Information about scientific research of planets. Exploration of solar system objects

Exploring the Planets 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 in Lately Many objects were discovered beyond the orbit of Neptune, some of them 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 usually called planets terrestrial group, and the next 4 massive gas bodies are called giant planets. Dwarf planets mainly inhabit the region beyond Neptune's orbit - the Kuiper Belt.

Moon

The Moon is the Earth's natural satellite 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 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 gravity on the Moon is six times less than on Earth. Day and night with temperature changes of up to 300 degrees last for two weeks. And yet, 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 explored 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) were the first to photograph the eastern and western parts of the lunar hemisphere, invisible from Earth. Artificial satellites of the Moon studied its gravitational field and relief. Self-propelled vehicles "Lunokhod-1 and -2" transmitted to Earth many images 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 about 400 kg of lunar rocks to Earth. The Luna-16, -20 and -24 probes automatically drilled 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 discovered deposits of hydrogen-containing materials, possibly water ice, on the surface. In particular, increased concentrations of these materials are found in permanently shadowed depressions near the poles.

The Chinese Chang'e-1 spacecraft, launched on October 24, 2007, photographed the lunar surface and collected data to compile a digital model of its relief. On March 1, 2009, the device was dropped onto the surface of the Moon. On November 8, 2008, the Indian spacecraft Chandrayaan 1 was launched into selenocentric orbit. On November 14, the probe separated from it and made a hard landing near the south pole of the Moon. The device operated for 312 days and transmitted distribution data chemical elements on the surface and on the heights of the relief. The Japanese AWS Kaguya and two additional microsatellites Okina and Oyuna, which operated in 2007-2009, completed scientific program studies 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 study of the Moon was the launch on June 18, 2009 of two American satellites, the Lunar Reconnaissance Orbiter (Lunar Reconnaissance Orbiter) and the LCROSS (lunar crater observation and detection satellite). On October 9, 2009, the LCROSS probe was sent to the Cabeo crater. 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 spacecraft (weighing 891 kg) fell there, which, before falling, rushed through the cloud of dust raised by the stage, having managed to do the necessary research until the destruction of the device. American researchers believe that they still managed to find some water in a cloud of lunar dust. Lunar Orbiter continues to explore the Moon from polar lunar orbit. The Russian LEND (Lunar Research Neutron Detector) instrument, designed to search for frozen water, is installed on board the spacecraft. In the area of ​​the South Pole, he discovered a large amount of hydrogen, which may be a sign of the presence of water in a bound state there.

In the near future, exploration of the Moon will begin. Already today, projects are being developed in detail to create a permanent inhabited base on its surface. The 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 from 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, at perigee it decreases to 363,300 km. The period of revolution of the Moon 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 is repeated 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 Moon rotates around its axis 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 visible; and the other hemisphere is always hidden from our eyes. This hemisphere, not visible from 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 area earth's surface, or about a quarter of the area of ​​the earth's continents. The mass ratio of the Moon and Earth is 1:81.3. The average density of the Moon (3.34 g/cm3) is significantly less than the average density of the Earth (5.52 g/cm3). The gravity on the Moon is six times less than on Earth. On a summer afternoon near the equator, the surface heats 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. There are two types of areas on the Moon: light - continental, occupying 83% of the entire surface (including the far side), and dark areas called seas. This division arose in the middle of the 17th century, when it was assumed that there was actually water on the Moon. In terms of mineralogical composition and the content of individual chemical elements, lunar rocks on dark areas of the surface (seas) are very close to terrestrial rocks such as basalts, and on light areas (continents) - to anorthosites.

The question of the origin of the Moon is not yet completely clear. The chemical composition of lunar rocks suggests that the Moon and 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 a period of heavy bombardment of the surface. About 3.5 billion years ago, as a result of internal heating, basaltic lavas poured out onto the surface from the depths of the Moon, filling the 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 outpourings. On the visible hemisphere, seas occupy 30% of the surface, and on the opposite hemisphere - only 3%. Thus, the evolution of the lunar surface basically ended about 3 billion years ago. The meteorite bombardment continued, but with less intensity. As a result of prolonged processing of the surface, the upper loose layer of rocks of the Moon was formed - regolith, several meters thick.

Mercury

The planet closest to the Sun is named after the ancient god Hermes (to 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, at perihelion it approaches the Sun at a distance of 0.31 AU, and at its maximum distance it is at a distance of 0.47 AU, making a full revolution in 88 Earth days. In 1965, using radar methods 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 rotation around its axis. The addition of axial and orbital motions leads to the fact that, being on the Sun-Earth line, Mercury is always turned with the same side towards us. A solar day (the period of time between the upper or lower culminations 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 features observed on the surface of Mercury. The best known are the works of Schiaparelli (1881-1889) and the American astronomer Percival Lovell (1896-1897). Interestingly, astronomer T. J. C. even announced in 1901 that he had seen craters on Mercury. Few believed it, but subsequently the 625-kilometer crater (Beethoven) ended up in the place marked by Xi. French astronomer Eugene Antoniadi compiled a map of the “visible hemisphere” of Mercury in 1934, since it was then believed that only one hemisphere was always illuminated. Antoniadi gave names to individual details on this map, which are partially used on modern maps.

It was possible for the first time to compile truly reliable maps of the planet and see the fine details of the surface relief 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 removed, 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 planet’s radius (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 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.

Acceleration free fall 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, occupying approximately half the volume of the planet, above which there is a mantle and a silicate shell. 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. Surface layer 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. An extremely rarefied helium atmosphere was discovered on Mercury, created by the “solar wind” that blows across the planet. The pressure of such an atmosphere at the surface is 500 billion times less than at the surface of the Earth. In addition to helium, an insignificant amount of hydrogen, traces of argon and neon were detected.

The American spacecraft Messenger (Messenger - from the English Courier), launched on August 3, 2004, made its first flyby of Mercury on January 14, 2008 at a distance of 200 km from the surface of the planet. She photographed the eastern half of the planet's previously unphotographed hemisphere. The studies of Mercury were carried out in two stages: first, surveys from the flight path during two encounters with the planet (2008), and then (September 30, 2009) - detailed ones. The entire surface of the planet was photographed in various spectral ranges and color images of the terrain were obtained, the chemical and mineralogical composition of the 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 difference in relief heights on this planet is less than 7 km. At the fourth approach, on March 18, 2011, the Messenger AMS should enter orbit artificial satellite 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 longitude on Mercury, is named Hun Kal, which is 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, such as Sobkou Plain or Odin Plain. There are two plains named for their location: the Northern Plain and the Heat Plain, located in the region of maximum temperatures at 180° longitude. The mountains bordering this plain were called the Heat Mountains. A distinctive feature of Mercury's topography is its extended ledges, which are named after marine research vessels. The valleys are named after radio astronomy observatories. The two ridges are named Antoniadi and Schiaparelli, in honor of the astronomers who compiled the first maps of this planet.

Venus

Venus is the planet closest to Earth; it is closer to us than the Sun and is therefore illuminated more brightly 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, completely hiding 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 that were obtained by radar.

The second planet from the Sun is named after the ancient goddess of love and beauty Aphrodite (for 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 the other planets, completing a full 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 rotation speeds of the planets. Thus, Venus's daily rotation is the slowest among all the planets. In addition, it occurs in the opposite direction: unlike most planets, for which the directions of orbit and rotation around the axis coincide, Venus rotates around its axis in the direction opposite to the orbital motion. If you look at it 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 Venus’s axis 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 it takes to rotate around its axis and is 117 Earth days (for other planets, the solar day is longer than the rotation period). And a year on Venus is only twice as long as a solar day.

The atmosphere of Venus consists of 96.5% carbon dioxide and almost 3.5% from 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 kept in mind that the Venusian atmosphere is about 100 times more massive than ours, so there is, for example, five times more nitrogen there than in the Earth’s atmosphere.

The 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 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 that hits them. At the top of the most high mountains Venus - Maxwell's Mountains (altitude about 11 km) - atmospheric pressure is 45 bar, and at the bottom of Diana Canyon - 119 bar. As you know, the pressure of the earth’s atmosphere at the surface of the planet is only 1 bar. Venus's powerful carbon dioxide atmosphere absorbs and partially transmits about 23% of 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 approximately 460-470 °C, the outgoing energy flow turns out to be equal to the incoming energy flow. It is because of this greenhouse effect that the surface of Venus remains hot, regardless of latitude. But in the mountains, over which the atmosphere is thinner, 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 Venus Express probe operated in orbit around it. Scientists were able to see the global features of the surface topography of Venus thanks to radar sounding from the Pioneer-Venera orbiters (1978), Venera-15 and -16 (1983-84) and Magellan (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 received 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.

Uplands account for only 8% of the surface. All noticeable details of the relief received their names. In the first ground-based radar images of individual areas of the surface of Venus, researchers used various names, of which now remain on the maps - Maxwell Mountains (the name reflects the role of radio physics in the study of Venus), the Alpha and Beta regions (the two brightest parts 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 decided to name the surface features of Venus with 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 in honor of outstanding 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 St. Petersburg Academy of Sciences), Akhmatova (Russian poetess) and other famous names. Russian names include 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 Earth. One orbital revolution takes Mars 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 find themselves at a minimum distance from each other, which can range from 56 to 101 million km. Such rapprochements of planets 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. Mars is ten times smaller in mass than Earth, and in surface area it is 3.5 times smaller. The axial rotation period of Mars was determined by ground-based telescopic observations of contrasting surface features: it is 24 hours 39 minutes and 36 seconds. The rotation axis 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 durations: summer in the northern hemisphere lasts 177 Martian days, and in the southern 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 on 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° characteristic meaning Temperatures in mid-autumn vary 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 changes in temperature on the surface are explained by the fact that the atmosphere of Mars is very rarefied, and the surface quickly cools at night and is quickly heated by the Sun during the day. The atmosphere of Mars consists of 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, 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 millibars. 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 remains 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 a parallel of 50°, and sometimes even crossing this line. In spring, as the temperature rises, the top layer evaporates, leaving only a permanent cap. The “wave of darkening” of surface areas observed with the change of seasons is explained by a change in the direction of the winds, constantly blowing in the direction 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 balance of the Martian environment is disrupted. 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 climate conditions on the entire Martian globe change 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 parts of the surface of Mars were transmitted by Mariner 4 in 1965, and then by Mariner 6 and 7 in 1969. The Mars 3 lander managed to make a soft landing. Based on the Mariner 9 images (1971), detailed maps of the planet were compiled. He transmitted to Earth 7329 photographs of Mars with a resolution of up to 100 m, as well as photographs of its satellites - Phobos and Deimos. A whole flotilla of four spacecraft Mars-4, -5, -6, -7, launched in 1973, reached the vicinity of Mars in early 1974. Due to a malfunction of the on-board braking system, Mars-4 passed at a distance about 2200 km from the surface of the planet, having only photographed it. 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 were transmitted to Earth. Mars 7 passed at a distance of 1,300 km from the surface without completing its program.

The most effective flights were the two American Vikings launched in 1975. On board the devices were television cameras, infrared spectrometers for recording water vapor in the atmosphere, and radiometers for obtaining temperature data. The Viking 1 landing unit made a soft landing on Chrysus Planitia on July 20, 1976, and the Viking 2 landing unit on Utopia Planitia 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. That 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 taken from 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 break, was to study Mars and its satellite Phobos. As a result of an incorrect command from Earth, Phobos-1 lost 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 using remote methods. 38 images with a resolution of up to 40 m were obtained, and the temperature of its surface was measured, which was 30 °C in the hottest spots. Unfortunately, it was not possible to implement the main program to study Phobos. Contact with the device was lost on March 27, 1989. This did not end the series of failures. The American Mars Observer spacecraft, launched in 1992, also failed to complete its mission. Contact with him was lost on August 21, 1993. It was not possible to place the Russian station “Mars-96” on the flight path to Mars.

One of NASA's most successful projects is the Mars Global Surveyor station, launched on November 7, 1996 to provide detailed mapping of the surface of Mars. The device also serves as a telecommunications satellite for the Spirit and Opportunity rovers, which were delivered in 2003 and continue to operate to this day. In July 1997, Mars Pathfinder delivered the first automatic Mars rover, Sogerner, weighing less than 11 kg, to the planet, which successfully explored chemical composition surfaces and weather conditions. The rover maintained contact with Earth through a landing module. 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 measuring 30 cm. "Mars Odyssey", "Mars Express" and "Mars Reconnaissance Satellite" “Research from orbit continues. The Phoenix apparatus operated in the polar region from May 25 to November 2, 2008. He drilled the surface for the first time and discovered ice. Phoenix delivered a digital library of science fiction to the planet. Programs are being developed to fly astronauts to Mars. Such an expedition will take more than two years, since 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 identified from space images, old geographical and mythological names proposed by Schiaparelli are also used. The largest elevated area, about 6,000 km in diameter and up to 9 km in height, was called Tharsis (as Iran was called on ancient maps), and a huge ring depression in the south with a diameter of more than 2,000 km was called Hellas (Greece). Areas of the surface densely covered with craters were called lands: Prometheus Land, Noah Land, 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 settlements Earth. Four giant extinct volcanoes rise above the surrounding area to a height of 26 m. The largest of them, Mount Olympus, located on the western edge 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 Askrian, Mount Pavolina and Mount Arsia - are located on one straight line at the top of the Tharsis Mountains. The volcanoes themselves rise another 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 area and height.

South of the equator there is a giant valley up to 6 km deep and more than 4000 km long. It was called the Valles Marineris. Many smaller valleys, as well as grooves and cracks, have also been identified, 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 areas, frozen streams, unusual for terrestrial planets, are visible on the surface near the craters, from which one can judge the presence of subsurface ice.

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

Phobos and Deimos - natural satellites of Mars

The moons of Mars were discovered during the great opposition of 1877 by American astronomer A. Hall. They were called 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 irregular shape. The semi-major axis of Phobos is 13.5 km, and the minor axis is 9.4 km; Deimos has 7.5 and 5.5 km, respectively. The Mariner 7 probe photographed Phobos against the backdrop of Mars in 1969, and Mariner 9 sent back numerous images of both moons, showing their rough, heavily cratered surfaces. The Viking and Phobos-2 probes made several close approaches to the satellites. The best photographs of Phobos show relief details up to 5 meters in size.

The orbits of the satellites are circular. Phobos orbits 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 surface of the planet, and its orbital period is 30 hours 18 minutes. The periods of rotation of satellites around their axis coincide with the periods of their revolution around Mars. The major axes of satellite figures 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 free fall on its surface is 0.5 cm/s 2 . A person on Phobos would weigh only a few tens of grams and could, by throwing a stone with his hand, make it fly off into space forever (the take-off 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. 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 “torn”, and Deimos has a smoother, dust-covered surface. Mysterious grooves have been discovered on Phobos, crossing almost the entire satellite. The 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 grooves, but so far there is no sufficiently convincing explanation, as well as an explanation of the origin of the satellites themselves. Most likely, these are asteroids captured by Mars.

Jupiter

It’s not for nothing that Jupiter is called the “king of the planets.” It is the largest planet in the solar system, exceeding Earth by 11.2 times in diameter and 318 times in mass. Jupiter has a low average density (1.33 g/cm3) because it consists almost entirely of hydrogen and helium. It is located at an average distance of 779 million km from the Sun and spends about 12 years on one orbital revolution. 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 (the ancient Greeks - Zeus, the Romans - Jupiter), it is five times farther from the Sun than the Earth. Due to its rapid rotation, Jupiter is greatly flattened: its equatorial radius (71,492 km) is 7% larger than its polar radius, which is easy to notice when observed through a telescope. The force of gravity at the planet's equator is 2.6 times greater than on Earth. Jupiter's equator is inclined only 3° to its orbit, so the planet does not experience a change of seasons. The inclination of the orbit to the ecliptic plane is even less - only 1°. Every 399 days, oppositions between the Earth and Jupiter are 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 light zones north and south of the equator to the parallels of 40° north and south latitude. The clouds form layers of brownish, red and bluish hues. The rotation periods of these cloud layers turned out to be not the same: the closer they are to the equator, the shorter their rotation period. So, near the equator they complete a revolution around the planet’s axis in 9 hours 50 minutes, and at middle latitudes - in 9 hours 55 minutes. Belts and zones are areas of downward and upward flows in the atmosphere. Atmospheric currents parallel to the equator are maintained by heat flows from the depths of the planet, as well as by the rapid rotation of Jupiter and energy from 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 the flights of spacecraft to Jupiter, it was established that the heat flow from the depths of Jupiter is twice the influx of solar heat received by the planet. This may be due to the slow sinking of heavier substances towards the center of the planet and the ascent of lighter ones. Meteorites falling 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 feature of varying sizes located in the southern tropical zone. Currently, it has dimensions of 15,000 × 30,000 km (i.e., two globe), 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 full revolution around its center in 6 Earth days. The first study of Jupiter at close range (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 extensive hydrogen and helium coronas. The cloud top appears to be composed of cirrus clouds of 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 was about -133 °C. A powerful magnetic field was discovered and the zone of the most intense radiation was recorded at a distance of 177 thousand km from the planet. The plume of Jupiter's magnetosphere is visible even beyond the orbit of Saturn.

The route of Pioneer 11, which flew at a distance of 43 thousand km from Jupiter in December 1974, was calculated differently. He passed between the radiation belts and the planet itself, avoiding a dangerous dose of radiation for electronic equipment. Analysis of color images of the cloud layer obtained with a photopolarimeter made it possible to identify 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 the atmosphere of Jupiter. As expected, the presence of phosphine was discovered - a gaseous compound of phosphorus with hydrogen (PH 3), which gives color to the cloud cover. When heated, it decomposes to release red phosphorus. The unique relative position in the orbits of the Earth and the giant planets, which occurred from 1976 to 1978, was used to successively 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 rotate the flight path from one planet to another. As a result, the flight to Uranus took 9 years, not 16, as it would have been according to the traditional scheme, and the flight to Neptune took 12 years instead of 20. Such a relative arrangement of the planets will be repeated only after 179 years.

Based on data obtained by space probes and theoretical calculations, mathematical models of Jupiter's cloud cover were constructed and ideas about its internal structure were refined. In a somewhat simplified form, Jupiter can be represented as shells with density increasing towards the center of the planet. At the bottom of the atmosphere, 1500 km thick, the density of which increases rapidly with depth, there is a layer of gas-liquid hydrogen about 7000 km thick. At a level of 0.9 radius of the planet, where the pressure is 0.7 Mbar and the temperature is about 6500 K, hydrogen passes into the liquid molecular state, and after another 8000 km - into the 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, 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.

There are 63 known satellites orbiting Jupiter, which can be divided into two groups - inner and outer, or regular and irregular; the first group includes 8 satellites, the second - 55. The satellites of the inner group orbit in almost circular orbits, practically lying in the plane of the planet’s equator. The four closest satellites to the planet - Adrastea, Metis, Amalthea and Theba - have diameters from 40 to 270 km and are located within 2-3 radii of Jupiter from the center of the planet. They differ sharply from the four satellites that follow them, located at a distance of 6 to 26 radii of Jupiter and having significantly larger sizes, 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 by 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 orbits strongly inclined towards Jupiter's equator. At the same time, five satellites closer to Jupiter move in their orbits in the direction of Jupiter’s rotation, and almost all of the more distant satellites move in the opposite direction. Detailed information about the nature of the surfaces of satellites 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 . Io's interior is heated due to the tidal influence of Jupiter and disturbances introduced into Io's motion 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 craters of volcanoes, sulfur dioxide and sulfur vapor are emitted at a speed of about 1 km/s to a height of hundreds of kilometers above the surface of the satellite. Although Io's surface temperature averages around -140 °C near the equator, there are hot spots ranging from 75 to 250 km in size where temperatures reach 100-300 °C. Io's surface is covered with eruption products and is orange in color. The average age of the parts on it is small - about 1 million years. Io's topography is mostly flat, but there are several mountains ranging in height from 1 to 10 km. Io’s atmosphere is very rarefied (it’s practically a vacuum), but a gas tail stretches behind the satellite: radiation of oxygen, sodium vapor and sulfur - 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 resulting from tectonic processes. The width of these faults varies from several kilometers to hundreds of kilometers, and their length reaches thousands of kilometers. Estimates of crustal thickness range from a few kilometers to tens of kilometers. In the depths of Europa, the energy of tidal interaction is also released, which maintains the mantle in liquid form - a subglacial ocean, possibly even a warm one. 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 features of this orange-brown surface is estimated at hundreds of thousands and millions of years. High-resolution images obtained 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 substance carried out from under the ice layer.

According to the American scientist Richard Greenberg, 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 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 surface. The sun's rays penetrate through the ice plug that prevents water from reaching the surface, 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. Many craters covering dark brown areas indicate 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 process of 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 contain not only light ray systems (similar to the lunar ones), but sometimes dark ones as well.

The diameter of Callisto is 4800 km. Based on the average density of the satellite (1.83 g/cm3), 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. There are no extended plains or furrow systems. The craters on Callisto have a poorly defined shaft and shallow depth. A unique feature of the relief 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 been discovered to have its own magnetic field.

On December 30, 2000, the Cassini probe passed near Jupiter on its way to 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 of recording the 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 USA. The results of their research were used along with Cassini data.

As a result of studying the Galilean satellites, it was stated interesting hypothesis that in the early stages of their evolution the giant planets emitted huge flows of heat into space. Radiation from Jupiter 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. That is why 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 of mostly liquid hydrogen and helium. Orbiting the Sun at a distance 10 times further than Earth, Saturn completes a complete orbit in a nearly circular orbit every 29.5 years. The angle of inclination of the orbit to the ecliptic plane 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 second-largest planet is 800 times larger than Earth in volume and 95 times larger in mass. It is easy to calculate that its average density (0.7 g/cm3) 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 movement of Uranus, the French astronomer Le Verrier determined that the seventh planet is 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. It later turned out that, starting with Galileo, astronomers noted 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. Neptune's equatorial radius (24,764 km) is almost 4 times the radius of the Earth, and Neptune's mass is 17 times greater than our planet. The average density of Neptune is 1.64 g/cm3. It orbits the Sun at a distance of 4.5 billion km (30 AU), completing a full cycle in almost 165 earthly years. The planet's orbital plane is inclined by 1.8° to the ecliptic plane. The inclination of the equator to the orbital plane is 29.6°. Due to its 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 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 Neptune's southern hemisphere, is a giant anticyclone that completes a revolution every 16 Earth days. This is the area high blood 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 west at a speed of 325 m/s. A dark spot of smaller size located at 74° south. sh., in a week it shifted 2000 km to the north. A light formation in the atmosphere, the so-called “scooter,” was also distinguished by its rather fast movement. In some places, the wind speed in Neptune's atmosphere reaches 400-700 m/s.

Like other giant planets, Neptune's atmosphere is mostly hydrogen. Helium accounts for about 15%, and methane accounts for 1%. 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 contained 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 hard ice. The hot, icy mantle probably accounts for 70% of the planet's mass. About 25% of Neptune's mass should, according to calculations, belong to the planet's core, 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 at its center is about 7 Mbar, and the temperature is about 7000 K. Unlike Uranus, the heat flow from the depths of Neptune is almost three times greater than the heat received from the Sun. This phenomenon is associated with the release of heat during the radioactive decay of substances with high 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 shifted 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 less than in the rings of Uranus. Individual arcs of the rings surrounding Neptune were discovered during occultations of stars by the planet. Voyager 2 images around Neptune show open formations called arches. They are located on a continuous outermost ring of low density. The diameter of the outer ring is 69.2 thousand km, and the width of the arches is approximately 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 clarified the diameters of Triton (2705 km) and Nereid (340 km). In 2002-03 During observations from Earth, 5 more distant satellites of Neptune were discovered.

Neptune's largest satellite, Triton, orbits the planet at a distance of 355 thousand km with a period of about 6 days in a circular orbit inclined at 23° to the equator of the planet. Moreover, it is the only one of Neptune’s inner satellites moving in orbit in the opposite direction. Triton's axial rotation period coincides with its orbital period. Triton's average density is 2.1 g/cm3. The surface temperature is very low (38 K). In satellite images, most of Triton's surface appears as a plain with many cracks, making it resemble a melon crust. The South Pole is surrounded by a light polar cap. Several depressions with a diameter of 150 - 250 km were discovered on the plain. It is likely that the icy crust of the satellite was reworked many times as a result of tectonic activity and meteorite falls. Triton appears to have a rocky core with a radius of about 1000 km. It is assumed that an ice crust about 180 km thick covers water ocean about 150 km deep, saturated with ammonia, methane, salts and ions. Triton's thin atmosphere is mostly nitrogen, with small amounts of methane and hydrogen. The snow on Triton's surface is nitrogen frost. The polar cap is also formed by nitrogen frost. Amazing formations identified on the polar cap are dark spots extended 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 other inner 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 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 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 lot of dwarf planets in the solar system.

Pluto orbits the Sun every 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 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. 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 away towards the aphelion (48.8 AU), which it will reach in 2112, and will complete the first full revolution around the Sun after its discovery only in 2176.

To understand astronomers' interest in Pluto, we 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 strangeness in their behavior and suggested that beyond the orbits of these planets there is another, undiscovered one, the gravitational influence of which affects the movement of the 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, American astronomer Clyde Tombaugh discovered the ninth planet, named after God underworld- Pluto. However, the discovery was apparently accidental: subsequent measurements showed that Pluto's mass is too small for its gravity to significantly affect the movement of Neptune and, especially, Uranus. Pluto's orbit turned out to be significantly 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 consider Pluto a "wrong" planet, more like a steroid or a lost moon of Neptune. However, Pluto has its own satellites, and sometimes there is an atmosphere when the ice covering its surface evaporates in the perihelion region of the orbit. In general, Pluto has been studied very poorly, since not a single probe has reached it yet; Until recently, even such attempts had not been made. But in January 2006, the New Horizons spacecraft (NASA) launched towards Pluto, which should fly past the planet in July 2015.

By measuring the intensity of sunlight reflected by Pluto, astronomers have determined that the planet's apparent brightness varies periodically. This period (6.4 days) was taken to be 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 speck of the image often blurred the protrusion on one side; its position also changed with a period of 6.4 days. Christie concluded that Pluto has a fairly large satellite, which was called Charon after the mythical boatman who transported the souls of the dead along the rivers in the underground kingdom of the dead (the ruler of this kingdom, as is known, 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 showed that the angle between Pluto's rotation axis and the plane of its orbit is about 32°, and the rotation is reverse. 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 and its satellites resemble Uranus, which rotates “lying on its side.”

Charon's rotation period of 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 typical for all satellites moving close to the planet. Another thing is surprising - Pluto is also always facing Charon with the same side; in this sense they are equal. Pluto and Charon are a unique binary system, very compact and with unprecedented high attitude masses of the satellite and planet (1:8). The ratio of the masses of the Moon and the Earth, for example, is 1:81, and other planets have similar ratios that are much smaller. 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 eclipses of stars by Pluto, as well as 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 ranges from 1.8 to 2.1 g/cm 3 , and that of Charon ranges 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 icy satellites of the giant planets. Charon's surface is 30% darker than Pluto's. The color of the planet and satellite are also different. Apparently, they formed independently of each other. Observations have shown that Pluto's brightness increases noticeably at perihelion of its orbit. This gave reason to assume the appearance of a temporary atmosphere at 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 is most likely nitrogen, and other components may include methane, argon and neon. The thickness of the haze layer is estimated at 45 km, and the thickness of the atmosphere itself is 270 km. Methane content should vary 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 present on its surface in the form of ice and frost, when the planet approaches the Sun, passes into the atmosphere. 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 appears and disappears, like that of a comet during its movement around the Sun. Using the Hubble Space Telescope, two new satellites were discovered in May 2005 dwarf planet Pluto, 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 environs of Pluto and the Kuiper Belt.

Close encounters with robotic spacecraft have transformed planets, moons, and countless small worlds from intriguing painted disks or distant points of light into full-fledged complex objects with a unique history.

NEAR THE SUN

The rapidly rotating Mercury is closest to the Sun, and it poses a daunting challenge for scientists as spacecraft encounter difficulties entering its orbit. Thanks to the Mariner 10 station, launched in 1973, we learned about the surface of Mercury.

Astronomers were delighted at any opportunity to see at least some detail on the surface of this planet. Now that the MESSENGER space station has finally entered Mercury's orbit, it will have to map its invisible side.

TWIN OF THE EARTH

Venus, the second planet from the Sun and Earth's closest neighbor, has hosted a fleet of orbiters and landers since the early 1960s. At the same time, its hostile surface quickly destroyed all the devices that tried to enter its dense atmosphere.

Soviet devices for studying Venus achieved unique successes: hard and soft landing on the surface, studying the atmosphere, detecting a hydrogen corona, the first radio communication session from another planet, etc. In the early 1990s, the American Magellan station used radar to map the surface of the planet , discovering a whole world of volcanoes.

Start windows. Sending a space station to another planet is very difficult, it is not a simple flight in a straight line from one orbit to another. Therefore, the spacecraft must travel beyond the shortest distance between two objects. The devices use the Hohmann trajectory (Hohmann-Vetchinkin orbit). Essentially, it is a segment of an elliptical orbit around the Sun that causes the craft to spiral toward the center of the solar system. Such orbits help to minimize fuel consumption, however, due to such conditions, the device can leave the Earth only in a narrow time window (about a couple of weeks), when it can definitely meet the desired object. If the space station's route passes by more than one planet, flight planning poses significant difficulties.

OUR SATELLITE

The Moon is on our cosmic porch, which is why it is so easy to observe it in some detail in any telescope. This is probably why the Moon has been and remains a popular target for spacecraft since the very first Soviet Luna missions in the late 1950s.

Many American stations in the 1960s were designed primarily to support the Apollo manned program. For example, the Ranger series vehicles took detailed photographs of the surface of our satellite. The resulting photos showed that the lunar craters do not have a lower limit on their size, and therefore are likely the result of meteorite impacts rather than volcanic activity.

Soon after, the American Surveyor probes, which performed a soft landing, explored conditions on the lunar surface, and the Lunar Orbiter series of orbiters compiled a detailed photographic atlas.

Since the 1990s, space stations have been sent to the Moon again, in particular the Lunar Prospector (which was the first to map the elemental composition of the lunar surface) and the Japanese KAGUYA orbiter, equipped with high-resolution cameras.

CHANGING MARS

The Red Planet served as a continuous source for the imagination of many specialists long before space age. The first Mariner stations flew over the cratered southern highlands. These first glimpses revealed what appears to be a rusty version of our lifeless Moon, debunking any illusions that Mars might be entirely hospitable to us. The arrival of the Mariner 9 orbiter in 1971 changed our understanding of the planet. It turned out that it is much more interesting world with huge volcanoes and ancient river beds.

GEOLOGICAL SECRETS

In 1996, the Mars Global Surveyor was launched and, along with other probes that followed, discovered exciting signs that water may still flow on or under the surface of Mars today.

Thanks to the landers, we learned the history of Mars. The Viking spacecraft gave us our first glimpse of the planet's desolate surface in 1976, when they searched in vain for signs of life. Mars Pathfinder and the Mars Exploration Rovers surveyed the planet's landscape in 1997 and since 2004. They helped uncover a number of important geological secrets and found compelling evidence that standing water was once widespread throughout the planet.

The Phoenix lander, launched in 2007, arrived at Mars' North Pole in May 2008 to confirm the existence of water on the planet. In September 2008, the module saw snow falling from the clouds of Mars.

SMALL WORLDS

Spacecraft have also visited asteroids and comets. Halley's Comet, the first such object to be visited by earth stations in 1986, turned out to be very spectacular. Subsequent missions examined comets in a variety of ways: taking samples of material from their tails, falling on them, and photographing their surfaces.

Galileo gave us the first close-up view of the asteroid on its flight to Jupiter in 1991. But the first detailed images were obtained as part of the NEAR project to track near-Earth asteroids, when the space station entered orbit around the asteroid (433) Eros for an entire year, starting in 2000.

AMONG THE GIANTS

Beyond the asteroid belt, flying on a date with Jupiter and Saturn in the 1970s. They paved the way for the Voyager spacecraft, which discovered the complexity of the giant planets.

Although the encounter with the celestial body was limited to only an extended flyby, the excellent cameras on board and carefully calculated trajectories allowed the stations to pass as close as possible to the largest satellites. That's why they were able to discover volcanic activity on Io, evidence of an ocean beneath Europa's icy crust, the thick atmosphere sheltering Titan, and the astonishing complexity of Saturn's ring system.

These discoveries were more than enough to confirm the feasibility of sending the Galileo and Cassini orbital stations to study Jupiter and Saturn. Galileo not only confirmed theories about the existence of a water ocean on Jupiter's moon Europa, but also found evidence of something similar beneath the surface of Ganymede and Callisto. Cassini discovered hydrocarbon lakes on Titan and also detected activity on the small moon Enceladus.

TO THE EDGE OF THE WORLD

If Voyager 1 flew into outer space from Saturn, then Voyager 2, using gravitational maneuvers, circled Uranus and Neptune, casting only a cursory glance at these cold worlds and their satellite systems.

None of these spacecraft have been able to fly past Kuiper belt objects on their way to the edge of the solar system, but the recently launched New Horizons station will fill this gap, and our first reconnaissance exploration of the solar system, which has lasted more than half a century, will be completed.

The science

Spacecraft that study planets today:

Planet Mercury

Of the terrestrial planets, perhaps the least researchers have paid attention to Mercury. Unlike Mars and Venus, Mercury is the least Earth-like planet in this group.. It is the smallest planet in the Solar System and the closest to the Sun.

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

So far only 2 spacecraft have been sent to Mercury - Mariner 10(NASA) and "Messenger"(NASA). The first device is still in 1974-75 circled the planet three times and came as close as possible to Mercury 320 kilometers.

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

Mariner 10 spacecraft before launch

Information received by ship Mariner 10, it turned out to be not enough, so in 2004 Americans launched a second apparatus to study Mercury - "Messenger", which reached the orbit of the planet March 18, 2011.

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

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

The Messenger spacecraft in flight (computer image)

"Messenger" is still in orbit of Mercury and continues to make discoveries, although the mission was designed for a shorter period. The task of scientists when working with the apparatus is to find out what the geological history of Mercury is, 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 "Messenger" The researchers were able to make an incredible and rather unexpected discovery: Mercury has water in the form of ice at its poles.

Craters of one of the poles of Mercury, where water was discovered

The strange thing about this phenomenon is 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 their axial tilt, the planets' poles are located in the shadow, where low temperatures remain, so the ice does not melt.

Future flights to Mercury

A new Mercury exploration mission called "BepiColombo", which is a joint effort between the European Space Agency (ESA) and Japan's JAXA. This ship is scheduled to launch in 2015, although he will only be able to finally reach his goal in 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, the launch date will likely be pushed back. This interplanetary station and lander will be the first spacecraft to land on the surface of the closest planet from the Sun.

Planet Venus

The inner planet Venus, Earth's neighbor, has been intensively explored by space missions starting since 1961. From 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 devices "Marier", "Pioneer-Venus-1", "Pioneer-Venus-2", "Magellan". The European Space Agency is currently working with the device "Venus Express", which acts since 2006. In 2010 Japanese ship went to Venus "Akatsuki".

Apparatus "Venus Express" reached my 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.

The spacecraft "Venus Express" in work according to the artist's ideas

The goal of this project was to study in more detail the complex chemistry 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 Earth took 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, was unable to enter its orbit.

It is not yet clear what to do with this device, but scientists do not lose hope that it will still be will be able to complete its task, albeit very late. Most likely, the ship did not reach orbit due to problems with a valve in the fuel line, which caused the engine to shut down prematurely.

New spaceships

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

The surface of Venus is hot, and earthly ships must have good protection

Also in 2016 Russia plans to send to Venus spaceship "Venera-D" to study the atmosphere and surface in order to find out where did the water disappear from this planet?

The lander 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 most similar to those on Earth, therefore, they are primarily looking for extraterrestrial life 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" entered orbit of the Red Planet. He suggested that under the surface of Mars there may be deposits of water in the form of ice. This has been confirmed in 2008 after years of studying the planet.

Mars Odyssey probe (computer image)

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

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

Mars rover "Spirit" stuck in the sand after 5 years of successful work, and ultimately Contact with him has been interrupted since March 2010. Because the winter on Mars was too harsh, the temperature was insufficient to maintain the battery's energy. Second rover of the project "Opportunity" It 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

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

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

Also with the help of the Mars rover "Curiosity" researchers want to prepare for human flight to the Red Planet. The mission discovered traces of oxygen and chlorine in the Martian atmosphere, and also found traces of a dried-up river.

Mars rover "Curiosity" at work. 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 inside. Soil samples from shallow depths 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 several missions to Mars, whose goal 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 drill the soil and analyze samples.

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

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

As is known, beyond the orbit of Mars there is asteroid belt, which separates 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 difficulties of flying over such vast distances.

Mostly Americans prepared space missions for distant planets. In the 70s of the last century a parade of planets was observed, which happens very rarely, so this opportunity to fly around all the planets at once could not be missed.

Planet Jupiter

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

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

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

Galileo spacecraft (computer image)

Using the device "Galileo" managed to record severe thunderstorms and lightning in the atmosphere of Jupiter, which are a thousand times stronger than those on Earth! The device also filmed Jupiter's Great Red Spot, which astronomers have replaced 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 establish that under the surface of the Europa 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 the upper layers of Jupiter's atmosphere.

Flight to Jupiter

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

The Juno spacecraft will reach its target only in 3 years

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

Planet Saturn

For the first time, a spacecraft has flown close to the planet Saturn "Pioneer-11" and this happened in 1979. A year later I visited the planet Voyager 1, and a year later - Voyager 2. These three spacecraft flew past Saturn, but managed to take many images useful to researchers.

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

Saturn and its moon Titan

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

Cassini-Huygens spacecraft (computer image)

Saturn's moon Titan

The existence of liquid and atmosphere on the Titan satellite was proven. Scientists have suggested that the satellite is quite the simplest forms of life may 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. New joint missions of Americans and Europeans to Saturn and its moons are planned in the near future. Titan and Enceladus.

Planets Uranus and Neptune

These distant planets, which are not visible to the naked eye, are studied by astronomers mainly from Earth using telescopes. The only vehicle that came close to them was Voyager 2, which, having visited Saturn, headed towards Uranus and Neptune.

At first Voyager 2 flew past Uranus in 1986 and took photographs 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)

Using a spacecraft Voyager 2 managed to discover a lot of details, including rings of Uranus, new satellites. Everything we know about this planet today is known thanks to Voyager 2, which flew past Uranus at great speed and took several pictures.

Voyager 2 flying past Neptune (computer image)

In 1989 Voyager 2 got to Neptune, taking photographs 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. Faint rings and new satellites were also discovered near Neptune.

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

The Urane Orbiter spacecraft heading towards 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 the other distant planets, neither Voyager 1, neither have 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 image)

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

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

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

Unfortunately, modern technologies won't allow the spacecraft to enter Pluto's orbit and slow down for now, 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 device "New Horizons".

This is a system of planets, in the center of which there is a bright star, a source of energy, heat and light - the Sun.
According to one theory, the Sun was formed along 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 new star The sun and our entire solar system.

At the center of the solar system is the Sun, around which nine large planets revolve in orbit. Since the Sun is displaced from the center of planetary orbits, 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 and are closest to the Sun.

Giant planets: And . These are large planets, consisting mainly of gas and characterized by the presence of rings consisting of icy dust and many rocky chunks.

And here does not fall into any group because, despite its location 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.

Planets of the Solar System

Let's begin 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 others 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 unique 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 in the solar system...

Rings and moons of Uranus: Titania, Oberon and others...
The planet Uranus has 17 satellites and, like other giant planets, there are thin rings surrounding the planet that have practically no ability to reflect light, so they were discovered not so long ago in 1977, completely by accident...

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

Details Category: About the planets of the solar system Published 10/15/2012 15:55 Views: 24664

Most of the planets in the solar system were discovered in ancient times. Since then they have been observed regularly. Mercury, Venus, Mars, Jupiter and Saturn are visible to the naked eye, so it is impossible to say with certainty who and when first discovered them.

You can read more about the planets of the Solar System on our website: http://site/index.php/3-planeti-solnechnoy-sistemi.
The closest planet to the Sun is small Mercury. Its orbit is close to the Sun (on astronomical scales) - the average distance between Mercury and the Sun is “only” 57,900,000 km.

It is difficult to establish a date for the discovery of this planet, but the earliest known observation of Mercury was recorded in the collection Babylonian astronomical tables by Assyrian astronomers around the 14th century BC. uh. The Sumerian name can be read as "jumping planet." The planet was originally associated with the god Ninurta (the god of happy war), and in later records it is called "Nabu" after the god of wisdom and scribal arts.
IN Ancient Greece during the times Hesiod the planet was known under the names Στίλβων (“Stilbon”) and Ἑρμάων (“Hermaon”) - a form of the name of the god Hermes. Later the Greeks began to call the planet "Apollo".
There is an assumption that the name “Apollo” corresponded to visibility in the morning sky, and “Hermes” (“Hermaon”) in the evening sky. The Romans named the planet after the god of commerce, Mercury, who is equivalent to the Greek god Hermes, because he moves through the sky faster than the other planets. Claudius Ptolemy, in his work “Hypotheses about the Planets,” wrote about the possibility of a planet moving through the disk of the Sun. But such a transit has never been observed because a planet like Mercury is too small to observe or because the moment of transit occurs infrequently.
Mercury was observed and V Ancient China , there they called him Chen-hsing (辰星), “Morning Star”. The synodic period of Mercury was recognized by Chinese scientists as equal to 115.91 days. In modern Chinese, Korean, Japanese and Vietnamese cultures, the planet came to be called "Water Star" (水星).
In Indian mythology Mercury was called Budha. This god, the son of Soma, was dominant on Wednesdays. In Germanic paganism the god Odin was also associated with the planet Mercury and the environment. Mayan Indians represented Mercury as an owl (or perhaps as four owls: two corresponding to the morning appearance of Mercury, and two to the evening), which was the messenger the afterlife. In Hebrew, Mercury was called "Kohav Hama" ("Solar Planet").
Medieval observations of Mercury in the northern parts of Europe were hampered by the fact that the planet is always observed at dawn - morning or evening - against the background of a twilight sky and quite low above the horizon (especially in northern latitudes). The period of its best visibility occurs several times a year (lasting about 10 days). Even during these periods, it is not easy to see Mercury with the naked eye (a relatively dim star against a fairly light background of the sky).
There is a well-known legend that Nicolaus Copernicus regretted that he had never seen Mercury in his entire life. Indeed, in Copernicus’s work “On the Rotations of the Celestial Spheres” there is not a single example of observations of Mercury. But he described the planet using the observations of other astronomers. As he himself said, Mercury can still be “caught” from northern latitudes by showing patience and cunning.
Mercury was seen for the first time through a telescope Galileo Galilei at the beginning of the 17th century, but his telescope was not powerful enough to observe the phases of Mercury. In 1631 Pierre Gassendi made the first telescopic observation of the passage of a planet across the disk of the Sun, but the moment of passage was calculated before that Johannes Kepler. In 1639 Giovanni Zupi using a telescope, he discovered that the orbital phases of Mercury are similar to the phases of the Moon and Venus - this finally confirmed that Mercury revolves around the Sun.
A very rare astronomical event is the overlap of one planet with the disk of another, observed from Earth. Venus overlaps Mercury once every few centuries, and this event has only been observed once in history - on May 28, 1737 John Bevis at the Royal Greenwich Observatory. Venus' next occultation of Mercury will be on December 3, 2133.
The difficulties surrounding the observation of Mercury led him to for a long time has been studied less than other planets.
The proximity of the Sun also creates some problems for the telescopic study of Mercury. For example, the Hubble telescope has never been used and will not be used to observe this planet. Its device does not allow observations of objects close to the Sun - if you try to do this, the equipment will suffer irreversible damage.
Mercury is the least studied terrestrial planet. In the 20th century, radio astronomy, radar and research using spacecraft were added to the telescopic methods of studying it.
Latest research data on Mercury:
Mercury's surface temperature: 600 K at the subsolar point and 150 K on the unlit side.
The reflective properties of Mercury and the Moon are similar.
Mercury's rotation period: 59 days.
In the picture you see Mariner 10, the first spacecraft to reach Mercury.
Two spacecraft were sent to study Mercury: Mariner 10 flew past Mercury three times in 1974-1975; the closest approach was 320 km. Several thousand images were taken. Further research from Earth showed the possibility of the existence of water ice in polar craters.
Of all the planets visible to the naked eye, only Mercury has never had its own artificial satellite. NASA is currently conducting a second mission to Mercury called Messenger. The device was launched on August 3, 2004, and in January 2008 it made its first flyby of Mercury. To enter orbit around the planet in 2011, the device performed two more gravity assist maneuvers near Mercury.
The European Space Agency (ESA), together with the Japan Aerospace Exploration Agency (JAXA), is developing the Bepi Colombo mission to explore the surface of Mercury and its depth, as well as observe magnetic field and the planet's magnetosphere. The launch of the device is planned for 2013.
More opportunities have emerged for ground-based observations of Mercury using CCD radiation receivers and subsequent computer processing of images. On March 17, 2011, the interplanetary probe Messenger entered Mercury orbit. According to the first studies, the planet's magnetic field is not symmetrical relative to the poles; Thus, different numbers of solar wind particles reach Mercury's north and south poles. An analysis of the prevalence of chemical elements on the planet was also carried out. Research continues.
Russia plans to send the first Mercury-P landing station to the planet. The project was planned for 2019, but was significantly delayed.

Venus was also observed in ancient times - it is easy to see in the sky, because in brilliance it far exceeds the brightest stars. For millennia, it has captivated people's gaze. The planet is named after the goddess of love. It has a smooth white color. Like Mercury, Venus has periods of morning and evening visibility, so in ancient times it was believed that morning and evening Venus were different stars. Using a telescope, you can easily observe changes in the visible phase of the planet's disk. I saw him for the first time in 1610 Galileo.
On Earth, you can observe the passage of Venus across the disk of the Sun, when from Earth through a telescope this planet is visible as a small black disk against the background of the huge Sun. For the first time, the passage of Venus across the disk of the Sun was observed by an English astronomer on December 4, 1639. Jeremiah Horrocks, but first he calculated this phenomenon.
“The appearance of Venus on the Sun” was observed by M. V. Lomonosov June 6, 1761. This phenomenon was observed all over the world, but only M.V. Lomonosov drew attention to the fact that when Venus came into contact with the disk of the Sun, a “thin, hair-like glow” appeared around the planet. The same light halo was observed during the descent of Venus from the solar disk. Thus, the presence of an atmosphere on Venus was discovered, and this was a hundred years before the discovery of spectral analysis!
Venus has been intensively studied by spacecraft. The first spacecraft intended to study Venus was the Soviet “Venera-1” (February 12, 1961), the Soviet spacecraft of the “Venera”, “Vega” series, the American “Mariner”, “Pioneer-Venera-1” series were sent to the planet. “Pioneer Venus 2”, “Magellan”, European “Venus Express”, Japanese “Akatsuki”. In 1975, the Venera-9 and Venera-10 spacecraft transmitted the first photographs of the surface of Venus to Earth. But the conditions on the surface of Venus are such that none of the spacecraft worked on the planet for more than two hours. Roscosmos plans to send the Venera-D station with a satellite of the planet and a more durable probe, which should work on the surface of the planet for at least a month.

The exploration of Mars also began a very long time ago - more than 3.5 thousand years ago in Ancient Egypt. The planet was named after Mars, the ancient Roman god of war (corresponding to the ancient Greek Ares). Mars is sometimes called the “red planet” because of the reddish tint of its surface given by iron oxide. Mars has moons Phobos and Deimos.
Descriptions of the position of Mars have been preserved, compiled by Babylonian astronomers, who developed a number of mathematical methods to predict the position of the planet. Using the data of the Egyptians and Babylonians, ancient Greek philosophers and astronomers developed a detailed geocentric model to explain the motion of the planets. Several centuries later Indian and Islamic astronomers Calculated the size of Mars and its distance from Earth. Johannes Kepler introduced a more accurate elliptical orbit of Mars, coinciding with the observed one.
In 1659 Francesco Fontana, examining Mars through a telescope, made the first drawing of the planet - in the form of a black spot.
In 1660, two polar caps were added to the black spot, added Jean Dominique Cassini.
In 1888 Giovanni Schiaparelli gave the first names to individual surface details: the seas of Aphrodite, Erythraean, Adriatic, Cimmerian; lakes Sun, Lunnoe and Phoenix.
The heyday of telescopic observations of Mars occurred at the end of the 19th - mid-20th centuries.
Since the 1960s, the exploration of Mars has been carried out by the USSR AMS (Mars and Phobos programs), ESA and the USA (Mariner, Viking, Mars Global Surveyor programs and others).
Currently, Mars is being actively explored. There are three actively operating spacecraft in Mars orbit:
"Mars Reconnaissance Satellite"
Mars Express with Marsis radar
"Mars Odysseus"
Rovers operating on the surface of the planet:
"Opportunity" (since January 25, 2004) as part of the Mars Exploration Rover program
Curiosity (since August 6, 2012) as part of the Mars Science Laboratory program.
Although Mars has been studied much better than other planets, it is still a mystery to us.

Jupiter

Together with Saturn, Uranus and Neptune, Jupiter is one of the gas giants. This planet has been known to people since ancient times, which is reflected in the mythology and religious beliefs of various cultures: Mesopotamian, Babylonian, Greek and others. Modern name Jupiter comes from the name of the ancient Roman supreme god of thunder. Jupiter has natural satellites. To date, scientists know 67 satellites of Jupiter.
At the beginning of the 17th century Galileo Galilei studied Jupiter using a telescope he invented and discovered the four largest satellites of the planet. In the 1660s Giovanni Cassini observed spots and stripes on the “surface” of the giant. In 1671, observing the eclipses of the satellites of Jupiter, Danish astronomer Ole Roemer discovered that the true position of the satellites did not coincide with the calculated parameters, and the magnitude of the deviation depended on the distance to the Earth. Based on these observations, Roemer concluded that the speed of light is finite and established its value as 215,000 km/s (the modern value is 299,792.458 km/s).
Since the second half of the 20th century, Jupiter has been actively studied both with the help of ground-based telescopes (including radio telescopes) and with the help of spacecraft - the Hubble telescope and a number of probes. Since the 1970s, 8 interplanetary NASA probes have been sent to the planet: Pioneers, Voyagers, Galileo and others.
Jupiter has been studied exclusively by US NASA apparatus.
To the naked eye, Jupiter appears as a bright star. Because of its enormous size, even small telescopes can see faintly colored ribbons of clouds and a large red spot on its disk.

Gas giant. Named after the Roman god of agriculture. Saturn has a prominent ring system made up primarily of ice particles and smaller amounts of heavy elements and dust. Seeing Saturn for the first time through a telescope in 1609-1610, Galileo Galilei noticed that Saturn does not look like a single celestial body, but like three bodies almost touching each other, and suggested that these are two large “companions” (satellites) of Saturn. In 1633 Gassendi drew a bright ring around Saturn. In 1656 Huygens confirms that there is a thin, flat ring around Saturn that does not touch the planet. In 1675 Cassini discovers a gap in the rings, which is later called the Cassini gap, and Encke in 1837 g. finds the second gap. IN 1852 Lascelles establishes that Saturn's ring is almost transparent, which means it cannot be solid. In addition, he suggested that this ring consists of individual particles located very close to each other, so they appear to be a continuous ribbon. In 1895 Keeler finds that individual parts of the rings rotate at different speeds, and this also confirms Lascelles' assumption that the rings cannot be solid.
Saturn has 62 known natural satellites with confirmed orbits, 53 of which have their own names. Most of the satellites are small in size and consist of rocks and ice.
Huygens also discovered Saturn's largest moon, Titan. There were no further significant discoveries until 1789, when W. Herschel discovered two more satellites - Mimas and Enceladus. Then a group of British astronomers discovered the satellite Hyperion, with a shape very different from spherical. In 1899, William Pickering discovered Phoebe, which belongs to the class of irregular satellites and does not rotate synchronously with Saturn like most satellites. The period of its revolution around the planet is more than 500 days, while the revolution goes in the opposite direction. In 1944 by Gerard Kuiper The presence of a powerful atmosphere on another satellite, Titan, was discovered. This phenomenon is unique for the satellite in the Solar System. In the 1990s, Saturn, its moons and rings were repeatedly studied by the Hubble Space Telescope.
Saturn is being explored by the automatic interplanetary stations (AIS) Cassini-Huygens, Voyager (program), and Pioneer 11. In 2009, a joint American-European project between NASA and ESA appeared to launch the Titan Saturn System Mission to study Saturn and its satellites Titan and Enceladus. During it, the station will fly to the Saturn system for 7-8 years, and then become a satellite of Titan for two years. It will also launch a probe balloon into Titan’s atmosphere and a landing module (possibly floating).
The planet is visible from Earth with the naked eye.

Uranium was discovered March 13, 1781 by English astronomer William Herschel. While studying the starry sky through his telescope, he noticed that Uranus was moving relative to the stars. Other people had seen Uranus before, even marked it on star charts, but they did not realize that it was not a star.
Outside the orbit of Saturn there are two planets that have much in common - Uranus and Neptune. Uranus has 27 known natural satellites.
The planet is named after the Greek god of the sky. Uranus is 19 times farther from the Sun than Earth. Uranus's orbital journey lasts more than 84 years. When Uranus is at its brightest, it can be seen with the naked eye as a star. Uranus stands out among other planets in that it makes its way in orbit around the Sun on its side. Maybe it collided with some celestial body and capsized? Uranus also has rings, they were discovered in 1977. True, they are faintly visible.
Uranus is being explored by NASA's Voyager 2 spacecraft and the Hubble Space Telescope.

Neptune is the eighth and most distant planet Solar system. The planet was named after the Roman god of the seas.
Based on small deviations in the orbit of Uranus, John Adams and Urbain Le Verrier predicted the existence of another, more distant planet. September 23, 1846 at the request of Le Verrier Johann Halle found a new planet - Neptune.
Many people have seen Neptune before, including Galileo Galilei, who, while observing Jupiter, noticed a "star" now believed to be Neptune. Neptune was the first planet discovered through mathematical calculations rather than through regular observations.
Neptune has natural satellites, as well as a fragmented ring system, discovered back in the 1960s, but only reliably confirmed by Voyager 2 in 1989. Triton is an amazing satellite of Neptune; it moves in orbit in the opposite direction relative to Neptune.
Voyager 2 explores Neptune. Voyager 2 came closest to Neptune on August 25, 1989. It turned out that Neptune is one of the most beautiful planets in the solar system.

The most distant planet in our solar system is Pluto. She was discovered February 18, 1930 by American astronomer Clyde Tombaugh. He photographed the same part of the night sky on different days, as a result of which he discovered an object moving relative to the stars. Further observations showed that this object is a planet.
However, there is serious disagreement on this matter. Pluto doesn't behave like a planet. Pluto's elongated orbit is more like that of a comet. Because Pluto is so far away, it is difficult to see. Even in the most powerful telescopes it is visible as a tiny circle. But observations made using advanced technology suggest that Pluto is similar to Neptune's moon Triton. Pluto was initially classified as a planet, but is now considered one of the largest objects (perhaps the largest) in the Kuiper Belt.