Make a schematic drawing of the location of the planets in 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 the giant planets. much more massive than the terrestrial planets. The largest planets of the solar system, Jupiter and Saturn, ;; the outer ones are the smaller ones, Uranus and Neptune.

The terrestrial planets (Mercury, Venus, Earth, Mars) are similar in size and chemical composition. A characteristic feature of all terrestrial planets is 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 with great speeds) and internal (tectonic movements and volcanic phenomena) factors. Also, all terrestrial planets except Mercury have an atmosphere. A distinctive feature of the Earth from other terrestrial planets is the presence of an atmosphere.

The atmospheres of Mars and Venus are very close in composition to each other, but at the same time they differ significantly from the earthly.
The terrestrial planets have some common characteristics. All of them have a hard surface, apparently, consist of a substance similar in composition, although the Earth and Mercury are more dense than Mars and Venus. Their orbits do not generally differ from circular ones, only the orbits of Mercury and Mars are more elongated than those of Earth and Venus.
Mercury and Venus are called inner planetsbecause their orbits lie inside the earth; they, like the moon, are 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, the Earth has one satellite - the Moon, Mars has 2 satellites - Phobos and Deimos, both are very small and differ in nature from the Moon.

MERCURY - the closest planet to the Sun in the solar system.

As the planet closest to the Sun, Mercury receives from the central luminary much more energy than, for example, the Earth (on average, 10 times. The surface of Mercury, covered with fragmented basalt-type matter, 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 a hot , a gradually cooling iron-nickel core and a silicate shell, at the border between which the temperature can approach 103 K. The core accounts for more than half of the planet's mass.

VENUS- the second planet from the Sun and closest to the Earth in the Solar System.

Venus is the only planet in the solar system whose proper rotation is opposite to the direction of its revolution around the sun. The surface of Venus is predominantly (90%) flat, although three elevated regions have been found. On the surface of Venus, craters, faults and other signs of intense tectonic processes taking place on it were found. Traces of shock 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 prevailing share of the atmosphere is carbon dioxide (~ 97%); nitrogen - about 3%; water vapor - less than a tenth of a percent, oxygen - thousandths of a percent. Venus's clouds are composed primarily of 75 to 80 percent sulfuric acid. Venus's magnetic field is negligible. Due to its relative proximity to the Sun, Venus experiences significant tidal effects, due to which an electric field arises above its surface, the intensity of which can be twice the intensity of that "clear weather field" observed above the Earth's surface. Venus has three shells. The first of them - the crust - is about 16 km thick. Further - the mantle, a silicate shell, extending to a depth of about 3300 km to the border with the iron core, the mass of which is about a quarter of the entire mass of the planet.

Earth - the third planet from the Sun in the solar system.

The Earth moves around the Sun. The surface area of \u200b\u200bthe Earth is 510.2 million km2, of which approximately 70.8% falls on the World Ocean. The land is respectively 29.2% 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 detect the presence of a solid inner core, which accounts for 1.7% of the Earth's mass. Presumably, this is an iron-nickel alloy (80% Fe, 20% Ni).

The earth is surrounded by an atmosphere (see Earth's Atmosphere). Its lower layer (troposphere) extends on average to an altitude of 14 km; the processes occurring here play a decisive role for the formation of weather on the planet. Even higher (up to about 80-85 km) is the mesosphere, above which (usually at an altitude of about 85 km) noctilucent clouds are observed. 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 not for ozone layer, the fluxes of radiation would reach the surface of the Earth, producing destruction in the living organisms available there. The Earth also has magnetic and electric fields.

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

Since the tilt of the equator to the plane of the orbit is significant (25.2 °), there are noticeable seasonal changes on the planet. Much of the surface of Mars is lighter areas ("continents"), which have a reddish-orange color; 25% of the surface is dark gray-green "seas", the level of which is lower than the "continents". Observations of Mars from satellites reveal distinct traces of volcanism and tectonic activity - faults, gorges with branching canyons,. The surface of Mars seems 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 rarefied and consists mainly of carbon dioxide (about 95%) and small additions of nitrogen (about 3%), argon (about 1.5%) and oxygen (0.15%). Chemical composition 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 the mass is about one tenth of the total mass of the planet. The mantle of Mars is enriched with iron sulfide. The lithosphere of Mars is several hundred kilometers thick, including about 100 kilometers of its crust. Two satellites revolve around Mars: Phobos (Fear) and Deimos (Horror). The gravitational fields of the satellites are so weak that they have no atmosphere. Meteorite craters were found on the surface.

Introduction

My topic of the essay is "Characteristics of the terrestrial planets." The relevance of this work is due to the fact that among the numerous celestial bodies studied by modern astronomy, planets occupy a special place. After all, we all know very well that the Earth on which we live is a planet, so that the planet-bodies are basically similar to our Earth.

But in the world of planets, we will not even meet two planets completely similar to each other. The variety of physical conditions on the planets is very great. The distance of the planet from the Sun, its size, the presence and composition of the atmosphere, the orientation of the axis of rotation, the internal structure and many other properties are different for all nine planets of the solar system. Large planets are divided into two main groups: terrestrial planets and giant planets. In the abstract, we will analyze the terrestrial planets.

The purpose of this work is to analyze scientific data and information on the terrestrial planets.

The structure of the solar system

The solar system is for us, the inhabitants of the Earth, the near space.

Each person, at least once in his life, looking at the night sky, asked himself the question: "I wonder, what's next?" After all, the human eye is able to discern only a tiny fraction of what the Universe shows us. Everything in the solar system is determined by the Sun, which is the most massive body and the only one with its own glow. It is by nature a star, just like the many stars that we see in the night sky. It's just close to us, that's why it's so big and bright.

In general, the sun has an exceptional role in the solar system. The powerful gravitational field of the Sun holds together all the other bodies of the solar system - without it, they would simply scatter, scatter across the boundless space. In the solar system, nine planets are still known: the four planets closest to the Sun are usually called terrestrial planets, and the next four are giant planets. The ninth planet Pluto, the most distant, does not belong to any group.

Features of the terrestrial planets

The asteroid belt divides the solar system into two parts, which are inhabited by planets completely different at first glance. Closer to the Sun are Mercury, Venus, Earth and Mars. They are called terrestrial planets. These are relatively small spheres with a hard surface, surrounded by a not too thick atmosphere. Terrestrial planets are similar in size, mass and composition of rocks. Their surfaces are composed of solid rocks with an average density of matter from 3.9 g / cm 3 for Mars to 5.5 g / cm 3 for Earth (for Mercury - 5.4 g / cm 3, for Venus - 5.2 g / cm 3). Their main components are silicates (silicon compounds) and iron. The composition of these planets indicates that their growth took place in the absence of light gases due to stony particles and bodies containing different amounts of iron and other metals.

All terrestrial planets have the same structure:

* in the very center there is a heavy and hot core. It mainly consists of iron, with an admixture of nickel;

* a mantle of silicates is located above the core;

* the uppermost layer is the crust formed due to the partial melting of the mantle. Therefore, it also consists of silicates enriched with other elements. Only Mercury has no crust - it was destroyed by strong meteorite bombings, due to the highly rarefied atmosphere. The earth's crust is very different from other planets, high in granite.

Pluto - they all have small masses and sizes, their average density exceeded the density of water several times; they are able to slowly rotate around personal axes; they have a small number of satellites (Mars has two, Earth has only one, and Venus and Mercury have none at all).

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

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

Perhaps, distant Pluto, the smallest of the nine planets, can also be attributed to the planets of the terrestrial group. Pluto's usual diameter was more than two thousand kilometers. Only 2 times smaller than the diameter of Pluto's satellite - Charon. Therefore, it is not a fact that the Pluto-Charon system, like the Earth system, is a double planet.

Similarities and differences are also found in the atmospheres of the terrestrial planets. Venus and Mars have an atmosphere, unlike Mercury, which, however, like the Moon, is practically devoid of it. Venus has a fairly dense atmosphere, mainly composed of sulfur compounds and carbon dioxide. The atmosphere of Mars, on the other hand, is too rarefied and very poor in nitrogen and oxygen. The pressure at the surfaces of Venus is almost a hundred times more, while that of Mars is almost one hundred and fifty times less than at the surfaces of the Earth.

The fever near the surfaces of Venus is quite high (about five hundred degrees Celsius) and remains almost the same all the time. The high temperature of Venus's surfaces is determined by the greenhouse effect. The dense atmosphere releases the rays of the sun, but traps the thermal infrared radiation that comes from heated surfaces. The gas in the atmosphere of the terrestrial group planet is in constant motion. Often during a dust storm that lasts more than one month, a large amount of dust rises into the atmosphere of Mars.

- have small sizes and masses, the average density of these planets is several times higher than the density of water; they slowly revolve around their axes; they have few satellites (Mercury and Venus do not have them at all, Mars has two tiny ones, and Earth has one).

The similarity of the terrestrial planets does not exclude a significant difference. For example, Venus, unlike other planets, rotates in the direction opposite to its movement around the Sun, and is 243 times slower than Earth (compare the length of a year and a day on Venus). The period of Mercury's revolution (i.e. the year of this planet) is only 1/3 longer than the period of its rotation around the axis (in relation to the stars). 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. And you know that this is one of the reasons that determines the nature of the change of seasons. The seasons of the year are the same as those of the Earth, therefore, on Mars (although each season is almost twice as long as on Earth).

It is possible that in terms of a number of physical characteristics, distant Pluto, the smallest of the 9 planets, belongs to the terrestrial planets. Pluto's average diameter is about 2,260 km. Only half the diameter of Charon, Pluto's satellite. Therefore, it is possible that the Pluto-Charon system, like the Earth system, is a “double planet”.

Atmosphere

Similarities and differences are also found in the study of the atmospheres of the terrestrial planets. Unlike Mercury, which, like the Moon, is practically devoid of an atmosphere, Venus and Mars have it. Modern data on the atmospheres of Venus and Mars were obtained as a result of flights of our (“Venus”, “Mars”) and American (“Pioneer-Venus”, “Mariner”, “Viking”) AMS. Comparing the atmospheres of Venus and Mars with that of Earth, we see that, unlike the nitrogen-oxygen atmosphere of the Earth, Venus and Mars have atmospheres mainly composed of carbon dioxide. The pressure at the surface of Venus is more than 90 times greater, and that of Mars is almost 150 times less than at the surface of the Earth.

The temperature near the surface of Venus is very high (about 500 ° C) and remains almost the same. What is the reason for this? At first glance, it seems, with the fact 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 heats both planets approximately equally. The high surface temperature of Venus is due to the greenhouse effect. It consists in the following: the atmosphere of Venus transmits the rays of the Sun, which heats the surface. The heated surface becomes a source of infrared radiation, which cannot leave the planet, as it is trapped by carbon dioxide and water vapor contained in the atmosphere of Venus, as well as the planet's cloud cover. As a result of this, the balance between the inflow of energy and its expenditure into peaceful space is established at a higher temperature than that of a planet that freely transmits infrared radiation.

We are accustomed to terrestrial clouds consisting of small water droplets or ice crystals. The composition of the clouds of Venus is different: they contain droplets of sulfuric and, possibly, hydrochloric acid. The cloudy layer greatly weakens the sunlight, but, as measurements performed on the Venera-11 and Venera-12 spacecraft have shown, the illumination near the surface of Venus is approximately the same as near the surface of the Earth on a cloudy day. Investigations carried out in 1982 by the Venera-13 and Venera-14 spacecraft showed that the sky of Venus and its landscape are orange. This is explained by the peculiarity of the scattering of light in the atmosphere of this planet.

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

Thus, despite some similarities, in general, the atmospheres of the planets closest to the Earth differ sharply from the atmosphere of the Earth. This is an example of a discovery that was impossible to predict. Common sense dictated that planets with similar physical characteristics (for example, Earth and Venus are sometimes called "twin planets") and approximately equally distant from the Sun should have very similar atmospheres. In fact, the reason for the observed difference is associated with the peculiarities of the evolution of the atmospheres of each of the terrestrial planets.

The study of the atmospheres of the terrestrial group not only allows a better understanding of the properties and history of the origin of the terrestrial atmosphere, but is also important for solving environmental problems. For example, fogs - smogs, formed in the earth's atmosphere as a result of air pollution, are very similar in composition to Venusian clouds. These clouds, like dust storms on Mars, remind us that it is necessary to limit the release of dust and various kinds of industrial waste into the atmosphere of our planet if we want to preserve conditions on Earth suitable for the existence and development of life for a long time. Dust storms, during which clouds of dust are held and spread over vast territories for several months in the atmosphere of Mars, make one think about some of the possible environmental consequences of a nuclear war.

Surfaces

The terrestrial planets, like the Earth and the Moon, have hard surfaces. Ground-based optical observations allow us to obtain little information about them, since Mercury is difficult to see through a telescope even during elongations, the surface of Venus is hidden from us by clouds. On Mars, even during the great oppositions (when the distance between the Earth and Mars is minimal - about 55 million km), occurring once every 15 - 17 years, large telescopes can see details about 300 km in size. And yet, in recent decades, it has been possible to learn a lot about the surface of Mercury and Mars, as well as get an idea of \u200b\u200bthe quite mysterious surface of Venus until recently. This became possible thanks to the successful flights of automatic interplanetary stations such as Venus, Mars, Viking, Mariner, Magellan, which flew near planets or landed on the surface of Venus and Mars, and thanks to ground-based radar observations.

The surface of Mercury, teeming with craters, is very similar to the moon. There are fewer "seas" than on the Moon, and they are small. The diameter of the Mercurian Sea of \u200b\u200bZnoy is 1300 km, as is the Sea of \u200b\u200bRains on the Moon. For tens and hundreds of kilometers, steep ledges stretch, probably generated by the former tectonic activity of Mercury, when the surface layers of the planet moved and advanced. Like on the Moon, most of the craters were formed by meteor impacts. Where there are few craters, we see relatively young surface areas. Old, destroyed craters differ markedly from younger well-preserved craters.

The rocky desert and many individual stones are visible in the first photo-television panoramas transmitted from the surface of Venus by automatic stations of the Venera series. Ground-based radar observations have found many shallow craters on this planet, with diameters ranging from 30 to 700 km. In general, this planet turned out to be the smoothest of all the terrestrial planets, although it also has large mountain ranges and extended elevations, twice the size of terrestrial Tibet. The extinct volcano Maxwell is grandiose, its height is 12 km (one and a half times more than Chomolungma), the base diameter is 1000 km, the diameter of the crater at the top is 100 km. The Gauss and Hertz volcanic cones are very large, but smaller than Maxwell. Like the rift gorges stretching along the bottom of the Earth's oceans, rift zones have also been found on Venus, indicating that active processes (for example, volcanic activity) once took place on this planet (and perhaps are still happening!).

1983 - 1984 Radar studies were carried out from the Venera-15 and Venera-16 stations, which made it possible to create a map and an atlas of the planet's surface (dimensions of surface details 1 - 2 km). A 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 Magellan spacecraft. This spacecraft reached the vicinity of Venus in August 1990 and entered an elongated elliptical orbit. Regular surveys have been carried out since September 1990. Clear images are transmitted to the Earth, some of them clearly show details up to 120 m in size. By May 1993, the survey covered almost 98% of the planet's surface. It is planned to complete the experiment, which includes not only photographing Venus, but also conducting other studies (gravitational field, atmosphere, etc.) in 1995.

The surface of Mars is also replete with craters. There are especially many of them in the southern hemisphere of the planet. Dark areas that occupy a significant part of the planet's surface are called seas (Hellas, Argir, etc.). The diameters of some seas exceed 2000 km. Uplands resembling earthly continents, representing light fields of orange-red color, are called continents (Farsis, Elisium). Like Venus, there are huge volcanic cones. The height of the largest of them (Olympus) exceeds 25 km, the diameter of the crater is 90 km. The base diameter of this giant cone-shaped mountain is over 500 km.

The fact that millions of years ago powerful volcanic eruptions occurred on Mars and surface layers were displaced is evidenced by the remnants of lava flows, huge surface faults (one of them - the Mariner - stretches for 4000 km), numerous gorges and canyons. It is possible that it was some of these formations (for example, chains of craters or long gorges) that Mars explorers took for “channels” 100 years ago, the existence of which was subsequently long tried to explain by the activity of intelligent inhabitants of Mars.

The red color of Mars also ceased to be a mystery. It is explained by the fact that the soil of this planet contains a lot of iron-rich clays.

Panoramas of the “Red Planet” surface were repeatedly photographed and transmitted from close range.

You know that almost 2/3 of the Earth's surface is occupied by oceans. There is no water on the surface of Venus and Mercury. There are no open reservoirs on the surface of Mars either. But, as scientists suggest, the water on Mars should be at least in the form of a layer of ice that forms the polar caps, or as an extensive layer of permafrost. Perhaps you will witness the discovery of ice reserves on Mars or even water under the ice. The fact that water was once on the surface of Mars is evidenced by the dry channel-like meandering hollows discovered there.

Terrestrial planets - 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 ones. Some stone asteroids, for example, Vesta, are close to the terrestrial planets in structure and composition.

Main characteristics

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

The terrestrial planets are mainly composed of oxygen, silicon, iron, magnesium, aluminum and other heavy elements.

All terrestrial planets have the following structure:

• In the center there is a core made of iron with an admixture of nickel.
• The mantle is composed of silicates.
• 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 Earth differs from other terrestrial planets in a high degree of chemical differentiation of matter and a wide distribution of granites in the crust.

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