According to their own physical properties Planets can be divided into two categories: giant planets and terrestrial planets.

Which planets are terrestrial planets?

Scientists have classified Mercury, Mars, Venus and Earth as terrestrial planets. All of them have a rather modest size and mass. The density of the planets in question is many times higher than the density of water. The speed of rotation around its own axis is quite small, as well as a small number of satellites (Venus and Mercury do not have them at all, but the Earth can boast of one satellite - the moon).

However, if these planets have similar features, this does not mean at all that there are no differences. For example, Venus rotates in the opposite direction to its rotation around the Sun, and the rotation speed is more than 240 times less than that of the Earth (this is evidenced by the number of days per year on Venus). The duration of a year on Mercury (that is, around the sun) is only a third longer than the duration of its revolution around its own axis. The axes to the planes of the Earth's and Martian orbits are inclined at approximately the same angle, but the inclination of the axes of Venus and Mercury is very different. And this, in turn, is one of the most important reasons why the change of seasons is determined. The Earth has its own seasons, and identical ones are observed on Mars (although each season lasts twice as long as the Earth’s).

There is a possibility that, based on their physical properties, both small and distant Pluto can be classified as planets in the category under consideration. Pluto's diameter exceeds 1,200 kilometers, which is only half the diameter of its own satellite, Charon. It is possible that Pluto and Charon, like the Earth and the Moon, are a “double planet”.

Characteristics of terrestrial planets

The atmospheric properties of planets in this category have both general features, and distinctive. For example, Mars and Venus have their own atmosphere, while Mercury, like the Moon, is almost deprived of an atmosphere. The density of the atmosphere on Venus is quite high, because it contains mainly carbon dioxide and sulfur compounds. And the Martian atmosphere is not rich in oxygen and nitrogen, as a result of which it is very rarefied. The surface pressure of Venus is almost a hundred times higher than the pressure of the Earth's surface, and Mars is 150 times behind the Earth in this parameter.

The temperature on Venus almost never changes and remains fairly constant. high level– approximately 500°C. This hot climate is due to the greenhouse effect. The atmosphere, which has a high density, although it transmits the sun's rays through itself, does not allow infrared thermal radiation emanating from the hot surface to escape. The gas masses contained in the atmosphere of the terrestrial planets are constantly moving. Often, during dust storms that last for months at a time, a colossal volume of dust masses rises into the Martian atmosphere. And during storm winds on Venus, occurring at the level of the cloud layer (approximately 50-70 km from Venus), closer to the planet, the wind speed is a few meters per second.

The surface of the terrestrial planets, just like the earth's surface, as well as the surface of its satellite, is solid. Mercury is similar to the Moon in that it is rich in many craters. 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 meteorites falling onto the surface. Thanks to this, it is possible to distinguish younger surface areas - the more craters, the older the area.

The surface of Venus is characterized by its numerous stones and rocky desert, which can be observed in the first photo panoramas sent from the surface of this planet by automated stations of the “Venus” series. Studies of the surface of Venus have revealed numerous small craters with a diameter ranging from 30-700 km. The surface of Venus is smoother than that of other terrestrial planets, although it boasts large mountain ranges and long hills that are twice the size of our Tibet.

About two-thirds of the earth's surface is covered by oceans, while Mercury or Venus have no water at all.

Mars is also rich in craters. Most of them are grouped in its southern hemisphere. Quite pronounced dark areas covering a fair portion of the planet are called seas. Some seas are over 2 thousand km in diameter. The light areas of orange and red colors, representing hills that are similar to the continents of the Earth, are called continents. Here you can see large volcanic cones, just like on the surface of Venus. The largest of them is Olympus. It rises more than 25 km, the diameter of the crater is 90 km, and the diameter of the base of this giant is over 500 km. Remains of lava flows, many canyons and gorges indicate that about millions of years ago, strong volcanic eruptions occurred on the Martian surface, and surface plates moved.

What are the similarities between the terrestrial planets?

The structure of planets of this type is approximately identical: in the center there is a core made of metal, which is formed largely from iron, surrounded by a silicate shell. Planets of this type have similar surface features: craters, elevations, canyons, mountain ranges, etc. Their presence is determined by two factors: whether there is water and what tectonic activity is.

Planets in this category have secondary atmospheres that appeared due to fallen comets or due to the activity of volcanoes. These planets have either few or no moons. Mercury and Venus do not have satellites, the Earth can boast of a single satellite - the Moon, but Mars has two of them - Phobos and Deimos, which themselves resemble more asteroids, not planetary satellites.

How are the terrestrial planets different?

• It is common for planets in this category to rotate around their axis in their own way: While one Earth revolution lasts 24 hours, for Venus it can last up to 243 days.
• Venus is the only one of the four planets that rotates opposite to its movement around the Sun.
• Mars and Earth have an almost identical angle of inclination of their axis to the plane of their orbits, while these angles are completely different for Venus and Mercury.
• The atmospheres of these planets range from a dense carbon dioxide atmosphere for Venus to almost no carbon dioxide for Mercury.
• Mercury and Venus are deprived of the presence of water, and two-thirds of the earth's surface is water.
• Venus lacks the iron core typical of other planets.

Atmosphere of terrestrial planets

The primary atmosphere of terrestrial planets appeared immediately after their creation. It included mostly carbon dioxide formed at the moment of layer-by-layer separation immediately after the accretion stage. For chemical composition earth's atmosphere the life that appeared on it was seriously affected: the amount of carbon dioxide decreased, and the proportion of oxygen increased. Mercury and the Moon did not have enough mass to retain an atmosphere. The atmospheres of Mars and Venus contain more carbon dioxide, unlike Earth.

Satellites of the terrestrial planets

Mercury and Venus do not have natural satellites. Therefore, we will only get acquainted with the Earth’s and Martian satellites.

Earth's satellite - Moon

Our planet is rich in one single satellite - the Moon. It was studied in such detail as no other cosmic body has been studied. Besides, this is the only place a person has managed to visit.

Although everyone knows that the Moon is a satellite, theoretically it could become a full-fledged planet if its orbit passed around the Sun. The lunar diameter is almost 3.5 thousand kilometers, which even exceeds the size of Pluto.

The Moon is a full participant in the Earth-Moon gravity system. The satellite's mass is not very large, but it has a common center of mass with the Earth.

Among all cosmic bodies, besides the Sun, the Moon has the greatest influence on the Earth. A striking example of this is the lunar ebb and flow, which changes the water level in the oceans.

The entire lunar surface is strewn with craters. This is explained by the fact that the Moon does not have its own atmosphere capable of protecting its surface from meteorites. In addition, the earth's satellite does not have water and wind, with the help of which the places where meteorites fall would be leveled. Over the entire existence of the Moon, that is, over four billion years, the lunar surface has collected a huge number of craters.

Martian satellites

Mars has two small satellites - Phobos and Deimos - discovered in 1877 by A. Hall. It is interesting that at a certain point he was so desperate to find the satellites of Mars that he almost completed the study, but his wife convinced him otherwise. And the next day Hall found Deimos. Another six days later - Phobos. On the surface of the second, he discovered a giant crater ten kilometers wide (which is about half the width of Phobos). The researcher named it after his wife’s maiden name – Stickney.

Both satellites are shaped like an ellipsoid. Due to their small size, gravity forces are not enough to squeeze the satellites into a round shape.

It is curious that Mars has an effect on Phobos, gradually reducing the speed of its movement. Because of this, the satellite’s orbit moves closer and closer to the planet. Phobos will eventually fall to Mars. Over a hundred years, this satellite approaches the surface of the planet by nine centimeters. Therefore, about eleven million years will pass until the moment of their collision. But Deimos, in turn, is systematically moving away from the planet and over time will be covered by solar forces. That is, at some point in its existence, Mars will be left without both satellites.

Martian satellites are always located with the same side to the planet, because the time of rotation around their own axis coincides with the time of rotation around Mars. In this property they are similar to the Moon, the far side of which can also never be seen from the earth’s surface.

Phobos and Deimos are very small in size. Even the lunar diameter exceeds Phobos by 158 times, and Deimos by 290.

Researchers are still arguing about the origin of the satellites of Mars. These could be asteroids caught in the gravitational field of Mars. However, their structure differs from asteroids, which argues against such a theory. Another version is that two satellites were formed due to the split of the once only Martian satellite into two parts.

Characteristics of the surface of terrestrial planets

The surface of the planets in question was formed under the influence of primary volcanic activity. At first, when the planets were quite 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 that of the moon. Only one thing distinguishes it - the presence of infrequent almost perfectly flat areas that are older than the same lunar areas, because they appeared during the fall of meteorites.

The Martian surface has a red tint due to a considerable amount of iron oxide impurities. Craters mainly cover only the southern Martian hemisphere. Scientists have not yet identified the exact reason for this: perhaps an unknown cataclysm is to blame, or maybe there was simply ocean water in this part.

It is known that rivers flowed on the Martian surface in the past, as evidenced by the remaining dry riverbeds. In addition to rivers, Mars is interesting for its volcanoes, the size of some of them is amazing.

Chemical composition and density of terrestrial planets

Planets similar to Jupiter are usually gas giants containing helium and hydrogen, because there is more of this gas. No matter how you add up these substances, you still end up with a planet consisting largely of gas.

The terrestrial rocky planets formed closer to the Sun. The closer to the star, the easier the gases from these planets were blown away. Thus, the formation of the chemical composition of the terrestrial planets occurred through the interaction of solid particles. The formation initially began with dust, which contained a very small amount of hydrogen, and almost no helium at all. Therefore, the rocky planets of the terrestrial group are formed from a universal system of elements.

There are four terrestrial planets in our solar system: Mercury, Venus, Earth and Mars. They got their name from their resemblance to our planet Earth. Planets of our Terrestrial group solar system are also known as inner planets because these planets are located in the region between the Sun and . All planets of the Terrestrial group have small sizes and masses, high density and consist mainly of silicates and metallic iron. Behind the main asteroid belt (in the outer region) there are asteroids that are tens of times larger in size and mass than the terrestrial planets. 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 regions.

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

Although the Moon is considered a satellite, it would technically be considered a planet if it had an orbit around the Sun. The Moon is a full participant in the Earth-Moon gravitational system.

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

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

Structure and similarity of terrestrial planets

• The terrestrial group is significantly smaller than the gas giants.
• Terrestrial planets (unlike all giant planets) do not have rings.
• In the center is a core of iron mixed with nickel.
• Above the core is a layer called the mantle. The mantle consists of silicates.
• Terrestrial planets consist mainly of oxygen, silicon, iron, magnesium, aluminum and other heavy elements.
• 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 meteorite bombardment.
• Planets have atmospheres: quite dense for Venus and almost imperceptible for Mercury.
• Terrestrial planets also have changing landscapes, such as volcanoes, canyons, mountains and craters.
• These planets have magnetic fields: almost imperceptible on Venus and noticeable on Earth.

Some differences between the terrestrial planets

• The terrestrial planets rotate quite differently around their axis: one revolution lasts from 24 hours for Earth to 243 days for Venus.
• Venus, unlike other planets, rotates in the direction opposite to its movement around the Sun.
• The angles of inclination of the axes to the planes of their orbits for the Earth and Mars are approximately the same, but completely different for Mercury and Venus.
• Planetary atmospheres can range from a thick carbon dioxide atmosphere on Venus to almost no atmosphere on Mercury.
• Almost 2/3 of the Earth's surface is occupied by oceans, but there is no water on the surface of Venus and Mercury.
• Venus does not have a molten iron core. The rest of the planets have part of their iron core in a liquid state.

It is believed that Earth-like planets are the most favorable for the emergence of life, so their search attracts close public attention. An example of terrestrial exoplanets are super-Earths. As of June 2012, more than 50 super-Earths have been found.

The terrestrial planets are the four planets of the solar system: Mercury, Venus, Earth and Mars. They are located in the inner region of the Solar System, in contrast to the giant planets located in the outer region. 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 regions. In structure and composition, some rocky asteroids, for example Vesta, are close to the terrestrial planets.

Main Features

Terrestrial planets are highly dense and consist predominantly of silicates and metallic iron (in contrast to gas planets and rock-ice dwarf planets, Kuiper belt objects and the Oort cloud). The largest terrestrial planet, Earth, has more than 14 times the mass of the least massive gas planet, Uranus, but is approximately 400 times more massive than the largest known Kuiper Belt object.

Terrestrial planets consist mainly of oxygen, silicon, iron, magnesium, aluminum and other heavy elements.

All terrestrial planets have the following structure:

• In the center is a core of iron mixed with nickel.
• The mantle consists of silicates.
• 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 meteorite bombardment. The Earth differs from other terrestrial planets in the high degree of chemical differentiation of matter and the wide distribution of granites in the crust.

Two of the terrestrial planets (the farthest from the Sun - Earth and Mars) have satellites. None of them (unlike all giant planets) have rings.

I once read that in 2024 it is planned to send the first settlers to Mars. Some of my friends expressed a desire to go on this unknown one-way journey. But I don’t really want something, because this planet is lifeless, and I love animals, flowers and wildlife. I especially didn’t want to fly there after watching the movie “The Martian,” which realistically depicted the dull landscapes and unbearable weather conditions of this celestial body. But Mars is our neighbor, it is the second closest planet to us (the first is Venus). There are four planets in the Earth group. They are so called because they consist of solid soil. Let's name them in order of distance from the Sun.

Mercury is the smallest terrestrial planet

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

Venus is the beauty of the terrestrial group

Beautiful When viewed through a telescope or binoculars, it can be seen with the naked eye at dawn. That's probably why she got the name goddess of love. It is characterized by clouds of sulfuric acid that float in atmosphere from carbon dioxide . The spectacle is beautiful, but absolutely unsuitable for life. In addition, the temperature on the planet is also goes beyond +400.

Earth is a living planet

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

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

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

Mars is a cold planet

Has red soil, which gave rise to naming him after god of war. Since Mars is located further from the sun's heat than Earth, its climate is very cold. At frost over 130 degrees colonization of the planet is problematic. Yes and atmosphere here is unsuitable for breathing, it consists mainly of carbon dioxide.

Draw a schematic diagram of the location of the planets of the solar system relative to the sun.

The four smaller inner planets: Mercury, Venus, Earth and Mars are terrestrial planets

The four outer planets: Jupiter, Saturn, Uranus and Neptune are giant planets. much more massive than the terrestrial planets. The largest planets of the solar system, Jupiter and Saturn;; the outer ones are smaller, Uranus and Neptune.

The terrestrial planets (Mercury, Venus, Earth, Mars) are similar in size and chemical composition. Characteristic feature of all terrestrial planets - the presence of a solid lithosphere. The relief of their surface was formed as a result of the action of external (impacts of bodies falling on planets at enormous speeds) and internal ( tectonic movements and volcanic phenomena) factors. Also, all terrestrial planets except Mercury have an atmosphere. Distinctive feature The Earth is distinguished from other terrestrial planets by the presence of an atmosphere.

The atmospheres of Mars and Venus are very similar in composition to each other, but at the same time they differ significantly from the earth's.
Terrestrial planets have some general characteristics. They all have a solid surface and appear to be composed of a substance similar in composition, although Earth and Mercury are more dense than Mars and Venus. Their orbits in general do not differ from circular ones, only the orbits of Mercury and Mars are more elongated than those of the Earth and Venus.
Mercury and Venus are called inner planets because their orbits lie inside the Earth's; they, like the Moon, come in different phases - from new to full - and remain in the same part of the sky as the Sun. Mercury and Venus have no satellites, Earth has one moon satellite, Mars has 2 satellites - Phobos and Deimos, both are very small and differ in nature from the Moon.

MERCURY- the planet closest to the Sun in the Solar System.

As the planet closest to the Sun, Mercury receives significantly more energy from the central star than, for example, the Earth (on average 10 times). The surface of Mercury, covered with crushed basalt-type material, is quite dark. Along with craters (usually less deep than on the Moon) there are hills and valleys. Above the surface of Mercury there are traces of a very rarefied atmosphere containing, in addition to helium, also hydrogen, carbon dioxide, carbon, oxygen and noble gases (argon, neon. Mercury also has a magnetic field. The planet consists of hot , a gradually cooling iron-nickel core and silicate shell, at the boundary between which the temperature can approach 103 K. The core accounts for more than half the mass of the planet.

VENUS- the second planet from the Sun and closest to Earth in the solar system.

Venus is the only planet in the solar system whose own rotation is opposite to the direction of its revolution around the Sun. The surface of Venus is predominantly (90%) flat, although three elevated areas have been discovered. On the surface of Venus, craters, faults and other signs of intense tectonic processes occurring on it were discovered. Traces of impact bombing are also clearly visible. The surface is covered with stones and slabs of various sizes; surface rocks are similar in composition to terrestrial sedimentary rocks. The predominant proportion of the atmosphere is carbon dioxide (~ 97%); nitrogen - about 3%; water vapor - less than a tenth of a percent, oxygen - thousandths of a percent. The clouds of Venus consist mainly of 75-80 percent sulfuric acid. Venus's magnetic field is negligible. Due to its relative proximity to the Sun, Venus experiences significant tidal influences, which creates an electric field above its surface, the intensity of which can be twice that of the “fair weather field” observed above the Earth’s surface. Venus has three shells. The first of them - the crust - is approximately 16 km thick. Next is the mantle, a silicate shell that extends to a depth of about 3,300 km to the border with the iron core, the mass of which is about a quarter of the total mass of the planet.

Earth- the third planet from the Sun in the Solar System.

The Earth moves around the Sun. The Earth's surface area is 510.2 million km2, of which approximately 70.8% is in the World Ocean. Land makes up 29.2%, respectively, and forms six continents and islands. The Earth has a single satellite - the Moon. 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 Earth is surrounded by an atmosphere (see Earth's Atmosphere). Its lower layer (troposphere) extends to an average altitude of 14 km; The processes occurring here play a decisive role in the formation of weather on the planet. Even higher (up to about 80-85 km) is the mesosphere, above which noctilucent clouds are observed (usually at an altitude of about 85 km). 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. If it were not for the ozone layer, radiation flows would reach the surface of the Earth, causing destruction in living organisms existing there. The Earth also has magnetic and electric fields.

MARS- the fourth planet from the Sun in the Solar System.

Since the inclination of the equator to the orbital plane is significant (25.2°), there are noticeable seasonal changes on the planet. A significant part of the surface of Mars is lighter areas (“continents”) that are reddish-orange in color; 25% of the surface are darker “seas” of gray-green color, the level of which is lower than that of the “continents”. Observations of Mars from satellites reveal clear traces of volcanism and tectonic activity - faults, gorges with branching canyons. The surface of Mars appears to be a waterless and lifeless desert, over which storms rage, raising sand and dust to a height of tens of kilometers. The atmosphere on Mars is thin and consists mainly of carbon dioxide (about 95%) and small additions of nitrogen (about 3%), argon (about 1.5%) and oxygen (0.15%). The chemical composition of Mars is typical of the terrestrial planets, although, of course, there are specific differences. The core of Mars is rich in iron and sulfur and is small in size, and its mass is about one tenth of the total mass of the planet. The mantle of Mars is enriched in iron sulfide. The thickness of the lithosphere of Mars is several hundred km, including approximately 100 km of its crust. Two satellites orbit around Mars: Phobos (Fear) and Deimos (Horror). The gravitational fields of satellites are so weak that they do not have an atmosphere. Meteorite craters were discovered on the surface.