The general characteristics of the terrestrial planets are brief. The structure and life of the universe. Milky Way Galaxy

By studying our solar system for centuries, astronomers have also learned a lot about the types of planets that exist in our universe. Thanks to the discovery of exoplanets, this knowledge has expanded significantly: many of these planets are similar to the one we call our home. True, "similar" does not mean exact identity: of the many planets discovered, hundreds are considered gas giants, and hundreds - "Earthlike." They are also known as planets. terrestrial group and this definition says a lot about the planet.

What is a terrestrial planet? Also known as solid planets, these are celestial bodies composed primarily of silicate rocks and metals and having a solid surface. This distinguishes them from gas giants, which are composed primarily of gases like hydrogen and helium, water and heavy elements in various states.

The terrestrial planets are similar in structure and composition to the planet Earth.

Composition and characteristics

All the terrestrial planets have roughly the same structure: a central metallic core, composed mostly of iron, surrounded by a silicate mantle. Such planets have similar surface features, including canyons, craters, mountains, volcanoes and other structures that are dependent on the presence of water and tectonic activity.

Terrestrial planets also have secondary atmospheres, which are created during volcanic activity or comet impact. This also distinguishes them from gas giants, whose planetary atmosphere is primary and captured directly from the original solar nebula.

Terrestrial planets are also known to have few or no moons. Venus and Mercury have no satellites, Earth has only one. Mars has two - Phobos and Deimos - but they look more like large asteroids than real satellites. Unlike the gas giants, the terrestrial planets also do not have a system of planetary rings.

Terrestrial planets in the solar system

All the planets found in the inner solar system - Mercury, Venus, Earth and Mars - are the brightest representatives of the terrestrial group. They are all composed mostly of silicate rock and metal, which are distributed between a dense metallic core and a silicate mantle. The moon is similar to these planets, but its iron core is much smaller.

Io and Europa are also satellites that are similar in structure to the terrestrial planets. Io's compositional modeling showed that the moon's mantle is composed almost entirely of silicate rock and iron, and surrounds a core of iron and iron sulfide. Europa, on the other hand, has an iron core that is surrounded by an outer layer of water.

Dwarf planets like Ceres and Pluto, as well as other large asteroids, are similar to terrestrial planets in that they have a solid surface. However, they consist more of ice materials than stone.

Exoplanets of the terrestrial group

Most of the planets discovered outside Solar system were gas giants because they are the easiest to spot. But since 2005, hundreds of potential terrestrial exoplanets have been discovered - thanks in large part to the Kepler space mission. Most of the planets became known as "super-earths" (that is, planets with a mass between Earth and Neptune).

Examples of exoplanets of the terrestrial group, a planet with a mass of 7-9 terrestrial. This planet orbits the red dwarf Gliese 876, located 15 light years from Earth. The existence of three (or four) terrestrial exoplanets was also confirmed between 2007 and 2010 in the Gliese 581 system, another red dwarf about 20 light years from Earth.

The smallest of these, Gliese 581 e, has a mass of only 1.9 Earths, but orbits too close to the star. The other two, Gliese 581 c and Gliese 581 d, as well as the alleged fourth planet Gliese 581 g, are more massive and orbit within the "" star. If this information is confirmed, the system will become interesting for the presence of potentially habitable terrestrial planets.

The first confirmed terrestrial exoplanet Kepler-10b, a planet with a mass of 3-4 Earths, located 460 light years from Earth, was discovered in 2011 during the Kepler mission. In the same year, the Kepler Space Observatory released a list of 1,235 exoplanetary candidates, including six "super-earths" located within its star's potentially habitable zone.

Since then, Kepler has discovered hundreds of planets ranging in size from the Moon to the great Earth, and many more candidates beyond those sizes.

Scientists have proposed several categories for classifying terrestrial planets. Silicate planets is a standard type of terrestrial planets in the solar system, consisting mainly of a silicate solid mantle and a metal (iron) core.

Iron planets- This is a theoretical type of terrestrial planets, which consists almost entirely of iron, which means it is denser and with a smaller radius than other planets of comparable mass. Planets of this type are believed to form in high-temperature regions close to the star, where the protoplanetary disk is rich in iron. Mercury can be an example of such a group: it was formed close to the Sun and has a metal core, which is equivalent to 60-70% of the planetary mass.

Planets without a core- Another theoretical type of terrestrial planets: they consist of silicate rocks, but do not have a metal core. In other words, planets without a core are the opposite of an iron planet. Nuclear-less planets are thought to form farther from the star, where the volatile oxidizer is more abundant. And although we do not have such planets, there is a mass of chondrites - asteroids.

Finally there is carbon planets(the so-called "diamond planets"), a theoretical class of planets that consist of a metal core surrounded by predominantly carbonaceous minerals. Again, there are no such planets in the solar system, but there are an abundance of carbon-saturated asteroids.

Until recently, everything scientists knew about planets - including their formation and the existence of different types - came from studying our own solar system. But with the advancement of exoplanet research, which has seen a powerful surge over the past ten years, our knowledge of planets has grown significantly.

On the one hand, we have come to understand that the size and scale of the planets is much higher than we previously thought. Moreover, this is the first time we have seen many Earth-like planets (which can also be inhabited) existing in other solar systems.

Who knows what we'll find when we get the opportunity to send probes and manned missions to other terrestrial planets?

Introduction

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

But in the world of planets, we will not even meet two completely similar to each other. Diversity physical conditions on the planets is very large. 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 rotation axis that determines the change of seasons, the presence and composition of the atmosphere, internal structure and many other properties are different for everyone. nine planets of the solar system.

Speaking about the variety of conditions on the planets, we can learn more deeply the laws of their development and find out their relationship between certain properties of the planets. So, for example, its ability to retain the atmosphere of a particular composition depends on the size, mass and temperature of a planet, and the presence of an atmosphere, in turn, affects the thermal regime of the planet.

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

The study of 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 in the solar system to the Sun. The average distance from Mercury to the Sun is only 58 million km. Among the major planets it has the smallest dimensions: its diameter is 4865 km (0.38 of the Earth's diameter), its mass is 3.304 * 10 23 kg (0.055 of the Earth's mass or 1: 6025000 of the Sun's mass); 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 to the left (east), then to the right (west) only a short distance, which does not exceed 28 O. Therefore, it can be seen only on those days of the year when it departs from the Sun at the 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, first the Sun sets, and after a little over an hour, Mercury sets, and we must look for this planet low above the Western horizon.

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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 full circle around the Sun in three Earth months or 88 days at a speed of 47.9 km / sec. Moving along its path around the Sun, Mercury at the same time turns around its axis so that one and the same half of it is always facing 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 its axis in the forward direction (i.e., as in orbital motion) with a period of 58.65 days (relative to the stars). The duration 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 one and corresponds to the angular velocity of its motion 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 may be devoid of an atmosphere, although polarization and spectral observations indicate a faint atmosphere. With the help of "Mariner-10", it was established that Mercury has a highly discharged gas envelope, consisting mainly of helium. This atmosphere is in dynamic equilibrium: each helium atom is in it for about 200 days, after which it leaves the planet, and another particle from the plasma of the solar wind takes its place. In addition to helium, an insignificant amount of hydrogen is found in the atmosphere of Mercury. It is about 50 times less 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 12 0 (near the Earth 11 0)

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

Temperature.

Mercury is much closer to the Sun than Earth. Therefore, the Sun shines and warms on it 7 times stronger than ours. On the daytime 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 severe 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, over 40% of the surface of Mercury was photographed with a resolution of 4 mm to 100 m, which made it possible to see Mercury in about the same way as the Moon in the dark from Earth. The abundance of craters is the most obvious feature of its surface, which at first impression can be likened to the Moon.

Indeed, the morphology of the craters is close to the lunar one, their impact origin is beyond doubt: the majority of them show traces of ejections of material shattered by impact, with the formation in some cases of characteristic bright rays and a field of secondary craters. Many craters have a central slide and a terraced structure on the inner slope. It is interesting that not only almost all large craters with a diameter of over 40-70 km have such features, but also a much larger number of smaller craters, within 5-70 km (of course, we are talking here about well-preserved craters). These features can be attributed both to the greater kinetic energy of bodies falling onto the surface, and to the surface material itself.

The degree of erosion and the smoothing of craters is different. In general, Mercury craters are shallower than lunar ones, which can also be explained by the higher kinetic energy of meteorites due to the greater acceleration of gravity on Mercury than on the Moon. Therefore, the crater forming upon impact is more efficiently filled with the ejected material. For the same reason, secondary craters are located closer to the central one than on the Moon, and deposits of shattered 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 debris falling onto the surface experience a greater acceleration of gravity.

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

In the predominant continental part of the surface of Mercury, one can distinguish both highly cratered regions with the highest degree of crater degradation, and old inter-crater plateaus occupying vast territories, which indicate a widespread ancient volcanism. These are the oldest surviving landforms on the planet. The leveled surfaces of the basins are obviously covered with the thickest layer of fragmented rocks - regolith. Along with a small number of craters, there are folded strokes resembling lunar ones. Some of the flat areas adjacent to the basins were probably formed by deposits of material ejected from them. At the same time, quite definite evidence of their volcanic origin has been found for most of the plains; however, this volcanism is of a later time than on the inter-crater plateaus. Careful study reveals another interesting feature that sheds light on the history of the formation of the planet. We are talking about the 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 their location on the surface, they differ from the usual tectonic ruptures and faults observed on the Moon and Mars, and were more likely formed due to thrusts, layers due to stress in the surface layer that arose during the compression of Mercury. This is evidenced by the horizontal displacement of the walls of some craters.

Some of the escarpments were bombarded and partially destroyed. This means that they formed earlier than the craters on their surface. After the narrowing of the erosion of these craters, one can come to the conclusion that the compression of the crust took place 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 hypothesis put forward by a number of specialists, an alternative mechanism of the planet's powerful tectonic activity during this period could be a tidal slowdown of the planet's rotation by about 175 times: from the originally assumed value of about 8 hours to 58.6 days.

Venus.

General information.

Venus is the second closest planet to the Sun, almost the same size as Earth, and its mass is more than 80% of the Earth's mass. For these reasons, Venus is sometimes referred to as the twin or sister of the Earth. However, the surface and atmosphere of these two planets are completely different. The Earth has rivers, lakes, oceans and an atmosphere that we breathe. Venus is a scorchingly 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. Nevertheless, from the shadow side on Venus, frost reigns more than 20 degrees below zero, since they do not get here Sun rays for a very long time. The planet has a very dense, deep and very cloudy atmosphere that prevents us from seeing the planet's surface. The atmosphere (gas envelope) was discovered by M.V. Lomonosov in 1761, which also showed the similarity of Venus with the Earth. The planet has no satellites.

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Venus has an almost circular orbit (eccentricity 0.007), which it orbits 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 the axis in 243 Earth days - the maximum time among all planets. Venus rotates around its axis in reverse side, that is, in the direction opposite to the orbital motion. Such a slow, and, moreover, the opposite, rotation means that, when viewed from Venus, the Sun rises and sets only twice a year, since Venusian days are equal to 117 Earth days. The axis of rotation of Venus is almost perpendicular to the orbital plane (inclination of 3 °), so there are no seasons there - 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. Venus, like the moon, has its 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 pass relatively easily through the clouds of its atmosphere and heat the planet's surface, 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 small, the natural greenhouse effect increases the global temperature by 30 ° C, and on Venus, it raises the temperature by another 400 ° C. Studying the physical consequences of the strongest greenhouse effect on Venus, we are well aware of the results that can lead to 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.

In 1970, the first spacecraft to arrive on Venus was able to withstand the terrible heat for only about one hour, but this was just enough to send data on the conditions on the surface to Earth.

Atmosphere.

The mysterious atmosphere of Venus has been at the center of robotic exploration programs over the past two decades. The most important aspects of her research were 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 penetration deep into the atmosphere. electromagnetic waves optical range. When filming Venus on television, only the cloud cover was captured. The extraordinary dryness of the air environment and its phenomenal greenhouse effect, due to which the actual temperature of the surface and the lower layers of the troposphere turned out to be more than 500 higher than the effective (equilibrium) one, were incomprehensible.

Venus's atmosphere is extremely hot and dry due to the greenhouse effect. It is a dense blanket of carbon dioxide that traps the heat that came from the sun. As a result, a large amount of thermal energy accumulates. Surface pressure 90 bar (as in the earth's seas at a depth of 900 m). Spaceships they 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 solar heat, 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 in the form of minor impurities. The total amount of carbon dioxide on Venus and Earth is approximately the same. Only on Earth is it 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 planet's surface is illuminated by diffused sunlight with approximately the same intensity as on a cloudy day on Earth. A lot of lightning has been seen on Venus at night.

Venus's clouds are composed 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 below 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 planet's surface, but much faster, making a revolution in 4 days; this phenomenon is called super-rotation, and no explanation has yet been found for it.

Surface.

The surface of Venus is covered with hundreds of thousands of volcanoes. There are some 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, so no significant weathering (weathering) occurs there. This means that volcanoes and craters have hardly changed since they formed millions of years ago.

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

On the surface of Venus, a rock rich in potassium, uranium and thorium was discovered, which in terrestrial conditions corresponds to the composition not of primary volcanic rocks, but of secondary ones that have undergone exogenous processing. In other places, coarse crushed and blocky material of dark rocks with a density of 2.7-2.9 g / cm3 and other elements characteristic of basalts lie on the surface. Thus, the surface rocks of Venus turned out to be the same as on the Moon, Mercury and Mars, erupted by igneous rocks of the basic composition.

Little is known about the internal structure of Venus. It probably has a metal core that occupies 50% of the radius. But the planet has no magnetic field due to its very slow rotation.

Venus is by no means the hospitable world 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 were dashed: after all, less than 20 years ago, many scientists considered Venus a more promising object for space exploration than Mars.

Earth.

General information.

The Earth is the third planet from the Sun in the Solar System. In shape, 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, the polar radius is 6356.777 km, and the equatorial radius is 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 World Ocean. Its average depth is about 3.8 km, maximum (the Mariana Trench in Pacific) is equal to 11.022 km; the volume of water is 1370 million km³, the average salinity is 35 g / l. The land area is respectively 29.2% and forms six continents and islands. It rises above sea level by an average of 875 m; the highest (Chomolungma peak in the Himalayas) is 8848 m. Mountains occupy over 1/3 of the land surface. Deserts cover about 20% of the land surface, savannas and woodlands - 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.

Due to its unique, perhaps the only one in the Universe natural conditions, The earth became the place where organic life originated and developed. By According to modern cosmogonic concepts, the planet was formed about 4.6 - 4.7 billion years ago from a protoplanetary cloud captured by the gravity of the Sun. The formation of the first, most ancient of the studied rocks took 100-200 million years. About 3.5 billion years ago, conditions favorable for the emergence of life arose. Homo sapiens (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.

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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 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 earth is tilted towards the Sun by its northern hemisphere, and in others by its southern hemisphere. The period of revolution around the Sun is 365.256 days, with a daily rotation - 23 hours 56 minutes. The Earth's axis of rotation is located at an angle of 66.5º to the plane of its motion 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 primary atmosphere of the Earth was rich in hydrogen, which then evaporated. The degassing of the subsoil filled the atmosphere with carbon dioxide and water vapor. But the steam condensed in the oceans, and the carbon dioxide became trapped in the 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 the current one.

Our planet is surrounded by a vast atmosphere. In accordance with the temperature, the composition and the physical properties of the atmosphere can be divided into different layers. The troposphere is an area lying between the Earth's surface and an altitude of 11 km. It is a fairly thick and dense layer containing most of the water vapor in the air. It contains almost all atmospheric phenomena that are of direct interest to the inhabitants of the Earth. In the troposphere there are clouds, atmospheric precipitation, etc. The layer that separates 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 is generated and concentrated in it. The ionosphere, that is, the ionized layer of air, is formed both in the troposphere and in the lower layers. It reflects high frequency radio waves.

The atmospheric pressure at the ocean surface is, under normal conditions, approximately 0.1 MPa. It is believed that the earth's atmosphere has changed greatly in the course of evolution: it was 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. Proof that such changes have actually taken place are, for example, deposits of coal and thick layers of carbonate deposits in sedimentary rocks, they contain an enormous amount of carbon, which was previously 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 samples studied, which are approximately 3.5 billion years old, contain approximately 60% of carbon dioxide, and the remaining 40% are sulfur compounds, ammonia, hydrogen chloride and fluoride. V small amount found nitrogen and inert gases. 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, the fluxes of radiation would reach the surface of the Earth, causing destruction in the living organisms available there. Finally, at distances of more than 1000 km, the gas is so rarefied that collisions between molecules cease to play an essential role, and atoms are more than half ionized. The first and second radiation belts are located at an altitude of about 1.6 and 3.7 Earth radii.

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) arising from seismic events - during natural earthquakes and as a result of explosions. Based on these studies, the Earth is conditionally divided into three regions: crust, mantle and 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 continent to the ocean, an intermediate type crust is developed. The thickness of the crust varies within fairly wide limits: the oceanic crust (taking into account the water layer) is about 10 km thick, while the thickness of the continental crust is tens of times greater. Surface deposits occupy a layer about 2 km thick. Beneath 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. Average densities are: 2.6 g / cm³ - near the Earth's surface, 2.67 g / cm³ - near granite, 2.85 g / cm³ - near basalt.

The Earth's mantle, which is also called the silicate shell, extends to a depth of about 35 to 2885 km. 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 depth from about 3.3 to 9.7 g / cm³. In the crust and (partly) in the mantle, there are extensive lithospheric plates. Their secular movements not only determine the continental drift, 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 decreases from 13.6 km / s (in the mantle) to 8.1 km / s (in the core), and 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 5,120 km, seismic methods reveal the presence of a solid inner core, which accounts for 1.7% of the Earth's mass. Presumably, it is an iron-nickel alloy (80% Fe, 20% Ni).

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

The earth also has magnetic and electric fields. The magnetic field above the Earth's surface consists of constant (or changing rather slowly) and variable parts; the latter is usually referred to as magnetic field variations. The main magnetic field has a structure close to a dipole one. The magnetic dipole moment of the Earth, equal to 7.98T10 ^ 25 CGSM units, is directed approximately in the opposite direction to the mechanical one, although at present the magnetic poles are somewhat displaced with respect to the geographic ones. Their position, however, changes over time, and although these changes are rather slow, over geological time intervals, according to paleomagnetic data, even magnetic reversals, 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 strength of about 100 V / m and is directed vertically downward - this is the so-called clear weather field, but this field experiences significant (both periodic and irregular) variations.

Moon.

The moon is a natural satellite of the Earth and the celestial body closest 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 Earth's average density. The satellite weighs 73 trillion tons. The acceleration of gravity on the lunar surface 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 as the vast majority of other bodies in the solar system, that is, counterclockwise when looking at the moon's orbit from the North Pole of the world. The period of the Moon's revolution around the Earth, the so-called sidereal month, is equal to 27.321661 average days, but it is subject to small fluctuations and a very small secular contraction.

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 deep into only a few decimeters due to the extremely weak thermal conductivity of the surface layers.

The relief of the lunar surface was mainly clarified as a result of many years of telescopic observations. "Lunar seas", which occupy about 40% of the visible surface of the Moon, are flat lowlands, crossed by cracks and low winding ramparts; 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, grooves, 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 moons - Phobos and Deimos.

Atmosphere.

The planet is shrouded in a shell of gas - 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 about 100 times less than at the surface of the Earth, 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 summer, in the daytime half of the planet, the air warms up to 20 ° C - a perfectly acceptable temperature for the inhabitants of the Earth. But on a winter night, frost can reach -125 ° C. Such sharp temperature changes 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 planet's surface, the speed of which reaches 100 m / s. Low gravity allows even thin air currents to lift huge clouds of dust. Sometimes quite large areas on Mars are engulfed in grandiose dust storms. A global dust storm raged from September 1971 to January 1972, raising about a billion tons of dust into the atmosphere to an altitude of more than 10 km.

There is very little water vapor in the atmosphere of Mars, but at low pressures and temperatures, it is in a state close to saturation, and often collects in clouds. Martian clouds are rather inexpressive compared to terrestrial ones, although they have various shapes and types: cirrus, wavy, leeward (near large mountains and under the slopes of large craters, in places protected from the wind). Fogs often stand over lowlands, canyons, valleys and at the bottom of craters in cold weather.

As the images from the American Viking-1 and Viking-2 landing stations 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 gas envelope of Mars is much more transparent than the earth's, including for ultraviolet rays, which are dangerous for living organisms.

Seasons.

A solar day on Mars lasts 24 hours 39 minutes. 35 s. A significant tilt of the equator to the orbital plane 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, i.e., there is a change of seasons. The Martian year lasts about 686.9 days. 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 covers 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 - when 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 mid-latitudes, winters are colder and summers are warmer than in the south, but shorter than in the north. When summer sets in in the northern hemisphere of Mars, the northern polar cap rapidly decreases, but at this time another grows - near the south pole, where winter comes. V late XIX- at the beginning of the 20th century, it was believed that the polar caps of Mars are glaciers and snow. According to modern data, both polar caps of the planet - northern and southern - are composed of solid carbon dioxide, i.e. dry ice, which is formed when carbon dioxide, which is part of the Martian atmosphere, freezes, and water ice with an admixture of mineral dust.

The structure of the planet.

Due to its low mass, the force of 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 across the planet. The core can have a radius of up to half that of the planet. Apparently, it consists of pure iron or an alloy 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 should have a thick crust 70-100 km thick. A silicate mantle enriched with iron is located between the core and the crust. The red iron oxides present in the surface rocks determine the color of the planet. Now Mars continues to cool down.

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 Mars' long geological history, 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 that cover the southern hemisphere, and the younger plains, concentrated in the northern latitudes. In addition, two large volcanic regions stand out - Elysium and Tarsis. The difference in altitude between mountainous and lowland areas reaches 6 km. Why the different districts differ so much is still unclear. Perhaps this division is associated with a very old catastrophe - the fall of a large asteroid on Mars.

The alpine part has preserved traces of an active meteorite bombardment that took place about 4 billion years ago. Meteorite craters cover 2/3 of the planet's surface. On the old highlands there are almost as many of them as on the Moon. But many Martian craters have managed to "lose shape" due to weathering. Some of them, most likely, were once washed away by streams of water. The northern plains look completely different. 4 billion years ago, there were many meteorite craters on them, but then the catastrophic event, which was already mentioned, erased them from 1/3 of the planet's surface and its relief in this area began to form anew. Some meteorites fell there even later, but in general there are few impact craters in the north.

The shape 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, froze, new streams flowed along them. These petrified "rivers" are centered around large volcanoes. At the ends of lava tongues, structures similar to terrestrial sedimentary rocks are observed. Probably when incandescent eruptive masses melted layers underground ice, on the surface of Mars, quite extensive reservoirs were formed, which gradually dried up. The interaction of lava and underground ice has also led to the appearance of numerous furrows and cracks. In the lowlands of the northern hemisphere, far from volcanoes, sand dunes stretch. There are especially many 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 Tarsis. 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, Farsis - 10 km. Around these bulges are concentrated numerous faults, cracks, ridges - traces of old processes in the Martian crust. The most grandiose system of canyons several kilometers deep - the Mariner Valley - begins at the top of the Tarsis 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 atmosphere of Mars was denser, water could flow into the canyons, creating deep lakes in them.

The volcanoes of Mars are exceptional phenomena by earthly standards. But even among them, the Olympus volcano, located in the northwest of the Tarsis 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 size of Everest, the highest peak on Earth. Olympus is crowned with a huge 60 km long crater. To the east of the highest part of the Tarsis mountains, another volcano, Alba, was discovered. Although it cannot rival Olympus in height, its base is nearly three times its diameter.

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

In the past, flowing water played a huge role in the formation of the Martian topography. At the first stages of exploration, Mars appeared to astronomers as a desert and waterless planet, but when the surface of Mars was photographed at close range, it turned out that in the old highlands there are often gullies as if left by running water. Some of them look like they were pierced by stormy, rushing currents many years ago. They sometimes stretch for many hundreds of kilometers. Some of these "streams" are of 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 confrontation by the American astronomer Asaf 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" - "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 found that Phobos and Deimos have an irregular shape and in their orbital position they always remain facing the planet with the same side. The dimensions of Phobos are about 27 km, and Deimos is about 15 km. The surface of the satellites of Mars is composed 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 were probably born of meteorite bombardment, the origin of the parallel groove system is unknown. The angular velocity of the orbital motion of Phobos is so great that, outrunning the axial rotation of the planet, it rises, unlike other luminaries, in the west, and sets in the east.

The search for life on Mars.

For a long time, Mars has been looking for forms of extraterrestrial life. When exploring the planet spacecraft In the Viking series, three complex biological experiments were performed: pyrolysis decomposition, gas exchange, and tag decomposition. They are based on the experience of studying earthly life. The pyrolysis decomposition experiment was based on determining the processes of photosynthesis with the participation of carbon, the label decomposition experiment was based on the assumption that water was 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 positive results, they are probably of a non-biological nature and can be explained by inorganic reactions of the nutrient solution with matter of a 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 terrestrial planets. The future of our planet, and of the entire planetary system, if nothing unexpected happens, seems clear. The likelihood that the established order of planetary motion will be disrupted by some wandering star is small, even for several billion years. In the near future, one should not expect strong changes in the flow of solar energy. Ice ages are likely to repeat. Man can change the climate, but he can make a mistake. Continents in subsequent eras will rise and fall, but we hope that the processes will proceed slowly. From time to time, massive meteorite falls are possible.

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

Plan.

1. Introduction.

2. Mercury.

3. Venus.

6. Conclusion.

7. Literature.

Planet Mercury.

Surface of Mercury.

Planet Venus.

Surface of Venus.

Planet Earth.

Ground surface.

The planet Mars.

Surface of Mars.

> Terrestrial planets

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 vastness of the solar system for centuries, noting various planetary types... Since the opening 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 the Terrestrial planets

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

The structure and features of the terrestrial planets

All bodies are endowed with a similar structure: a core of metal, filled with iron and surrounded by a mantle of silicates. Their surface sphere 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 few or no satellites. The Earth has the Moon, and Mars has Phobos and Deimos. Not endowed with ring systems. Let's see what the characteristics of the terrestrial planets look like, and also notice what are their similarities and differences using 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. 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. On the surface, there are many deep crater scars and a weak layer of silicate particles. In 2012, traces of organic material were noticed. These are the building blocks for life and also found water ice.

Venus It is similar in size to Earth, but its atmosphere is too dense and overflowing with carbon monoxide. Because of this, heat is trapped on the planet, making it the hottest in the system. Most of the surface is home to active volcanoes and deep canyons. Only a few devices managed to penetrate the surface and survive for a short period of time. Craters are few because the meteors burn out.

Earth- the largest in the terrestrial type and has a huge amount of liquid water. It is needed for a life that develops in all forms. There is a rocky surface sheltered by canyons and hills, as well as a heavy metal core. The atmosphere contains water vapor, which helps to soften the daily temperature regime. There is a change of 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 sediments and crater formations. But you can also find younger sites. There are polar caps that shrink in size during the summer and spring. It is inferior in density to the Earth, and the core is solid. Researchers have yet to uncover evidence of life, but there are all hints and conditions in the past. The planet has water ice, organic matter and methane.

Formation and general features of the terrestrial planets

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

Analysis shows that at an early stage in the development of the solar system, about a hundred protoplanets, whose sizes varied between the Moon and Mars, could have been present. They constantly collided, due to which they merged, throwing out debris. As a result, 4 large terrestrial planets 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 also stand out overall structure structures, including the core, mantle and crust. Only two planets (Earth and Mars) have satellites.

Ongoing exploration of the terrestrial planets

Researchers believe that terrestrial planets are the best candidates for detecting life. Of course, the conclusions are based on the fact that the only planet with life is Earth, therefore 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 of all attention is paid to Mars. It is not only the main 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 may be sent to the Red Planet. Rovers and orbiters are constantly on the planet, looking for water and signs of life.

Terrestrial exoplanets

Many of the exoplanets found 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 have been nicknamed the super-land class.

Among these, it is worth remembering Gliese 876d, whose mass is 7-9 times that of 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 is only 1.9 times our mass, but it is located extremely close to its star. The first confirmed terrestrial exoplanet was Kepler-10b, 3-4 times larger than 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 terrestrial and located in the habitable zone.

Super Earth

Among exoplanets, it was possible to find many super-lands (in size between Earth and Neptune). This species cannot be found on the territory of our system, therefore it is not yet clear whether they look more like giants or the terrestrial type.

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

Categories of terrestrial planets

There is a division of the 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 more density but shorter radius. Such planets can appear only in areas with a high temperature index.

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

We used to think that we had studied in detail the process of planetary formation. But looking at exoplanets forces you 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.

There are four Terrestrial planets in our solar system: Mercury, Venus, Earth and Mars, and they get their name for their similarity to our planet Earth. The terrestrial planets of our solar system are also known as inner planets because these planets are located in the region between the Sun and. All the planets of the Terrestrial group are small in size and mass, high in density and consist mainly of silicates and metallic iron. Behind the main belt of asteroids (in the outer region) are located, in size and mass, dozens of times larger than the planets of the Earth group. According to a number of cosmogonic theories, in a significant part of extrasolar planetary systems, exoplanets are also divided into solid planets in the inner regions and gas planets in the outer ones.

The terrestrial planets are poor in natural satellites. There are only three satellites on the four terrestrial planets. The two most distant planets from the Sun, of the terrestrial planets, have satellites, one large near the Earth and two tiny ones near Mars.

Although the Moon is considered a satellite, it could technically be considered a planet if it had an orbit around the Sun. The moon is a full-fledged member of the Earth-Moon gravitational system.

Mars has two small moons: Phobos and Deimos. Both satellites have a shape close to a triaxial ellipsoid. Due to their small size, gravity is not sufficient to compress them into a round shape.

The most massive of the terrestrial planets, the Earth, is 330,000 times lighter than the Sun.

The structure and similarity of the terrestrial planets

• The terrestrial group is significantly smaller than the gas giants.
• The terrestrial planets (unlike all giant planets) do not have rings.
• In the center there is a core made of iron with an admixture of nickel.
• Above the core is a layer called the mantle. The mantle is composed of silicates.
• Terrestrial planets are composed mainly of oxygen, silicon, iron, magnesium, aluminum and other heavy elements.
• The crust, formed as a result of partial melting of the mantle and also consisting of silicate rocks, but enriched in incompatible elements. Of the terrestrial planets, Mercury does not have a crust, which is explained by its destruction as a result of a meteorite bombardment.
• The planets have atmospheres: rather dense in Venus and almost imperceptible in Mercury.
• Terrestrial planets also have a changing landscape, such as volcanoes, canyons, mountains, and craters.
• These planets have magnetic fields: almost imperceptible on Venus and perceptible on Earth.

Some differences of the terrestrial planets

• The terrestrial planets rotate quite differently around their axis: one revolution lasts from 24 hours for the Earth and up to 243 days for Venus.
• Venus, unlike other planets, rotates in the opposite direction to its movement around the Sun.
• The angles of inclination of the axes to the planes of their orbits for the Earth and for Mars are approximately the same, but completely different for Mercury and Venus.
• The atmospheres of planets can range from a thick atmosphere of carbon dioxide on Venus to almost none on Mercury.
• Almost 2/3 of the Earth's surface is occupied by oceans, but there is no water on the surfaces of Venus and Mercury.
• Venus does not have a molten iron core. In other planets, part of the iron core is in a liquid state.

It is believed that earth-like planets are the most favorable for the emergence of life, therefore, their search attracts close public attention. Super-Earths are an example of terrestrial exoplanets. As of June 2012, over 50 SuperLands have been found.

Once I read that it is planned to send the first settlers to Mars in 2024. Some of my acquaintances have expressed a desire to go on this unknown one-way trip. And I don't really want something, because this planet is lifeless, and I love animals, flowers and wildlife. I especially got sick of flying there after watching the movie "The Martian", where the dull landscapes and unbearable weather conditions of this celestial body were realistically depicted. But Mars is our neighbor, it is the second planet closest to us (the first is Venus). There are four planets in the Earth group in total. They are so called because they consist of solid ground. Let's call them in the order of their distance from the Sun.

Mercury is the smallest planet in the terrestrial group

A small body characterized by rapid movement around the Sun, for which it received its name god of trade... But around its axis, Mercury rotates slowly, so here a day longer than a year. The atmosphere is composed of hydrogen, argon, helium and oxygen impurities... The climate is hot, the temperature is up to +420 degrees.

Venus is a beauty of the terrestrial group

Beautiful when viewed through a telescope or binoculars, at dawn it can be seen with the naked eye. This is probably why she got the name goddess of love... It is characterized by clouds of sulfuric acid that float into carbon dioxide atmosphere... The sight is beautiful, but absolutely unsuitable for life. In addition, the temperature on the planet is also goes off scale for +400.

Earth is a living planet

This is our planet. Its main feature is life, which is possible thanks to:

• an atmosphere consisting of air;
• a large amount of liquid water;
• mild climate.

Ancient people idolized their wet nurse - soil, the second name of which is earth. In honor of her, the name of the home planet was given.

Mars is a cold planet

It has red soil, which gave a reason to call him by his name god of war... Since Mars is located farther from the sun's heat than Earth, the climate on it is very cold. At frost more than 130 degrees colonizing the planet is problematic. Yes and atmosphere here is unbreathable, it consists mainly of carbon dioxide.