The solar system is the only one available fordirect study us a planetary structure. Information obtained on the basis of research in this area of space is used by scientists to understand the processes occurring in the Universe. They provide an opportunity to understand how our system was born and similar to it, what future awaits us all.
Classification of the Solar System Planets
Astrophysic studies allowedto classify the planets of the solar system. They were divided into two types: land-like and gas giants. The terrestrial planets include Mercury, Venus, Earth, Mars. The gas giants are Jupiter, Saturn, Uranus and Neptune. Since 2006, Pluto has received the status of a dwarf planet and belongs to the Kuiper belt objects, differing in their characteristics from representatives of both these groups.
Characteristics of the terrestrial planets
Each type has a set of features,related to the internal structure and composition. High average density and the predominance of silicates and metals at all levels are the main characteristics that distinguish the terrestrial planets. Giants, in contrast to them, have a low density index and consist primarily of gases.
All four planets have similar innerstructure: under the hard crust is a viscous mantle, enveloping the core. The central structure, in turn, is divided into two levels: liquid and solid core. The main components of it are nickel and iron. The mantle differs from the core by the predominance of silicon and manganese oxides.
The sizes of the planets of the Solar system belonging to the terrestrial group are distributed in this way (from the smallest to the largest): Mercury, Mars, Venus, Earth.
Air shell
Earth-like planets are already in the early stagestheir formations were surrounded by the atmosphere. Initially, carbon dioxide prevailed in its composition. The change of atmosphere on Earth was promoted by the appearance of life. To the terrestrial planets are, therefore, space bodies, surrounded by the atmosphere. However, among them there is one that has lost its air envelope. This is Mercury, the mass of which did not allow to preserve the primary atmosphere.
Closest to the sun
The smallest planet of the terrestrial group isMercury. His research is hampered by close proximity to the Sun. Since the beginning of the space age, data on Mercury has been obtained only from two vehicles: the Mariner 10 and the Messenger. On their basis, we managed to create a map of the planet and identify some of its features.
Mercury can truly be recognized as the mosta small planet of the earth group: its radius is a little less than 2.5 thousand kilometers. Its density is close to that of the earth. The ratio of this indicator to the size gives reason to believe that the planet is largely composed of metals.
The movement of Mercury has a number of features.Its orbit is strongly extended: at the most remote point the distance to the Sun is 1.5 times longer than the closest one. The planet makes one revolution around a star in about 88 Earth days. In this case, for such a year, Mercury has time to turn around its axis only one and a half times. Such a "behavior" is not typical for other planets of the solar system. Presumably, the deceleration of the initially faster movement was caused by the tidal influence of the Sun.
Beautiful and terrible
К планетам земной группы относятся одновременно the same and different cosmic bodies. Similar in structure, they all have features that make them impossible to confuse. Mercury closest to the Sun is not the hottest planet. It even has areas forever covered with ice. Venus, following him in proximity to the star, is characterized by higher temperatures.
Named after the goddess of love, the planet is longtime was a candidate for livable space objects. However, the first flights to Venus refuted this hypothesis. The true essence of the planet is hidden by a dense atmosphere consisting of carbon dioxide and nitrogen. Such an air envelope contributes to the development of the greenhouse effect. As a result, the temperature on the surface of the planet reaches +475 ºС. Here, therefore, there can be no life.
Second largest and remote from the sunThe planet has a number of features. Venus - the brightest point in the night sky after the moon. Its orbit is an almost perfect circle. Around its axis, it moves from east to west. This direction is not typical for most planets. It makes a revolution around the Sun in 224.7 Earth days, and around the axis in 243, that is, a year is shorter here than a day.
Third planet from the sun
The land is unique in many ways.It is located in the so-called life zone, where the sun's rays are not able to turn the surface into a desert, but there is enough heat so that the planet does not become covered with ice. Slightly less than 80% of the surface is occupied by the World Ocean, which, together with rivers and lakes, forms the hydrosphere, which is absent on the other planets of the solar system.
The formation of a special atmosphere of the Earth, consistingmainly from nitrogen and oxygen, contributed to the development of life. As a result of an increase in the concentration of oxygen, an ozone layer has been formed, which, together with the magnetic field, protects the planet from the damaging effects of solar radiation.
The only satellite of the Earth
The moon has a fairly serious impact.to the ground. Our planet acquired a natural satellite almost immediately after its formation. The origin of the moon is still a mystery, although there are several plausible hypotheses on this score. The satellite has a stabilizing effect on the slope of the earth's axis, and also causes a slowdown of the planet. As a result, each new day becomes a little longer. Slowdown is a consequence of the tidal influence of the moon, the same force that causes the ebb and flow in the ocean.
Red Planet
To the question, what are the terrestrial planetsbest investigated after ours, always follows a definite answer: Mars. Due to the location and climate, Venus and Mercury are studied to a much lesser extent.
If we compare the size of the planets of the solar system, then Mars will be in seventh place in the list. Its diameter is 6800 km, and its mass is 10.7% of the similar parameter of the Earth.
On the red planet, a very rarefied atmosphere.Its surface is dotted with craters, you can also see volcanoes, valleys and glacial polar caps. Mars has two satellites. The closest to the planet - Phobos - is gradually decreasing and in the future it will be broken by the gravity of Mars. Deimos, on the contrary, is characterized by slow removal.
The idea of the possibility of life on Mars already existsmore than a century. Recent studies conducted in 2012, discovered on the red planet organic matter. It was suggested that organic matter to the surface could bring the Mars rover from Earth. However, studies have confirmed the origin of the substance: its source is the red planet itself. Nevertheless, an unequivocal conclusion about the possibility of life on Mars cannot be made without additional research.
The terrestrial planets are the mostspace objects close to us. That is why they are better studied today. Astronomers have already discovered several exoplanets, presumably also related to this type. Of course, each such discovery increases the hope of finding life outside the solar system.
