How many of them. Exploration of the solar system Modern exploration of the planets

Exploring the Planets of the Solar System

Until the end of the 20th century, it was generally accepted that there were nine planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto. But recently, a lot of objects have been discovered beyond the orbit of Neptune, some of them similar to Pluto, and others even larger than it. Therefore, in 2006, astronomers refined the classification: 8 largest bodies - from Mercury to Neptune - are considered classical planets, and Pluto became the prototype of a new class of objects - dwarf planets. The 4 planets closest to the Sun are called terrestrial planets, and the next 4 massive gas bodies are called giant planets. Dwarf planets mainly inhabit the area beyond the orbit of Neptune - the Kuiper belt.

Moon

The Moon is a natural satellite of the Earth and the brightest object in the night sky. Formally, the Moon is not a planet, but it is significantly larger than all the dwarf planets, most satellites of the planets, and is not much inferior in size to Mercury. There is no atmosphere familiar to us on the Moon, there are no rivers and lakes, vegetation and living organisms. The force of gravity on the Moon is six times less than on Earth. Day and night with temperature drops up to 300 degrees last for two weeks. Nevertheless, the Moon is increasingly attracting earthlings with the opportunity to use its unique conditions and resources. Therefore, the Moon is our first step in getting to know the objects of the solar system.

The moon has been well studied both with the help of ground-based telescopes and thanks to the flights of more than 50 spacecraft and ships with astronauts. The Soviet automatic stations "Luna-3" (1959) and "Zond-3" (1965) photographed for the first time the eastern and western parts of the hemisphere of the Moon, invisible from Earth. Artificial satellites of the Moon explored its gravitational field and relief. Self-propelled vehicles "Lunokhod-1 and -2" transmitted to Earth a lot of pictures and information about the physical and mechanical properties of the soil. Twelve American astronauts with the help of the Apollo spacecraft in 1969-1972. visited the Moon, where they conducted surface studies at six different landing sites on the visible side, installed scientific equipment there and brought back to Earth about 400 kg of lunar rocks. The probes "Luna-16, -20 and -24" performed drilling in automatic mode and delivered lunar soil to Earth. The new-generation spacecraft Clementine (1994), Lunar Prospector (1998-99) and Smart-1 (2003-06) received more accurate information about the relief and gravitational field of the Moon, as well as found on the surface deposits of hydrogen-bearing materials, possibly water ice. In particular, an increased concentration of these materials is found in permanently shaded depressions near the poles.

The Chinese apparatus "Change-1", launched on October 24, 2007, photographed the lunar surface and collected data to compile a digital model of its relief. March 1, 2009 the device was dropped on the surface of the moon. On November 8, 2008, the Indian spacecraft Chandrayan 1 was launched into a selenocentric orbit. On November 14, the probe separated from it, making a hard landing near the south pole of the moon. The apparatus worked for 312 days and transmitted data on the distribution of chemical elements over the surface and on the heights of the relief. The Japanese AMS "Kaguya" and two additional microsatellites "Okina" and "Oyuna", operating in 2007-2009, completed the scientific program of lunar exploration and transmitted data on the heights of the relief and the distribution of gravity on its surface with high accuracy.

A new important stage in the study of the Moon was the launch on June 18, 2009 of two American AMS "Lunar Reconnaissance Orbiter" (Lunar Orbital Reconnaissance) and "LCROSS" (satellite for observation and detection of lunar craters). October 9, 2009 AMS "LCROSS" was sent to the crater Cabeo. The spent stage of the Atlas-V rocket weighing 2.2 tons first fell to the bottom of the crater. Approximately four minutes later, the LCROSS AMS (weight 891 kg) fell there, which, before falling, rushed through the dust cloud raised by the stage, having managed to do the necessary research until the death of the device. American researchers believe that they still managed to find some water in a cloud of lunar dust. Lunar Reconnaissance Orbiter continues to explore the Moon from a polar lunar orbit. On board the spacecraft is the Russian LEND instrument (lunar research neutron detector) designed to search for frozen water. In the region of the South Pole, he discovered a large amount of hydrogen, which may be a sign of the presence of water there in a bound state.

In the near future, the exploration of the moon will begin. Already today, projects are being developed in detail to create a permanent habitable base on its surface. Long-term or permanent presence on the Moon of replacement crews of such a base will make it possible to solve more complex scientific and applied problems.

The Moon moves under the influence of gravity, mainly two celestial bodies - the Earth and the Sun at an average distance of 384,400 km from the Earth. At apogee, this distance increases to 405,500 km, and at perigee it decreases to 363,300 km. The period of revolution of the Moon around the Earth with respect to distant stars is about 27.3 days (sidereal month), but since the Moon revolves around the Sun together with the Earth, its position relative to the Sun-Earth line repeats after a slightly longer period of time - about 29.5 days (synodic month). During this period, a complete change of lunar phases takes place: from the new moon to the first quarter, then to the full moon, to the last quarter and again to the new moon. The rotation of the Moon around its axis occurs at a constant angular velocity in the same direction in which it revolves around the Earth, and with the same period of 27.3 days. That is why from the Earth we see only one hemisphere of the Moon, which we call so - visible; and the other hemisphere is always hidden from our eyes. This hemisphere, which is not visible from the Earth, is called the far side of the Moon. The figure formed by the physical surface of the Moon is very close to a regular sphere with an average radius of 1737.5 km. The surface area of ​​the lunar globe is about 38 million km 2, which is only 7.4% of the earth's surface area, or about a quarter of the area of ​​the earth's continents. The ratio of the masses of the Moon and the Earth is 1:81.3. The average density of the Moon (3.34 g / cm 3) is much less than the average density of the Earth (5.52 g / cm 3). The force of gravity on the Moon is six times less than on Earth. On a summer afternoon, near the equator, the surface warms up to +130°C, in some places even higher; and at night the temperature drops to -170 °C. Rapid cooling of the surface is also observed during lunar eclipses. Two types of regions are distinguished on the Moon: light - continental, occupying 83% of the entire surface (including the reverse side), and dark regions, called seas. Such a division arose as early as the middle of the 17th century, when it was assumed that there really was water on the Moon. In terms of mineralogical composition and content of individual chemical elements, lunar rocks in dark areas of the surface (seas) are very close to terrestrial rocks such as basalts, and in light areas (continents) - to anorthosites.

The question of the origin of the Moon is still not completely clear. Features of the chemical composition of lunar rocks suggest that the Moon and the Earth were formed in the same region of the solar system. But the difference in their composition and internal structure makes us think that both of these bodies were not a single whole in the past. Most of the large craters and huge depressions (multi-ring basins) appeared on the surface of the lunar ball during the period of heavy bombardment of the surface. About 3.5 billion years ago, as a result of internal heating, basalt lavas poured onto the surface from the bowels of the Moon, filling lowlands and round depressions. Thus the lunar seas were formed. On the reverse side, due to the thicker crust, there were significantly fewer effusions. On the visible hemisphere, the seas occupy 30% of the surface, and on the reverse - only 3%. Thus, the evolution of the lunar surface was basically completed about 3 billion years ago. Meteor bombardment continued, but with less intensity. As a result of long-term processing of the surface, the upper loose layer of the rocks of the Moon was formed - regolith, several meters thick.

Mercury

The planet closest to the Sun is named after the ancient god Hermes (among the Romans Mercury) - the messenger of the gods and the god of dawn. Mercury is at an average distance of 58 million km or 0.39 AU. from the sun. Moving along a highly elongated orbit, it approaches the Sun at a distance of 0.31 AU at perihelion, and at a distance of 0.47 AU at its maximum distance, making a complete revolution in 88 Earth days. In 1965, it was established by radar methods from the Earth that the period of rotation of this planet is 58.6 days, that is, in 2/3 of its year it completes a complete rotation around its axis. The addition of axial and orbital motions leads to the fact that, being on the Sun-Earth line, Mercury always turns the same side towards us. A solar day (the time interval between the upper or lower culminations of the Sun) continues on the planet for 176 Earth days.

At the end of the 19th century, astronomers tried to draw the dark and light details observed on the surface of Mercury. The most famous are the works of Schiaparelli (1881-1889) and the American astronomer Percival Lovell (1896-1897). Interestingly, the astronomer T. J. C. even announced in 1901 that he had seen craters on Mercury. Few people believed in this, but subsequently the 625-kilometer crater (Beethoven) turned out to be in the place marked by Xi. In 1934, the French astronomer Eugène Antoniadi mapped the "visible hemisphere" of Mercury, since it was then believed that only one of its hemispheres was always illuminated. Individual details on this map Antoniadi gave names that are partially used on modern maps.

It was possible for the first time to make really reliable maps of the planet and see the fine details of the surface topography thanks to the American space probe Mariner-10, launched in 1973. It approached Mercury three times and transmitted television images of various parts of its surface to Earth. In total, 45% of the planet's surface was filmed, mainly the western hemisphere. As it turned out, its entire surface is covered with many craters of different sizes. It was possible to clarify the value of the radius of the planet (2439 km) and its mass. Temperature sensors made it possible to establish that during the day the surface temperature of the planet rises to 510 ° C, and at night it drops to -210 ° C. The strength of its magnetic field is about 1% of the strength of the earth's magnetic field. More than 3 thousand photographs taken during the third approach had a resolution of up to 50 m.

The free fall acceleration on Mercury is 3.68 m/s 2 . An astronaut on this planet would weigh almost three times less than on Earth. Since it turned out that the average density of Mercury is almost the same as that of the Earth, it is assumed that Mercury has an iron core, which occupies about half the volume of the planet, over which the mantle and silicate shell are located. Mercury receives 6 times more sunlight per unit area than Earth. Moreover, most of the solar energy is absorbed, since the surface of the planet is dark, reflecting only 12-18 percent of the incident light. The surface layer of the planet (regolith) is very crushed and serves as excellent thermal insulation, so that at a depth of several tens of centimeters from the surface the temperature is constant - about 350 degrees K. Mercury has an extremely rarefied helium atmosphere created by the "solar wind" that blows the planet. The pressure of such an atmosphere at the surface is 500 billion times less than at the Earth's surface. In addition to helium, an insignificant amount of hydrogen, traces of argon and neon were detected.

The American AMS "Messenger" (Messenger - from the English Courier), launched on August 3, 2004, made its first flight around Mercury on January 14, 2008 at a distance of 200 km from the surface of the planet. She photographed the eastern half of the previously unphotographed hemisphere of the planet. The studies of Mercury were carried out in two stages: first survey from the flyby flight trajectory during two encounters with the planet (2008), and then (September 30, 2009) - detailed. The entire surface of the planet was surveyed in various ranges of the spectrum and color images of the terrain were obtained, the chemical and mineralogical composition of rocks was determined, and the content of volatile elements in the near-surface soil layer was measured. The laser altimeter measured the heights of the surface relief of Mercury. It turned out that the height difference of the relief on this planet is less than 7 km. During the fourth rendezvous, on March 18, 2011, AMS "Messenger" should enter the orbit of the artificial satellite of Mercury.

According to the decision of the International Astronomical Union, craters on Mercury are named after figures: writers, poets, artists, sculptors, composers. For example, the largest craters with a diameter of 300 to 600 km were named Beethoven, Tolstoy, Dostoevsky, Shakespeare and others. There are exceptions to this rule - one crater with a diameter of 60 km with a ray system is named after the famous astronomer Kuiper, and another crater with a diameter of 1.5 km near the equator, taken as the origin of longitudes on Mercury, is named Hun Kal, which is in the language of the ancient Maya means twenty. It was agreed to draw a meridian through this crater, with a longitude of 20°.

The plains are given the names of the planet Mercury in various languages, such as Sobkow Plain or Odin Plain. There are two plains named for their location: the Northern Plain and the Zhara Plain, located in the region of maximum temperatures at 180° longitude. The mountains bordering this plain were called the mountains of Heat. A distinctive feature of the relief of Mercury is the extended ledges, which received the names of marine research vessels. The valleys are named after radio astronomy observatories. Two ridges are named Antoniadi and Schiaparelli, in honor of the astronomers who made the first maps of this planet.

Venus

Venus is the planet closest to the Earth, it is closer to the Sun than us and therefore it is illuminated by it brighter; finally, it reflects sunlight very well. The fact is that the surface of Venus is covered under a powerful cover of the atmosphere, which completely hides the surface of the planet from our view. In the visible range, it cannot be seen even from the orbit of the artificial satellite of Venus, and, nevertheless, we have "images" of the surface, which were obtained by radar.

The second planet from the Sun is named after the ancient goddess of love and beauty Aphrodite (among the Romans - Venus). The average radius of Venus is 6051.8 km, and the mass is 81% of the mass of the Earth. Venus revolves around the Sun in the same direction as the other planets, making a complete revolution in 225 days. The period of its rotation around its axis (243 days) was determined only in the early 1960s, when radar methods began to be used to measure the speeds of planetary rotation. Thus, the daily rotation of Venus is the slowest among all the planets. In addition, it occurs in the opposite direction: unlike most planets, in which the directions of orbiting and rotation around the axis coincide, Venus rotates around the axis in the direction opposite to the orbital movement. If you look formally, then this is not a unique property of Venus. For example, Uranus and Pluto also rotate in the opposite direction. But they rotate almost "lying on their side", and the axis of Venus is almost perpendicular to the orbital plane, so it is the only one that "really" rotates in the opposite direction. That is why the solar day on Venus is shorter than the time of its rotation around the axis and is 117 Earth days (for other planets, the solar day is longer than the rotation period). A year on Venus is only twice as long as a solar day.

The atmosphere of Venus is 96.5% carbon dioxide and almost 3.5% nitrogen. Other gases - water vapor, oxygen, sulfur oxide and dioxide, argon, neon, helium and krypton - add up to less than 0.1%. But it should be borne in mind that the Venusian atmosphere is about 100 times more massive than ours, so there is, for example, five times more nitrogen in mass than in the Earth's atmosphere.

The foggy haze in the atmosphere of Venus extends upwards to a height of 48-49 km. Further up to a height of 70 km there is a cloud layer containing droplets of concentrated sulfuric acid, and hydrochloric and hydrofluoric acids are also present in the uppermost layers. The clouds of Venus reflect 77% of the sunlight falling on them. At the top of the highest mountains of Venus - the Maxwell Mountains (about 11 km high) - the atmospheric pressure is 45 bar, and at the bottom of the Diana Canyon - 119 bar. As you know, the pressure of the earth's atmosphere at the surface of the planet is only 1 bar. The powerful atmosphere of Venus, consisting of carbon dioxide, absorbs and partially transmits about 23% of solar radiation to the surface. This radiation heats the surface of the planet, but thermal infrared radiation from the surface passes through the atmosphere back into space with great difficulty. And only when the surface is heated to about 460-470 ° C, the outgoing energy flux is equal to the incoming to the surface. It is because of this greenhouse effect that the surface of Venus maintains a high temperature regardless of the latitude of the area. But in the mountains, over which the thickness of the atmosphere is less, the temperature is several tens of degrees lower. Venus was explored by more than 20 spacecraft: Venus, Mariners, Pioneer Venus, Vega and Magellan. In 2006, the Venera Express probe worked in orbit around it. Scientists were able to see the global features of the relief of the surface of Venus thanks to radar sounding from the Pioneer-Venus (1978), Venera-15 and -16 (1983-84) and Magellan (1990-94) orbiters .). Ground-based radar allows you to "see" only 25% of the surface, and with much lower detail resolution than spacecraft are capable of. For example, Magellan obtained images of the entire surface with a resolution of 300 m. It turned out that most of the surface of Venus is occupied by hilly plains.

Elevations account for only 8% of the surface. All noticeable details of the relief got their names. On the first ground-based radar images of individual sections of the surface of Venus, researchers used various names, of which now remain on the maps - the Maxwell Mountains (the name reflects the role of radiophysics in Venus research), the Alpha and Beta regions (the two brightest details of the relief of Venus in radar images are named after the first letters of the Greek alphabet). But these names are exceptions to the naming rules adopted by the International Astronomical Union: astronomers have decided to call the details of the relief of the surface of Venus by female names. Large elevated areas were named: Land of Aphrodite, Land of Ishtar (in honor of the Assyrian goddess of love and beauty) and Land of Lada (Slavic goddess of love and beauty). Large craters are named after outstanding women of all times and peoples, and small craters bear personal female names. On the maps of Venus, you can find such names as Cleopatra (the last queen of Egypt), Dashkova (director of the St. Petersburg Academy of Sciences), Akhmatova (Russian poetess) and other famous names. Of the Russian names, there are Antonina, Galina, Zina, Zoya, Lena, Masha, Tatyana and others.

Mars

The fourth planet from the Sun, named after the god of war Mars, is 1.5 times farther from the sun than the Earth. One orbit around Mars takes 687 Earth days. The orbit of Mars has a noticeable eccentricity (0.09), so its distance from the Sun varies from 207 million km at perihelion to 250 million km at aphelion. The orbits of Mars and Earth lie almost in the same plane: the angle between them is only 2°. Every 780 days, Earth and Mars are at a minimum distance from each other, which can range from 56 to 101 million km. These planetary encounters are called oppositions. If at this moment the distance between the planets is less than 60 million km, then the opposition is called great. Great confrontations occur every 15-17 years.

The equatorial radius of Mars is 3394 km, 20 km more than the polar one. In terms of mass, Mars is ten times smaller than the Earth, and in terms of surface area it is 3.5 times smaller. The period of the axial rotation of Mars was determined by ground-based telescopic observations of the contrasting details of the surface: it is 24 hours 39 minutes and 36 seconds. The axis of rotation of Mars is deflected by an angle of 25.2° from the perpendicular to the plane of the orbit. Therefore, Mars also experiences a change of seasons, but the seasons are almost twice as long as on Earth. Due to the elongation of the orbit, the seasons in the northern and southern hemispheres have different durations: summer in the northern hemisphere lasts 177 Martian days, and in the southern hemisphere it is 21 days shorter, but warmer than summer in the northern hemisphere.

Due to its greater distance from the Sun, Mars receives only 43% of the energy that falls on the same area of ​​​​the earth's surface. The average annual temperature on the surface of Mars is about -60 °C. The maximum temperature there does not exceed a few degrees above zero, and the minimum was recorded at the northern polar cap and is -138 °C. During the day, the surface temperature changes significantly. For example, in the southern hemisphere at a latitude of 50°, the typical temperature in mid-autumn varies from -18°C at noon to -63°C at night. However, already at a depth of 25 cm below the surface, the temperature is almost constant (about -60 ° C), regardless of the time of day and season. Large temperature changes on the surface are explained by the fact that the atmosphere of Mars is very rarefied, and at night the surface cools down quickly, and during the day it is quickly heated by the Sun. The atmosphere of Mars is 95% carbon dioxide. Other constituents: 2.5% nitrogen, 1.6% argon, less than 0.4% oxygen. The average pressure of the atmosphere at the surface is 6.1 mbar, i.e., 160 times less than the pressure of the earth's air at sea level (1 bar). In the deepest depressions on Mars, it can reach 12 mbar. The atmosphere of the planet is dry, there is practically no water vapor in it.

The polar caps of Mars are multi-layered. The lower, main layer, several kilometers thick, is formed by ordinary water ice mixed with dust; this layer is preserved in the summer, forming permanent caps. And the observed seasonal changes in the polar caps occur due to the upper layer less than 1 meter thick, consisting of solid carbon dioxide, the so-called "dry ice". The area covered by this layer grows rapidly in winter, reaching the 50° parallel, and sometimes even crossing this line. In spring, as the temperature rises, the upper layer evaporates, and only a permanent cap remains. The “darkening wave” of surface areas observed with the change of seasons is explained by the change in the direction of the winds, constantly blowing in the direction from one pole to another. The wind carries away the top layer of loose material - light dust, exposing areas of darker rocks. During periods when Mars passes perihelion, the heating of the surface and atmosphere increases, and the balance of the Martian environment is disturbed. The wind speed increases to 70 km/h, whirlwinds and storms begin. Sometimes more than a billion tons of dust rises and is held in suspension, while the climatic situation on the entire Martian globe changes dramatically. Duration of dust storms can reach 50 - 100 days. The exploration of Mars by spacecraft began in 1962 with the launch of the Mars-1 probe. The first images of areas of the surface of Mars were transmitted by Mariner-4 in 1965, and then by Mariner-6 and -7 in 1969. The Mars-3 descent vehicle managed to make a soft landing. Based on the images of Mariner 9 (1971), detailed maps of the planet were compiled. He transmitted to Earth 7329 images of Mars with a resolution of up to 100 m, as well as photographs of his satellites - Phobos and Deimos. A whole flotilla of four Mars-4, -5, -6, -7 spacecraft, launched in 1973, reached the vicinity of Mars in early 1974. Due to a malfunction of the onboard braking system, Mars-4 passed at a distance about 2200 km from the surface of the planet, having performed only its photography. "Mars-5" carried out remote studies of the surface and atmosphere from the orbit of an artificial satellite. The Mars 6 lander made a soft landing in the southern hemisphere. Data on the chemical composition, pressure and temperature of the atmosphere were transmitted to Earth. "Mars-7" passed at a distance of 1300 km from the surface without fulfilling its program.

The flights of two American Vikings launched in 1975 were the most productive. On board the vehicles were television cameras, infrared spectrometers for recording water vapor in the atmosphere, and radiometers for obtaining temperature data. The Viking-1 lander made a soft landing on Chris Plain on July 20, 1976, and Viking-2 on Utopia Plain on September 3, 1976. Unique experiments were carried out at the landing sites in order to detect signs of life in the Martian soil. A special device captured a soil sample and placed it in one of the containers containing a supply of water or nutrients. Since any living organisms change their habitat, the instruments had to record this. Although some changes in the environment in a tightly closed container were observed, the presence of a strong oxidizing agent in the soil could lead to the same results. This is why scientists have not been able to confidently attribute these changes to bacteria. The orbital stations took detailed photographs of the surface of Mars and its satellites. Based on the data obtained, detailed maps of the planet's surface, geological, thermal and other special maps were compiled.

The task of the Soviet stations "Phobos-1, -2", launched after a 13-year break, included the study of Mars and its satellite Phobos. As a result of an incorrect command from the Earth, Phobos-1 lost its orientation, and communication with it could not be restored. "Phobos-2" entered the orbit of the artificial satellite of Mars in January 1989. Data on temperature changes on the surface of Mars and new information about the properties of the rocks that make up Phobos were obtained by remote methods. 38 images were obtained with a resolution of up to 40 m, the temperature of its surface was measured, which is 30 °C at the hottest points. Unfortunately, it was not possible to carry out the main program for the study of Phobos. Communication with the device was lost on March 27, 1989. The series of failures did not end there. The American spacecraft "Mars-Observer", launched in 1992, also did not fulfill its task. Communication with it was lost on August 21, 1993. It was not possible to put the Russian Mars-96 station on the flight path to Mars.

One of NASA's most successful projects is the Mars Global Surveyor, launched on November 7, 1996 to map the Martian surface in detail. The device also serves as a telecommunications satellite for the Spirit and Opportunity rovers, delivered in 2003 and still operating today. In July 1997, the Mars Pathfinder delivered the first sub-11 kg robotic rover, the Sojerner, to the planet, which successfully probed surface chemistry and meteorological conditions. The rover maintained contact with the Earth through the lander. NASA's automatic interplanetary station "Mars Reconnaissance Satellite" began its work in orbit in March 2006. Using a high-resolution camera on the surface of Mars, it was possible to distinguish details of 30 cm in size. "Mars Odyssey", "Mars - Express" and "Mars reconnaissance satellite continue research from orbit. The device "Phoenix" worked in the polar region from May 25 to November 2, 2008. He was the first to drill the surface and discover ice. The Phoenix delivered a digital library of science fiction to the planet. Programs for the flight of astronauts to Mars are being developed. Such an expedition will take more than two years, because in order to return, they will have to wait for a convenient relative position of Earth and Mars.

On modern maps of Mars, along with the names assigned to landforms that are identified from satellite images, the old geographical and mythological names proposed by Schiaparelli are also used. The largest elevated area, with a diameter of about 6000 km and a height of up to 9 km, was named Tharsis (as Iran was called on ancient maps), and a huge ring depression in the south with a diameter of more than 2000 km was named Hellas (Greece). Densely cratered areas of the surface were called lands: the Land of Prometheus, the Land of Noah, and others. The valleys are given the names of the planet Mars from the languages ​​of different peoples. Large craters are named after scientists, and small craters are named after settlements on Earth. Four giant extinct volcanoes rise above the surrounding area to a height of up to 26 m. The largest of them, Mount Olympus, located on the western outskirts of the Arsida mountains, has a base with a diameter of 600 km and a caldera (crater) at the top with a diameter of 60 km. Three volcanoes - Mount Askriyskaya, Mount Pavlina and Mount Arsia - are located on the same straight line at the top of the Tharsis Mountains. The volcanoes themselves tower over Tharsis for another 17 km. In addition to these four, more than 70 extinct volcanoes have been found on Mars, but they are much smaller in area and in height.

To the south of the equator is a giant valley up to 6 km deep and over 4,000 km long. It was called the Valley of the Mariner. Many smaller valleys have also been identified, as well as furrows and cracks, indicating that in ancient times there was water on Mars and, therefore, the atmosphere was denser. Under the surface of Mars in some areas there should be a layer of permafrost, several kilometers thick. In such regions, on the surface near the craters, frozen flows unusual for terrestrial planets are visible, which can be used to judge the presence of subsurface ice.

With the exception of the plains, the surface of Mars is heavily cratered. Craters tend to look more eroded than those on Mercury and the Moon. Traces of wind erosion can be seen everywhere.

Phobos and Deimos are natural satellites of Mars

The satellites of Mars were discovered during the great opposition of 1877 by the American astronomer A. Hall. They were named Phobos (translated from Greek Fear) and Deimos (Horror), since in ancient myths the god of war was always accompanied by his children - Fear and Horror. Satellites are very small in size and have an irregular shape. The semi-major axis of Phobos is 13.5 km, and the minor one is 9.4 km; at Deimos, respectively, 7.5 and 5.5 km. The Mariner 7 probe photographed Phobos against the background of Mars in 1969, and Mariner 9 transmitted many images of both satellites, which show that their surfaces are uneven, abundantly covered with craters. Several close approaches to the satellites were made by the Viking and Phobos-2 probes. The best photographs of Phobos show relief details up to 5 meters in size.

The orbits of the satellites are circular. Phobos revolves around Mars at a distance of 6000 km from the surface with a period of 7 hours 39 minutes. Deimos is 20,000 km away from the planet's surface, and its orbital period is 30 hours and 18 minutes. The periods of rotation of satellites around the axis coincide with the periods of their revolution around Mars. The major axes of the figures of the satellites are always directed towards the center of the planet. Phobos rises in the west and sets in the east 3 times per Martian day. The average density of Phobos is less than 2 g/cm 3 , and the free fall acceleration on its surface is 0.5 cm/s 2 . A person would weigh only a few tens of grams on Phobos and could, by throwing a stone with his hand, make it forever fly into space (the separation speed on the surface of Phobos is about 13 m/s). The largest crater on Phobos has a diameter of 8 km, comparable to the smallest diameter of the satellite itself. On Deimos, the largest depression has a diameter of 2 km. Small craters on the surfaces of the satellites are dotted in much the same way as the Moon. With a general similarity, an abundance of finely fragmented material covering the surfaces of the satellites, Phobos looks more “ragged”, and Deimos has a smoother surface covered with dust. On Phobos, mysterious furrows have been discovered that cross almost the entire satellite. Furrows are 100-200 m wide and stretch for tens of kilometers. Their depth is from 20 to 90 meters. There are several about the origin of these furrows, but so far there is no convincing enough explanation, as well as an explanation for the origin of the satellites themselves. Most likely, these are asteroids captured by Mars.

Jupiter

Jupiter is called the "king of the planets" for a reason. It is the largest planet in the solar system, exceeding the Earth by 11.2 times in diameter and 318 times in mass. Jupiter has a low average density (1.33 g / cm 3), since it is almost entirely composed of hydrogen and helium. It is located at an average distance of 779 million km from the Sun and spends about 12 years per orbit. Despite its gigantic size, this planet rotates very quickly - faster than the Earth or Mars. The most surprising thing is that Jupiter does not have a solid surface in the generally accepted sense - it is a gas giant. Jupiter leads the group of giant planets. Named after the supreme god of ancient mythology (the ancient Greeks - Zeus, the Romans - Jupiter), it is five times further from the Sun than the Earth. Due to the rapid rotation, Jupiter is strongly oblate: its equatorial radius (71,492 km) is 7% larger than the polar one, which is easy to see when viewed through a telescope. The force of gravity at the planet's equator is 2.6 times greater than on Earth. Jupiter's equator is tilted only 3° to its orbit, so there are no seasons on the planet. The inclination of the orbit to the plane of the ecliptic is even less - only 1 °. Every 399 days, the opposition of the Earth and Jupiter is repeated.

Hydrogen and helium are the main components of this planet: by volume, the ratio of these gases is 89% hydrogen and 11% helium, and by mass 80% and 20%, respectively. The entire visible surface of Jupiter is dense clouds, forming a system of dark belts and bright zones north and south of the equator to the parallels of 40 ° north and south latitude. Clouds form layers of brownish, red and bluish hues. The periods of rotation of these cloud layers turned out to be not the same: the closer they are to the equator, the shorter period they rotate. So, near the equator, they complete a revolution around the planet's axis in 9 hours and 50 minutes, and at middle latitudes - in 9 hours and 55 minutes. Belts and zones are areas of downdrafts and updrafts in the atmosphere. Atmospheric currents parallel to the equator are supported by heat flows from the depths of the planet, as well as the rapid rotation of Jupiter and the energy of the Sun. The visible surface of the zones is located approximately 20 km above the belts. At the boundaries of belts and zones, strong turbulent motions of gases are observed. The hydrogen-helium atmosphere of Jupiter has a huge extent. The cloud cover is located at an altitude of about 1000 km above the "surface", where the gaseous state changes to liquid due to high pressure.

Even before the flights of spacecraft to Jupiter, it was established that the heat flux from the bowels of Jupiter is twice the influx of solar heat received by the planet. This may be due to the slow sinking towards the center of the planet of heavier substances and the ascent of lighter ones. The fall of meteorites on the planet can also be a source of energy. The color of the belts is explained by the presence of various chemical compounds. Closer to the poles of the planet, at high latitudes, clouds form a continuous field with brown and bluish spots up to 1000 km across. Jupiter's most famous feature is the Great Red Spot, an oval formation of varying size located in the southern tropical zone. At present, it has dimensions of 15,000 × 30,000 km (i.e., two globes will be freely located in it), and a hundred years ago, observers noted that the size of the Spot was twice as large. Sometimes it is not visible very clearly. The Great Red Spot is a long-lived vortex in the atmosphere of Jupiter, making a complete revolution around its center in 6 Earth days. The first study of Jupiter at close range (130,000 km) took place in December 1973 using the Pioneer-10 probe. Observations made by this apparatus in ultraviolet rays showed that the planet has an extended hydrogen and helium corona. The upper cloud layer appears to be cirrus ammonia, while below is a mixture of hydrogen, methane, and frozen ammonia crystals. An infrared radiometer showed that the temperature of the outer cloud cover is about -133 °C. A powerful magnetic field was discovered and a zone of the most intense radiation was registered at a distance of 177 thousand km from the planet. The plume of Jupiter's magnetosphere is noticeable even beyond the orbit of Saturn.

The path of Pioneer 11, which flew at a distance of 43,000 km from Jupiter in December 1974, was calculated differently. He passed between the radiation belts and the planet itself, avoiding a dose of radiation dangerous for electronic equipment. An analysis of color images of the cloud layer obtained by a photopolarimeter made it possible to reveal the features and structure of the clouds. The height of the clouds turned out to be different in belts and zones. Even before the Pioneer-10 and -11 flights from Earth, with the help of an astronomical observatory flying on an airplane, it was possible to determine the content of other gases in Jupiter's atmosphere. As expected, the presence of phosphine, a gaseous compound of phosphorus with hydrogen (PH 3), was detected, which gives color to the cloud cover. When heated, it decomposes with the release of red phosphorus. The unique mutual arrangement in the orbits of the Earth and the giant planets, which took place from 1976 to 1978, was used to sequentially study Jupiter, Saturn, Uranus and Neptune using the Voyager 1 and 2 probes. Their routes were calculated in such a way that it was possible to use the gravity of the planets themselves to accelerate and turn the flight path from one planet to another. As a result, the flight to Uranus took 9 years, and not 16, as it would have been according to the traditional scheme, and the flight to Neptune - 12 years instead of 20. Such a mutual arrangement of the planets will be repeated only after 179 years.

On the basis of data obtained by space probes and theoretical calculations, mathematical models of Jupiter's cloud cover are constructed and ideas about its internal structure are refined. In a somewhat simplified form, Jupiter can be represented as shells with a density that increases towards the center of the planet. At the bottom of the atmosphere with a thickness of 1500 km, the density of which increases rapidly with depth, there is a layer of gas-liquid hydrogen with a thickness of about 7000 km. At the level of 0.9 of the planet's radius, where the pressure is 0.7 Mbar and the temperature is about 6500 K, hydrogen passes into a liquid-molecular state, and after another 8000 km - into a liquid metallic state. Along with hydrogen and helium, the composition of the layers includes a small amount of heavy elements. The inner core, 25,000 km in diameter, is metallosilicate, including water, ammonia, and methane. The temperature in the center is 23,000 K and the pressure is 50 Mbar. Saturn has a similar structure.

63 known satellites revolve around Jupiter, which can be divided into two groups - internal and external, or regular and irregular; the first group includes 8 satellites, the second - 55. The satellites of the inner group circulate in almost circular orbits, practically lying in the plane of the planet's equator. The four satellites closest to the planet - Adrastea, Metis, Amalthea and Theba have diameters from 40 to 270 km and are within 2-3 radii of Jupiter from the center of the planet. They differ sharply from the four satellites following them, located at a distance of 6 to 26 radii of Jupiter and having much larger dimensions, close to the size of the Moon. These large satellites - Io, Europa, Ganymede and Callisto were discovered at the beginning of the 17th century. almost simultaneously Galileo Galilei and Simon Marius. They are usually called the Galilean satellites of Jupiter, although the first tables of the motion of these satellites were compiled by Marius.

The outer group consists of small - with a diameter of 1 to 170 km - satellites moving in elongated and strongly inclined orbits to Jupiter's equator. At the same time, five satellites closer to Jupiter move along their orbits in the direction of rotation of Jupiter, and almost all more distant satellites move in the opposite direction. Detailed information about the nature of the surfaces of the satellites was obtained by spacecraft. Let us dwell in more detail on the Galilean satellites. The diameter of Io, the closest satellite to Jupiter, is 3640 km, and its average density is 3.55 g/cm 3 . The bowels of Io are heated due to the tidal influence of Jupiter and the perturbations introduced into the motion of Io by its neighbors - Europa and Ganymede. Tidal forces deform Io's outer layers and heat them up. In this case, the accumulated energy breaks out to the surface in the form of volcanic eruptions. From the mouths of volcanoes, sulfur dioxide and sulfur vapor are ejected at a speed of about 1 km / s to a height of hundreds of kilometers above the surface of the satellite. Although Io's equatorial region averages about -140°C, there are hot spots ranging in size from 75 to 250 km, where temperatures reach 100-300°C. The surface of Io is covered with eruptions and has an orange color. The average age of details on it is small - about 1 million years. The relief of Io is mostly flat, but there are several mountains from 1 to 10 km high. The atmosphere of Io is very rarefied (practically it is a vacuum), but a gas tail stretches behind the satellite: radiation of oxygen, sodium and sulfur vapors, products of volcanic eruption, was detected along Io's orbit.

The second of the Galilean satellites, Europa, is somewhat smaller in size than the Moon, its diameter is 3130 km, and the average density of matter is about 3 g/cm3. The surface of the satellite is dotted with a network of light and dark lines: apparently, these are cracks in the ice crust resulting from tectonic processes. The width of these faults varies from a few kilometers to hundreds of kilometers, and the length reaches thousands of kilometers. Estimates of crustal thickness range from a few kilometers to tens of kilometers. In the bowels of Europe, the energy of tidal interaction is also released, which maintains the mantle in liquid form - the subglacial ocean, possibly even warm. It is not surprising, therefore, that there is an assumption about the possibility of the existence of the simplest forms of life in this ocean. Based on the average density of the satellite, there should be silicate rocks under the ocean. Since there are very few craters on Europa, which has a fairly smooth surface, the age of the details of this orange-brown surface is estimated at hundreds of thousands and millions of years. The high-resolution images taken by Galileo show individual irregularly shaped fields with elongated parallel ridges and valleys, reminiscent of highways. In a number of places, dark spots stand out, most likely these are deposits of matter taken out from under the ice layer.

According to the American scientist Richard Greenberg, the conditions for life on Europa should be sought not in the deep subglacial ocean, but in numerous cracks. Due to the tidal effect, the cracks periodically narrow and expand to a width of 1 m. When the crack narrows, the ocean water goes down, and when it starts to expand, the water rises along it almost to the very surface. Through the ice plug, which prevents water from reaching the surface, the sun's rays penetrate, carrying the energy necessary for living organisms.

The largest satellite in the Jupiter system - Ganymede has a diameter of 5268 km, but its average density is only twice that of water; this suggests that about 50% of the satellite's mass is ice. Numerous craters covering areas of dark brown color testify to the ancient age of this surface, about 3-4 billion years. The younger areas are covered with systems of parallel grooves formed by lighter material during the stretching of the ice crust. The depth of these furrows is several hundred meters, the width is tens of kilometers, and the length can reach up to several thousand kilometers. Some Ganymede craters have not only light ray systems (similar to the moon), but sometimes dark ones.

The diameter of Callisto is 4800 km. Based on the average density of the satellite (1.83 g / cm 3), it is assumed that water ice makes up about 60% of its mass. The thickness of the ice crust, like that of Ganymede, is estimated at tens of kilometers. The entire surface of this satellite is completely dotted with craters of various sizes. It does not have extended plains or systems of furrows. Craters on Callisto have a weakly expressed shaft and shallow depth. A unique detail of the relief is a multi-ring structure with a diameter of 2600 km, consisting of ten concentric rings. The surface temperature at the equator of Callisto reaches -120 °C at noon. The satellite has its own magnetic field.

On December 30, 2000, the Cassini probe passed near Jupiter, heading towards Saturn. At the same time, a number of experiments were carried out in the vicinity of the “king of the planets”. One of them was aimed at detecting the very rarefied atmospheres of the Galilean satellites during their eclipse by Jupiter. Another experiment consisted in recording radiation from Jupiter's radiation belts. Interestingly, in parallel with the work of Cassini, the same radiation was recorded using ground-based telescopes by schoolchildren and students in the United States. The results of their research were used along with the Cassini data.

As a result of the study of the Galilean satellites, an interesting hypothesis was put forward that in the early stages of their evolution, the giant planets radiated huge heat fluxes into space. Jupiter's radiation could melt the ice on the surface of three Galilean satellites. On the fourth - Callisto - this should not have happened, since it is 2 million km away from Jupiter. Therefore, its surface is so different from the surfaces of satellites closer to the planet.

Saturn

Among the giant planets, Saturn stands out for its remarkable ring system. Like Jupiter, it is a huge, rapidly spinning ball composed primarily of liquid hydrogen and helium. Orbiting around the Sun at a distance 10 times farther than the Earth, Saturn completes a complete revolution in a nearly circular orbit in 29.5 years. The angle of inclination of the orbit to the plane of the ecliptic is only 2 °, while the equatorial plane of Saturn is tilted 27 ° to the plane of its orbit, so the change of seasons is inherent in this planet.

The name of Saturn goes back to the Roman counterpart of the ancient titan Kronos, the son of Uranus and Gaia. This second largest planet exceeds the Earth in volume by 800 times, and in mass by 95 times. It is easy to calculate that its average density (0.7 g/cm 3 ) is less than the density of water - uniquely low for the planets of the solar system. The equatorial radius of Saturn along the upper boundary of the cloud layer is 60,270 km, and the polar radius is several thousand kilometers less. Saturn's rotation period is 10 hours 40 minutes. Saturn's atmosphere contains 94% hydrogen and 6% helium (by volume).

Neptune

Neptune was discovered in 1846 as a result of an accurate theoretical prediction. After studying the movement of Uranus, the French astronomer Le Verrier determined that the seventh planet is affected by the attraction of an equally massive unknown body, and calculated its position. Guided by this forecast, the German astronomers Halle and D'Arrest discovered Neptune. It later turned out that, starting from Galileo, astronomers marked the position of Neptune on maps, but mistook it for a star.

Neptune is the fourth of the giant planets, named after the god of the seas in ancient mythology. The equatorial radius of Neptune (24,764 km) is almost 4 times the radius of the Earth, and in terms of mass, Neptune is 17 times larger than our planet. The average density of Neptune is 1.64 g/cm3. It revolves around the Sun at a distance of 4.5 billion km (30 AU), making a complete cycle in almost 165 Earth years. The plane of the planet's orbit is inclined by 1.8° to the plane of the ecliptic. The inclination of the equator to the plane of the orbit is 29.6°. Due to the great distance from the Sun, the illumination on Neptune is 900 times less than on Earth.

Data transmitted by Voyager 2, which passed within 5,000 km of the surface of Neptune's cloud layer in 1989, revealed details of the planet's cloud cover. The stripes on Neptune are weakly expressed. A large dark spot the size of our planet, discovered in the southern hemisphere of Neptune, is a giant anticyclone that completes a revolution in 16 Earth days. This is an area of ​​high pressure and temperature. Unlike the Great Red Spot on Jupiter, which drifts at 3 m/s, the Great Dark Spot on Neptune moves westward at 325 m/s. A smaller dark spot located at 74° S. sh., has shifted 2000 km to the north in a week. A light formation in the atmosphere, the so-called "scooter", was also distinguished by a fairly fast movement. In some places, the wind speed in the atmosphere of Neptune reaches 400-700 m/s.

Like other giant planets, Neptune's atmosphere is mostly hydrogen. Helium accounts for about 15%, and 1% for methane. The visible cloud layer corresponds to a pressure of 1.2 bar. It is assumed that at the bottom of the Neptunian atmosphere there is an ocean of water saturated with various ions. A significant amount of methane appears to be stored deeper in the planet's icy mantle. Even at a temperature of thousands of degrees, at a pressure of 1 Mbar, a mixture of water, methane and ammonia can form solid ice. The hot icy mantle probably accounts for 70% of the mass of the entire planet. About 25% of the mass of Neptune should, according to calculations, belong to the core of the planet, consisting of oxides of silicon, magnesium, iron and its compounds, as well as rocks. A model of the internal structure of the planet shows that the pressure in its center is about 7 Mbar, and the temperature is about 7000 K. Unlike Uranus, the heat flux from the interior of Neptune is almost three times the heat received from the Sun. This phenomenon is associated with the release of heat during the radioactive decay of substances with a large atomic weight.

Neptune's magnetic field is twice as weak as that of Uranus. The angle between the axis of the magnetic dipole and the axis of rotation of Neptune is 47°. The center of the dipole is shifted by 6000 km to the southern hemisphere, so the magnetic induction at the south magnetic pole is 10 times higher than at the north.

The rings of Neptune are generally similar to the rings of Uranus, with the only difference being that the total area of ​​matter in the rings of Neptune is 100 times smaller than in the rings of Uranus. Separate arcs of the rings surrounding Neptune were discovered during the occultations of the stars by the planet. The images of Voyager 2 show open formations around Neptune, which are called arches. They are located on a solid outermost ring of low density. The diameter of the outer ring is 69.2 thousand km, and the width of the arches is about 50 km. Other rings located at distances from 61.9 thousand km to 62.9 thousand km are closed. During observations from the Earth, by the middle of the twentieth century, 2 satellites of Neptune were found - Triton and Nereid. Voyager 2 discovered 6 more satellites ranging in size from 50 to 400 km and specified the diameters of Triton (2705 km) and Nereid (340 km). In 2002-03 during observations from the Earth, 5 more distant satellites of Neptune were discovered.

The largest satellite of Neptune - Triton revolves around the planet at a distance of 355 thousand km with a period of about 6 days in a circular orbit inclined by 23 ° to the planet's equator. At the same time, it is the only one of Neptune's inner satellites that orbits in the opposite direction. Triton's axial rotation period coincides with its orbital period. The average density of Triton is 2.1 g/cm3. The surface temperature is very low (38 K). In satellite images, most of Triton's surface is a plain with many cracks, which is why it resembles a melon crust. The South Pole is surrounded by a bright polar cap. Several depressions with a diameter of 150 - 250 km were found on the plain. Probably, the ice crust of the satellite was repeatedly processed as a result of tectonic activity and the fall of meteorites. Triton, apparently, has a stone core with a radius of about 1000 km. It is assumed that an ice crust about 180 km thick covers a water ocean about 150 km deep, saturated with ammonia, methane, salts and ions. Triton's rarefied atmosphere is mostly nitrogen, with small amounts of methane and hydrogen. Snow on Triton's surface is nitrogen frost. The polar cap is also formed by nitrogen frost. Amazing formations found on the polar cap - dark spots, elongated to the northeast (about fifty of them were found). They turned out to be gas geysers, rising to a height of up to 8 km, and then turning into plumes stretching for about 150 km.

Unlike the rest of the inner satellites, Nereid moves in a very elongated orbit, with its eccentricity (0.75) more like the orbit of comets.

Pluto

Pluto, after its discovery in 1930, was considered the smallest planet in the solar system. In 2006, by decision of the International Astronomical Union, it was deprived of the status of a classical planet and became the prototype of a new class of objects - dwarf planets. So far, the group of dwarf planets, in addition to it, includes the asteroid Ceres and several recently discovered objects in the Kuiper belt, beyond the orbit of Neptune; one of them even exceeds the size of Pluto. There is no doubt that other similar objects will be found in the Kuiper belt; so there may be quite a lot of dwarf planets in the solar system.

Pluto revolves around the sun in 245.7 years. At the time of its discovery, it was quite far from the Sun, occupying the place of the ninth planet in the solar system. But Pluto's orbit, as it turns out, has a significant eccentricity, so in each orbital cycle it is closer to the Sun than Neptune for 20 years. At the end of the 20th century, there was just such a period: on January 23, 1979, Pluto crossed the orbit of Neptune, so that it turned out to be closer to the Sun and formally became the eighth planet. It remained in this status until March 15, 1999. Having passed through the perihelion of its orbit (29.6 AU) in September 1989, Pluto is now moving towards aphelion (48.8 AU), which it will reach in 2112, and the first complete revolution around the Sun after its discovery will complete only in 2176.

To understand the interest of astronomers in Pluto, you need to remember the history of its discovery. At the beginning of the 20th century, observing the movement of Uranus and Neptune, astronomers noticed some oddity in their behavior and suggested that beyond the orbits of these planets there is another, undiscovered, gravitational influence of which affects the movement of known giant planets. Astronomers have even calculated the supposed location of this planet - "Planet X" - although not very confidently. After a long search, in 1930 the American astronomer Clyde Tombaugh discovered the ninth planet, named after the god of the underworld - Pluto. However, the discovery, apparently, was accidental: subsequent measurements showed that the mass of Pluto is too small for its gravity to noticeably affect the movement of Neptune and, especially, Uranus. The orbit of Pluto turned out to be much more elongated than that of other planets, and noticeably inclined (17 °) to the ecliptic, which is also not typical for planets. Some astronomers tend to think of Pluto as a "wrong" planet, more like a steroid or a lost moon of Neptune. However, Pluto has its own satellites, and at times there is also an atmosphere, when the ice covering its surface evaporates in the region of the perihelion of the orbit. In general, Pluto has been studied very poorly, since not a single probe has yet flown to it; Until recently, even such attempts have not been made. But in January 2006, the New Horizons (NASA) spacecraft launched to Pluto, which should fly past the planet in July 2015.

By measuring the intensity of sunlight reflected by Pluto, astronomers have found that the apparent brightness of the planet changes periodically. This period (6.4 days) was taken as the period of Pluto's axial rotation. In 1978, the American astronomer J. Christie drew attention to the irregular shape of the image of Pluto in photographs taken with the best angular resolution: a blurry spot in the image often covered a protrusion on one side; its position also changed with a period of 6.4 days. Christie concluded that Pluto has a rather large satellite, which was named Charon after the mythical boatman who transported the souls of the dead along the rivers in the underworld kingdom of the dead (the ruler of this kingdom, as you know, was Pluto). Charon appears either from the north or from the south of Pluto, so it became clear that the satellite's orbit, like the axis of rotation of the planet itself, is strongly inclined to the plane of its orbit. Measurements have shown that the angle between Pluto's axis of rotation and the plane of its orbit is about 32°, and the rotation is reversed. Charon's orbit lies in the equatorial plane of Pluto. In 2005, two more small satellites were discovered - Hydra and Nix, orbiting further than Charon, but in the same plane. Thus, Pluto with its satellites resembles Uranus, which rotates, "lying on its side."

Charon's rotation period, which is 6.4 days, coincides with the period of its movement around Pluto. Like the Moon, Charon always faces the planet on one side. This is characteristic of all satellites moving close to the planet. Surprisingly, Pluto is also facing Charon always with the same side; in this sense they are equal. Pluto and Charon are a unique binary system, very compact and having an unprecedentedly high ratio of the masses of the satellite and the planet (1:8). The ratio of the masses of the Moon and the Earth, for example, is 1:81, while other planets have similar ratios much less. Essentially, Pluto and Charon are a double dwarf planet.

The best images of the Pluto-Charon system were taken by the Hubble Space Telescope. They were able to determine the distance between the satellite and the planet, which turned out to be only about 19,400 km. Using the eclipses of stars by Pluto, as well as the mutual eclipses of the planet by its satellite, it was possible to refine their sizes: the diameter of Pluto, according to recent estimates, is 2300 km, and the diameter of Charon is 1200 km. The average density of Pluto is in the range from 1.8 to 2.1 g / cm 3, and Charon - from 1.2 to 1.3 g / cm 3. Apparently, the internal structure of Pluto, consisting of rocks and water ice, differs from the structure of Charon, which is more like the ice satellites of the giant planets. Charon's surface is 30% darker than Pluto's. The color of the planet and satellite is also different. Apparently, they formed independently of each other. Observations have shown that in the perihelion of the orbit, the brightness of Pluto increases markedly. This gave grounds to assume the appearance of a temporary atmosphere near Pluto. During the occultation of the star by Pluto in 1988, the brightness of this star decreased gradually over several seconds, from which it was finally established that Pluto had an atmosphere. Its main component, most likely, is nitrogen, and other components may contain methane, argon, and neon. The thickness of the haze layer is estimated at 45 km, and the atmosphere itself - at 270 km. The methane content should change depending on the position of Pluto in its orbit. Pluto passed perihelion in 1989. Calculations show that some of the deposits of frozen methane, nitrogen and carbon dioxide present on its surface in the form of ice and hoarfrost pass into the atmosphere as the planet approaches the Sun. Pluto's maximum surface temperature is 62 K. Charon's surface appears to be formed by water ice.

So, Pluto is the only planet (albeit a dwarf one) whose atmosphere either appears or disappears, like a comet during its movement around the Sun. Using the Hubble Space Telescope in May 2005, two new satellites of the dwarf planet Pluto were discovered, called Nix and Hydra. The orbits of these satellites are located beyond the orbit of Charon. Nyx is about 50,000 km from Pluto, and Hydra is about 65,000 km. The New Horizons mission, launched in January 2006, is designed to study the vicinity of Pluto and the Kuiper Belt.

History and structure

The solar system is our planetary system, which includes the Sun and all natural objects revolving around it. It appeared 4.57 billion years ago, when the temperature and pressure created by gravity inside the primary gas and dust cloud led to the onset of a thermonuclear reaction.

The bulk of the mass of the solar system is contained in the Sun, while the rest is contained in the planets, dwarf planets, asteroids, comets, dust and gas. Eight relatively solitary planets have relatively circular orbits and are located within the boundaries of an almost flat disk - the plane of the ecliptic. The Earth is part of the so-called terrestrial group, which includes the first four planets from the Sun - Mercury, Venus, and Earth, consisting mainly of silicates and metals. They are followed by a group of four planets more distant from the Sun - Uranus and Neptune (also called gas giants), compared to terrestrial-type planets, their sizes are huge. Especially large are Jupiter and Saturn, the largest in the solar system, consisting mainly of helium and hydrogen; in the composition of Uranus and Neptune, in addition to hydrogen and helium, carbon monoxide and methane are also determined. These planets are also called "ice giants". All gas giants are surrounded by rings of dust and other particles.

Our system has two regions with small bodies. Asteroid belt between Mars and Jupiter includes many objects consisting of silicates and metals, which indicates similarities with terrestrial planets. The largest objects in it are the dwarf planet and the asteroids Vesta, Hygiea and Pallas. Beyond the orbit of Neptune is the so-called Kuiper belt, its objects are composed of water ice, ammonia and methane. Largest Kuiper Belt Objects discovered on this day are considered to be Sedna, Haumea, Makemake, Quaoar, Orc and Eridu.

There are other populations of small bodies in the solar system, such as planetary quasi-satellites and Trojans, near-Earth asteroids, centaurs, damocloids, as well as comets, meteoroids and cosmic dust moving through the system.

The solar wind (a stream of plasma from the Sun) creates a bubble in the interstellar medium called heliosphere, which extends to the edge of the scattered disk. The hypothetical Oort cloud, which is the source of long-period comets, can extend to a distance of about a thousand times beyond the heliosphere.

The solar system is part of the Milky Way galaxy.

The central object of the system, the Sun, is a so-called yellow dwarf and belongs to the G2V main-sequence stars. Despite this name, the Sun is not a small star at all. Its mass is approximately 99.866% of the mass of the entire system. Approximately 99% of the remaining mass falls on the gas giants (most of this went to Jupiter and Saturn - about 90%).

The movement of most large objects of the solar system occurs in almost one plane, called plane of the ecliptic, but the movement of comets and many Kuiper belt objects often characterizes a large angle of inclination to this plane.

The direction of rotation of all planets and most other objects repeats direction of rotation of the sun, there are exceptions to this rule, for example, Halley's comet.

Mercury has the highest angular velocity - it spends 88 Earth days for a complete revolution around the Sun, and for the most distant planet, Neptune, one revolution around the Sun occurs in 165 Earth years.

For most planets, the direction of rotation around its axis and the direction of rotation around the Sun are the same, the exceptions to this rule are Venus and Uranus. Venus rotates in the opposite direction, and very slowly, one revolution occurs in 243 Earth days, and the axis of rotation of Uranus is inclined to the axis of the ecliptic by almost 90 °, practically it “lies on its side”.

Many planets in the solar system have moons, some of which are larger than Mercury. Often large satellites rotate synchronously, which means that the satellite is always turned to the planet on one side.

The science

Spacecraft that study the planets today:

Planet Mercury

Of the terrestrial planets, perhaps the least of all researchers paid attention to Mercury. Unlike Mars and Venus, Mercury in this group is the least reminiscent of Earth.. It is the smallest planet in the solar system and the closest to the sun.

Photos of the planet's surface taken by the Messenger unmanned spacecraft in 2011 and 2012

So far, only 2 spacecraft have been sent to Mercury - "Mariner-10"(NASA) and "Messanger"(NASA). The first apparatus in 1974-75 circumnavigated the planet three times and came as close as possible to Mercury at a distance 320 kilometers.

Thanks to this mission, thousands of useful photographs were obtained, conclusions were drawn regarding night and day temperatures, relief, and the atmosphere of Mercury. Its magnetic field was also measured.

Spacecraft "Mariner-10" before launch

Information received from the ship "Mariner-10", was not enough, so in 2004 Americans launched a second apparatus to study Mercury - "Messanger", which made it to the orbit of the planet March 18, 2011.

Work on the Messenger spacecraft at the Kennedy Space Center, Florida, USA

Despite the fact that Mercury is a relatively close planet from the Earth, in order to enter its orbit, the spacecraft "Messanger" it took over 6 years. This is due to the fact that it is impossible to get directly from the Earth to Mercury due to the high speed of the Earth, so scientists should develop complex gravity maneuvers.

Spacecraft "Messanger" in flight (computer image)

"Messanger" is still orbiting Mercury and continues to make discoveries, though the mission was scheduled for a shorter period. The task of scientists when working with the apparatus is to find out what is the geological history of Mercury, what magnetic field the planet has, what is the structure of its core, what unusual materials are at the poles, and so on.

At the end of November 2012 using the device "Messanger" researchers were able to make an incredible and rather unexpected discovery: At the poles of Mercury there is water in the form of ice.

Craters at one of the poles of Mercury where water was found

The strangeness of this phenomenon lies in the fact that, since the planet is located very close to the Sun, the temperature on its surface can rise up to 400 degrees Celsius! However, due to the tilt of the axis, the planet's poles are located in the shadow, where low temperatures persist, so the ice does not melt.

Future flights to Mercury

A new Mercury exploration mission is currently under development called "Bepi Colombo", which is a collaboration between the European Space Agency (ESA) and JAXA from Japan. This ship is scheduled to launch in 2015, although he can finally reach the goal only after 6 years.

The BepiColombo project will include two spacecraft, each with its own tasks

The Russians also plan to launch their ship to Mercury "Mercury-P" in 2019. However, launch date likely to be pushed back. This interplanetary station with a lander will be the first ship to land on the surface of the closest planets to the Sun.

Planet Venus

The inner planet Venus, a neighbor of the Earth, has been extensively explored by space missions, starting since 1961. Since this year, Soviet spacecraft began to be sent to the planet - "Venus" And "Vega".

Comparison of the planets Venus and Earth

Flights to Venus

At the same time, the Americans explored the planet using spacecraft "Marier", "Pioner-Venus-1", "Pioner-Venus-2", "Magellan". The European Space Agency is currently working with the spacecraft "Venus Express", which operates since 2006. In 2010 The Japanese ship went to Venus "Akatsuki".

Apparatus "Venus Express" reached the destination in April 2006. It was planned that this ship would complete the mission in 500 days or 2 Venusian years, but over time the mission was extended.

Spacecraft "Venera-Express" in operation according to the artist's ideas

The aim of this project was to study in more detail the complex chemical composition of the planet, the characteristics of the planet, the interaction between the atmosphere and the surface, and more. Scientists also want to know more about the history of the planet and understand why a planet so similar to the Earth went a completely different evolutionary path.

"Venus-Express" during construction

Japanese spacecraft "Akatsuki", also known as PLANET-C, was launched in May 2010, but after approaching Venus December, could not reach its orbit.

What to do with this device is not yet clear, but scientists do not lose hope that it is still can complete his task albeit very late. Most likely, the ship did not enter orbit due to problems with a valve in the fuel line, which caused the engine to stop prematurely.

New spaceships

November 2013 planned to launch "European explorer of Venus"- the probe of the European Space Agency, which is being prepared to study the atmosphere of our neighbor. The project will include two satellites, which, turning around the planet in different orbits, will collect the necessary information.

The surface of Venus is hot, and Earth ships should have good protection.

Also in 2016 Russia plans to send a spacecraft to Venus "Venus-D" to study the atmosphere and surface in order to find out Where did the water from this planet go?

The descent vehicle and balloon probe will have to work on the surface of Venus about a week.

The planet Mars

Today, Mars is studied and explored most intensively, and not only because this planet is so close to Earth, but also because conditions on Mars are closest to those on Earth, therefore, extraterrestrial life is primarily looked for there.

Currently working on Mars three orbiting satellites and 2 rovers, and before them, Mars was visited by a huge number of terrestrial spacecraft, some of which, unfortunately, failed.

In October 2001 NASA orbiter "Mars Odysseus" went into orbit around the Red Planet. He allowed to put forward the assumption that under the surface of Mars there may be deposits of water in the form of ice. It's confirmed in 2008 after years of exploring the planet.

Mars Odysseus probe (computer image)

Apparatus "Mars Odysseus" successfully operates today, which is a record for the duration of the operation of such devices.

In 2004 in different parts of the planet Gusev crater and on meridian plateau rovers landed accordingly "Spirit" And "Opportunity", which were supposed to find evidence of the existence of liquid water on Mars in the past.

rover "Spirit" stuck in the sand after 5 years of successful work, and eventually communication with him was interrupted from March 2010. Because of the harsh winter on Mars, the temperature was not enough to keep the batteries running. Project's second rover "Opportunity" also turned out to be quite tenacious and is still working on the Red Planet.

Panorama of Erebus crater taken by the Opportunity rover in 2005

From August 6, 2012 NASA's newest rover is working on the surface of Mars "Curiosity", which is several times larger and heavier than previous rovers. Its task is to analyze the Martian soil and atmospheric components. But the main task of the device is to establish, Is there life on Mars, or perhaps she's been here in the past. It is also a task to obtain detailed information about the geology of Mars and its climate.

Comparison of rovers from smallest to largest: Sojourner, Oppotunity and Curiosity

Also with the help of the rover "Curiosity" researchers want to prepare for human flight to the red planet. During the mission, traces of oxygen and chlorine were found in the Martian atmosphere, and traces of a dried-up river were also found.

The Curiosity rover in action. February 2013

A couple of weeks ago, the rover managed to drill small hole in the ground Mars, which turned out to be not red at all, but gray. Soil samples from a shallow depth were taken by the rover for analysis.

Using a drill, a hole 6.5 centimeters deep was made in the ground and samples were taken for analysis.

Missions to Mars in the future

In the near future, researchers from various space agencies are planning more multiple missions to Mars, the purpose of which is to obtain more detailed information about the Red Planet. Among them is an interplanetary probe "MAVEN"(NASA), which will go to the Red Planet in November 2013.

European mobile laboratory planned to go to Mars in 2018, which will continue to work "Curiosity", will be engaged in soil drilling and sample analysis.

Russian automatic interplanetary station "Phobos-Grunt 2" planned for launch in 2018 and is also going to take soil samples from Mars to bring back to Earth.

Work on the device "Phobos-Grunt 2" after an unsuccessful attempt to launch "Phobos-Grunt-1"

As you know, beyond the orbit of Mars is asteroid belt, which separates the terrestrial planets from the rest of the outer planets. Very few spacecraft have been sent to the far corners of our solar system, which is due to huge energy costs and other complexities of flying over such vast distances.

Basically, Americans prepared space missions for distant planets. In the 70s of the last century the parade of planets was observed, which happens very rarely, so it was impossible to miss such an opportunity to fly around all the planets at once.

Planet Jupiter

So far, only NASA spacecraft have been launched to Jupiter. Late 1980s - early 1990s The USSR planned their missions, however, due to the collapse of the Union, they were never implemented.

The first vehicles that flew up to Jupiter were "Pioneer-10" And "Pioneer-11", which approached the giant planet in 1973-74 years. In 1979 high-resolution images were taken by devices Voyagers.

The last spacecraft orbiting Jupiter was "Galileo" whose mission began in 1989, but ended in 2003. This device was the first to enter the orbit of the planet, and not just fly by. He helped to study the atmosphere of the gas giant from the inside, its satellites, and also helped to observe the fall of fragments comet Shoemakerov-Levy 9 that crashed into Jupiter in July 1994.

Galileo spacecraft (computer image)

With the help of the device "Galileo" managed to fix severe thunderstorms and lightning in the atmosphere of Jupiter, which are a thousand times stronger than the earth! The device also captured Jupiter's Great Red Spot, which astronomers have replaced yet 300 years ago. The diameter of this giant storm is larger than the diameter of the Earth.

Discoveries were also made related to the satellites of Jupiter - very interesting objects. For example, "Galileo" helped to establish that under the surface of Europa's satellite there is ocean of liquid water, and the satellite Io has its magnetic field.

Jupiter and its moons

After completing the mission "Galileo" melted in Jupiter's upper atmosphere.

Flight to Jupiter

In 2011 NASA launched a new device to Jupiter - a space station "Juno", which must reach the planet and go into orbit in 2016. Its purpose is to help in the study of the planet's magnetic field, as well as "Juno" should find out if Jupiter has hard core Or is it just a hypothesis.

Spacecraft "Juno" will reach the goal only after 3 years

Last year, the European Space Agency announced its intention to prepare for 2022 new European-Russian mission to study Jupiter and its satellites Ganymede, Callisto and Europa. The plans also include landing the device on the Ganymede satellite. in 2030.

Planet Saturn

For the first time, an apparatus flew up to the planet Saturn at a close distance "Pioneer-11" and this happened in 1979. A year later the planet visited Voyager 1, and a year later Voyager 2. These three devices flew past Saturn, but managed to make a lot of useful images for researchers.

Detailed images of Saturn's famous rings were taken, the planet's magnetic field was discovered, and powerful storms were seen in the atmosphere.

Saturn and its moon Titan

It took 7 years for an automatic space station "Cassini-Huygens", to in July 2007 enter the orbit of the planet. This apparatus, consisting of two elements, was supposed, in addition to Saturn itself, to study its Titan's largest moon, which was successfully completed.

Cassini-Huygens spacecraft (computer image)

Saturn's moon Titan

The existence of liquid and atmosphere on the Titan satellite has been proven. Scientists have suggested that the satellite is quite the simplest forms of life can exist, however, this still needs to be proven.

Photo of Saturn's moon Titan

At first it was planned that the mission "Cassini" will be until 2008, but later it was extended several times. In the near future, new joint missions of Americans and Europeans to Saturn and its satellites are planned. Titan and Enceladus.

Planets Uranus and Neptune

These distant planets, which are not visible to the naked eye, are mostly studied by astronomers from Earth. with telescopes. The only apparatus that approached them was Voyager 2, which, having visited Saturn, went to Uranus and Neptune.

At first Voyager 2 flew past Uranus in 1986 and took pictures up close. Uranus turned out to be completely inexpressive: storms or cloud bands that other giant planets have were not noticed on it.

Voyager 2 flying past Uranus (computer image)

With the help of a spacecraft Voyager 2 found a lot of details, including rings of Uranus, new satellites. Everything we know about this planet today is thanks to Voyager 2, which swept past Uranus at great speed and took several pictures.

Voyager 2 flying past Neptune (computer image)

In 1989 Voyager 2 got to Neptune, taking pictures of the planet and its satellite. Then it was confirmed that the planet has magnetic field and the Great Dark Spot, which is a persistent storm. Neptune has also been found to have faint rings and new moons.

New devices to Uranus are planned to be launched in the 2020s, but exact dates have not yet been announced. NASA intends to send not only an orbiter to Uranus, but also an atmospheric probe.

Spacecraft "Urane Orbiter" heading for Uranus (computer image)

Planet Pluto

In the past the planet, and today dwarf planet Pluto- one of the most distant objects in the solar system, which makes it difficult to study. Flying past other distant planets, neither Voyager 1, neither Voyager 2 it was not possible to visit Pluto, so all our knowledge about this object we got thanks to telescopes.

New Horizons spacecraft (computer render)

Until the end of the 20th century astronomers were not particularly interested in Pluto, and all their forces were thrown into the study of closer planets. Due to the remoteness of the planet, large costs were required, especially so that a potential device could be powered by energy while away from the Sun.

Finally, only at the beginning of 2006 NASA spacecraft successfully launched "New Horizons". He is still on the way: it is planned that in August 2014 it will be next to Neptune, and only in July 2015.

Rocket launch with the New Horizons spacecraft from Cape Canaveral, Florida, USA, 2006

Unfortunately, modern technology will not yet allow the device to enter Pluto's orbit and slow down, so it just will pass by a dwarf planet. Within six months, researchers will have the opportunity to study the data they will receive using the apparatus. "New Horizons".

In January 2016, scientists announced that there might be another planet in the solar system. Many astronomers are looking for it, studies so far lead to ambiguous conclusions. Nevertheless, the discoverers of Planet X are confident in its existence. talks about the latest results of work in this direction.

On the possible detection of Planet X beyond the orbit of Pluto, astronomers and Konstantin Batygin from the California Institute of Technology (USA). The ninth planet of the solar system, if it exists, is about 10 times heavier than the Earth, and in its properties resembles Neptune, a gas giant, the most distant known planet revolving around our star.

According to the authors, the period of revolution of Planet X around the Sun is 15 thousand years, its orbit is highly elongated and inclined relative to the plane of the earth's orbit. The maximum distance from the Sun of Planet X is estimated at 600-1200 astronomical units, which brings its orbit beyond the Kuiper belt, in which Pluto is located. The origin of Planet X is unknown, but Brown and Batygin believe that this cosmic object was knocked out of a protoplanetary disk near the Sun 4.5 billion years ago.

Astronomers discovered this planet theoretically by analyzing the gravitational perturbation it exerts on other celestial bodies in the Kuiper belt - the trajectories of six large trans-Neptunian objects (that is, located beyond the orbit of Neptune) turned out to be combined into one cluster (with similar perihelion arguments, ascending node longitude and inclination). Brown and Batygin initially estimated the probability of error in their calculations at 0.007 percent.

Where exactly is Planet X - it is not known what part of the celestial sphere should be tracked by telescopes - it is not clear. The celestial body is located so far from the Sun that it is extremely difficult to notice its radiation with modern means. And the evidence for the existence of Planet X, based on its gravitational influence on celestial bodies in the Kuiper belt, is only circumstantial.

Video: caltech / YouTube

In June 2017, astronomers from Canada, the UK, Taiwan, Slovakia, the US, and France searched for Planet X using the Outer Solar System Origins Survey (OSSOS) catalog of trans-Neptunian objects. The elements of the orbit of eight trans-Neptunian objects were studied, the movement of which Planet X would have to influence - the objects would be grouped in a certain way (clustered) according to their inclinations. Among the eight objects, four are considered for the first time, all of them are more than 250 astronomical units away from the Sun. It turned out that the parameters of one object, 2015 GT50, do not fit into the clustering, which cast doubt on the existence of Planet X.

However, the discoverers of Planet X believe that the 2015 GT50 does not contradict their calculations. As Batygin noted, numerical modeling of the dynamics of the solar system, including Planet X, shows that outside the semi-major axis of 250 astronomical units, there should be two clusters of celestial bodies whose orbits are aligned by Planet X: one is stable, the second is metastable. Although the 2015 GT50 object is not included in any of these clusters, it is still reproduced by the simulation.

Batygin believes that there may be several such objects. Probably, the position of the minor semiaxis of Planet X is connected with them. The astronomer emphasizes that since the publication of data on Planet X, not six, but 13 trans-Neptunian objects indicate its existence, of which 10 celestial bodies belong to a stable cluster.

While some astronomers doubt Planet X, others are finding new evidence in its favor. Spanish scientists Carlos and Raul de la Fuente Marcos investigated the parameters of the orbits of comets and asteroids in the Kuiper belt. The detected anomalies in the movement of objects (correlations between the longitude of the ascending node and inclination) are easily explained, according to the authors, by the presence of a massive body in the solar system, the semi-major axis of the orbit of which is 300-400 astronomical units.

Moreover, in the solar system there may be not nine, but ten planets. Recently, astronomers from the University of Arizona (USA) discovered another celestial body in the Kuiper belt, with dimensions and mass close to Mars. Calculations show that the hypothetical tenth planet is at a distance of 50 astronomical units from the star, and its orbit is inclined to the ecliptic plane by eight degrees. The celestial body perturbs known objects from the Kuiper belt and, most likely, was closer to the Sun in ancient times. Experts note that the observed effects are not explained by the influence of Planet X, located much further than the "second Mars".

Currently, about two thousand trans-Neptunian objects are known. With the introduction of new observatories, in particular LSST (Large Synoptic Survey Telescope) and JWST (James Webb Space Telescope), scientists plan to bring the number of known objects in the Kuiper belt and beyond to 40,000. This will allow not only to determine the exact parameters of the trajectories of trans-Neptunian objects and, as a result, indirectly prove (or disprove) the existence of Planet X and the “second Mars”, but also directly detect them.

The solar system is a group of planets revolving in certain orbits around a bright star - the Sun. This luminary is the main source of heat and light in the solar system.

It is believed that our system of planets was formed as a result of the explosion of one or more stars and this happened about 4.5 billion years ago. At first, the solar system was a collection of gas and dust particles, however, over time and under the influence of its own mass, the Sun and other planets arose.

Planets of the solar system

In the center of the solar system is the Sun, around which eight planets move in their orbits: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

Until 2006, Pluto also belongs to this group of planets, it was considered the 9th planet from the Sun, however, due to its considerable distance from the Sun and its small size, it was excluded from this list and called a dwarf planet. Rather, it is one of several dwarf planets in the Kuiper belt.

All the above planets are usually divided into two large groups: the terrestrial group and the gas giants.

The terrestrial group includes such planets as: Mercury, Venus, Earth, Mars. They are distinguished by their small size and rocky surface, and in addition, they are located closer than the others to the Sun.

The gas giants include: Jupiter, Saturn, Uranus, Neptune. They are characterized by large sizes and the presence of rings, which are ice dust and rocky pieces. These planets are made up mostly of gas.

Sun

The sun is the star around which all the planets and moons in the solar system revolve. It is made up of hydrogen and helium. The Sun is 4.5 billion years old, only in the middle of its life cycle, gradually increasing in size. Now the diameter of the Sun is 1,391,400 km. In the same number of years, this star will expand and reach the orbit of the Earth.

The sun is the source of heat and light for our planet. Its activity increases or becomes weaker every 11 years.

Due to the extremely high temperatures on its surface, a detailed study of the Sun is extremely difficult, but attempts to launch a special apparatus as close as possible to the star continue.

Terrestrial group of planets

Mercury

This planet is one of the smallest in the solar system, its diameter is 4,879 km. In addition, it is closest to the Sun. This neighborhood predetermined a significant temperature difference. The average temperature on Mercury during the day is +350 degrees Celsius, and at night it is -170 degrees.

If we focus on the earth's year, then Mercury makes a complete revolution around the sun in 88 days, and one day there lasts 59 earth days. It was noticed that this planet can periodically change the speed of its rotation around the Sun, its distance from it and its position.

There is no atmosphere on Mercury, in connection with this, asteroids often attack it and leave behind a lot of craters on its surface. Sodium, helium, argon, hydrogen, oxygen were discovered on this planet.

A detailed study of Mercury presents great difficulties due to its close proximity to the Sun. Mercury can sometimes be seen from Earth with the naked eye.

According to one theory, it is believed that Mercury was previously a satellite of Venus, however, this assumption has not yet been proven. Mercury has no satellite.

Venus

This planet is the second from the Sun. In size, it is close to the diameter of the Earth, the diameter is 12,104 km. In all other respects, Venus is significantly different from our planet. A day here lasts 243 Earth days, and a year - 255 days. The atmosphere of Venus is 95% carbon dioxide, which creates a greenhouse effect on its surface. This leads to the fact that the average temperature on the planet is 475 degrees Celsius. The atmosphere also includes 5% nitrogen and 0.1% oxygen.

Unlike the Earth, most of whose surface is covered with water, there is no liquid on Venus, and almost the entire surface is occupied by solidified basaltic lava. According to one theory, there used to be oceans on this planet, however, as a result of internal heating, they evaporated, and the vapors were carried away by the solar wind into outer space. Near the surface of Venus, weak winds blow, however, at an altitude of 50 km, their speed increases significantly and amounts to 300 meters per second.

There are many craters and hills on Venus, reminiscent of terrestrial continents. The formation of craters is associated with the fact that earlier the planet had a less dense atmosphere.

A distinctive feature of Venus is that, unlike other planets, its movement does not occur from west to east, but from east to west. It can be seen from Earth even without the help of a telescope after sunset or before sunrise. This is due to the ability of its atmosphere to reflect light well.

Venus has no satellite.

Earth

Our planet is located at a distance of 150 million km from the Sun, and this allows us to create on its surface a temperature suitable for the existence of water in liquid form, and, therefore, for the emergence of life.

Its surface is 70% covered with water, and it is the only one of the planets that has such an amount of liquid. It is believed that many thousands of years ago, the steam contained in the atmosphere created the temperature on the Earth's surface necessary for the formation of water in liquid form, and solar radiation contributed to photosynthesis and the birth of life on the planet.

A feature of our planet is that under the earth's crust there are huge tectonic plates that, moving, collide with each other and lead to a change in the landscape.

The diameter of the Earth is 12,742 km. An Earth day lasts 23 hours 56 minutes 4 seconds, and a year - 365 days 6 hours 9 minutes 10 seconds. Its atmosphere is 77% nitrogen, 21% oxygen and a small percentage of other gases. None of the atmospheres of other planets in the solar system has such an amount of oxygen.

According to scientists, the age of the Earth is 4.5 billion years, about the same time its only satellite, the Moon, exists. It is always turned to our planet with only one side. There are many craters, mountains and plains on the surface of the Moon. It reflects sunlight very weakly, so it can be seen from Earth in a pale moonshine.

Mars

This planet is the fourth in a row from the Sun and is 1.5 times more distant from it than the Earth. The diameter of Mars is smaller than Earth's and is 6,779 km. The average air temperature on the planet ranges from -155 degrees to +20 degrees at the equator. The magnetic field on Mars is much weaker than that of the Earth, and the atmosphere is quite rarefied, which allows solar radiation to freely affect the surface. In this regard, if there is life on Mars, it is not on the surface.

When surveyed with the help of rovers, it was found that there are many mountains on Mars, as well as dried riverbeds and glaciers. The surface of the planet is covered with red sand. Iron oxide gives Mars its color.

One of the most frequent events on the planet are dust storms, which are voluminous and destructive. Geological activity on Mars could not be detected, however, it is reliably known that significant geological events took place on the planet earlier.

The atmosphere of Mars is 96% carbon dioxide, 2.7% nitrogen and 1.6% argon. Oxygen and water vapor are present in minimal quantities.

A day on Mars is similar in duration to that on Earth and is 24 hours 37 minutes 23 seconds. A year on the planet lasts twice as long as the earth - 687 days.

The planet has two moons Phobos and Deimos. They are small and uneven in shape, reminiscent of asteroids.

Sometimes Mars is also visible from Earth with the naked eye.

gas giants

Jupiter

This planet is the largest in the solar system and has a diameter of 139,822 km, which is 19 times larger than the earth. A day on Jupiter lasts 10 hours, and a year is approximately 12 Earth years. Jupiter is mainly composed of xenon, argon, and krypton. If it were 60 times larger, it could become a star due to a spontaneous thermonuclear reaction.

The average temperature on the planet is -150 degrees Celsius. The atmosphere is made up of hydrogen and helium. There is no oxygen or water on its surface. There is an assumption that there is ice in the atmosphere of Jupiter.

Jupiter has a huge number of satellites - 67. The largest of them are Io, Ganymede, Callisto and Europa. Ganymede is one of the largest moons in the solar system. Its diameter is 2634 km, which is approximately the size of Mercury. In addition, a thick layer of ice is visible on its surface, under which there may be water. Callisto is considered the oldest of the satellites, since it is its surface that has the largest number of craters.

Saturn

This planet is the second largest in the solar system. Its diameter is 116,464 km. It is most similar in composition to the Sun. A year on this planet lasts quite a long time, almost 30 Earth years, and a day is 10.5 hours. The average surface temperature is -180 degrees.

Its atmosphere consists mainly of hydrogen and a small amount of helium. Thunderstorms and auroras often occur in its upper layers.

Saturn is unique in that it has 65 moons and several rings. The rings are made up of small ice particles and rock formations. Ice dust perfectly reflects light, so the rings of Saturn are very clearly visible in a telescope. However, he is not the only planet to have a diadem, it is just less noticeable on other planets.

Uranus

Uranus is the third largest planet in the solar system and the seventh from the sun. It has a diameter of 50,724 km. It is also called the "ice planet", as the temperature on its surface is -224 degrees. A day on Uranus lasts 17 hours, and a year is 84 Earth years. At the same time, summer lasts as long as winter - 42 years. Such a natural phenomenon is due to the fact that the axis of that planet is located at an angle of 90 degrees to the orbit, and it turns out that Uranus, as it were, "lies on its side."

Uranus has 27 moons. The most famous of them are: Oberon, Titania, Ariel, Miranda, Umbriel.

Neptune

Neptune is the eighth planet from the Sun. In its composition and size, it is similar to its neighbor Uranus. The diameter of this planet is 49,244 km. A day on Neptune lasts 16 hours, and a year is equal to 164 Earth years. Neptune belongs to the ice giants and for a long time it was believed that no weather events occur on its icy surface. However, it has recently been found that Neptune has raging eddies and wind speeds the highest of the planets in the solar system. It reaches 700 km / h.

Neptune has 14 moons, the most famous of which is Triton. It is known that it has its own atmosphere.

Neptune also has rings. This planet has 6.

Interesting facts about the planets of the solar system

Compared to Jupiter, Mercury appears to be a dot in the sky. These are actually the proportions in the solar system:

Venus is often called the Morning and Evening Star, since it is the first of the stars visible in the sky at sunset and the last to disappear from visibility at dawn.

An interesting fact about Mars is the fact that methane was found on it. Due to the rarefied atmosphere, it is constantly evaporating, which means that the planet has a constant source of this gas. Such a source can be living organisms inside the planet.

Jupiter has no seasons. The biggest mystery is the so-called "Great Red Spot". Its origin on the surface of the planet is still not fully understood. Scientists suggest that it is formed by a huge hurricane that has been rotating at a very high speed for several centuries.

An interesting fact is that Uranus, like many planets in the solar system, has its own system of rings. Due to the fact that the particles that make up their composition reflect light poorly, the rings could not be detected immediately after the discovery of the planet.

Neptune has a rich blue color, so it was named after the ancient Roman god - the master of the seas. Due to its remote location, this planet was one of the last to be discovered. At the same time, its location was calculated mathematically, and over time it could be seen, and it was in the calculated place.

Light from the Sun reaches the surface of our planet in 8 minutes.

The solar system, despite its long and thorough study, is still fraught with many mysteries and mysteries that have yet to be revealed. One of the most fascinating hypotheses is the assumption of the presence of life on other planets, the search for which is actively continuing.