across the sky on its way around the Earth, it often covers the stars. The disappearance of a star behind the disk of the Moon can already be observed through a small telescope, and it always occurs 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 appear displaced from its place . All these phenomena are completely absent when the stars are covered by the Moon.

Lunar landscapes observed through telescopes amaze with the sharpness and contrast of their illumination. There are no penumbras on the Moon. Near bright, sunlit places there are deep black shadows. This happens because, due to the absence of an atmosphere, there is no blue daytime sky on the Moon, which would soften the shadows with its light; the sky there is always black. There is no twilight on the Moon, and after sunset the dark night immediately sets in.

Mercury is much further from us than the Moon. Therefore, we cannot observe such details as on the Moon. We do not know the appearance of its landscape. The occultation of stars by Mercury, due to its apparent smallness, is an extremely rare phenomenon, and there is no indication that such occultations have 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 dot, slowly creeps along the bright solar surface. In this case, the edge of Mercury is sharply outlined, and the phenomena that were seen when Venus passed in front of the Sun were not observed on Mercury. But it is still possible that small traces of Mercury’s atmosphere remain, but this atmosphere has a very negligible density compared to Earth’s.

Temperature conditions on the Moon and Mercury are completely unfavorable for life. The moon rotates around its axis extremely slowly, due to which day and night last for fourteen days. The heat of the sun's rays is not moderated by the air envelope, and as a result, during the day on the Moon the surface temperature rises to 120°, i.e. above the boiling point of water. During the long night, the temperature drops to 150° below zero.

During the lunar eclipse, it was observed how, in just over an hour, the temperature dropped from 70° heat to 80° below zero, and after the end of the eclipse, in almost the same short time it returned to its original value. This observation indicates 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 a meter, the contrasts of heat and cold are smoothed out “to the extent that an average temperature probably prevails there, differing little from the average temperature of the earth’s surface, i.e., several degrees above zero. It may be that some embryos of living matter have been preserved there, but their fate, of course, is unenviable.

On Mercury, the difference in temperature conditions is even sharper. This planet always faces the Sun with 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, the 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 frozen. Only on the border between the day and night 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 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 energetically combines with most chemical elements.

So, with regard to the possibility of life on the Moon, the prospects are quite unfavorable.

Venus

Unlike Mercury, Venus shows 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. Such passages of Venus in front of the solar disk are very rare: the last passage took place in 18S2, the next one will occur in 2004. However, almost every year Venus passes, although not through the solar disk itself, but close enough to it, and then it can be visible in the shape of a very narrow crescent, like the Moon immediately after the new moon. According to the laws of perspective, the crescent of Venus illuminated by the Sun should form an arc of exactly 180°, but in reality a longer bright arc is observed, which occurs due to the reflection and bending of solar 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 Venus's atmosphere is still poorly understood. In 1932, using spectral analysis, the presence of a large amount of carbon dioxide was discovered in it, corresponding to a layer 3 km thick under standard conditions (i.e. at 0° and 760 mm pressure).

The surface of Venus always appears to us dazzlingly 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 don’t see what is underneath them, but it is clear that the clouds must moderate 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° heat for the daytime hemisphere, and 20° frost for the nighttime hemisphere. Such contrasts are explained by the slow rotation of Venus around its axis. Although the exact period of its rotation is unknown due to the absence of noticeable spots on the surface of the planet, apparently, a day on Venus lasts no less than our 15 days.

What are the chances of life existing on Venus?

In this regard, scientists have different opinions. Some believe that all the oxygen in its atmosphere is chemically bound and exists only as part of carbon dioxide. Since this gas has low thermal conductivity, in this case 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 solid surface. In any case, one must think that the conditions on Venus resemble a greenhouse or greenhouse, but probably with an even much higher temperature.

Mars

The planet Mars is of greatest interest from the point of view of the question of the existence of life. In many ways it is similar to Earth. Based on the spots that are clearly visible on its surface, it has been established that Mars rotates around its axis, making one revolution every 24 hours and 37 meters. 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 axis tilt, the seasons change on Earth. Obviously, the same change exists on Mars, but each 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, completes its revolution around the Sun in almost two Earth years, or more precisely 689 days.

The most distinct detail on the surface of Mars, noticeable when viewing it through a telescope, is a white spot, its position coinciding with one of its poles. The spot at the south pole of Mars is best visible, because during periods of its greatest proximity to the Earth, Mars is tilted towards the Sun and Earth with its southern hemisphere. It has been noticed that with the onset of winter in the corresponding hemisphere of Mars, the white spot begins to increase, and in the summer it decreases. There were even cases (for example, in 1894) when the polar spot almost completely disappeared in the fall. One might think that this is snow or ice, which is deposited in winter as a thin layer near the poles of the planet. That this cover is very thin follows from the above observation of the disappearance of the white spot.

Due to the distance of Mars from the Sun, the temperature on it is relatively low. The summer there is very cold, and yet 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 little snow falls there, perhaps only a few centimeters, and it is even possible that the white polar spots consist not of snow, but of frost.

This circumstance is in full agreement with the fact that, according to all data, there is little moisture and little water on Mars. No seas or large expanses of water were 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 from the ancient Roman god of war), is explained by most observers by the fact that the surface of Mars is a waterless sandy desert, colored by iron oxides.

Mars moves around the Sun in a noticeably elongated ellipse. Due to this, its distance from the Sun varies over a fairly wide range - from 206 to 249 million km. When the Earth is on the same side of the Sun as Mars, so-called Mars oppositions occur (because Mars is on the opposite side of the sky from the Sun at that time). During oppositions, Mars appears in the night sky under favorable conditions. Oppositions alternate on average every 780 days, or two years and two months.

However, not at every opposition does Mars approach the Earth to its shortest distance. To do this, it is necessary that the opposition coincide with the time of Mars' closest approach to the Sun, which occurs only every seventh or eighth opposition, i.e., 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. The main observations of Mars and related discoveries are dated precisely to these dates. Mars was closest to Earth during the confrontation in 1924, but even then its distance from us was 55 million km. Mars never comes closer to Earth.

"Canals" on Mars

In 1877, the Italian astronomer Schiaparelli, making observations with a relatively modest-sized telescope, but under the transparent sky of Italy, discovered on the surface of Mars, in addition to dark spots called, although incorrectly, seas, a whole network of narrow straight lines or stripes, which he called straits (canale in Italian). 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 plotted, connecting dark spots of “seas” between each other. Later, the American astronomer Lowell, who even built a special observatory in Arizona to observe Mars, discovered channels in the dark spaces of the “seas.” He found that both the “seas” and the channels change their visibility depending on the seasons: in the summer they become darker, sometimes taking on a gray-greenish tint; in the winter they turn pale and become brownish. Lowell's maps are even more detailed than Schiaparelli's maps; they show many channels, forming a complex but fairly regular geometric network.

To explain the phenomena observed on Mars, Lowell developed a theory that became widespread, mainly among amateur astronomers. This theory boils down to the following.

Lowell, like most other observers, mistakes the orange surface of the planet 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 carried out by intelligent beings living on the surface of the planet. However, the channels themselves are not visible to us from 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, which puts out its green leaves when the channel itself, running in the middle of this strip, is filled in the spring with water flowing from the poles, where it is formed from the melting of the polar snows.

However, little by little doubts began to arise about the reality of such straightforward channels. The most significant was the fact that observers armed with the most powerful modern telescopes did not see any channels, but observed only an unusually rich picture of various details and shades on the surface of Mars, devoid, however, of correct 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. Much work and various experiments have been carried out to clarify this circumstance.

The most convincing results are those obtained by the German physicist and physiologist Kühl. He created a special model depicting Mars. On a dark background, Kühl pasted a circle he had cut out of an ordinary newspaper, on which were placed several gray spots, reminiscent in their outlines of the “sea” on Mars. If you look at such a model up close, you can clearly see what it is - you can read a newspaper text and no illusion is created. But if you move further away, then with the right lighting, straight thin stripes begin to appear, running from one dark spot to another and, moreover, not coinciding with the lines of printed text.

Kühl studied this phenomenon in detail.

He showed that there are many small details and shades that gradually transform into one another, when the eye cannot catch them “in all the details, there is a desire to combine these details with simpler geometric patterns, as a result of which the illusion of straight stripes appears where there are no regular outlines. The eminent modern observer Antoniadi, who is at the same time a good artist, paints Mars as spotty, with a lot of irregular details, but without any straight-line channels.

One might think that this question would be best resolved by three aids of photography. The photographic plate cannot be deceived: it should, it would seem, show what is actually on Mars. Unfortunately, it is not. Photography, which, when applied to stars and nebulae, has given so much, when applied to the surface of the planets, gives less than what the eye of an observer sees with the same instrument. This is explained by the fact that the image of Mars, obtained even with the help of the largest and longest-focus instruments, turns out to be very small in size on the plate - with a diameter of only up to 2 mm. Of course, it is impossible to make out large details in such an image. With a strong magnification, such In photographs, there is a defect from which modern photography enthusiasts who shoot with cameras like Leica suffer so much: namely, the graininess of the image, which obscures all the small details.

Life on Mars

However, photographs of Mars taken through different filters clearly proved the existence of an atmosphere on Mars, although much rarer than that of the Earth. Sometimes in the evening, bright points are noticed in this atmosphere, 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.

Currently, almost all Mars observers 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 issue is complicated by 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 what temperature such a small amount of heat can warm its surface to depends on the structure of the atmosphere of Mars, which is a “fur coat” of thickness and composition unknown to us.

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 there is a strong cooling, and the night is apparently accompanied by constant severe frosts.

Conditions on Mars are similar to those observed on our high mountains: rarefied and transparent air, significant heating by direct sunlight, cold in the shade and severe night frosts. The conditions are undoubtedly very harsh, but we can assume that the plants have acclimatized and 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 regarding animals, and especially intelligent ones, we cannot yet say anything definite.

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, low temperature due to the distance from the Sun and, secondly, 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.

Life is even less likely on the most distant planet from the Sun - the recently discovered Pluto, about the physical conditions of which we still know nothing.

So, of all the planets in our solar system (except 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 applies to the present time. Over time, with the evolution of planets, conditions can change greatly. We will not talk about this due to lack of data.

The article talks about which planet does not have an atmosphere, why an atmosphere is needed, how it arises, why some are deprived of it, and how it could be created artificially.

Start

Life on our planet would be impossible without an atmosphere. And the point is not only in the oxygen that we breathe, by the way, it contains only a little more than 20%, but also in the fact that it creates the pressure necessary for living beings and protects from solar radiation.

According to scientific definition, the atmosphere is the gaseous shell of the planet that rotates with it. To put it simply, a huge accumulation of gas is constantly hanging over us, but we won’t notice its weight just like the Earth’s gravity, because we were born in such conditions and are used to it. But not all celestial bodies are lucky enough to have it. So we will not take into account which planet, since it is still a satellite.

Mercury

The atmosphere of planets of this type consists mainly of hydrogen, and the processes in it are very violent. Consider the atmospheric vortex alone, which has been observed for more than three hundred years - that same red spot in the lower part of the planet.

Saturn

Like all gas giants, Saturn is composed primarily of hydrogen. The winds do not subside, lightning flashes and even rare auroras are observed.

Uranus and Neptune

Both planets are hidden by a thick layer of clouds of hydrogen, methane and helium. Neptune, by the way, holds the record for the speed of winds on the surface - as much as 700 kilometers per hour!

Pluto

When recalling such a phenomenon as a planet without an atmosphere, it is difficult not to mention Pluto. It is, of course, far from Mercury: its gas shell is “only” 7 thousand times less dense than the earth’s. But still, this is the most distant and so far little-studied planet. Little is known about it either - only that it contains methane.

How to create an atmosphere for life

The thought of colonizing other planets has haunted scientists since the very beginning, and even more so about terraformation (creation in conditions without means of protection). All this is still at the level of hypotheses, but on Mars, for example, it is quite possible to create an atmosphere. This process is complex and multi-stage, but its main idea is as follows: spray bacteria on the surface, which will produce even more carbon dioxide, the density of the gas shell will increase, and the temperature will rise. After this, the polar glaciers will begin to melt, and due to increased pressure, the water will not evaporate without a trace. And then the rains will come and the soil will become suitable for plants.

So we figured out which planet is practically devoid of an atmosphere.