Mass of the planets of the earth group. Features of the planets of the earth group. Chemical composition and density of the planets of the earth group

- have small sizes and masses, the average density of these planets is several times greater than the density of water; They slowly rotate around their axes; They have few satellites (Mercury and Venus are not at all, Mars has two tiny, the Earth is one).

The similarity of the planets of the earth group does not exclude a significant difference. For example, Venus, unlike other planets, rotates in the direction opposed to its movement around the Sun, and 243 times slower the earth (compare the duration of the year and day on Venus). The period of treatment of Mercury (that is, the year of this planet) is only 1/3 more than the period of its rotation around the axis (in relation to the stars). The angle of tilt axes to the planes of their orbits by the Earth and Mars is about the same, but completely different in Mercury and Venus. And you know that this is one of the reasons that determines the nature of the change of the seasons. The same as the earth, the seasons, therefore, in Mars (though, every time of the year is almost twice a longer than on Earth).

It is possible that for a number of physical characteristics, the planets of the Earth Group also includes the distant Pluto - the smallest of the 9 planets. The average diameter of Pluto is about 2260 km. Only twice smaller than the diameter of Charon - Pluto satellite. Therefore, it is possible that the Pluto system is Haron, as well as the Earth System -, is a "double planet".

Atmosphere

The similarities and differences are also found when studying the atmosphere of the planets of the earth group. Unlike Mercury, which, like the moon, practical atmospheric, Venus and Mars have it. Modern data on the atmospheres of Venus and Mars were obtained as a result of our flights (Venus, Mars) and American (Pioneer-Venus, Mariner, Viking) AMS. Comparing the atmosphere of Venus and Mars with the earth, we see that, unlike the nitrogen-oxygen earthly atmosphere, Venus and Mars have an atmosphere, mainly consisting of carbon dioxide. The pressure of the Venus surface is more than 90 times more, and Mars has almost 150 times less than that of the earth's surface.

The temperature of the Venus surface is very high (about 500 ° C) and remains almost the same. What is it connected with? At first glance, it seems that Venus is closer to the Sun than the Earth. But, as observations show, the reflectivity of Venus is greater than that of the Earth, and therefore both planets are approximately the same. High temperature of the venera surface is caused by a greenhouse effect. It consists in the following: the atmosphere of Venus skips the rays of the sun, which heat the surface. The heated surface becomes a source of infrared radiation that cannot leave the planet, since it is delayed in the atmosphere of venera carbon dioxide and water vapor, as well as cloud cover of the planet. As a result, the balance between the influx of energy and its flow rate in the peaceful space is set at a higher temperature than the one that would be in the planet freely transmitting infrared radiation.

We are accustomed to terrestrial clouds consisting of small droplets of water or ice crystals. The composition of the clouds of Venus is different: they contain droplets sulfur and, possibly, hydrochloric acid. The cloud layer greatly relaxes the sunlight, but, as the measurements were shown, made on the AMS "Venus-11" and "Venus-12", the illumination at the surface of Venus is approximately the same as the surface of the earth on a cloudy day. Studies performed in 1982 AMS "Venus - 13" and "Venus-14" showed that the sky of Venus and its landscape are orange. This explains the feature of the dispersion of light in the atmosphere of this planet.

Gas in the atmospheres of the planets of the earth group is in continuous motion. Often during dust storms, which last for several months, a huge amount of dust rises into the atmosphere of Mars. Hurricane winds are fixed in the atmosphere of Venus at altitudes where the cloud layer is located (from 50 to 70 km above the surface of the planet), but near the surface of this planet, the wind speed reaches only a few meters per second.

Thus, despite some similarity, as a whole, the atmosphere of the planets closest to Earth differ sharply from the Earth's atmosphere. This is an example of a discovery that was impossible to predict. Common sense suggested that the planets with similar physical characteristics (for example, the land and Venus are sometimes called "twin planets") and approximately equally distant from the Sun should have a very similar atmosphere. In fact, the cause of the observed difference is associated with the peculiarities of the evolution of the atmosphere of each of the planets of the earth group.

The study of the atmosphere of the Earth Group plan not only allows you to better understand the properties and history of the origin of the earth's atmosphere, but also matters to solve an environmental problem. For example, fogs - the smughs formed in the earth's atmosphere as a result of air pollution, in their composition very much resemble the Venusian clouds. These clouds, like dust storms on Mars, remind us that it is necessary to limit the emission of dust and all sorts of industrial waste into the atmosphere of our planet, if we want to preserve conditions suitable for the existence and development of life on Earth. Dust storms, during which for several months in the atmosphere of Mars are held and applied to the enormous territories of the clouds of dust, are forced to think about some possible environmental consequences of the nuclear war.

Surface

The planets of the earth group, like the Earth and the Moon, have solid surfaces. Ground optical observations allow you to get some information about them, since Mercury is difficult to consider in a telescope even during the elongations, the surface of Venus is hidden from us clouds. On Mars even during the great confrontations (when the distance between the land and Mars is minimal - about 55 million km), which occur once every 15 - 17 years, it is possible to consider the details of about 300 km in large telescopes. Nevertheless, in recent decades, it was possible to learn a lot about the surface of Mercury and Mars, and also to get an idea of \u200b\u200beven recently completely mysterious surface of Venus. This became possible thanks to the successful flights of automatic interplanetary stations of the Venus type, Mars, Viking, Mariner, Magellan, who flew near the planets or landing on the surface of Venus and Mars, and thanks to ground radar observations.

The surface of Mercury, replete with craters, is very reminiscent of the lunar. "Seas" is less than on the moon, and they are small. The diameter of the Mercurian Sea heat is 1300 km, like the sea of \u200b\u200brains on the moon. Tens and hundreds of kilometers stretch cool ledges, probably generated by the former tectonic activity of Mercury, when the surface layers of the planet were shifted and the surface layers were moved. As in the moon, most crater formed as a result of meteorites. Where craters are a bit, we see relatively young surface areas. Old, destroyed crater differ markedly from younger crater, well preserved.

The rocky desert and many separate stones are visible on the first phototelevice panorama view, transmitted from the surface of Venus with automatic stations of the Venus series. Radar terrestrial observations found on this planet a set of shallow craters, the diameters of which are from 30 to 700 km. In general, this planet turned out to be the most smooth of all the planets of the earthly group, although it has large mountain ranges and long-standing hills, twice as large as the size of the Earth Tibet. Maxwell's extinct Vulcan, his height is 12 km (one and a half times more jomolungma), the diameter of the sole is 1000 km, the diameter of the crater at the top of 100 km. Very great, but less than Maxwell, volcanic cones Gauss and Hertz. Like the rift gorges drawn through the bottom of the earth's oceans, rift zones also discovered on Venus, indicating that on this planet once occurred (and maybe now!) Active processes (for example, volcanic activity).

In 1983 - 1984 From the stations "Venus - 15" and "Venus - 16", radar studies were conducted, which allowed to create a map and the atlas of the surface of the planet (the dimensions of the surface parts 1-2 km). The new step in the study of the surface of Venus is associated with the use of a more advanced radar system installed on board the American AMS "Magellan". This spacecraft reached the surroundings of Venus in August 1990 and went on an elongated elliptical orbit. Regular shooting is carried out since September 1990. Distinct images are transmitted to Earth, some of them are well distinguishable the details of up to 120 m. To May 1993, almost 98% of the surface of the planet was covered. It is planned to complete an experiment comprising not only photographing Venus, but also carrying out other studies (gravitational field, atmosphere, etc.) in 1995

I abound with craters and the surface of Mars. Especially many of them in the southern hemisphere of the planet. Dark areas occupying a significant part of the surface of the planet, got the name of the seas (Ellad, Argir, etc.). The diameters of some seas exceed 2000 km. Hill, resembling earth continents, which are bright fields of orange-red color, are named by the mainland (Farsida, Elysis). As in Venus, there are huge volcanic cones. The height of the greatest of them (Olymp) exceeds 25 km, the diameter of the crater is 90 km. The diameter of the base of this gigantic cone-shaped mountain is more than 500 km.

That millions of years ago, there were powerful volcanic eruptions on Mars, and surface layers were shifted, the remains of lava flows, huge surface faults (one of them - Mariner - stretches for 4000 km), numerous gorges and canyons. It is possible that it is some of these formations (for example, a chain of crater or extended gorge), Mars researchers took another 100 years ago for "channels", the existence of which subsequently tried to explain the activities of the intelligent inhabitants of Mars for a long time.

It stopped being a mystery and a red Mars. It is explained by the fact that the soil of this planet contains a lot of clay rich in iron.

From a close distance, the panoramas of the "Red Planet" surface were repeatedly photographed and passed.

You know that almost 2/3 of the ground surface occupy the oceans. There is no water on the surface of Venus and Mercury. Open reservoirs are absent and on the surface of Mars. But, as scientists suggest, water on Mars must be at least in the form of a layer of ice forming the polar caps, or as an extensive layer of permafrost. Perhaps you will be witnesses to the discovery on Mars of ice reserves or even under the ice of water. The fact that the water was once on the surface of Mars, testifies the dried surround-like winding hollows.

Pluto - they all have small masses and dimensions, their average density has several times surpassed the density of water; They are able to rotate slowly around the personal axes; They have a small number of satellites (from Mars - two, in the earth - only one, and the Venus with Mercury is not at all).

The similarity of the planets in the earth group does not exclude some differences. For example, Venus rotates in the opposite direction from the movement around the Sun, and in two hundred forty three times slower. The period of rotation of Mercury (that is, the year of this planet) only one third more of the period of rotation around its axis.

The angle of inclination of the axis to the planes of the orbits from Mars and the Earth is about the same, but completely different in Venus and Mercury. Just like the earth, there are times of the year, which means that on Mars, although almost 2 times longer than on earth.

Perhaps the planets of the ground group include the distant Pluto - the smallest of nine planets. The usual diameter of Pluto amounted to more than two thousand kilometers. Only 2 times less than the diameter of the Pluto - Charon satellite. Therefore, it is not a fact that the Pluto system is Charon, as well as the system of the Earth - is a double planet.

Similarities and differences are found in the atmospheres of the planets of the earth group. Venus and Mars have an atmosphere in contrast to Mercury, which, like the moon, is almost deprived of it. Venus has a sufficiently dense atmosphere, mainly consisting of sulfur compounds and carbon dioxide. The atmosphere of Mars is too raised and very poor nitrogen and oxygen. Pressures near the surfaces of Venus almost, which is a hundred times more, Mars has almost a hundred and fifty times less than among the surfaces of the Earth.

The hotness in the surfaces of Venus is high enough (about five hundred degrees Celsius) and it remains almost the same all the time. The high temperature of the Venus surfaces is determined by a greenhouse effect. The thick atmosphere densely produces the rays of the sun, however, it delays thermal infrared radiation that comes from heated surfaces. The gas in the atmosphere of the planet of the ground group is in constant motion. Often during the dust storm, lasting not at one month, a large number of dust rises to the atmosphere of Mars.

According to its physical properties, the planet can be divided into two categories: planets-giants and planets of the earth group.

What planets relate to the planets of the earth group

The discharge of the planets of the earth group, scientists attributed Mercury, Mars, Venus and Earth. All of them have a rather modest size and mass. The density of the planets under consideration is many times higher than the density of water. The rate of treatment around its own axis is rather small, as well as a small number of satellites (Venus and Mercury, they are generally absent, but the Earth boasts one satellite - Moon).

However, if these planets have similar features, it does not mean at all that there are no differences. For example, the rotation of Venus occurs in the opposite rotation around its direction around the sun, and the speed of rotation is more than 240 times less than that of the Earth (this is evidenced by the number of days a year on Venus). The duration of the year on Mercury (that is, around the Sun) only by a third exceeds the duration of its appeal around its own axis. The axes to the planes of the earth and Martian orbits are inclined about at one angle, but the tilt of the axes of Venus and Mercury is very different. And this, in turn, one of the most important reasons why the change of seasons is determined. The Earth has its own seasons of the year, identical are observed on Mars (at least he lasts two times longer than that of the earth).

There is a chance that the physical properties can also be a small and far Pluto to consider the category of category. In the diameter, Pluto exceeds 1200 kilometers, which is only two times less than the diameter of its own satellite - charon. It is possible that Pluto and Charon, like Earth with the Moon, is a "double planet".

Characteristics of the planets of the earth group

The atmospheric properties of the planets of this category have both shafts and distinctive features. For example, Mars and Venus have their own atmosphere, while Mercury, as well as the moon, is almost deprived of the atmosphere. The atmosphere density on Venus is quite high, because it has in its composition mainly carbon dioxide and sulfur compounds. And the Martian atmosphere is rich in oxygen nitrogen, as a result of which is very resolved. The surface pressure of Venus is almost a hundred times the pressure of the earth's surface, and Mars on this parameter lags behind 150 times.

The temperature on Venus almost never changes and keeps at a rather high level - approximately 500 ° C. Such a hot climate is due to the greenhouse effect. Atmosphere with high density, although it passes through itself the sun's rays, but does not give the exit infrared thermal radiation emanating from the hot surface. Gas masses contained in the atmosphere of the planets of the earth group are constantly moving. Often during the period of dust storms flowing for no one month, the colossal volume of dust masses raises in the Martian atmosphere. And during the storm winds on the Venus, occurring at the level of the layer of clouds (approximately 50-70 km from Venus), closer to the planet the speed of wind movement is read meters per second.

The surface of the planets of the earth group, as well as the earth's surface, as well as the surface of its satellite, solid. Mercury is similar to the moon by which is rich in multiple crater. The so-called "seas" here are quite small, and their number, compared to the same moon, is much less. Most of the craters appeared due to the fall on the surface of meteorites. Thanks to this, you can distinguish younger superficial areas - the more crater, the one is older.

The surface of Venus is characteristic of its numerous stones and rocky deserts, which can be observed on the first photopadars sent from the surface of this planet by automated stations of the Venus series. The study of the surface of Venus spoke about numerous small craters with a diameter within 30-700 km. The surface of Venus is smoother than the other planets of the earth group, although it can boast by large mountain chains and long hills, which are twice the size of our Tibet.

Approximately two thirds of the earth's surface are covered with oceans, while Mercury or Venus of water in the presence at all.

Mars is also rich in crater. Most of them are grouped in its southern hemisphere. Pretty pronounced dark areas covering the decent part of the planet are called seas. Some seas in diameter over 2 thousand km. The bright areas of orange and red colors, which are hills that are similar to the continents of the Earth, received the names of the mainland. Here you can see large cones of volcanoes, as well as on the surface of Venus. The most important of them - Olympus. It rises more than 25 km, the diameter of the crater is 90 km, and the diameter of this giant is over 500 km. The remnants of the lava flows, many canyons and gorges say that the order of millions of years ago at the Martian surface occurred strong eruptions of volcanoes, and the surface board was moved.

What is the similarity of the planets of the earth group

The structure of the planets of this type is approximately identical: in the center of the core from the mtela, which is formed by and large from iron, around the silicate sheath. The planets of this type are similar to the surface line: crater, elevations, canyons, mountain chains, etc. Their presence is due to two factors: there is water and what is tectonic activity.

The planets of this category contain a secondary atmosphere, which emerged due to the fallen comet or due to the activities of volcanoes. These planets have a moon or a little or no. Mercury and Venus satellites do not possess, the Earth can boast the only satellite - Moon, but Mars have them at once two - Phobos and Dimos, who themselves resemble more asteroids, and not planetary satellites.

What is the difference between the planets of the earth group

• For the planets of this category, it is characteristic of rotating around the axis in its own way: in about the time, as one earth turnover is 24 hours, then Venus can last up to 243 days.
• Venus is the only one of the four planets makes rotations, returning it to moving around the sun.
• Mars and the Earth have an almost identical angle of tilt axis to the orbits plane, while these corners are completely different in Venus and Mercury.
• The range of the atmosphere of these planets varies from a dense atmosphere of carbon dioxide at Venus to its almost absolute lack of nonsense in Mercury.
• Mercury and Venus are genuined by the presence of water, and the earth's surface is two-thirds - water surface.
• Venus does not have a typical planets of the iron core.

The atmosphere of the planets of the earth group

The primary atmosphere of the earth-type planet appeared immediately after their creation. It included in its composition for the most part carbon dioxide formed at the time of layer-by-layer division immediately after the accretion stage. The chemical composition of the earth's atmosphere was seriously affected by life appeared on it: the amount of carbon dioxide decreased, and the proportion of oxygen increased. Mercury and the Moon did not have a sufficient mass in order to keep the atmosphere. The atmosphere of Mars and Venus is more maintaining carbon dioxide, unlike the Earth.

Satellites planets earth group

Mercury and Venus do not possess natural satellites. Therefore, you will review only with earth and Martian satellites.

Earth satellite - Moon

Our planet is rich in one satellite - moon. She was studied in such detail how no longer was the same cosmic body. In addition, only here managed to visit a person.

Although everyone knows that the moon is a satellite, theoretically, she could become a full-fledged planet, if her orbit took place around the sun. The lunar diameter has almost 3.5 thousand kilometers, which exceeds even the dimensions of the pluto.

The moon is a full participant in the Earth-Moon gravity system. Maas Satellite is not very big, but they have a common mass center with Earth.

Among all cosmic bodies, in addition to the Sun, the moon has the greatest influence on the ground. The bright example of this is the lunar cells and tides, changing the water level in the oceans.

The entire moon surface is covered with craters. This is explained by the fact that the moon does not have its own atmosphere capable of defending its surface from meteorites. In addition, the earthly satellite has no water and wind, with the help of which there would be places where meteorites fall. For the entire existence of the moon, that is, four billion years old, the lunar surface has collected a huge number of crater.

Martian satellites

Mars has two small satellites - Phobos and Demos - open in 1877 by A. Holl. Interestingly, at a certain point he was already so desperate to find satellites of Mars, which was almost completed the study, but his wife was convicted. And the next day Hall found Dimimos. Even six days later - Phobos. On the second surface, he found a crater giant ten kilometers width (which is about half of the width of phobos). The researcher gave him the name of his wife's name to the name of his wife - Stickie.

And the one and the other satellite shape resemble an ellipsoid. Gravity forces because of small sizes are not enough to survive satellites in a rounded shape.

It is curious that Mars has an impact on Phobos, gradually reducing the speed of its movement. Because of this satellite orbit, the satellite is moving closer to the planet. Ultimately, Phobos will fall on Mars. For a hundred years, this satellite approaches the surface of the planet for nine centimeters. Therefore, before the time of their collision, there will be about eleven million years. But Dimimos, in turn, is systematically distinguished from the planet and over time will be covered by sunny forces. That is, at some point in its existence, Mars will remain without both satellites.

Martian satellites are always located one and the same side to the planet, because the time of handling around its own axis coincides with the time of rotation around Mars. They are similar to this property to the moon, the opposite side of which also never consider from the earth's surface.

Phobos and Dimimos in their size are very small. Even the lunar diameter exceeds Phobos 158 times, and Dimimos - at 290.

On the origin of Mars satellites, researchers argue to this day. It could be asteroids that fell in the field of gravity of Mars. However, their asteroids are distinguished by the structure, which indicates against such a theory. Another version - two satellites was formed due to the split once the only Martian satellite into two parts.

Characteristics of the surface of the planets of the earth group

The surface of the planets under consideration was formed under the influence of the primary activities of volcanoes. At first, when the planets were rather hot, volcanic activity was very active. And later the surface of the planets was modified due to the activity of tectonic plates, volcanic eruptions and meteorites falling on it.

The surface of Mercury resembles a moon. Only one distinguishes - the presence of infrequent almost perfectly smooth areas, which are older than the same lunar areas, because they appeared during the fall of meteorites.

The Martian surface has a red tint due to the considerable volume of iron oxide impurities. Craters cover mostly only southern Martian hemisphere. Scientists have not yet revealed the exact reason for this: perhaps everything is chain an unknown cataclysm, and maybe in this part they were simply ocean water.

It is known that on the Martian surface in the past, rivers flowed, as evidenced by the remaining dried beds. In addition to rivers, Mars is interesting in volcanoes, the sizes of some of them are amazed.

Chemical composition and density of the planets of the earth group

The planets similar to Jupiter are usually gas giants that have helium and hydrogen in their composition, because this gas is greater. Nor to fold these substances, it is still the result of a planet consisting by and large from the gas.

Stone planets of the earth group were formed closer to the sun. The closer to the star, the gases from these planets were blown. Thus, the formation of the chemical composition of the planets of the earth group proceeded with the interaction of solid particles. The formation began, initially, from dust, which includes a very small amount of hydrogen, and helium is almost absent. Therefore, the structural planets of the earth group are formed from the universal system of elements.

They are divided into 2 groups based on their planetary surfaces: gas giants and planets of the earth group. The planets of the earth group are characterized by a dense surface and, as a rule, consist of silicate compounds. In the solar system there are only four planets: Mars, Earth, Venus and Mercury.

Planets of the earth group in the solar system:

Mercury

Mercury is the smallest of four land-like planets of the solar system with an equatorial radius of 2439.7 ± 1.0 km. The planet surpasses such satellites such as titanium. Nevertheless, Mercury has a second density (5427 grams per cubic centimeter) among the planets of the solar system, a little yielding to this indicator of the earth. High density gives an idea of \u200b\u200bthe internal structure of the planet, which, as scientists believed, rich in iron. It is believed that the nucleus of Mercury has the highest iron content among all the planets of our system. Astronomers believe that the molten core is 55% of the total volume of the planet. The shell of the rich core is a mantle, which mainly consists of silicates. The rocky bark of the planet reaches 35 km in thickness. Mercury is located at a distance of 0.39 astronomical units from the Sun, which makes it the most nearby planet to our luminaries. Due to approximity to the Sun, the surface temperature of the planet rises to more than 400º C.

Venus

Venus is the nearest neighbor of the Earth and one of the four planets of the earth group in the solar system. This is the second largest planet from this category with a diameter of 12,092 km; Given only the earth. However, the thick atmosphere of Venus is considered the most dense in the solar system, the atmospheric pressure is 92 times higher than the atmospheric pressure on our planet. The dense atmosphere consists of carbon dioxide, which has a greenhouse effect and leads to an increase in temperature on the surface of Venus to 462º C, and is. Volcanic plains prevailed on the planets, covering about 80% of its surface. There are also numerous shock crater on Venus, some of which reaches a diameter of about 280 km.

Land

Of the four planets of the earth group, the Earth is the largest with an equatorial diameter of 12,756.1 km. She is also the only planet from this group, which is known to have a hydrosphere. Earth is the third closest planet to the Sun, located at a distance of about 150 million km (1 Astronomical unit) from it. The planet also has the highest density (5,514 grams per cubic centimeter) in the solar system. Silicat and alumina are two compounds found in the highest concentrations in the earth's crust, and they account for 75.4% of the continental bark and 65.1% of the oceanic bark.

Mars

Mars is another planet from the earth's group in the solar system, located furthest from the Sun at a distance of 1.5 astronomical units. The planet has an equatorial radius of 3396.2 ± 0.1 km, which makes it the second smallest planet in our system. The surface of Marsa mainly consists of basalt rocks. The planet's bark is pretty thick and ranges from 125 km to 40 km in depth.

Dwarf planets

There are other smaller dwarf planets that have some characteristics comparable to the global plantes of the earth group, such as the presence of a dense surface. Nevertheless, the surface of the dwarf planets is formed by ice cover and therefore they do not belong to this group. Examples of dwarf planets in the solar system are Pluto and Ceres.

There are four planets of the earth group in our solar system: Mercury, Venus, Earth and Mars. They got their name for the similarity with our planet Earth. The planets of the earth group of our solar system are also known as inner planets, because these planets are located in the area between the Sun and. All planets of the earth group have small size and masses, high density and consist mainly of silicates and metallic iron. The main belt of asteroids (in the outer domain) is, in size and mass ten times greater than the planets of the Earth Group. According to a number of cosmogonic theories, in a large part of the extraction planetary systems, exoplanets are also divided into solid-state planets in the inner areas and gas planets in external.

The planet of the earth group is poor natural satellites. There are only three satellites on four planets of the earth group. The two most distant planets from the Sun, from the planets of the earth group have satellites, one large in the earth and two tiny Mars.

Although the moon is considered a satellite, technically she could be considered a planet if he had an orbit around the sun. The moon is a full-fledged participant in the gravitational system of the Earth-Moon.

Mars has two small satellites: Phobos and Dimimos. Both satellites have a form close to three-axis ellipsoid. Because of their small sizes, the force is not enough to squeeze them to a round form.

The most massive out of the planets of the earth group - the Earth is 330,000 times easier than the Sun.

The structure and similarity of the planets of the earth group

• The earth group is significantly less than gas giants.
• The planets of the earth group (in contrast to all the planets-giants) do not have rings.
• In the center of the kernel of iron with an admixture of nickel.
• Above the kernel is a layer, which is called Mantia. Mantle consists of silicates.
• The planets of the earth group consist mainly of oxygen, silicon, iron, magnesium, aluminum and other heavy elements.
• The bark formed as a result of partial melting of the mantle and also consisting of silicate rocks, but enriched with incompatible elements. From the planets of the earth group there is no crust in Mercury, which explains its destruction as a result of a meteorite bombardment.
• The planets have an atmosphere: a rather dense of Venus and almost imperceptible in Mercury.
• The planets of the earth group also have a changing landscape, for example, volcanoes, canyons, mountains and craters.
• These planets have magnetic fields: almost imperceptible from Venus and tangible in the earth.

Some differences in the planets of the earth group

• The planet of the earth group is pretty differently rotated around its axis: one turn is lasting from 24 hours for the Earth and until 243 days from Venus.
• Venus, unlike other planets, rotates in the direction opposed to its movement around the Sun.
• The angle of tilt axes to the planes of their orbits by the Earth and Mars is about the same, but completely different in Mercury and Venus.
• The atmosphere of the planets can vary from the thick atmosphere of carbon dioxide at Venus to almost the complete absence of Mercury.
• Almost 2/3 of the surface of the earth occupy oceans, but there are no water on the surface of Venus and Mercury.
• Venus has no molten iron kernel. The rest of the planets are part of the iron kernel in a liquid state.

It is believed that land-like planets are most favorable for the occurrence of life, so their search attracts close attention to the public. An example of an exoplanet of the earth's type can serve as supest. As of June 2012, more than 50 supermenities have been found.