Introduction

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

But in the world of planets, we will not even meet two planets that are completely similar to each other. The variety of physical conditions on the planets is very great. The distance of the planet from the Sun, 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. solar system. Major planets They are divided into two main groups: the terrestrial planets and the giant planets. In the abstract we will analyze the planets of the terrestrial group.

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, 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 see only an insignificant part 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. By its nature, it is a star, the same as those numerous stars that we see in the night sky. It's just that it's close to us, that's why it's so big and bright.

In general, the sun plays 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 run away, scattered across the boundless space. So far, nine planets are known in the solar system: the four planets closest to the Sun are usually called terrestrial planets, and the next four are called 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 completely different planets at first glance. Closer to the Sun are Mercury, Venus, Earth and Mars. They are called the terrestrial planets. These are relatively small balls with a solid surface, surrounded by a not too thick atmosphere. The terrestrial planets are similar in size, mass and rock composition. 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 the Earth (for Mercury - 5.4 g / cm 3, for Venus - 5.2 g / cm 3). Their main constituents are silicates (silicon compounds) and iron. The composition of these planets indicates that their growth occurred in the absence of light gases due to stony particles and bodies containing various 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 consisting of silicates is located above the core;

* the topmost layer is the crust formed due to the partial melting of the mantle. Therefore, it also consists of silicates enriched with other elements. Only Mercury does not have a crust - it was destroyed by strong meteorite bombardments, due to a highly rarefied atmosphere. The Earth's crust is very different from other planets, high content of granite.

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

The similarity of the planets in the terrestrial group does not exclude some differences. For example, Venus revolves around reverse direction from moving around the Sun, and two hundred and forty-three times slower than the Earth. The period of rotation of Mercury (that is, the year of this planet) is only one third more 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 the Earth is approximately the same, but quite different for Venus and Mercury. Just like the Earth, there are seasons, which means that on Mars, although almost 2 times longer than on Earth.

It is possible that distant Pluto, the smallest of the nine planets, can also be attributed to the terrestrial planets. The usual diameter of Pluto 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, mostly composed of sulfur compounds and carbon dioxide. The atmosphere of Mars, on the contrary, is too rarefied and very poor in nitrogen and oxygen. The pressure at the surfaces of Venus is almost a hundred times more, while at Mars it is almost a 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 the surfaces of Venus is determined by the greenhouse effect. The dense atmosphere releases the rays of the Sun, but delays the thermal infrared radiation that comes from heated surfaces. The gas in the atmosphere of a terrestrial 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.

planets related to terrestrial group - Mercury, Venus, Earth, Mars, Pluto- have small sizes and masses, the average density of these planets several times greater than the density of water; they slowly rotate around their axes; they have few satellites (Mercury and Venus have none at all, Mars has two, Earth- one).

similarity planets terrestrial groups does not rule out some difference.. For example, Venus, unlike other planets, rotates in the opposite direction to its movement around sun, and 243 times slower than the Earth .. Mercury's orbital period (i.e., the year of this planets) is only 1/3 more than the period of its rotation around the axis.

The angles of inclination of the axes to the planes of their orbits for the Earth and Mars are approximately the same, but quite different for Mercury and Venus. The same as the Earth, the seasons are, therefore, on Mars, although almost twice as long as on Earth.

Possibly to planets terrestrial groups attributed and distant Pluto- the smallest of 9 planets. The average diameter of Pluto is about 2260 km. Only half the diameter of Pluto's moon Charon. Therefore, it is possible that the Pluto-Charon system, like the Earth-Moon system, is "double planet«.

Similarities and differences are also found in the atmospheres planets terrestrial groups. Unlike Mercury, which, like the Moon, is practically devoid of an atmosphere, Venus and Mars have it. Venus has a very dense atmosphere, mainly composed of carbon dioxide and sulfur compounds. The atmosphere of Mars, on the contrary, is extremely rarefied and also poor in oxygen and nitrogen. The pressure at the surface of Venus is almost 100 times greater, and that of Mars is almost 150 times less than that of the surface of the Earth.

The temperature at the surface of Venus is very high (about 500 ° C) and remains almost the same all the time. The high surface temperature of Venus is due to the greenhouse effect. A dense dense atmosphere transmits the rays of the Sun, but delays infrared thermal radiation coming from a heated surface .. Gas in atmospheres planets terrestrial groups is in constant motion. Often, during dust storms that last for several months, a huge amount of dust rises into the atmosphere of Mars. Hurricane winds were recorded in the atmosphere of Venus at altitudes where the cloud layer is located (from 50 to 70 km above the surface planets), but near the surface of this planets Wind speeds are only a few meters per second.

planets terrestrial groups, like the Earth and the Moon, have hard surfaces ty. The surface of Mercury, replete with craters, is very similar to the moon. There are fewer “seas” than on the Moon, and they are small. As on the Moon, most of the craters were formed as a result of meteorite impacts. Where there are few craters, we see relatively young areas of the surface.

The stony desert and many individual stones are visible on the first photo-television panoramas transmitted from the surface of Venus by automatic stations of the Venera series. Radar ground observations were found on this planet many shallow craters with diameters from 30 to 700 km. In general, this planet turned out to be the smoothest planets terrestrial groups, although it also has large mountain ranges and extended hills, twice the size of terrestrial Tibet.

Almost 2/3 of the Earth's surface is occupied by oceans, but there is no water on the surface of Venus and Mercury.

Replete with craters and the surface of Mars. Especially a lot of them in the southern hemisphere planets. Dark areas occupying a significant part of the surface planets, are called the seas. The diameters of some seas exceed 2000 km. Hills, reminiscent of terrestrial continents, which are light fields of orange-red color, are called continents. 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 diameter of the base of this giant cone-shaped mountain is more than 500 km. The fact that millions of years ago powerful volcanic eruptions occurred on Mars and the surface layers shifted is evidenced by the remnants of lava flows, huge surface fractures (one of them - Mariner - stretches for 4000 km), numerous gorges and canyons.

- 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 do not have them at all, Mars has two tiny ones, Earth has one).

The similarity of the terrestrial planets does not exclude a significant difference. For example, Venus, unlike other planets, rotates in the opposite direction to its movement around the Sun, and is 243 times slower than the Earth (compare the length of the year and day on Venus). Mercury's period of revolution (i.e., 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 angles of inclination of the axes to the planes of their orbits for the Earth and Mars are approximately the same, but quite 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 same as the Earth, the seasons are, therefore, on Mars (although each season is almost twice as long as on Earth).

It is possible that, according to a number of physical characteristics, distant Pluto, the smallest of the 9 planets, also belongs to the terrestrial planets. The average diameter of Pluto is about 2260 km. Only half the diameter of Pluto's moon Charon. Therefore, it is possible that the Pluto-Charon system, like the Earth-system, is a “double planet”.

atmospheres

Features of similarity and differences are also found in the study of the atmospheres of the planets of the terrestrial group. 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 the flights of our (“Venus”, “Mars”) and American (“Pioner-Venus”, “Mariner”, “Viking”) AMS. Comparing the atmospheres of Venus and Mars with Earth's, we see that, in contrast to the nitrogen-oxygen atmospheres of the Earth, Venus and Mars have atmospheres mainly composed of carbon dioxide. The pressure near the surface of Venus is more than 90 times greater, and that of Mars is almost 150 times less than that of the surface of the Earth.

The temperature at the surface of Venus is very high (about 500°C) and remains almost the same. What is it connected with? 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 heat the surface. The heated surface becomes a source of infrared radiation, which cannot leave the planet, as it is retained by the carbon dioxide and water vapor contained in the atmosphere of Venus, as well as the cloud cover of the planet. As a result of this, the equilibrium between the influx of energy and its consumption in peaceful space is established at a higher temperature than that which would be on a planet that freely transmits infrared radiation.

We are accustomed to terrestrial clouds, consisting of small drops of water or ice crystals. The composition of the clouds of Venus is different: they contain droplets of sulfuric and, possibly, hydrochloric acid. The cloud layer greatly attenuates the sunlight, but, as the measurements performed on the Venera-11 and Venera-12 AMS showed, the illumination near the surface of Venus is approximately the same as near the Earth's surface on a cloudy day. Research carried out in 1982 by AMS Venera-13 and Venera-14 showed that the sky of Venus and its landscape are orange. This is explained by the peculiarity of light scattering 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 have been recorded in the atmosphere of Venus at heights 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 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 could not have been predicted. Common sense suggested that planets with similar physical characteristics(for example, Earth and Venus are sometimes called “twin planets”) and are roughly the same distance from the Sun and should have very similar atmospheres. In fact, the reason for the observed difference is related to the peculiarities of the evolution of the atmospheres of each of the terrestrial planets.

The study of the atmospheres of the earth group plan not only allows a better understanding of the properties and history of the origin of the earth's atmosphere, but is also important for solving an environmental problem. 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 maintain conditions on Earth suitable for the existence and development of life for a long time. Dust storms, during which dust clouds are held in the atmosphere of Mars for several months and spread over vast territories, make us think about some of the possible environmental consequences of a nuclear war.

surfaces

The terrestrial planets, like the Earth and the Moon, have solid 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 great oppositions (when the distance between 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, much has been learned about the surface of Mercury and Mars, as well as getting an idea of ​​the until recently completely mysterious surface of Venus. This became possible thanks to the successful flights of automatic interplanetary stations of the Venera, Mars, Viking, Mariner, Magellan types, flying near the planets or landing on the surface of Venus and Mars, and thanks to ground-based radar observations.

The surface of Mercury, replete with craters, is very similar to the moon. There are fewer “seas” than on the Moon, and they are small. The diameter of the Mercury Sea of ​​Heat is 1300 km, like the Sea of ​​Rains on the Moon. Steep ledges stretch for tens and hundreds of kilometers, probably generated by the former tectonic activity of Mercury, when the surface layers of the planet were shifting and advancing. As on the Moon, most of the craters were formed as a result of meteorite impacts. Where there are few craters, we see relatively young areas of the surface. Old, destroyed craters are noticeably different from younger, well-preserved craters.

The stony desert and many separate stones are visible on the first photo-television panoramas transmitted from the surface of Venus by automatic stations of the Venus 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 planets of the terrestrial group, although it also has large mountain ranges and lingering hills, 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 diameter of the sole is 1000 km, the diameter of the crater at the top is 100 km. Very large, but smaller than Maxwell, are the volcanic cones Gauss and Hertz. Like rift gorges stretching along the bottom of the Earth's oceans, rift zones have also been discovered on Venus, indicating that active processes once took place on this planet (and maybe they are happening now!) Active processes (for example, volcanic activity).

In 1983 - 1984 From the stations "Venera - 15" and "Venera - 16" radar research was carried out, which made it possible to create a map and an atlas of the planet's surface (the dimensions of the surface details are 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 AMS Magellan. 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 distinguish details up to 120 m in size. By May 1993, almost 98% of the planet's surface was covered by the survey. It is planned to complete the experiment, which includes not only photographing Venus, but also conducting other studies (gravitational field, atmosphere, etc.) in 1995.

Replete with craters and the surface of Mars. Especially a lot of them in the southern hemisphere of the planet. The dark regions, which occupy a significant part of the planet's surface, are called the seas (Hellas, Argir, etc.). The diameters of some seas exceed 2000 km. Hills, reminiscent of terrestrial continents, which are light fields of orange-red color, are called continents (Tharsis, Elysium). 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 diameter of the base of this giant cone-shaped mountain is more than 500 km.

The fact that millions of years ago powerful volcanic eruptions occurred on Mars and the surface layers shifted is evidenced by the remains of lava flows, huge surface fractures (one of them - 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 extended gorges) that explorers of Mars 100 years ago mistook for “channels”, the existence of which subsequently for a long time was tried to be explained by the activities of intelligent inhabitants of Mars.

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

Panoramas of the surface of the Red Planet were repeatedly photographed and transmitted from a close distance.

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 bodies of water on the surface of Mars either. But, as scientists suggest, the water on Mars must be at least in the form of a layer of ice that forms the polar caps, or as a vast 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 dried up channel-like winding hollows found there.

Draw a schematic diagram of the position 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 in the solar system, Jupiter and Saturn;;; outer - smaller, Uranus and Neptune.

The terrestrial planets (Mercury, Venus, Earth, Mars) are similar in size and chemical composition. Characteristic 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 great speeds) and internal (tectonic movements and volcanic phenomena) factors. Also, all terrestrial planets except Mercury have an atmosphere. Distinctive feature Earth from other terrestrial planets is 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.
The terrestrial planets have some General characteristics. All of them have a solid surface, apparently, consist of a substance similar in composition, although the Earth and Mercury are denser than Mars and Venus. Their orbits generally 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 the inner planets because 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 is the closest planet to the Sun in the solar system.

As the planet closest to the Sun, Mercury receives much more energy from the central luminary than, for example, the Earth (10 times on average. The surface of Mercury, covered with crushed basalt-type matter, is rather dark. Along with craters (as a rule, 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 boundary between which the temperature can approach 103 K. The core accounts for more than half of the planet's mass.

VENUS It is the second planet from the Sun and the closest planet 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 regions have been found. On the surface of Venus, craters, faults, and other signs of intense tectonic processes were found. Traces of shock bombardment are also clearly visible. The surface is covered with stones and slabs of various sizes; surface rocks are close in composition to terrestrial sedimentary rocks. The predominant 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. The clouds of Venus are mostly composed of 75-80% sulfuric acid. The magnetic field of Venus is negligible. Due to its relative proximity to the Sun, Venus experiences significant tidal influences, due to which an electric field arises above its surface, the strength of which can be twice the strength of the "clear weather field" observed above the Earth's surface. There are three shells on Venus. The first of them - the crust - has a thickness of about 16 km. Next is 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 is the third planet from the sun in the solar system.

The Earth moves around the Sun. The surface area of ​​the Earth is 510.2 million km2, of which approximately 70.8% is in the oceans. 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 5120 km, seismic methods reveal the presence of a solid inner core, which accounts for 1.7% of the Earth's mass. Presumably, this is an iron-nickel alloy (80% Fe, 20% Ni).

The earth is surrounded by an atmosphere (see Atmosphere of the Earth). Its lower layer (troposphere) extends on average to a height of 14 km; the processes taking place 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 ozone layer, radiation fluxes would reach the surface of the Earth, causing destruction in the living organisms existing there. The Earth also has magnetic and electric fields.

MARS is the fourth planet from the sun in the solar system.

Since the inclination of the equator to the plane of the orbit 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 have a reddish-orange color; 25% of the surface are darker "seas" of a gray-green color, the level of which is lower than that of 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 planets of the Earth group, 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 entire mass of the planet. The mantle of Mars is enriched with iron sulfide. The thickness of the lithosphere of Mars is several hundred km, including about 100 km of its crust. Two satellites circulate around Mars: Phobos (Fear) and Deimos (Horror). The gravitational fields of satellites are so weak that they have no atmosphere. Meteor craters have been found on the surface.