Characteristics of the terrestrial group. What are "terrestrial planets"? Earth's only satellite

Lecture: Solar system: terrestrial planets and giant planets, small bodies of the solar system

The solar system is made up of various kinds of bodies. The main one, of course, is the sun. But if you do not take it into account, then the planets are considered the main elements of the solar system. They are the second most important elements after the sun. The solar system itself bears this name due to the fact that the sun plays a key role here, since all the planets revolve around the sun.

terrestrial planets

There are currently two groups of planets in the solar system. The first group is the terrestrial planets. These include Mercury, Venus, Earth, and Mars. In this list, they are all listed based on the distance from the Sun to each of these planets. They got their name due to the fact that their properties are somewhat reminiscent of the characteristics of the planet Earth. All terrestrial planets have a solid surface. A feature of each of these planets is that they all rotate around their own axis in different ways. For example, for the Earth, one revolution of a complete rotation occurs during the day, that is, 24 hours, while for Venus, a complete rotation occurs in 243 Earth days.

Each of the terrestrial planets has its own atmosphere. It is different in terms of density and composition, but it definitely exists. For example, in Venus it is quite dense, while in Mercury it is almost invisible. In fact, at the moment there is an opinion that Mercury has no atmosphere at all, however, in fact, this is not so. All the atmospheres of the planets of the terrestrial group consist of substances whose molecules are relatively heavy. For example, the atmosphere of Earth, Venus and Mars is composed of carbon dioxide and water vapor. In turn, the atmosphere of Mercury consists mainly of helium.

In addition to the atmosphere, all terrestrial planets have approximately the same chemical composition. In particular, they consist predominantly of silicon compounds, as well as iron. However, there are other elements in the composition of these planets, but their number is not so large.

A feature of the terrestrial planets is that in their center there is a core of various masses. At the same time, all the nuclei are in a liquid state - the only exception is, presumably, only Venus.

Each of the terrestrial planets has its own magnetic fields. At the same time, on Venus their influence is almost imperceptible, while on the Earth, Mercury and Mars they are quite noticeable. As for the Earth, its magnetic fields do not stand still, but move. And although their speed is extremely small compared to human notions, scientists suggest that the movement of fields can further lead to a change in magnetic belts.

Another feature of the terrestrial planets is that they have practically no natural satellites. In particular, to date they have been found only near the Earth and Mars.

giant planets

The second group of planets is called "giant planets". These include Jupiter, Saturn, Uranus and Neptune. By their mass, they significantly exceed the mass of the planets of the terrestrial group.

The lightest giant to date is Uranus, however, its mass exceeds the mass of the earth

about 14 and a half times. And the heaviest planet in the solar system (with the exception of the Sun) is Jupiter.

None of the giant planets actually have their own surface, since they are all in a gaseous state. The gases of which these planets are composed, as they approach the center or equator, as it is called, pass into a liquid state. In this regard, one can notice the difference in the features of the rotation of the giant planets around their own axis. It should be noted that the duration of a complete rotation is a maximum of 18 hours. Meanwhile, each layer of the planet rotates around its axis at a different speed. This feature is due to the fact that the giant planets are not solid. In this regard, their individual parts, as it were, are not interconnected.

At the center of all giant planets is a solid core of small size. Most likely, one of the main substances of these planets is hydrogen, which has metallic characteristics. Thanks to this, at the moment it has been proven that the giant planets have their own magnetic field. However, in science at the moment there is very little convincing evidence and a lot of contradictions that could characterize the giant planets.

Their distinctive feature is that such planets have many natural satellites, as well as rings. Rings in this case are called small clusters of particles that rotate directly around the planet and collect various kinds of small particles flying by.

To date, science officially knows only 9 major planets. However, only eight are included in the composition of the terrestrial planets and giant planets. The ninth planet, which is Pluto, does not fit into any of the listed groups, since it is located at a very distant distance from the Sun and is practically not studied. The only thing that can be said about Pluto is that its state is close to solid. At the moment, there is an assumption that Pluto is not a planet at all. This assumption has existed for more than 20 years, but the decision to exclude Pluto from the composition of the planets has not yet been made.

Small bodies of the solar system

In addition to the planets in the solar system, there are a lot of all kinds of relatively small bodies in their weight, which are called asteroids, comets, minor planets, and so on. In general, these celestial bodies are included in the group of small celestial bodies. They differ from the planets in that they have a solid state, are relatively small in size and can move around the Sun not only in the forward but also in the opposite direction. Their size is much smaller than any of the planets discovered to date. Losing cosmic attraction, small celestial bodies of the solar system fall into the upper layers of the earth's atmosphere, where they burn out or fall in the form of meteorites. The change in the state of bodies revolving around other planets has not yet been studied.

> Planets of the Earth group

terrestrial planets- the first four planets of the solar system with a photo. Find out the characteristics and description of terrestrial planets, search for exoplanets, research.

Researchers have been studying the expanses of the solar system for many centuries, noting various planetary types. Since the discovery of access to exoplanets, our information base has become even wider. In addition to gas giants, we also found terrestrial objects. What is this?

Definition of terrestrial planets

terrestrial planet- a celestial body, represented by silicate rocks or metal, and has a solid surface layer. This is the main difference from gas giants filled with gases. The term is taken from the Latin word "Terra", which translates as "Earth". Below is a list of what are the terrestrial planets.

The structure and features of the planets of the Earth group

All bodies are endowed with a similar structure: a core of metal filled with iron and surrounded by a mantle of silicates. Their surface ball is covered with craters, volcanoes, mountains, canyons and other formations.

There are secondary atmospheres created by volcanic activity or the arrival of comets. They have a small number of satellites or are completely devoid of such features. Earth has the Moon, and Mars has Phobos and Deimos. Not endowed with ring systems. Let's see how the characteristics of the terrestrial planets look like, and also notice what their similarities and differences are on the example of Mercury, Venus, Earth and Mars.

Basic facts of the terrestrial planets

Mercury- the smallest planet in the system, reaching 1/3 of the earth's size. It is endowed with a thin atmospheric layer, which is why it constantly freezes and heats up. It is characterized by high density with iron and nickel. The magnetic field reaches only 1% of the earth's. Many deep crater scars and a faint layer of silicate particles are visible on the surface. In 2012, traces of organic material were noticed. These are the building blocks for life and also found water ice.

Venus similar in size to the Earth, but its atmosphere is too dense and filled with carbon monoxide. Because of this, heat is retained on the planet, making it the hottest in the system. Most of the surface has active volcanoes and deep canyons. Only a few vehicles managed to penetrate the surface and survive for a short period of time. There are few craters because meteors burn up.

Earth- the largest in the terrestrial type and has a huge amount of liquid water. It is necessary for life, which develops in all forms. There is a rocky surface covered with canyons and uplands, as well as a heavy metal core. Water vapor is present in the atmosphere, which contributes to the mitigation of the daily temperature regime. There are regular seasons. The greatest heating goes to areas near the equatorial line. But now the numbers are rising due to human activity.

Mars has the highest mountain in the solar system. Most of the surface is represented by ancient deposits and crater formations. But you can find younger sites. There are polar caps that shrink in size in summer and spring. It is inferior to the Earth in density, and the core is solid. Researchers have not yet obtained evidence of life, but there are all hints and conditions in the past. The planet has water ice, organics and methane.

Formation and common features of the planets of the Earth group

It is believed that terrestrial planets appeared first. Initially, dust particles merged, creating large objects. They were located closer to the Sun, so volatile substances evaporated. Celestial objects grew to a kilometer size, becoming planetesimals. Then they accumulate more and more dust.

The analysis shows that at an early stage in the development of the solar system, about a hundred protoplanets could have been present, whose sizes varied between the Moon and Mars. They constantly collided, due to which they merged, throwing out garbage fragments. As a result, 4 large planets of the terrestrial group survived: Mercury, Venus, Mars and Earth.

All of them are distinguished by a high density index, and the composition is represented by silicates and metallic iron. The largest representative of the terrestrial type is the Earth. These planets are also distinguished by the general structure of the structure, including the core, mantle and crust. Only two planets (Earth and Mars) have moons.

Current research on the Terrestrial planets

Researchers believe that terrestrial planets are the best candidates for discovering life. Of course, the conclusions are based on the fact that the only planet with life is the Earth, so its characteristics and features serve as a kind of standard.

Everything suggests that life is able to survive in extreme conditions. Therefore, it is expected to be found even on Mercury and Venus, despite their high temperatures. Most attention is paid to Mars. This is not only a prime candidate for finding life, but also a potential future colony.

If everything goes according to plan, then in the 2030s. the first batch of astronauts can be sent to the Red Planet. Now the planet is constantly rovers and orbiters looking for water and signs of life.

Earth-like exoplanets

Many exoplanets found have turned out to be gas giants because they are much easier to find. But since 2005, we began to actively capture terrestrial objects thanks to the Kepler mission. Most of it was called the super-earth class.

Among these, it is worth remembering Gliese 876d, whose mass is 7-9 times greater than the earth. It orbits a red dwarf, 15 light-years distant from us. In the Gliese 581 system, 3 terrestrial exoplanets were found with a distance of 20 light years.

The smallest is Gliese 581e. It exceeds our mass by only 1.9 times, but is located extremely close to its star. The first confirmed terrestrial exoplanet was Kepler-10b, 3-4 times our mass. It is 460 light years distant and was found in 2011. At the same time, the mission team issued a list of 1235 applicants, where 6 were of the terrestrial type and were located in the habitable zone.

super earth

Among the exoplanets managed to find many super-Earths (in size between Earth and Neptune). This species is not found in the territory of our system, so it is not yet clear whether they look more like giants or terrestrial types.

Now the scientific world is waiting for the launch of the James Webb telescope, which promises to increase the power of the search and reveal to us the depths of space.

Categories of terrestrial planets

There is a division of terrestrial planets. Silicate - typical objects of our system, represented by a stone mantle and a metal core. Iron - a theoretical variety consisting entirely of iron. This gives a greater density index, but reduces the radius. Such planets can only appear in areas with a high temperature index.

Rocky - Another theoretical species, where there is a silicate rock, but no metal core. They should form away from the star. Carbonaceous - endowed with a metal core, around which a carbon-containing mineral has accumulated.

We used to think that we had studied in detail the process of planetary formation. But the consideration of exoplanets forces us to find many gaps and start new research. This also expands the conditions for the search for life in alien worlds. Who knows what we'll see there if we can send a probe.

Introduction

Among the numerous celestial bodies studied by modern astronomy, the planets occupy a special place. After all, we all know very well that the Earth on which we live is a planet, so the planets are bodies, basically similar to our Earth.

But in the world of planets, we will not even meet two that are completely similar to each other. The variety of physical conditions on the planets is very great. The distance of the planet from the Sun (and hence the amount of solar heat and surface temperature), its size, gravity stress on the surface, the orientation of the axis of rotation, which determines the change of seasons, the presence and composition of the atmosphere, the internal structure and many other properties are different for everyone nine planets in the solar system.

Speaking about the diversity of conditions on the planets, we can better understand the laws of their development and find out their relationship between certain properties of the planets. So, for example, its ability to hold an atmosphere of one composition or another depends on the size, mass and temperature of the planet, and the presence of the atmosphere, in turn, affects the thermal regime of the planet.

As the study of the conditions under which the origin and further development of living matter is possible shows, only on the planets can we look for signs of the existence of organic life. That is why the study of planets, in addition to general interest, is of great importance from the point of view of space biology.

The study of the planets is of great importance, in addition to astronomy, for other areas of science, primarily the Earth sciences - geology and geophysics, as well as for cosmogony - the science of the origin and development of celestial bodies, including our Earth.

The terrestrial planets include the planets: Mercury, Venus, Earth and Mars.

Mercury.

General information.

Mercury is the closest planet to the Sun in the solar system. The average distance from Mercury to the Sun is only 58 million km. Among the large planets, it has the smallest dimensions: its diameter is 4865 km (0.38 of the diameter of the Earth), its mass is 3.304 * 10 23 kg (0.055 of the mass of the Earth or 1: 6025000 of the mass of the Sun); average density 5.52 g/cm 3 . Mercury is a bright star, but it is not so easy to see it in the sky. The fact is that, being near the Sun, Mercury is always visible to us not far from the solar disk, moving away from it either to the left (to the east), then to the right (to the west) only a short distance, which does not exceed 28 O. Therefore, it can be see only on those days of the year when it moves away from the Sun at its greatest distance. Let, for example, Mercury moved away from the Sun to the left. The sun and all the luminaries in their daily movement float across the sky from left to right. Therefore, the Sun sets first, and after a little over an hour Mercury sets, and we must look for this planet low above the Western horizon.

Motion.

Mercury moves around the Sun at an average distance of 0.384 astronomical units (58 million km) in an elliptical orbit with a large eccentricity e-0.206; at perihelion, the distance to the Sun is 46 million km, and at aphelion, 70 million km. The planet makes a complete flight around the Sun in three Earth months or 88 days at a speed of 47.9 km / s. Moving along its path around the Sun, Mercury at the same time rotates around its axis so that one and the same half of it always faces the Sun. This means that it is always day on one side of Mercury and night on the other. In the 60s. using radar observations, it was found that Mercury rotates around the axis in the forward direction (i.e., as in orbital motion) with a period of 58.65 days (relative to the stars). The length of a solar day on Mercury is 176 days. The equator is inclined to the plane of its orbit by 7°. The angular velocity of the axial rotation of Mercury is 3/2 of the orbital and corresponds to the angular velocity of its movement in orbit when the planet is at perihelion. Based on this, it can be assumed that the speed of rotation of Mercury is due to tidal forces from the Sun.

Atmosphere.

Mercury is possibly devoid of an atmosphere, although polarization and spectral observations indicate the presence of a faint atmosphere. With the help of Mariner-10, the presence of a highly rarefied gaseous envelope near Mercury, consisting mainly of helium, was established. This atmosphere is in dynamic equilibrium: each helium atom stays in it for about 200 days, after which it leaves the planet, and another particle from the solar wind plasma takes its place. In addition to helium, an insignificant amount of hydrogen has been found in the atmosphere of Mercury. It is about 50 times smaller than helium.

It also turned out that Mercury has a weak magnetic field, the strength of which is only 0.7% of the earth's. The inclination of the dipole axis to the axis of rotation of Mercury is 12 0 (earth is 11 0)

The pressure at the surface of the planet is approximately 500 billion times less than that at the surface of the Earth.

Temperature.

Mercury is much closer to the Sun than Earth. Therefore, the Sun on it shines and warms 7 times stronger than ours. On the day side of Mercury, it is terribly hot, there is eternal hell. Measurements show that the temperature there rises to 400 O above zero. But on the night side there should always be a strong frost, which probably reaches 200 O and even 250 O below zero. It turns out that one half of it is a hot stone desert, and the other half is an icy desert, perhaps covered with frozen gases.

Surface.

From the flyby trajectory of the Mariner 10 spacecraft in 1974, more than 40% of the surface of Mercury was photographed with a resolution from 4 mm to 100 m, which made it possible to see Mercury in much the same way as the Moon in the dark from the Earth. The abundance of craters is the most obvious feature of its surface, which at first glance can be likened to the moon.

Indeed, the morphology of the craters is close to that of the moon, and their impact origin is beyond doubt: in most of them, traces of ejections of material crushed upon impact are visible with the formation in some cases of characteristic bright rays and a field of secondary craters. Many craters have a central mound and a terraced structure of the inner slope. Interestingly, not only almost all large craters with a diameter of more than 40-70 km have such features, but also a much larger number of smaller craters, within 5-70 km (of course, we are talking about well-preserved craters). These features can be attributed both to the greater kinetic energy of the bodies falling onto the surface and to the surface material itself.

The degree of erosion and smoothing of craters is different. In general, Mercury craters are less deep than lunar craters, which can also be explained by the greater kinetic energy of meteorites due to the greater acceleration of gravity on Mercury than on the Moon. Therefore, the impact crater is more efficiently filled with ejected material. For the same reason, secondary craters are located closer to the central one than on the Moon, and deposits of crushed material mask the primary landforms to a lesser extent. The secondary craters themselves are deeper than the lunar ones, which again is explained by the fact that the fragments falling to the surface experience a greater acceleration of gravity.

Just as on the Moon, it is possible, depending on the relief, to distinguish predominantly uneven “continental” and much smoother “marine” regions. The latter are mainly hollows, which, however, are much smaller than on the Moon, their sizes usually do not exceed 400-600 km. In addition, some basins are hardly distinguishable against the background of the surrounding relief. The exception is the mentioned vast basin Kanoris (Sea of Heat) with a length of about 1300 km, reminiscent of the well-known Sea of Rains on the Moon.

In the predominant continental part of the surface of Mercury, one can distinguish both heavily cratered areas, with the highest degree of degradation of craters, and old intercrater plateaus occupying vast territories, indicating a widely developed ancient volcanism. These are the most ancient surviving landforms of the planet. The leveled surfaces of the basins are obviously covered with the thickest layer of crushed rocks - regolith. Along with a small number of craters, there are folded ridges resembling those of the moon. Some of the flat areas adjacent to the basins were probably formed during the deposition of material ejected from them. At the same time, quite definite evidence of their volcanic origin has been found for most of the plains, but this is volcanism of a later time than on the intercrater plateaus. A careful study reveals another interesting feature that sheds light on the history of the formation of the planet. We are talking about characteristic traces of tectonic activity on a global scale in the form of specific steep ledges, or escarp slopes. Escarps have a length of 20-500 km and a height of slopes from several hundred meters to 1-2 km. In their morphology and geometry of location on the surface, they differ from the usual tectonic ruptures and faults observed on the Moon and Mars, and rather formed due to thrusts, stratifications due to stress in the surface layer that arose during the compression of Mercury. This is evidenced by the horizontal displacement of the ridges of some craters.

Some of the scarps were bombarded and partially destroyed. This means that they formed earlier than the craters on their surface. From the narrowing of the erosion of these craters, it can be concluded that the crustal compression occurred during the formation of the “seas” about 4 billion years ago. The most probable reason for the contraction must, apparently, be considered the beginning of the cooling of Mercury. According to another interesting assumption put forward by a number of experts, an alternative mechanism for the powerful tectonic activity of the planet during this period could be a tidal slowdown of the planet's rotation by about 175 times: from the originally estimated value of about 8 hours to 58.6 days.

Introduction

The terrestrial planets include the planets: Mercury, Venus, Earth and Mars.

Mercury.

General information.

Motion.

Atmosphere.

The pressure at the surface of the planet is approximately 500 billion times less than that at the surface of the Earth.

Temperature.

Surface.

Venus.

General information.

Venus is the second closest planet to the Sun, almost the same size as the Earth, and its mass is more than 80% of the Earth's mass. For these reasons, Venus is sometimes referred to as Earth's twin or sister. However, the surface and atmosphere of these two planets are completely different. The Earth has rivers, lakes, oceans and the atmosphere we breathe. Venus is a scalding hot planet with a dense atmosphere that would be fatal to humans. The average distance from Venus to the Sun is 108.2 million km; it is practically constant, since the orbit of Venus is closer to a circle than our planet. Venus receives from the Sun more than twice as much light and heat as the Earth. However, on the shadow side, Venus is dominated by a frost of more than 20 degrees below zero, since the sun's rays do not fall here for a very long time. The planet has a very dense, deep and very cloudy atmosphere, preventing us from seeing the surface of the planet. The atmosphere (gas shell) was discovered by M. V. Lomonosov in 1761, which also showed the similarity of Venus with the Earth. The planet has no satellites.

Motion.

Venus has an almost circular orbit (eccentricity 0.007), which it bypasses in 224.7 Earth days at a speed of 35 km/sec. at a distance of 108.2 million km from the Sun. Venus rotates around its axis in 243 Earth days - the maximum time among all the planets. Venus rotates around its axis in the opposite direction, that is, in the opposite direction to its orbit. This slow and reverse rotation means that, as seen from Venus, the Sun rises and sets only twice a year, since a Venusian day is equal to 117 Earth days. The axis of rotation of Venus is almost perpendicular to the orbital plane (tilt 3 °), so there are no seasons of the year - one day is similar to another, has the same duration and the same weather. This weather uniformity is further enhanced by the specificity of the Venusian atmosphere - its strong greenhouse effect. Also, Venus, like the Moon, has its own phases.

Temperature.

The temperature is about 750 K over the entire surface both day and night. The reason for such a high temperature near the surface of Venus is the greenhouse effect: the sun's rays relatively easily pass through the clouds of its atmosphere and heat the surface of the planet, but the thermal infrared radiation of the surface itself escapes through the atmosphere back into space with great difficulty. On Earth, where the amount of carbon dioxide in the atmosphere is low, the natural greenhouse effect raises the global temperature by 30°C, while on Venus it raises the temperature by another 400°C. By studying the physical consequences of the strongest greenhouse effect on Venus, we have a good idea of the results that the accumulation of excess heat on Earth, caused by the growing concentration of carbon dioxide in the atmosphere due to the burning of fossil fuels - coal and oil, can lead to.

In 1970, the first spacecraft to land on Venus could only endure the sweltering heat for about one hour, but that was just enough time to send back data on surface conditions.

Atmosphere.

The enigmatic atmosphere of Venus has been the centerpiece of the robotic exploration program for the past two decades. The most important aspects of her research were the chemical composition, vertical structure and dynamics of the air environment. Much attention was paid to the cloud cover, which plays the role of an insurmountable barrier to the penetration of electromagnetic waves of the optical range into the depths of the atmosphere. When filming Venus on television, it was possible to obtain an image of only the cloud cover. The extraordinary dryness of the air and its phenomenal greenhouse effect, due to which the actual temperature of the surface and lower layers of the troposphere turned out to be more than 500 above the effective (equilibrium) were incomprehensible.

The atmosphere of Venus is extremely hot and dry due to the greenhouse effect. It is a dense blanket of carbon dioxide that retains the heat that comes from the sun. As a result, a large amount of thermal energy accumulates. The pressure at the surface is 90 bar (as in the Earth's seas at a depth of 900 m). Spaceships have to be designed to withstand the crushing, crushing force of the atmosphere.

The atmosphere of Venus consists mainly of carbon dioxide (CO 2) -97%, which is able to act as a kind of blanket, trapping the heat of the sun, as well as a small amount of nitrogen (N 2) -2.0%, water vapor (H 2 O) -0.05% and oxygen (O) -0.1%. Hydrochloric acid (HCl) and hydrofluoric acid (HF) were found as small impurities. The total amount of carbon dioxide on Venus and Earth is approximately the same. Only on Earth it is bound in sedimentary rocks and partly absorbed by the water masses of the oceans, while on Venus it is all concentrated in the atmosphere. During the day, the surface of the planet is illuminated by scattered sunlight with about the same intensity as on an overcast day on Earth. A lot of lightning has been seen on Venus at night.

The clouds of Venus are made up of microscopic droplets of concentrated sulfuric acid (H 2 SO 4). The upper layer of clouds is 90 km away from the surface, the temperature there is about 200 K; the lower layer is 30 km away, the temperature is about 430 K. Even lower it is so hot that there are no clouds. Of course, there is no liquid water on the surface of Venus. The atmosphere of Venus at the level of the upper cloud layer rotates in the same direction as the surface of the planet, but much faster, making a revolution in 4 days; this phenomenon is called superrotation, and no explanation has yet been found for it.

Surface.

The surface of Venus is covered with hundreds of thousands of volcanoes. There are several very large ones: 3 km high and 500 km wide. But most of the volcanoes are 2-3 km across and about 100 m high. The outpouring of lava on Venus takes much longer than on Earth. Venus is too hot for ice, rain, or storms to occur, so there is no significant weathering (weathering) to occur. This means that volcanoes and craters have hardly changed since they formed millions of years ago.

Venus is covered with solid rocks. Hot lava circulates beneath them, causing tension in a thin surface layer. Lava is constantly erupting from holes and fissures in solid rock. In addition, volcanoes constantly emit jets of small droplets of sulfuric acid. In some places, thick lava, gradually oozing, accumulates in the form of huge puddles up to 25 km wide. In other places, huge bubbles of lava form on the surface of the dome, which then fall off.

On the surface of Venus, a rock rich in potassium, uranium and thorium was found, which, under terrestrial conditions, corresponds not to the composition of primary volcanic rocks, but to secondary ones that have undergone exogenous processing. In other places, coarse rubble and blocky material of dark rocks with a density of 2.7-2.9 g/cm and other elements typical of basalts occur on the surface. Thus, the surface rocks of Venus turned out to be the same as on the Moon, Mercury and Mars, erupted igneous rocks of the basic composition.

Little is known about the interior of Venus. It probably has a metal core taking up 50% of its radius. But the planet does not have a magnetic field due to its very slow rotation.

Venus is by no means a hospitable world, as it was once supposed. With its atmosphere of carbon dioxide, clouds of sulfuric acid and terrible heat, it is completely unsuitable for humans. Under the weight of this information, some hopes collapsed: after all, less than 20 years ago, many scientists considered Venus to be a more promising object for space research than Mars.

Earth.

General information.

Earth is the third planet from the Sun in the solar system. The shape of the Earth is close to an ellipsoid, flattened at the poles and stretched in the equatorial zone. The average radius of the Earth is 6371.032 km, polar - 6356.777 km, equatorial - 6378.160 km. Weight - 5.976 * 1024 kg. The average density of the Earth is 5518 kg/m³. The surface area of the Earth is 510.2 million km², of which approximately 70.8% is in the oceans. Its average depth is about 3.8 km, the maximum (the Mariana Trench in the Pacific Ocean) is 11.022 km; the volume of water is 1370 million km³, the average salinity is 35 g/l. Land makes up 29.2%, respectively, and forms six continents and islands. It rises above sea level by an average of 875 m; the highest height (the peak of Chomolungma in the Himalayas) is 8848 m. Mountains occupy more than 1/3 of the land surface. Deserts cover about 20% of the land surface, savannas and light forests - about 20%, forests - about 30%, glaciers - over 10%. Over 10% of the land is occupied by agricultural land.

The Earth has only one satellite, the Moon.

Thanks to its unique, perhaps the only natural conditions in the Universe, the Earth became the place where organic life arose and developed. By According to modern cosmogonic concepts, the planet was formed approximately 4.6 - 4.7 billion years ago from a protoplanetary cloud captured by the attraction of the Sun. The formation of the first, most ancient of the studied rocks took 100-200 million years. Approximately 3.5 billion years ago, conditions favorable for the emergence of life arose. Homo sapiens (the Homo sapiens) as a species appeared about half a million years ago, and the formation of the modern type of man is attributed to the time of the retreat of the first glacier, that is, about 40 thousand years ago.

Motion.

Like other planets, it moves around the Sun in an elliptical orbit, the eccentricity of which is 0.017. The distance from the Earth to the Sun at different points of the orbit is not the same. The average distance is about 149.6 million km. In the process of the movement of our planet around the Sun, the plane of the earth's equator moves parallel to itself in such a way that in some parts of the orbit the globe is inclined to the Sun with its northern hemisphere, and in others - with its southern one. The period of revolution around the Sun is 365.256 days, with a daily rotation - 23 hours 56 minutes. The axis of rotation of the Earth is located at an angle of 66.5º to the plane of its movement around the Sun.

Atmosphere .

The Earth's atmosphere consists of 78% nitrogen and 21% oxygen (there are very few other gases in the atmosphere); it is the result of a long evolution under the influence of geological, chemical and biological processes. Perhaps the Earth's early atmosphere was rich in hydrogen, which then escaped. The degassing of the bowels filled the atmosphere with carbon dioxide and water vapor. But the vapor condensed in the oceans, and the carbon dioxide was trapped in carbonate rocks. Thus, nitrogen remained in the atmosphere, and oxygen appeared gradually as a result of the vital activity of the biosphere. Even 600 million years ago, the oxygen content in the air was 100 times lower than today.

Our planet is surrounded by a vast atmosphere. According to temperature, the composition and physical properties of the atmosphere can be divided into different layers. The troposphere is the region between the Earth's surface and a height of 11 km. This is a rather thick and dense layer containing most of the water vapor in the air. Almost all atmospheric phenomena that are of direct interest to the inhabitants of the Earth take place in it. The troposphere contains clouds, precipitation, etc. The layer separating the troposphere from the next atmospheric layer, the stratosphere, is called the tropopause. This is an area of very low temperatures.

The composition of the stratosphere is the same as that of the troposphere, but ozone appears and concentrates in it. The ionosphere, that is, the ionized layer of air, is formed both in the troposphere and in lower layers. It reflects high frequency radio waves.

Atmospheric pressure at the level of the ocean surface is approximately 0.1 MPa under normal conditions. It is believed that the earth's atmosphere has changed greatly in the process of evolution: it has been enriched with oxygen and acquired a modern composition as a result of long-term interaction with rocks and with the participation of the biosphere, i.e., plant and animal organisms. Evidence that such changes have indeed taken place are, for example, deposits of coal and thick layers of carbonate deposits in sedimentary rocks, they contain a huge amount of carbon, which used to be part of the earth's atmosphere in the form of carbon dioxide and carbon monoxide. Scientists believe that the ancient atmosphere originated from the gaseous products of volcanic eruptions; its composition is judged by the chemical analysis of gas samples "walled up" in the cavities of ancient rocks. The studied samples, which are approximately 3.5 billion years old, contain approximately 60% carbon dioxide, and the remaining 40% are sulfur compounds, ammonia, hydrogen chloride and fluoride. Nitrogen and inert gases were found in a small amount. All oxygen was chemically bound.

For biological processes on Earth, the ozonosphere is of great importance - the ozone layer located at an altitude of 12 to 50 km. The area above 50-80 km is called the ionosphere. Atoms and molecules in this layer are intensely ionized by solar radiation, in particular ultraviolet radiation. If it were not for the ozone layer, radiation fluxes would reach the surface of the Earth, causing destruction in the living organisms present there. Finally, at distances greater than 1000 km, the gas is so rarefied that collisions between molecules cease to play a significant role, and the atoms are more than half ionized. At a height of about 1.6 and 3.7 Earth radii are the first and second radiation belts.

The structure of the planet.

The main role in the study of the internal structure of the Earth is played by seismic methods based on the study of the propagation in its thickness of elastic waves (both longitudinal and transverse) that occur during seismic events - during natural earthquakes and as a result of explosions. Based on these studies, the Earth is conventionally divided into three regions: the crust, the mantle, and the core (in the center). The outer layer - the crust - has an average thickness of about 35 km. The main types of the earth's crust are continental (mainland) and oceanic; in the transition zone from the mainland to the ocean, an intermediate type of crust is developed. The thickness of the crust varies over a fairly wide range: the oceanic crust (taking into account the water layer) has a thickness of about 10 km, while the thickness of the continental crust is tens of times greater. Surface deposits occupy a layer about 2 km thick. Below them is a granite layer (on the continents its thickness is 20 km), and below - about 14 km (both on the continents and in the oceans) basalt layer (lower crust). The density at the center of the Earth is about 12.5 g/cm³. The average densities are: 2.6 g / cm³ - at the surface of the Earth, 2.67 g / cm³ - for granite, 2.85 g / cm³ - for basalt.

To a depth of about 35 to 2885 km, the Earth's mantle extends, which is also called the silicate shell. It is separated from the crust by a sharp boundary (the so-called Mohorovich boundary), deeper than which the velocities of both longitudinal and transverse elastic seismic waves, as well as the mechanical density, increase abruptly. Densities in the mantle increase with increasing depth from about 3.3 to 9.7 g/cm3. Extensive lithospheric plates are located in the crust and (partially) in the mantle. Their secular movements not only determine the drift of the continents, which noticeably affects the appearance of the Earth, but are also related to the location of seismic zones on the planet. Another boundary discovered by seismic methods (the Gutenberg boundary) - between the mantle and the outer core - is located at a depth of 2775 km. On it, the velocity of longitudinal waves drops from 13.6 km/s (in the mantle) to 8.1 km/s (in the core), while the velocity of transverse waves decreases from 7.3 km/s to zero. The latter means that the outer core is liquid. According to modern concepts, the outer core consists of sulfur (12%) and iron (88%). Finally, at depths greater than 5120 km, seismic methods reveal the presence of a solid inner core, which accounts for 1.7% of the Earth's mass. Presumably, this is an iron-nickel alloy (80% Fe, 20% Ni).

The Earth's gravitational field is described with high accuracy by Newton's law of universal gravitation. The free fall acceleration over the Earth's surface is determined by both the gravitational and centrifugal force due to the Earth's rotation. The free fall acceleration at the surface of the planet is 9.8 m/s².

The earth also has magnetic and electric fields. The magnetic field above the Earth's surface consists of a constant (or changing slowly enough) and a variable part; the latter is usually referred to as variations of the magnetic field. The main magnetic field has a structure close to dipole. The magnetic dipole moment of the Earth, equal to 7.98T10^25 cgsm units, is directed approximately opposite to the mechanical one, although at present the magnetic poles are somewhat shifted with respect to the geographic ones. Their position, however, changes with time, and although these changes are quite slow, over geological time intervals, according to paleomagnetic data, even magnetic inversions, that is, polarity reversals, are detected. The magnetic field strengths at the north and south magnetic poles are 0.58 and 0.68 Oe, respectively, and about 0.4 Oe at the geomagnetic equator.

The electric field above the Earth's surface has an average intensity of about 100 V / m and is directed vertically downward - this is the so-called fair weather field, but this field experiences significant (both periodic and irregular) variations.

Moon.

The Moon is a natural satellite of the Earth and the closest celestial body to us. The average distance to the Moon is 384,000 kilometers, the diameter of the Moon is about 3476 km. The average density of the Moon is 3.347 g/cm³, or about 0.607 of the average density of the Earth. The mass of the satellite is 73 trillion tons. The acceleration of gravity on the surface of the moon is 1.623 m/s².

The Moon moves around the Earth at an average speed of 1.02 km / s in an approximately elliptical orbit in the same direction in which the vast majority of other bodies in the Solar System move, that is, counterclockwise when viewed from the Moon's orbit from the North Pole of the World. The period of revolution of the Moon around the Earth, the so-called sidereal month, is equal to 27.321661 mean days, but is subject to slight fluctuations and a very small secular reduction.

Not being protected by the atmosphere, the surface of the Moon heats up to + 110 ° C during the day, and cools down to -120 ° C at night, however, as radio observations have shown, these huge temperature fluctuations penetrate only a few decimeters deep due to the extremely weak thermal conductivity of the surface layers.

The relief of the lunar surface was mainly elucidated as a result of many years of telescopic observations. The "lunar seas", occupying about 40% of the visible surface of the Moon, are flat lowlands, crossed by cracks and low winding shafts; there are relatively few large craters on the seas. Many seas are surrounded by concentric ring ridges. The rest, lighter surface is covered with numerous craters, ring-shaped ridges, furrows, and so on.

Mars.

General information.

Mars is the fourth planet in the solar system. Mars - from the Greek "Mas" - male power - the god of war. According to the main physical characteristics, Mars belongs to the terrestrial planets. In diameter, it is almost half the size of Earth and Venus. The average distance from the Sun is 1.52 AU. The equatorial radius is 3380 km. The average density of the planet is 3950 kg/m³. Mars has two satellites - Phobos and Deimos.

Atmosphere.

The planet is shrouded in a gaseous shell - an atmosphere that has a lower density than the earth's. Even in the deep depressions of Mars, where the atmospheric pressure is greatest, it is approximately 100 times less than at the Earth's surface, and at the level of the Martian mountain peaks, it is 500-1000 times less. In composition, it resembles the atmosphere of Venus and contains 95.3% carbon dioxide with an admixture of 2.7% nitrogen, 1.6% argon, 0.07% carbon monoxide, 0.13% oxygen and approximately 0.03% water vapor, the content which changes, as well as impurities of neon, krypton, xenon.

The average temperature on Mars is much lower than on Earth, about -40 ° C. Under the most favorable conditions in the summer in the daytime half of the planet, the air warms up to 20 ° C - quite an acceptable temperature for the inhabitants of the Earth. But on a winter night, frost can reach -125 ° C. Such sharp temperature drops are caused by the fact that the rarefied atmosphere of Mars is not able to retain heat for a long time.

Strong winds often blow over the surface of the planet, the speed of which reaches 100 m/s. Low gravity allows even rarefied air currents to raise huge clouds of dust. Sometimes quite vast areas on Mars are covered by grandiose dust storms. The global dust storm raged from September 1971 to January 1972, lifting about a billion tons of dust into the atmosphere to a height of more than 10 km.

There is very little water vapor in the atmosphere of Mars, but at low pressure and temperature it is in a state close to saturation, and often collects in clouds. Martian clouds are rather inexpressive compared to those on Earth, although they have a variety of shapes and types: cirrus, wavy, leeward (near large mountains and under the slopes of large craters, in places protected from the wind). Over lowlands, canyons, valleys - and at the bottom of craters in the cold time of the day there are often fogs.

As the images from the American landing stations "Viking-1" and "Viking-2" showed, the Martian sky in clear weather has a pinkish color, which is explained by the scattering of sunlight on dust particles and the illumination of the haze by the orange surface of the planet. In the absence of clouds, the gaseous envelope of Mars is much more transparent than the earth's, including for ultraviolet rays dangerous to living organisms.

Seasons.

A solar day on Mars lasts 24 hours 39 minutes. 35 s. A significant inclination of the equator to the plane of the orbit leads to the fact that in some parts of the orbit, mainly the northern latitudes of Mars are illuminated and heated by the Sun, in others - the southern ones, that is, there is a change of seasons. The Martian year is about 686.9 days long. The change of seasons on Mars is the same as on Earth. Seasonal changes are most pronounced in the polar regions. In winter, the polar caps occupy a significant area. The boundary of the northern polar cap can move away from the pole by a third of the distance from the equator, and the boundary of the southern cap overcomes half this distance. This difference is due to the fact that in the northern hemisphere winter occurs when Mars passes through the perihelion of its orbit, and in the southern hemisphere when it passes through aphelion. Because of this, winters in the southern hemisphere are colder than in the northern. The ellipticity of the Martian orbit leads to significant differences in the climate of the northern and southern hemispheres: in the middle latitudes, winters are colder and summers are warmer than in the southern ones, but shorter than in the northern ones .. When summer comes in the northern hemisphere of Mars, the northern polar cap decreases rapidly, but at this time, another grows - near the south pole, where winter sets in. At the end of the 19th - beginning of the 20th century, it was believed that the polar caps of Mars were glaciers and snow. According to modern data, both polar caps of the planet - northern and southern - consist of solid carbon dioxide, that is, dry ice, which is formed when carbon dioxide, which is part of the Martian atmosphere, freezes, and water ice mixed with mineral dust.

The structure of the planet.

Due to the low mass, gravity on Mars is almost three times lower than on Earth. At present, the structure of the gravitational field of Mars has been studied in detail. It indicates a slight deviation from the uniform density distribution in the planet. The core can have a radius up to half the radius of the planet. Apparently, it consists of pure iron or an alloy of Fe-FeS (iron-iron sulfide) and, possibly, hydrogen dissolved in them. Apparently, the core of Mars is partially or completely in a liquid state.

Mars must have a thick crust 70-100 km thick. Between the core and the crust is a silicate mantle enriched in iron. The red iron oxides present in the surface rocks determine the color of the planet. Now Mars continues to cool.

The seismic activity of the planet is weak.

Surface.

The surface of Mars, at first glance, resembles the moon. However, in fact, its relief is very diverse. Throughout the long geological history of Mars, its surface has been altered by volcanic eruptions and marsquakes. Deep scars on the face of the god of war were left by meteorites, wind, water and ice.

The surface of the planet consists, as it were, of two contrasting parts: the ancient highlands covering the southern hemisphere, and the younger plains concentrated in the northern latitudes. In addition, two large volcanic regions stand out - Elysium and Tharsis. The height difference between mountainous and flat areas reaches 6 km. Why different areas differ so much from each other is still unclear. Perhaps such a division is associated with a very old catastrophe - the fall of a large asteroid on Mars.

The high-mountain part has preserved traces of an active meteorite bombardment that took place about 4 billion years ago. Meteor craters cover 2/3 of the planet's surface. There are almost as many of them in the old highlands as on the Moon. But many Martian craters have "lost their shape" due to weathering. Some of them, apparently, were once washed away by streams of water. The northern plains look completely different. 4 billion years ago they had a lot of meteorite craters, but then the catastrophic event, which has already been mentioned, erased them from 1/3 of the planet's surface and its relief in this area began to form anew. Separate meteorites fell there later, but in general there are few impact craters in the north.

The appearance of this hemisphere was determined by volcanic activity. Some of the plains are completely covered with ancient igneous rocks. Streams of liquid lava spread over the surface, solidified, and new streams flowed along them. These petrified "rivers" are concentrated around large volcanoes. At the ends of lava tongues, structures similar to terrestrial sedimentary rocks are observed. Probably, when the hot eruptive masses melted the layers of underground ice, quite extensive reservoirs formed on the surface of Mars, which gradually dried up. The interaction of lava and underground ice also led to the appearance of numerous furrows and cracks. Far from volcanoes, low-lying areas of the northern hemisphere are covered by sand dunes. Especially a lot of them near the northern polar cap.

The abundance of volcanic landscapes indicates that in the distant past, Mars experienced a rather turbulent geological era, most likely it ended about a billion years ago. The most active processes took place in the regions of Elysium and Tharsis. At one time they were literally squeezed out of the bowels of Mars and now rise above its surface in the form of grandiose swellings: Elysium 5 km high, Tharsis - 10 km. Numerous faults, cracks, ridges are concentrated around these swellings - traces of ancient processes in the Martian crust. The most grandiose system of canyons several kilometers deep - the Mariner Valley - begins at the top of the Tharsis Mountains and stretches 4 thousand kilometers to the east. In the central part of the valley, its width reaches several hundred kilometers. In the past, when the Martian atmosphere was denser, water could drain into the canyons, creating deep lakes in them.

The volcanoes of Mars are exceptional phenomena by earthly standards. But even among them, the volcano Olympus, located in the northwest of the Tharsis Mountains, stands out. The diameter of the base of this mountain reaches 550 km, and the height is 27 km, i.e. it is three times the height of Everest, the highest peak on Earth. Olympus is crowned with a huge 60-kilometer crater. To the east of the highest part of the Tharsis Mountains, another volcano has been discovered - Alba. Although it cannot compete with Olympus in height, its base diameter is almost three times larger.

These volcanic cones are the result of calm eruptions of very liquid lava, similar in composition to the lava of the terrestrial volcanoes of the Hawaiian Islands. Traces of volcanic ash on the slopes of other mountains suggest that catastrophic eruptions have occasionally occurred on Mars.

In the past, flowing water played a huge role in shaping the Martian relief. At the first stages of the study, Mars seemed to astronomers a desert and waterless planet, but when the surface of Mars was photographed from a close distance, it turned out that in the old highlands there are often gullies left as if by flowing water. Some of them look like they were pierced many years ago by stormy, swift currents. They sometimes stretch for many hundreds of kilometers. Some of these "brooks" have a rather respectful age. Other valleys are very similar to the beds of calm earthly rivers. They probably owe their appearance to the melting of underground ice.

Some additional information about Mars can be obtained by indirect methods based on studies of its natural satellites - Phobos and Deimos.

Satellites of Mars.

The moons of Mars were discovered on August 11 and 17, 1877 during the great opposition by American astronomer Asaph Hall. The satellites received such names from Greek mythology: Phobos and Deimos, the sons of Ares (Mars) and Aphrodite (Venus), always accompanied their father. Translated from Greek, “phobos” means “fear”, and “deimos” means “horror”.

Phobos. Deimos.

Both satellites of Mars move almost exactly in the plane of the planet's equator. With the help of spacecraft, it was established that Phobos and Deimos have an irregular shape and in their orbital position always remain turned to the planet by the same side. The dimensions of Phobos are about 27 km, and Deimos - about 15 km. The surface of the moons of Mars consists of very dark minerals and is covered with numerous craters. One of them - on Phobos has a diameter of about 5.3 km. The craters are probably produced by meteorite bombardment; the origin of the system of parallel furrows is unknown. The angular velocity of the orbital motion of Phobos is so great that, unlike other luminaries, Phobos rises in the west, overtaking the axial rotation of the planet, and sets in the east.

The search for life on Mars.

For a long time, the search for forms of extraterrestrial life was conducted on Mars. During the study of the planet by spacecraft of the Viking series, three complex biological experiments were performed: pyrolysis decomposition, gas exchange, label decomposition. They are based on the experience of studying earthly life. The pyrolysis decomposition experiment was based on the definition of photosynthesis processes involving carbon, the label decomposition experiment was based on the assumption that water is necessary for existence, and the gas exchange experiment took into account that Martian life must use water as a solvent. Although all three biological experiments gave a positive result, they are probably non-biological in nature and can be explained by inorganic reactions of the nutrient solution with the material of the Martian nature. So, we can summarize that Mars is a planet that does not have the conditions for the emergence of life.

Conclusion

We got acquainted with the current state of our planet and the planets of the Earth group. The future of our planet, and indeed the entire planetary system, if nothing unforeseen happens, seems clear. The probability that the established order of the planets will be disturbed by some wandering star is small, even within a few billion years. In the near future, one should not expect strong changes in the flow of solar energy. It is likely that ice ages will repeat. A person is able to change the climate, but in doing so, he can make a mistake. The continents will rise and fall in subsequent epochs, but we hope that the processes will be slow. Massive meteorite impacts are possible from time to time.

But for the most part, the solar system will retain its current appearance.

Plan.

1. Introduction.

2. Mercury.

3. Venus.

6. Conclusion.

7. Literature.

Planet Mercury.

surface of Mercury.

Planet Venus.

Surface of Venus.

Planet Earth.

Land surface.

The planet Mars.

Surface of Mars.

The terrestrial planets (those that have a solid surface) are found inside the asteroid belt located between the orbits of Mars and Jupiter. Therefore, they are also called the inner planets. These include Mercury, Venus, Earth and Mars. Below will be given a brief description of the terrestrial planets.

These planets, to a greater extent, consist of silicates and metallic iron, in contrast to. They also contain a lot of oxygen, magnesium, aluminum, silicon, iron and other heavy metals.

All inner planets have the same structure:

in the very center there is a heavy and hot core. It mainly consists of iron, with an admixture of nickel;
above the core is a mantle consisting of silicates;
the topmost layer is the crust, formed due to the partial melting of the mantle. Therefore, it also consists of silicates enriched with other elements. Only Mercury does not have a crust - it was destroyed by strong meteorite bombardments, due to a highly rarefied atmosphere. The Earth's crust is very different from other planets, high content of granite.

Two terrestrial planets have satellites (Earth and Mars).

The table below shows a selective characteristic of the terrestrial planets.

planet name	Mercury	Venus	Earth	Mars
Distance to the Sun, million km	57,9	108,2	149,6	227,9
Distance to the Sun, a.u.	0,24085	0,61521	1,00004	1,88078
Orbital inclination, degrees	7,005	3,395	0,0002	1,850
Eccentricity	0,20564	0,00676	0,01672	0,09344
Period of rotation around its axis, days	58,6	243,0	0,9973	1,026
Orbital speed, km/s	47,9	35,0	29,8	24,1
Inclination of the equator to the orbit, degree	0,01	177,36	23,44	25,19
Number of satellites, pcs.	-	-	1	2

Mercury

Mercury is the smallest and closest planet to the Sun in the solar system. Its radius is 2439.7 km., Mass - 3.3 10 23 kg. The average density of Mercury is slightly less than the earth's, and is 5.43 g / cm 3. The free fall acceleration on the surface is 3.70 m/s 2 .

Due to the highly elongated orbit of Mercury, its distance from the Sun varies from 45.9 million km. up to 69.7 million km.

Mercury, by its rotation, is a unique planet in the solar system. First of all, a day on it takes up 2/3 of its year. Those. in one Mercurian year, only a day with a "tail" will pass there. This is explained by the strong tidal effect of the Sun on the planet. Another of its uniqueness lies in the fact that near the perihelion (the point of the orbit closest to the Sun), during 8 Earth days, the angular velocity of the orbit exceeds the angular velocity of Mercury around its axis. As a result, in the Mercury sky, the Sun stops and starts moving in the opposite direction!

There are no seasons on Mercury due to the fact that the plane of its axis is almost at right angles to the plane of its own orbit. Through this fact, there are areas at the poles of the planet that sunlight does not reach.

The temperature on Mercury varies greatly, from -180 degrees (at night) to +430 degrees during the day. Because of this temperature, there is practically no atmosphere on the planet, and it is very rarefied.

Venus

It is often called the morning star. Venus can be seen with the naked eye, at sunset and at dawn.

Venus is Earth's sister. They are very similar in size, density and mass. The radius is 6051.8 km, weight - 4.87 10 24 kg. The average density is 5.24 g / cm 3, and the acceleration of free fall on the surface has a value of 8.87 m / s 2.

Venus has a very dense atmosphere (only 14 times less than the density of water), consisting of 96% carbon dioxide, almost 4% nitrogen, water vapor and oxygen make up 0.1%. Because of this density, the pressure on the surface is 93 atm. and a temperature of 475 degrees Celsius. This high temperature is due to the greenhouse effect. Moreover, the difference between day and night temperatures is not observed - the thermal inertia of the Venusian atmosphere is very large.

Earth

Our planet is truly a unique phenomenon in the solar system. The composition of its atmosphere, distance from the Sun, dimensions, periods of rotation - all this makes it possible for the existence of one of the most important elements of the existence of earthly life. This is liquid water.

The average radius of the Earth is 6371 km. The earth's mass is 5.9736 10 24 kg, the average density is 5.5153 g / cm 3, and the speed of free fall is 9.780327 m / s 2.

Earth's atmosphere is 78% nitrogen and 21% oxygen. The rest is occupied by carbon dioxide, argon and other elements.

The Earth has one natural satellite, the Moon.

Mars

Mars is also called the red planet because of its appearance. It's just that strong winds always blow on it, and therefore, when observed, its soil gives a red tint.

The Martian radius is 3389.5 km. Mass has a value of 6.423 10 23 kg, density 3933 kg / m 3, free fall acceleration - 3.711 m / s 2.

Mars is home to the highest point in the solar system, Mount Olympus, and the largest canyon in the solar system, the Mariner Valley.

The Martian atmosphere consists of 95% carbon dioxide, 2.7% nitrogen, 1.6% argon, and only 0.13% oxygen. The pressure has a value from 0.4 kPa to 0.87 kPa.

The surface temperature ranges from -85 degrees to -5 degrees Celsius.

There is a lot of controversy around Mars - does water exist there or not, was there life there, or maybe it is still there? I hope humanity will receive answers to these and other questions soon!

Mars has two natural satellites, Deimos and Phobos.

This article does not provide a complete description of the planets of the terrestrial group and each planet separately, and gives only a small idea on the above topic.