Modern research of the solar system. New scientific research of the planets of the solar system Exploration of giant planets by spacecraft

Exploring the Planets of the Solar System

Until the end of the 20th century, it was believed that there are nine planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto. But in Lately many objects have been discovered beyond the orbit of Neptune, some of which are similar to Pluto, and others even larger in size. Therefore, in 2006, astronomers clarified the classification: the 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 planets. terrestrial group, and the next 4 massive gas bodies are called giant planets. Dwarf planets mainly inhabit the region 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 dwarf planets, most satellites of the planets and is not much inferior in size to Mercury. On the moon there is no atmosphere familiar to us, 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 of up to 300 degrees last for two weeks. And 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 acquaintance with 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 spacecraft with astronauts. The Soviet automatic stations Luna-3 (1959) and Zond-3 (1965) for the first time photographed the eastern and western parts of the lunar hemisphere invisible from Earth. Artificial satellites of the moon investigated its gravitational field and relief. Self-propelled vehicles "Lunokhod-1 and -2" transmitted to the Earth a lot of images and information about the physical and mechanical properties of the soil. Twelve American Astronauts Using Apollo Spacecraft 1969-1972 visited the Moon, where they carried out surface studies at six different landing sites on the visible side, installed scientific equipment there and brought about 400 kg of lunar rocks to Earth. The probes "Luna-16, -20 and -24" in the automatic mode performed drilling and delivered the lunar soil to the 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 discovered on the surface deposits of hydrogen-containing materials, possibly water ice. In particular, an increased concentration of these materials was found in constantly shaded depressions near the poles.

China's Chanye-1, launched on October 24, 2007, took photographs of the lunar surface and collected data to compile a digital elevation model. On March 1, 2009, the device was dropped onto the lunar surface. On November 8, 2008, the Indian Chandrayan 1 spacecraft was launched into selenocentric orbit. On November 14, a probe separated from it, which made a hard landing in the region of the south pole of the moon. The device 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, which operated in 2007-2009, carried out a scientific program for the exploration of the Moon 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 exploration of the Moon was the launch on June 18, 2009 of two American spacecraft, Lunar Reconnaissance Orbiter (Lunar orbital reconnaissance) and LCROSS (satellite for observation and detection of lunar craters). On October 9, 2009, LCROSS was sent to Cabeo Crater. At first, the spent stage of the Atlas-V rocket weighing 2.2 tons fell to the bottom of the crater. About four minutes later, the LCROSS AMS (weighing 891 kg) fell there, which rushed through the dust cloud raised by the stage, before falling, having done the necessary research until the death of the device. American researchers believe that they still managed to find some water in a cloud of moon dust. Lunar Orbital Scout continues to explore the Moon from polar circumlunar orbit. A Russian instrument LEND (lunar research neutron detector), designed to search for frozen water, is installed on board the spacecraft. In the South Pole area, he found a large amount of hydrogen, which may be an indication 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, of two celestial bodies - the Earth and the Sun at an average distance of 384 400 km from the Earth. At the apogee, this distance increases to 405,500 km, at perigee it decreases to 363,300 km. The period of the Moon's revolution around the Earth in relation 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 with 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 not visible from Earth is called reverse side The moon. The figure formed by the physical surface of the Moon is very close to a regular sphere with an average radius of 1,737.5 km. The surface area of ​​the lunar ball is about 38 million km 2, which is only 7.4% of the earth's surface, 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 significantly 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. In summer noon, near the equator, the surface heats up to + 130 ° C, in some places and higher; and at night the temperature drops to -170 ° С. Rapid cooling of the surface is also observed during lunar eclipses. Regions of two types are distinguished on the Moon: light - continental, occupying 83% of the entire surface (including the reverse side), and dark areas called seas. Such a division arose back in the middle of the 17th century, when it was assumed that there really was water on the moon. In terms of the mineralogical composition and the 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 not yet completely clear. The 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 one think that both of these bodies were not in the past a single whole. Most of the large craters and huge depressions (multi-ring basins) appeared on the surface of the lunar ball during the period of strong bombardment of the surface. About 3.5 billion years ago, as a result of internal heating from the bowels of the Moon, basalt lavas poured onto the surface, filling lowlands and round depressions. This is how the lunar seas were formed. On the reverse side, due to the thicker bark, there were significantly fewer effusions. On the visible hemisphere, seas occupy 30% of the surface, and on the opposite, only 3%. Thus, the evolution of the lunar surface was basically completed about 3 billion years ago. The meteorite bombardment continued, but with less intensity. As a result of long-term processing of the surface, the upper loose layer of the lunar rocks - regolith, several meters thick was formed.

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 located at an average distance of 58 million km or 0.39 AU. from the sun. Moving in a highly elongated orbit, at perihelion it approaches the Sun at a distance of 0.31 AU, and at the maximum distance it is at a distance of 0.47 AU, making a complete revolution in 88 Earth days. In 1965, using the methods of radar from the Earth, it was established that the rotation period of this planet is 58.6 days, that is, in 2/3 of its year it completes a full revolution around its axis. The addition of the axial and orbital motions leads to the fact that, being on the Sun-Earth line, Mercury is always turned by the same side to us. A solar day (the time interval between the upper or lower climaxes of the Sun) lasts 176 Earth days on the planet.

At the end of the 19th century, astronomers tried to sketch the dark and light details seen on the surface of Mercury. The best known are the work of Schiaparelli (1881-1889) and the American astronomer Percival Lovell (1896-1897). Interestingly, astronomer T.J.Ce even announced in 1901 that he had seen craters on Mercury. Few believed this, but later the 625-kilometer crater (Beethoven) ended up in the place marked by Xi. The French astronomer Eugene Antoniadi made a map of the "visible hemisphere" of Mercury in 1934, since then it was believed that only one of its hemisphere was always illuminated. Antoniadi gave names to individual details on this map, which are partially used on modern maps.

The American space probe Mariner 10, launched in 1973, was the first to compile truly reliable maps of the planet and see fine details of the surface relief. 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 captured, mainly in 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 planet's radius (2439 km) and its mass. Temperature sensors made it possible to establish that during the day the temperature of the planet's surface rises to 510 ° C, and at night drops to -210 ° C. The intensity of its magnetic field is about 1% of the intensity 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 acceleration due to gravity on Mercury is 3.68 m / s 2. An astronaut on this planet will 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 planet's surface is dark, reflecting only 12-18 percent of the incident light. The surface layer of the planet (regolith) is highly 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" blowing over 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 revealed.

The American AMS "Messenger" (Messenger - from the English. Courier), launched on August 3, 2004, made its first flyby near Mercury on January 14, 2008 at a distance of 200 km from the planet's surface. She photographed the eastern half of the planet's previously undiscovered hemisphere. Investigations of Mercury were carried out in two stages: first, survey from the flyby trajectory of flight with 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 layer of the soil was measured. The laser altimeter has taken measurements of the heights of the relief of the surface of Mercury. It turned out that the difference in the heights of the relief on this planet is less than 7 km. At the fourth rendezvous, on March 18, 2011, Messenger is to enter the orbit of an artificial satellite of Mercury.

According to the decision of the International Astronomical Union, craters on Mercury are named after figures: writers, poets, painters, 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 also exceptions to this rule - one crater 60 km in diameter with a ray system is named after the famous astronomer Kuiper, and another crater 1.5 km in diameter near the equator, taken as the origin of longitudes on Mercury, is named Hun Kal, which in the language of the ancient Mayans 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 different languages, for example, Sobkou Plain or Odin Plain. There are two plains, named for their location: the Northern Plain and the Heat Plain, which are at 180 ° longitude maximum temperatures. The mountains bordering this plain were called the Heat Mountains. A distinctive feature of the relief of Mercury is the extended ledges, named after sea research vessels. The valleys are named after the radio astronomy observatories. Two ranges 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 us to the Sun and therefore it is illuminated brighter by it; 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 an artificial satellite of Venus, and, nevertheless, we have "images" of the surface, which were obtained by the method of 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 its mass is 81% of the mass of the Earth. Venus revolves around the Sun in the same direction as other planets, making a complete revolution in 225 days. The period of its rotation around the axis (243 days) was determined only in the early 1960s, when radar methods were used to measure the planetary rotation rates. 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 revolution in orbit and rotation around the axis coincide, Venus rotates around the axis in the direction opposite to the orbital motion. Formally, this is not a unique property of Venus. For example, Uranus and Pluto also rotate in the opposite direction. But they rotate practically "lying on their side", and the axis of Venus is almost perpendicular to the orbital plane, so that it is the only "really" rotating in the opposite direction. That is why solar days on Venus are shorter than the time of its revolution around the axis and are 117 Earth days (for other planets, solar days are longer than the rotation period). And 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 that nitrogen there, for example, is five times more in mass than in the Earth's atmosphere.

Foggy haze in the atmosphere of Venus extends upward to an altitude of 48-49 km. Further, up to an altitude of 70 km, there is a cloudy layer containing droplets of concentrated sulfuric acid, and hydrochloric and hydrofluoric acids are also present in the uppermost layers. Venus's clouds reflect 77% of the incident sunlight. At the top of the highest mountains of Venus - the Maxwell Mountains (height about 11 km) - 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 planet's surface is only 1 bar. The powerful atmosphere of Venus, consisting of carbon dioxide, absorbs and partially transmits about 23% of the solar radiation to the surface. This radiation heats the planet's surface, but thermal infrared radiation from the surface travels through the atmosphere back into space with great difficulty. And only when the surface heats up to about 460-470 ° C, the outgoing energy flux turns out to be equal to the one coming to the surface. It is because of this greenhouse effect that the surface of Venus remains hot, regardless of the latitude of the area. But in the mountains, over which the thickness of the atmosphere is less, the temperature is lower by several tens of degrees. 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-Venera (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 captured 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.

The hills account for only 8% of the surface. All the visible relief details have got their names. On the first ground-based radar images of individual parts of the surface of Venus, researchers used various names, of which they now remain on the maps - Maxwell Mountains (the name reflects the role of radiophysics in Venus research), the Alpha and Beta regions (the two brightest in radar images of the relief of Venus 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 decided to call the details of the relief of the surface of Venus by female names. Large elevated areas were named: the Land of Aphrodite, the Land of Ishtar (in honor of the Assyrian goddess of love and beauty) and the Land of Lada (the Slavic goddess of love and beauty). Large craters are named after prominent women of all times and peoples, and small craters are personal female names... On the maps of Venus you can find such names as Cleopatra (the last queen of Egypt), Dashkova (director of the Petersburg Academy of Sciences), Akhmatova (Russian poet) and other famous names. From Russian names there are Antonina, Galina, Zina, Zoya, Lena, Masha, Tatiana and others.

Mars

The fourth planet from the Sun, named after the god of war Mars, is 1.5 times farther from the Earth. One revolution in its orbit takes 687 Earth days for Mars. 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. Such convergence of the planets is called opposition. 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 less than the Earth, and in terms of surface area, it is less than 3.5 times. The period of axial rotation of Mars was determined by ground-based telescopic observations of contrasting surface features: it is 24 hours 39 minutes and 36 seconds. The axis of rotation of Mars is tilted at an angle of 25.2 ° from the perpendicular to the orbital plane. Therefore, on Mars, there is also a change of seasons, but the duration of the seasons is almost twice as long as on Earth. Due to the elongation of the orbit, the seasons in the northern and southern hemispheres have different lengths: summer in the northern hemisphere lasts 177 Martian days, and in the southern it is 21 days shorter, but at the same time 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 is 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 latitude 50 °, the characteristic 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 practically constant (about -60 ° C), regardless of the time of day and season. Large changes in surface temperature are explained by the fact that the atmosphere of Mars is very rarefied, and at night the surface quickly cools down and quickly heats up by the Sun during the day. The atmosphere of Mars is 95% carbon dioxide. Its other components: 2.5% nitrogen, 1.6% argon, less than 0.4% oxygen. The average atmospheric pressure at the surface is 6.1 mbar, that is, 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.

Mars' polar caps are multi-layered. The lower, main layer, several kilometers thick, is formed by ordinary water ice mixed with dust; this layer persists in the summer, forming permanent caps. And the observed seasonal changes in the polar caps are due to the upper layer less than 1 meter thick, consisting of solid carbon dioxide, the so-called "dry ice". The area covered with this layer grows rapidly in winter, reaching a parallel of 50 °, and sometimes even crossing this boundary. In spring, as the temperature rises, the upper layer evaporates, and only a permanent cap remains. The “wave of darkening” of surface areas, observed with the change of seasons, is explained by the change in the direction of the winds, constantly blowing from one pole to the other. 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 equilibrium 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 across the entire Martian ball changes dramatically. The duration of dust storms can reach 50 - 100 days. 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. Detailed maps of the planet were compiled from the photographs of Mariner-9 (1971). He transmitted to Earth 7329 images of Mars with a resolution of up to 100 m, as well as photographs of its satellites - Phobos and Deimos. An entire 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 photographing. Mars-5 carried out remote sensing 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 have been transmitted to Earth. Mars-7 passed at a distance of 1300 km from the surface without fulfilling its program.

The most productive were the flights of two American "Vikings", launched in 1975. 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 II 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 grabbed 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 devices should have recorded this. Although some environmental changes have been observed in a tightly closed container, the presence of a strong oxidizing agent in the soil could have produced the same results. This is why scientists could not confidently attribute these changes to the activity of bacteria. Detailed photographs of the surface of Mars and its satellites were carried out from the orbital stations. 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 hiatus, 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 an artificial satellite of Mars in January 1989. Remote methods obtained data on temperature changes on the surface of Mars and new information on the properties of the rocks that make up Phobos. 38 images were obtained with a resolution of up to 40 m, its surface temperature was measured, which is 30 ° C in the hottest spots. Unfortunately, the main program for the study of Phobos failed. 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 failed to fulfill its mission. Communication with him was lost on August 21, 1993. It was not possible to bring the Russian station "Mars-96" to the flight trajectory to Mars.

One of NASA's most successful projects is the Mars Global Surveyor Station, launched on November 7, 1996, to map the surface of Mars in detail. The device also serves as a telecommunications satellite for Spirit and Opportunity rovers, delivered in 2003 and still in operation. In July 1997, Mars-Pasfinder delivered to the planet the first robotic rover Sogerner weighing less than 11 kg, which successfully explored chemical composition surfaces and meteorological conditions. The rover maintained communication with the Earth through the lander. NASA's Mars Reconnaissance Satellite, an automated interplanetary station, began operations in orbit in March 2006. high resolution on the surface of Mars 30 cm details could be discerned. Mars Odysseus, Mars Express and Mars Reconnaissance Satellite continue their exploration from orbit. The Phoenix apparatus operated in the circumpolar region from May 25 to November 2, 2008. He drilled the surface for the first time and discovered ice. Phoenix brought a digital science fiction library to the planet. Flight programs for astronauts to Mars are being developed. Such an expedition will take more than two years, since in order to return, they will have to wait for the convenient relative position of Earth and Mars.

On modern maps of Mars, along with the names assigned to the landforms, which were identified from space images, the old geographical and mythological names proposed by Schiaparelli are also used. The largest elevated area, about 6,000 km across and up to 9 km high, was named Farsis (as Iran was called on ancient maps), and a huge circular 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 terrain to a height of 26 m. The largest of them is Mount Olympus, located on the western edge of the Arsida mountains, has a base 600 km in diameter and a caldera (crater) at the top with a diameter of 60 km. Three volcanoes - Mount Askrian, Mount Peacock and Mount Arsia - are located on one straight line on the top of the Tarsis mountains. The volcanoes themselves rise 17 km above Tharsis. In addition to these four, more than 70 extinct volcanoes have been found on Mars, but they are much smaller in terms of area and height.

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

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

Phobos and Deimos are natural satellites of Mars

The moons of Mars were discovered during the great opposition of 1877 by the American astronomer A. Hall. They were named Phobos (translated from Greek as Fear) and Deimos (Horror), since in ancient myths the god of war was always accompanied by his children - Fear and Horror. The satellites are very small and irregular in shape. The major axis of Phobos is 13.5 km, and the minor axis is 9.4 km; at Deimos, respectively, 7.5 and 5.5 km. The Mariner 7 probe photographed Phobos against the backdrop 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 flights 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 thousand km away from the planet's surface, and its orbital period is 30 hours 18 minutes. The periods of rotation of the 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 acceleration of gravity on its surface is 0.5 cm / s 2. A man would weigh only a few tens of grams on Phobos and could, by throwing a stone with his hand, make it fly into space forever (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. The largest depression on Deimos is 2 km in diameter. The surfaces of the satellites are dotted with small craters in much the same way as the Moon. Despite the general similarity, the abundance of finely crushed material covering the surfaces of the satellites, Phobos looks more "peeled", and Deimos has a smoother, dusty surface. On Phobos, mysterious grooves have been discovered that intersect 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 of 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, surpassing 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 takes about 12 years to complete one orbit. Despite its gigantic size, this planet rotates very quickly - faster than 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 (among the ancient Greeks - Zeus, among the Romans - Jupiter), it is located five times farther from the Sun than the Earth. Due to its fast rotation, Jupiter will be strongly flattened: its equatorial radius (71,492 km) is 7% larger than the polar one, which is easy to see when observing 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 is no change of 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 that form a system of dark belts and light zones north and south of the equator to the parallels of 40 ° north and south latitude. Clouds form layers of brownish, reddish 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 the period they rotate. So, near the equator, they complete their revolution around the planet's axis in 9 hours 50 minutes, and at mid-latitudes - in 9 hours 55 minutes. Belts and zones are areas of downdrafts and ascents in the atmosphere. Atmospheric currents parallel to the equator are supported by heat flows from deep within 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. Strong turbulent gas movements are observed at the boundaries of belts and zones. Jupiter's hydrogen-helium atmosphere is enormous. 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 spacecraft flights to Jupiter, it was found that the heat flux from the interior of Jupiter is twice the inflow of solar heat received by the planet. This may be due to the slow sinking to the center of the planet of heavier substances and the emergence of lighter ones. The fall of meteorites on the planet can also be a source of energy. The color of the belts is due to 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. The most famous feature of Jupiter is the Great Red Spot, an oval formation of varying dimensions located in the southern tropical zone. At present, it has dimensions of 15,000 × 30,000 km (that is, two worlds 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 very clearly visible. 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 from a close distance (130 thousand km) took place in December 1973 using the Pioneer-10 probe. Observations carried out by this apparatus in ultraviolet rays showed that the planet has extended hydrogen and helium corona. The upper cloud layer appears to be composed of cirrus clouds of ammonia, and 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 recorded at a distance of 177 thousand km from the planet. The trail of Jupiter's magnetosphere is visible even beyond the orbit of Saturn.

The route of Pioneer 11, which flew 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 that is dangerous for electronic equipment. Analysis of the color images of the cloud layer obtained with the 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 flights of "Pioneer-10 and -11" 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 found to impart color to the cloud cover. When heated, it decomposes with the release of red phosphorus. The unique relative position in the orbits of the Earth and the giant planets, which took place from 1976 to 1978, was used for the successive study of Jupiter, Saturn, Uranus and Neptune using the Voyager 1 and -2 probes. Their paths were calculated so 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 be according to the traditional scheme, and the flight to Neptune took 12 years instead of 20. Such mutual arrangement of the planets will be repeated only after 179 years.

Based on the data obtained by space probes and theoretical calculations, mathematical models of Jupiter's cloud cover have been constructed and ideas about its internal structure have been refined. In a somewhat simplified form, Jupiter can be represented as shells with a density increasing towards the center of the planet. At the bottom of the atmosphere 1500 km thick, the density of which grows rapidly with depth, there is a layer of gas-liquid hydrogen about 7000 km thick. 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 layers contain a small amount of heavy elements. The inner core, 25,000 km in diameter, is metallosilicate, containing water, ammonia and methane. The temperature in the center is 23,000 K and the pressure is 50 Mbar. Saturn has a similar structure.

There are 63 known satellites orbiting 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 revolve 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 Teba have diameters from 40 to 270 km and are within 2-3 Jupiter's radii from the center of the planet. They differ sharply from the four satellites following them, located at a distance of 6 to 26 Jupiter's radii and having much larger sizes, close to the size of the Moon. These large moons - 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 - from 1 to 170 km in diameter - satellites moving in elongated orbits strongly inclined to the equator of Jupiter. In this case, five satellites closer to Jupiter move in their orbits in the direction of Jupiter's rotation, and almost all more distant satellites move in the opposite direction. Detailed information on the nature of satellite surfaces was obtained by spacecraft. Let us dwell in more detail on the Galilean satellites. The diameter of the satellite Io, closest to Jupiter, is 3640 km, and its average density is 3.55 g / cm 3. The bowels of Io are warmed up by the tidal influence of Jupiter and the disturbances introduced to the movement of Io by its neighbors - Europa and Ganymede. Tidal forces deform and heat the outer layers of Io. In this case, the accumulated energy breaks out to the surface in the form of volcanic eruptions. From the crater of volcanoes, sulfur dioxide and sulfur vapor are ejected at a speed of about 1 km / s to an altitude of hundreds of kilometers above the satellite's surface. Although around the equator, Io's surface temperature averages about -140 ° C, there are hot spots ranging in size from 75 to 250 km, in which temperatures reach 100-300 ° C. Io's surface is covered in eruption products and is orange in color. The average age of the parts on it is small - about 1 million years. The relief of Io is mostly flat, but there are several mountains ranging in height from 1 to 10 km. Io's atmosphere 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 eruptions - was detected along Io's orbit.

The second of the Galilean satellites, Europa, is slightly 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, which have arisen as a result of tectonic processes. The width of these faults varies from several kilometers to hundreds of kilometers, and the length reaches thousands of kilometers. Estimated crustal thickness ranges from several kilometers to tens of kilometers. In the depths of Europe, the energy of tidal interaction is also released, which maintains the mantle in a liquid form - an under-ice 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 details of this orange-brown surface are estimated to be hundreds of thousands and millions of years old. Galileo's high-resolution imagery shows individual fields of irregular shape 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 carried out from under the ice layer.

According to the American scientist Richard Greenberg, the conditions for life in Europe should be sought not in the deep subglacial ocean, but in numerous cracks. Due to the tidal effect, the cracks periodically narrow and widen to a width of 1 m. When the crack narrows, the ocean water goes down, and when it begins 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. The many craters covering dark brown areas testify to the ancient age of this surface, about 3-4 billion years. 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 several thousand kilometers. Some craters of Ganymede have not only light ray systems (similar to lunar ones), but sometimes also dark ones.

Callisto's diameter 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 in tens of kilometers. The entire surface of this moon is completely dotted with craters of various sizes. There are no extended plains or furrow systems on it. The craters on Callisto have a weakly defined ridge and shallow depth. A unique relief feature is a multi-ring structure with a diameter of 2600 km, consisting of ten concentric rings. The surface temperature at Callisto's equator reaches -120 ° C at noon. The satellite has its own magnetic field.

On December 30, 2000, the Cassini probe, bound for Saturn, passed near Jupiter. 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 of detecting radiation from Jupiter's radiation belts. Interestingly, in parallel with the work of Cassini, the same radiation was recorded with ground-based telescopes by schoolchildren and students in the United States. The results of their research were used along with the data of "Cassini".

As a result of the study of the Galilean satellites, an interesting hypothesis was put forward that in the early stages of their evolution, giant planets emitted huge streams of heat into space. Jupiter's radiation could melt ice on the surface of three Galilean moons. 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, made up mostly of liquid hydrogen and helium. Orbiting the Sun at a distance of 10 times the Earth, Saturn makes a complete revolution in an almost 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 inclined by 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 planet, the second in mass, exceeds the Earth by 800 times in volume and 95 times in mass. 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. The rotation period of Saturn 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. Having studied the motion of Uranus, the French astronomer Le Verrier determined that the seventh planet was influenced 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. Later it turned out that, starting with Galileo, astronomers marked the position of Neptune on maps, but took 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 the mass of Neptune is 17 times larger than our planet. The average density of Neptune is 1.64 g / cm 3. It revolves around the Sun at a distance of 4.5 billion km (30 AU), completing a full cycle in almost 165 Earth years. The orbital plane of the planet is inclined by 1.8 ° to the plane of the ecliptic. The inclination of the equator to the orbital plane 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 about 5,000 km from the surface of the cloud layer of Neptune in 1989, made it possible to see the details of the planet's cloud cover. The stripes on Neptune are weak. A large dark spot the size of our planet, found in the southern hemisphere of Neptune, is a giant anticyclone that makes a complete revolution in 16 Earth days. This is an area of ​​increased pressure and temperature. Unlike the Great Red Spot on Jupiter, which drifts at a speed of 3 m / s, the Great Dark Spot on Neptune moves westward at a speed of 325 m / s. A smaller dark spot located at 74 ° S. sh., in a week it shifted by 2000 km to the north. The light formation in the atmosphere - the so-called "scooter" was also distinguished by a rather 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. Significant amounts of methane appear to be found deeper in the planet's icy mantle. Even at temperatures of thousands of degrees, at a pressure of 1 Mbar, a mixture of water, methane and ammonia can form solid ices. The hot ice 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. The model of the internal structure of the planet shows that the pressure at its center is about 7 Mbar, and the temperature is about 7000 K. Unlike Uranus, the heat flow from the bowels of Neptune is almost three times higher than 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 half 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 displaced 6,000 km to the southern hemisphere, so the magnetic induction at the south magnetic pole is 10 times higher than that of the north.

The rings of Neptune are generally similar to the rings of Uranus, with the only difference that the total area of ​​matter in the rings of Neptune is 100 times less than in the rings of Uranus. Separate arcs of the rings surrounding Neptune have been discovered when stars are covered by the planet. Voyager 2 images show open formations around Neptune, which are called arches. They are located on the 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 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.

Neptune's largest satellite, Triton, revolves around the planet at a distance of 355 thousand km with a period of about 6 days in a circular orbit inclined 23 ° to the planet's equator. Moreover, it is the only one of the inner satellites of Neptune, orbiting in the opposite direction. The period of Triton's axial rotation coincides with its orbital period. The average density of Triton is 2.1 g / cm3. The surface temperature is very low (38 K). On satellite images, most of Triton's surface is a plain with many cracks, which makes it look like a melon crust. The South Pole is surrounded by a light 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 recycled as a result of tectonic activity and the fall of meteorites. Triton appears to have a rocky core with a radius of about 1000 km. It is believed that an ice crust about 180 km thick covers an aquatic ocean about 150 km deep, saturated with ammonia, methane, salts and ions. Triton's thin atmosphere is mostly nitrogen, small amounts of methane and hydrogen. Snow on the surface of Triton is a frost of nitrogen. The polar cap is also formed by nitrogen frost. The amazing formations revealed on the polar cap are 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 other internal satellites, Nereid moves in a very elongated orbit, with its eccentricity (0.75) more similar to the orbit of comets.

Pluto

Pluto, after its discovery in 1930, was considered the smallest planet in the solar system. In 2006, by the decision of the International Astronomical Union, he 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 also includes the asteroid Ceres and several recently discovered objects in the Kuiper belt, beyond the orbit of Neptune; one of them is even larger than Pluto. There is no doubt that other similar objects will be found in the Kuiper belt; so there may be quite a few dwarf planets in the solar system.

Pluto orbits 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 turned 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 twentieth century, there was just such a period: on January 23, 1979, Pluto crossed the orbit of Neptune, so that it was closer to the Sun and formally turned into the eighth planet. He stayed 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 away towards the aphelion (48.8 AU), which he will reach in 2112, and the first full revolution around the Sun after its discovery will complete only in 2176.

To understand the astronomers' interest in Pluto, you need to remember the history of its discovery. At the beginning of the twentieth 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, the gravitational influence of which affects the movement of the known giant planets. Astronomers have even calculated the estimated 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 God underworld- Pluto. However, the discovery, apparently, was accidental: subsequent measurements showed that Pluto's mass is too small for its gravity to noticeably affect the motion of Neptune and, moreover, Uranus. Pluto's orbit 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 satellites, and at times there is 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 reached it; until recently, not even such an attempt was made. But in January 2006, the New Horizons spacecraft (NASA) launched to Pluto, which is supposed to fly by the planet in July 2015.

By measuring the intensity of the sunlight reflected by Pluto, astronomers have established that the apparent brightness of the planet periodically changes. 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 obtained with the best angular resolution: a blurry speck of the image was often shallow 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 of the dead (the ruler of this kingdom, as you know, was Pluto). Charon appears now from the north, now 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 moons were discovered - Hydra and Nyx, orbiting further than Charon, but in the same plane. Thus, Pluto with its moons resembles Uranus, which rotates "lying on its side."

The period of rotation of Charon, which is 6.4 days, coincides with the period of its movement around Pluto. Like the Moon, Charon always faces the planet with one side. This is characteristic of all satellites moving near the planet. Another thing is surprising - Pluto also faces Charon with one and the same side; in this sense they are equal. Pluto and Charon is a unique binary system, very compact and having an unprecedented high satellite-to-planet mass ratio (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 obtained by the Hubble Space Telescope. From them, it was possible 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 clarify 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 is 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 looks more like the ice satellites of the giant planets. Charon's surface is 30% darker than Pluto's. The color of the planet and the satellite is also different. Apparently, they formed independently of each other. Observations have shown that at the perihelion of the orbit, the brightness of Pluto increases markedly. This gave reason to assume the appearance of a temporary atmosphere at Pluto. When the star was covered 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 is most likely nitrogen, while other components may contain methane, argon and neon. The thickness of the haze layer is estimated at 45 km, and the atmosphere itself is 270 km. Methane content should change depending on Pluto's position in orbit. Pluto passed perihelion in 1989. Calculations show that part of the deposits of frozen methane, nitrogen and carbon dioxide, available on its surface in the form of ice and frost, passes into the atmosphere as the planet approaches the Sun. Pluto has a maximum surface temperature of 62 K. Charon's surface appears to be formed by water ice.

So, Pluto is the only planet (albeit a dwarf one), the atmosphere of which sometimes appears, then disappears, like a comet during its movement around the Sun. In May 2005, the Hubble Space Telescope discovered two new satellites of the dwarf planet Pluto, named Nikta and Hydra. The orbits of these satellites are located outside the orbit of Charon. Nikta 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 explore the environs of Pluto and the Kuiper Belt.

This is a system of planets, in the center of which is a bright star, the source of energy, heat and light - the Sun.
According to one theory, the Sun was formed together with the solar system about 4.5 billion years ago as a result of the explosion of one or more supernovae. Initially, the solar system was a cloud of gas and dust particles, which, in motion and under the influence of their mass, formed a disk in which a new star, the Sun and our entire solar system, arose.

In the center of the solar system is the Sun, around which nine large planets revolve in orbits. Since the Sun is displaced from the center of planetary orbits, then during the cycle of revolution around the Sun the planets either approach or move away in their orbits.

Terrestrial planets: and ... These planets are small in size with a rocky surface, they are closer to the Sun than others.

Planets giants: and ... These are large planets, mostly made of gas, and are characterized by rings of ice dust and many rocky pieces.

But does not fall into any group, because, despite being in the solar system, it is located too far from the sun and has a very small diameter, only 2320 km, which is half the diameter of Mercury.

The planets of the solar system

Let's start a fascinating acquaintance with the planets of the solar system in order of their location from the sun, and also consider their main satellites and some other space objects (comets, asteroids, meteorites) in the gigantic expanses of our planetary system.

Rings and moons of Jupiter: Europa, Io, Ganymede, Callisto and others ...
The planet Jupiter is surrounded by a whole family of 16 satellites, and each of them has its own, unlike other features ...

Rings and moons of Saturn: Titan, Enceladus and others ...
Not only the planet Saturn has characteristic rings, but also other giant planets. Around Saturn, the rings are especially clearly visible, because they consist of billions of small particles that revolve around the planet, in addition to several rings, Saturn has 18 satellites, one of which is Titan, its diameter is 5000 km, which makes it the largest satellite of the solar system ...

Rings and moons of Uranus: Titania, Oberon and others ...
The planet Uranus has 17 satellites and, like other giant planets, thin rings encircling the planet, which practically do not have the ability to reflect light, so they were discovered not so long ago in 1977, quite by accident ...

Rings and moons of Neptune: Triton, Nereid and others ...
Initially, before the exploration of Neptune by the Voyager 2 spacecraft, it was known about two satellites of the planet - Triton and Nerida. Interesting fact that the satellite Triton has the opposite direction of orbital motion, strange volcanoes were also discovered on the satellite, which spewed nitrogen gas, like geysers, spreading a dark mass (from a liquid state to vapor) for many kilometers into the atmosphere. During its mission, Voyager 2 discovered six more satellites of the planet Neptune ...

The solar system is a group of planets revolving in specific 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 planetary system was formed as a result of the explosion of one or more stars and this happened about 4.5 billion years ago. Initially, the solar system was an accumulation of gas and dust particles, however, over time and under the influence of its own mass, the sun and other planets arose.

The 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 belongs to this group of planets, it was considered the 9th planet from the Sun, however, due to its significant distance from the Sun and its small size, it was excluded from this list and named 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 to the Sun.

Gas giants include: Jupiter, Saturn, Uranus, Neptune. They are characterized by large sizes and the presence of rings, which are ice dust and rocky lumps. These planets consist mainly of gas.

The sun

The sun is the star around which all the planets and satellites in the solar system revolve. It is composed of hydrogen and helium. The age of the Sun is 4.5 billion years, it is 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 Earth's orbit.

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; attempts to launch a special apparatus as close to the star as possible continue.

Terrestrial group of planets

Mercury

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

If you focus on the Earth 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, distance from it and its position.

There is no atmosphere on Mercury, in this regard, it is often attacked by asteroids and leave behind a lot of craters on its surface. Sodium, helium, argon, hydrogen, oxygen have been discovered on this planet.

A detailed study of Mercury is very difficult due to its close proximity to the Sun. Sometimes Mercury can be seen from Earth with the naked eye.

According to one of the theories, it is believed that Mercury was previously a satellite of Venus, however, it has not yet been possible to prove this assumption. Mercury does not have its own satellite.

Venus

This planet is the second from the Sun. In terms of its size, it is close to the diameter of the Earth; its 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 basalt lava. According to one theory, there were oceans on this planet earlier, however, as a result of internal heating, they evaporated, and the vapors were carried away by the solar wind into outer space. Gentle winds blow near the surface of Venus, 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 that resemble 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 a telescope after sunset or before sunrise. This is due to the ability of its atmosphere to reflect light well.

Venus has no satellite.

Land

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 planet on which there is such an amount of liquid. It is believed that many thousands of years ago, the vapor contained in the atmosphere created the temperature on the Earth's surface to form 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 there are huge tectonic plates under the earth's crust, which, while moving, collide with each other and lead to a change in the landscape.

The diameter of the Earth is 12,742 km. The earth's 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 the rest of the gases. None of the atmospheres of other planets in the solar system has this amount of oxygen.

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

Mars

This planet is the fourth in a row from the Sun and is at a distance of 1.5 times greater than the Earth. The diameter of Mars is smaller than that of the Earth and is 6,779 km. The average air temperature on the planet ranges from -155 degrees to +20 degrees in the equator. The magnetic field on Mars is much weaker than that of the Earth, and the atmosphere is rather thin, which allows solar radiation to influence the surface unhindered. 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 river beds and glaciers. The planet's surface is covered with red sand. Iron oxide gives this color to Mars.

One of the most frequent events on the planet is dust storms, which are voluminous and destructive. It was not possible to detect geological activity on Mars, however, it is reliably known that significant geological events previously took place on the planet.

The atmosphere of Mars is 96% carbon dioxide, 2.7% nitrogen and 1.6% argon. Oxygen and water vapor are found 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 in size 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 the size of 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 composed of hydrogen and helium. There is no oxygen and water on its surface. There is speculation that there is ice in Jupiter's atmosphere.

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 2,634 km, which roughly corresponds to 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 moons, 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 - 10.5 hours. The average surface temperature is -180 degrees.

Its atmosphere is mostly hydrogen and small amounts of helium. Thunderstorms and auroras often occur in its upper layers.

Saturn is unique in that it has 65 moons and multiple rings. The rings are made up of small ice particles and rocky formations. Ice dust perfectly reflects light, so Saturn's rings are very visible through a telescope. However, it is not the only planet to have a tiara, 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 lasts 84 Earth years. Moreover, 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 satellites. The most famous of them are: Oberon, Titania, Ariel, Miranda, Umbriel.

Neptune

Neptune is the eighth planet from the Sun. In 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 phenomena occur on its icy surface. However, it has recently been found that Neptune has violent eddies and wind speeds that are 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 to have its own atmosphere.

Neptune also has rings. This planet has 6 of them.

Interesting facts about the planets of the solar system

Compared to Jupiter, Mercury appears to be a point 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 the beginning of sunset and the last one to disappear from view at dawn.

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

There is no change of seasons on Jupiter. 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 was 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 of the solar system, has its own ring system. Due to the fact that the particles that make up their composition poorly reflect light, the rings could not be detected immediately after the discovery of the planet.

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

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

The solar system, despite its long and careful study, is fraught with many more mysteries and secrets 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.

The solar system in which we live is gradually being studied more and more by earthly researchers.

We will consider the stages and results of the research:

• Mercury,
• Venus,
• Moon,
• Mars,
• Jupiter,
• Saturn,
• Uranus,
• Neptune.

Terrestrial planets and satellite of the Earth

Mercury.

Mercury is the closest planet to the Sun.

In 1973, the American probe "Mariner-10" was launched, with the help of which it was possible for the first time to compile sufficiently reliable maps of the surface of Mercury. In 2008, the eastern hemisphere of the planet was captured for the first time.

However, Mercury remains at the time of 2018 the least studied planet of the terrestrial group - Venus, Earth and Mars. Mercury is small in size, has a disproportionately large molten core, and has less oxidized material than its neighbors.

In October 2018, the Bepi Colombo mission, a joint project of the European and Japanese space agencies, is expected to launch to Mercury. The result of a seven-year journey should be the study of all the features of Mercury and an analysis of the reasons for the appearance of such features.

Venus.

Venus has been explored by more than 20 spacecraft, mainly Soviet and American. The relief of the planet was seen with the help of radar sounding of the planet's surface by the spacecraft Pioneer-Venus (USA, 1978), Venera-15 and -16 (USSR, 1983-84) and Magellan (USA, 1990 -94).

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 captured 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.

From the latest exploration of Venus, we note the mission of the European Space Agency Venus Express to study the planet and the features of its atmosphere. Observation of Venus took place from 2006 to 2015, in 2015 the device burned up in the atmosphere. Thanks to these studies, a picture of the southern hemisphere of Venus was obtained, as well as information about the recent volcanic activity of the giant volcano Idunn, which has a diameter of 200 kilometers, was obtained.

Moon.

The Moon became the first object of close attention from the earthlings.

Back in 1959 and 1965, the Soviet spacecraft Luna - 3 and Zond - 3 for the first time photographed the "dark" hemisphere of a satellite invisible from Earth.

In 1969, humans landed on the moon for the first time. The most famous American astronaut to visit the moon is Neil Amstrong. In total, 12 American expeditions visited the moon with the help of spaceships"Apollo". As a result of research, about 400 kilograms of lunar rock were brought to Earth.

Subsequently, due to the enormous costs of the lunar program, manned flights to the moon ceased. Moon exploration began to be carried out with the help of automatic and controlled from the Earth spacecraft.

In the last quarter of a century, a new stage in the study of the moon has been taking place. As a result of research of the spacecraft "Clementine" in 1994, "Lunar Prospector" in 1998-1999, and "Smart-1" in 2003-2006, Earth researchers were able to obtain newer and more refined data. In particular, deposits of presumably water ice were discovered. A large number of these deposits have been discovered near the poles of the moon.

And in 2007, it was the turn of the Chinese spacecraft. Chanye-1 became such a device, which was launched on October 24. On November 8, 2008, the Indian spacecraft "Chandrayan 1" was launched into lunar orbit. The moon is one of the main goals in the exploration of near space by mankind.

Mars.

The next target of terrestrial explorers is the planet Mars. The first research apparatus, which laid the foundation for the study of the Red Planet, was the Soviet probe "Mars-1". According to the data of the American apparatus "Mariner - 9" obtained in 1971, it was possible to compile detailed maps of the surface of Mars.

With regard to modern research, we note the following research. So, in 2008, the Phoenix spacecraft succeeded in drilling the surface for the first time and discovering ice.

And in 2018, the MARSIS radar, which is installed aboard the European Space Agency's Mars Express orbiter, was able to provide the first evidence that Mars has liquid water. This conclusion follows from a lake of considerable size discovered at the south pole, hidden under the ice.

Giant planets

Jupiter.

Jupiter was first explored at close range in 1973 with the Soviet Pioneer 10 probe. The flights of the American Voyager spacecraft carried out in the 1970s were also of great importance for the study of Jupiter.

From modern research, we note the following fact. In 2017, a team of American astronomers led by Scott S. Sheppard, while searching for a potential ninth planet outside Pluto's orbit, accidentally discovered new moons around Jupiter. There were 12 such moons. As a result, the number of Jupiter's satellites increased to 79.

Saturn.

In 1979, the Pioneer-11 spacecraft, exploring the vicinity of Saturn, was able to detect a new ring near the planet, measure the temperature of the atmosphere and reveal the boundaries of the planet's magnetosphere.

In 1980, Voyager 1 transmitted clear images of Saturn's rings for the first time. From these images, it became clear that Saturn's rings are made up of thousands of individual, narrow rings. Also, 6 new satellites of Saturn were found.

The largest contribution to the study of the giant planet was made by the Cassini spacecraft, which worked in the orbit of Saturn from 2004 to 2017. With the help of it, it was possible to establish, in particular, what the upper atmosphere of Saturn consists of and the features of its chemical interaction with materials that come from the rings.

Uranus.

The planet Uranus was discovered in 1781 by the astronomer V. Herschel. Uranus is an ice giant.

In 1977, it was discovered that Uranus also has its own rings.

Remark 1

The only spacecraft on Earth that has visited Uranus is Voyager 2, which flew past it back in 1986. He photographed the planet, found 2 new rings and 10 new moons of Uranus.

Neptune.

Neptune is a giant planet and the first planet discovered through mathematical calculations.

The only vehicle that has been there so far is Voyager-2. It passed near Neptune in 1989, which allowed us to see some details of the planet's atmosphere, as well as a giant anticyclone, the size of the Earth in the southern hemisphere.

Dwarf planets

Dwarf planets include those celestial bodies that revolve around the Sun and have sufficient mass to maintain their own spherical shape. Such planets are not satellites of other planets, but unlike planets, they cannot clear their orbit from other space objects.

Dwarf planets include such objects as Pluto, excluded from the list of planets, Makemake, Ceres, Haumea and Eris.

Remark 2

Note that there is still controversy about Pluto whether to consider it a planet or a dwarf planet.

Planet Nine

On January 20, 2016, astronomers at the California Institute of Technology Konstantin Batygin and Michael Brown hypothesized the supposed existence of a massive trans-Neptunian planet outside Pluto's orbit. However, until now, planet Nine has not been discovered.