Brief information about Mercury. Mercury compared to our planet
0.147 Earth
0.056 Earth
0.055 Earth
0.984 Earth
0,38
281.01°
0.106 (geom. albedo)
24.9% sodium
9.5%, A. oxygen
7.0% argon
5.9% helium
5.6%, M. oxygen
5.2% nitrogen
3.6% carbon dioxide
3.4% water
3.2% hydrogen
Mercury in natural color (Image Mariner 10)
Mercury- the closest planet to the Sun in the solar system, revolves around the Sun in 88 Earth days. Mercury is an inner planet because its orbit is closer to the Sun than the main asteroid belt. After depriving Pluto of the status of a planet in 2006, Mercury passed the title of the smallest planet in the solar system. Mercury's apparent magnitude ranges from −2.0 to 5.5, but is not easy to see due to its very small angular distance from the Sun (maximum 28.3°). At high latitudes, the planet can never be seen in the dark night sky: Mercury is always hidden in the morning or evening dawn. Optimal time for observations of the planet are morning or evening twilight during periods of its elongations (periods of maximum removal of Mercury from the Sun in the sky, occurring several times a year).
It is convenient to observe Mercury at low latitudes and near the equator: this is due to the fact that the duration of twilight is the shortest there. In middle latitudes, finding Mercury is much more difficult and only during the period of the best elongations, and in high latitudes it is impossible at all.
Relatively little is known about the planet. The Mariner-10 apparatus, which studied Mercury in -1975, managed to map only 40-45% of the surface. In January 2008, the interplanetary station MESSENGER flew past Mercury, which will enter orbit around the planet in 2011.
In terms of its physical characteristics, Mercury resembles the Moon and is heavily cratered. The planet has no natural satellites, but has a very rarefied atmosphere. The planet has a large iron core, which is the source of the magnetic field in its totality, which is 0.1 of the earth's. Mercury's core makes up 70 percent of the planet's total volume. The temperature on the surface of Mercury ranges from 90 to 700 (from −180 to +430 ° C). The solar side heats up much more than the polar regions and the far side of the planet.
Despite the smaller radius, Mercury still surpasses in mass such satellites of the giant planets as Ganymede and Titan.
The astronomical symbol of Mercury is a stylized depiction of the winged helmet of the god Mercury with his caduceus.
History and name
The oldest evidence for the observation of Mercury can be found in Sumerian cuneiform texts dating back to the third millennium BC. e. The planet is named after the god of the Roman pantheon Mercury, an analogue of the Greek Hermes and Babylonian Naboo. The ancient Greeks of the time of Hesiod called Mercury "Στίλβων" (Stilbon, Brilliant). Until the 5th century BC e. the Greeks believed that Mercury, visible in the evening and morning sky, are two different objects. In ancient India, Mercury was called Buddha(बुध) and Roginea. In Chinese, Japanese, Vietnamese and Korean, Mercury is called water star(水星) (in accordance with the concept of the "Five Elements". In Hebrew, the name of Mercury sounds like "Kokhav Hama" (כוכב חמה) ("Solar Planet").
planet movement
Mercury moves around the Sun in a rather strongly elongated elliptical orbit (eccentricity 0.205) at an average distance of 57.91 million km (0.387 AU). At perihelion, Mercury is 45.9 million km from the Sun (0.3 AU), at aphelion - 69.7 million km (0.46 AU) At perihelion, Mercury is more than one and a half times closer to the Sun than at aphelion. The inclination of the orbit to the plane of the ecliptic is 7°. Mercury spends 87.97 days per orbit. The average speed of the planet in orbit is 48 km/s.
For a long time it was believed that Mercury is constantly facing the Sun with the same side, and one revolution around its axis takes the same 87.97 days. Observations of detail on the surface of Mercury, made at the limit of resolution, did not seem to contradict this. This misconception was due to the fact that the most favorable conditions for the observation of Mercury are repeated through a triple synodic period, that is, 348 Earth days, which is approximately equal to the sixfold period of Mercury's rotation (352 days), therefore, approximately the same part of the planet's surface was observed at different times. On the other hand, some astronomers believed that the Mercury day is approximately equal to the Earth day. The truth was revealed only in the mid-1960s, when the radar of Mercury was carried out.
It turned out that the Mercury sidereal day is equal to 58.65 Earth days, that is, 2/3 of the Mercury year. Such a commensurability of the periods of rotation and revolution of Mercury is a unique phenomenon for the solar system. This is presumably due to the fact that the tidal action of the Sun took away the angular momentum and slowed down the rotation, which was initially faster, until the two periods were connected by an integer ratio. As a result, in one Mercury year, Mercury has time to rotate around its axis by one and a half turns. That is, if at the moment Mercury passes perihelion, a certain point of its surface faces exactly the Sun, then during the next passage of perihelion, exactly the opposite point of the surface will face the Sun, and after another Mercury year, the Sun will again return to the zenith over the first point. As a result, a solar day on Mercury lasts two Mercury years or three Mercury sidereal days.
As a result of such a movement of the planet, “hot longitudes” can be distinguished on it - two opposite meridians, which alternately face the Sun during the passage of perihelion by Mercury, and on which, because of this, it is especially hot even by Mercury standards.
The combination of the movements of the planet gives rise to another unique phenomenon. The speed of rotation of the planet around its axis is practically constant, while the speed of orbital motion is constantly changing. In the segment of the orbit near the perihelion, for about 8 days, the speed of orbital motion exceeds the speed of rotational motion. As a result, the Sun in the sky of Mercury stops, and begins to move in the opposite direction - from west to east. This effect is sometimes called the Joshua effect, after the protagonist of the Book of Joshua from the Bible, who stopped the movement of the Sun (Joshua, x, 12-13). For an observer at longitudes 90° away from the "hot longitudes", the Sun rises (or sets) twice.
It is also interesting that, although Mars and Venus are the closest orbits to Earth, it is Mercury that is the closest planet to Earth most of the time than any other (because others move away to a greater extent without being so “tied” to the Sun).
physical characteristics
Comparative sizes of Mercury, Venus, Earth and Mars
Mercury is the smallest terrestrial planet. Its radius is only 2439.7 ± 1.0 km, smaller than that of Jupiter's moon Ganymede and Saturn's moon Titan. The mass of the planet is 3.3 × 10 23 kg. The average density of Mercury is quite high - 5.43 g / cm³, which is only slightly less than the density of the Earth. Considering that the Earth is larger in size, the value of the density of Mercury indicates increased content in its bowels of metals. The free fall acceleration on Mercury is 3.70 m/s². The second space velocity is 4.3 km/s.
Kuiper Crater (just below center). MESSENGER image
One of the most noticeable details of the surface of Mercury is the Heat Plain (lat. Caloris Planitia). This crater got its name because it is located near one of the "hot longitudes". Its diameter is about 1300 km. Probably, the body, upon impact of which the crater was formed, had a diameter of at least 100 km. The impact was so strong that seismic waves, having passed the entire planet and focused at the opposite point of the surface, led to the formation of a kind of intersected "chaotic" landscape here.
Atmosphere and physical fields
During the flight of the Mariner-10 spacecraft past Mercury, it was established that the planet has an extremely rarefied atmosphere, the pressure of which is 5 × 10 11 times less than the pressure of the earth's atmosphere. Under such conditions, atoms collide with the surface of the planet more often than with each other. It consists of atoms captured from the solar wind or knocked out by the solar wind from the surface - helium, sodium, oxygen, potassium, argon, hydrogen. The average lifetime of an atom in the atmosphere is about 200 days.
Mercury has a magnetic field, the intensity of which is 300 times less than the intensity magnetic field Earth. The magnetic field of Mercury has a dipole structure and is highly symmetrical, and its axis deviates by only 2 degrees from the axis of rotation of the planet, which imposes a significant limitation on the range of theories explaining its origin.
Research
An image of a portion of the surface of Mercury taken by the MESSENGER spacecraft
Mercury is the least explored terrestrial planet. Only two vehicles were sent for his research. The first was Mariner 10, which flew past Mercury three times in -1975; the maximum approach was 320 km. As a result, several thousand images were obtained, covering approximately 45% of the planet's surface. Further studies from Earth showed the possibility of the existence of water ice in polar craters.
Mercury in art
- In Boris Lyapunov's science fiction short story "Nearest to the Sun" (1956), Soviet cosmonauts land on Mercury and Venus for the first time to study them.
- In Isaac Asimov's story " big sun Mercury ”(series about Lucky Starr) the action takes place on Mercury.
- Isaac Asimov's stories Runaround and The Dying Night, written in 1941 and 1956 respectively, describe Mercury facing the Sun on one side. At the same time, in the second story, the key to the detective story is built on this fact.
- In the science fiction novel The Flight of the Earth by Francis Karsak, along with the main plot, a scientific station for studying the Sun is described, located at the North Pole of Mercury. Scientists live on a base located in the eternal shadow of deep craters, and observations are made from giant towers constantly illuminated by the luminary.
- In Alan Nurse's science fiction novel Across the Sunny Side, the main characters cross the side of Mercury facing the Sun. The story was written in accordance with the scientific views of its time, when it was assumed that Mercury was constantly facing the Sun on one side.
- In the anime animated series Sailor Moon, the planet is personified by the warrior girl Sailor Mercury, she is Ami Mitsuno. Her attack lies in the power of water and ice.
- In Clifford Simak's science fiction story "Once Upon a Time on Mercury", the main field of action is Mercury, and the energy form of life on it - balls, surpasses humanity by millions of years of development, having long passed the stage of civilization.
Notes
see also
Literature
- Bronstein V. Mercury is the closest to the Sun // Aksenova M.D. Encyclopedia for children. T. 8. Astronomy - M.: Avanta +, 1997. - S. 512-515. - ISBN 5-89501-008-3
- Xanfomality L.V. Unknown Mercury // In the world of science. - 2008. - № 2.
Links
- MESSENGER mission website
- Pictures of Mercury taken by Messenger
- BepiColombo mission section on the JAXA website
- A. Levin. Iron Planet Popular Mechanics #7, 2008
- "The closest" Lenta.ru, October 5, 2009, photographs of Mercury taken by "Messenger"
- “New images of Mercury published” Lenta.ru, November 4, 2009, about the approach on the night of September 29 to 30, 2009 of Messenger and Mercury
Mercury with his physical characteristics like the moon. It has no natural satellites, its atmosphere is very rarefied. This planet has a large iron core, accounting for 83% of the volume of the entire planet. This core is the source of a magnetic field with a strength of 0.01 of the earth's. The surface temperature of the planet is - 90 - 700 K (-183.15-426.85 C). The solar side of the planet heats up much more than its reverse side and the polar regions.
Mercury craters
On the surface of Mercury there are a large number of craters, this landscape is very similar to the moon. In different parts of Mercury, the density of craters is different. It is possible that areas of the planet's surface that are more heavily cratered are older, and those that are less dotted are younger. They were formed as a result of flooding with lava. old surface. At the same time, there are fewer large craters on Mercury than on the Moon. The diameter of the largest crater on Mercury is 716 km, it was named after Rembrandt, the great Dutch painter. Also on Mercury there are formations that are not like on the Moon. For example, scarps are numerous jagged slopes that stretch for hundreds of kilometers. When studying the scarps, it was found that they were formed during the compression of the surface, which accompanied the cooling of Mercury, in which the surface area of the planet decreased by 1%. Because there are well-preserved large craters on the surface of Mercury, this means that over the past 3-4 billion years there has been no movement of sections of the crust on a large scale, there was no erosion on the surface (by the way, the latter almost completely confirms the impossibility of the existence of any kind of some significant atmosphere).
During the research, the Messenger probe took photographs of more than 80% of the planet's surface, as a result of which it was determined that it is homogeneous, unlike the surface of Mars or the Moon, in which one hemisphere is very different from the other.
The elemental composition of the surface of Mercury, obtained by the X-ray fluorescence spectrometer of the Messenger spacecraft, showed that the surface of the planet is rich in plagioclase feldspar, characteristic of the continental regions of the Moon, and, in comparison, is poor in calcium and aluminum. It is also rich in magnesium and poor in iron and titanium, which allows it to occupy the gap between ultramafic rocks, like terrestrial komatiites, and typical basalts. A relative abundance of sulfur has also been found, which means that the planet was formed in reducing conditions.
Mercury's craters are different. They range from small bowl-shaped depressions to multi-ringed impact craters that are hundreds of kilometers across. Mercury's craters varying degrees destroyed. There are more or less well-preserved, with long rays located around them, formed in the process of ejection of matter from the impact of the impact. There are also very destroyed remains of craters.
The Plain of Heat (lat. Caloris Planitia) is one of the most visible features of the relief of Mercury. It is so named because it is located next to one of the "hot longitudes". The diameter of this plain is about 1550 km.
Most likely, the body, in the collision of which with the surface of Mercury a crater was formed, was at least 100 km in diameter. The impact was so strong that seismic waves, having passed through the entire planet and gathered at the opposite point of the surface, caused the formation of a kind of “chaotic” rugged landscape on Mercury. The strength of the impact is also evidenced by the fact that it provoked the ejection of lava, as a result of which the Zhara Mountains, more than 2 km high, formed around the crater. The Kuiper crater (60 km across) is the point on the surface of the planet with the highest albedo. Most likely, the Kuiper crater is one of the "last" formed large craters of Mercury.
Another interesting arrangement of craters on the planet was discovered by scientists in 2012: the sequence of the location of the craters forms the face of Mickey Mouse. Maybe in the future this configuration will be named that way.
Geology of Mercury
More recently, it was believed that in the bowels of Mercury there is a metal core, the radius of which 
1800 - 1900 km, it is 60% of the mass of the planet, since a weak magnetic field was detected by the Mariner-10 spacecraft. In addition, according to scientists, it was believed that the core of Mercury, due to the small size of the planet, should not be liquid. After five years of radar observations, Jean-Luc Margot's team in 2007 took stock, and as a result, various variations in Mercury's rotation were noted, which are too large for a planet with a solid core. Based on this, it can be stated with almost 100% accuracy that the core of Mercury is liquid.
Compared to any planet in the solar system, the percentage of iron in the core of Mercury is higher. There are several versions of the explanation for this. The most widely accepted theory in the world of science says that Mercury, initially having a mass 2.25 times greater than today, had the same proportion of silicates and metal as an ordinary meteorite. But at the very beginning of the history of the solar system, a planet-like body with a diameter of several hundred kilometers and a mass six times smaller collided with Mercury. Because of this collision, most of the primary crust and mantle came off the planet, as a result of which the relative proportion of the core in Mercury increased. By the way, to explain the formation of the Moon, a similar hypothesis was proposed, called the Giant Impact Theory. But this theory is contradicted by the first data that were obtained in the process of studying the elemental composition of the surface of Mercury using the AMS Messenger gamma spectrometer (it allows you to measure the content of radioactive isotopes). It turned out that there is a lot of potassium on the planet (a volatile element when compared with thorium and uranium, which are more refractory). This is inconsistent with the high temperatures that are inevitable in a collision. Based on this, it becomes clear that the elemental composition of Mercury coincides with the primary elemental composition of the material that formed it, which is close to anhydrous cometary particles and enstatite chondrites, while the iron content in the latter, today, is small to explain the high average density of the planet.
A silicate mantle (500-600 km thick) surrounds the core of Mercury. The thickness of its crust is in the range of 100 - 300 km (according to Mariner-10 data).
Geological history of Mercury
The geological history of the planet is divided into eras, like those of Mars, the Moon and the Earth. These eras are called as follows (to the later from the earlier): 1 - pre-Tolstoy, 2 - Tolstoy, 3 - Kalorian, 4 - late Caloric, 5 - Mansur and 6 - Kuiper. And the relative geological age of Mercury is divided into periods according to given eras. True, the absolute age measured in years has not been precisely established.
About 4.6 billion years ago, when the planet was already formed, there was an intense collision with comets and asteroids. The last massive bombardment of Mercury was 3.8 billion years ago. Some areas (for example, the Zhara Plain) were created, among other things, by filling them with lava. As a result, smooth cavities similar to those of the moon formed inside the craters.
After that, as Mercury cooled and contracted, faults and ridges formed. The later time of their formation is evidenced by their location on the surface of large relief objects, such as plains and craters. The time of volcanism on the planet ended after the mantle contracted enough to prevent the release of lava on the surface of Mercury. It is possible that this happened during the first 700-800 million years from the time of the formation of Mercury. Later changes in the landscape of the planet were caused by impacts on its surface of cosmic bodies.
Mercury's magnetic field
The magnetic field strength of Mercury is about a hundred times less than that of the earth and is equal to ~300 nT. Mercury's magnetic field has a dipole structure, very symmetrical, its axis is only 10 degrees off Mercury's axis of rotation. This significantly reduces the number of hypotheses explaining the origin of the magnetic field of Mercury. It is assumed that the magnetic field of Mercury arises due to the dynamo effect (similarly occurs on Earth). Perhaps this effect is the consequence of the circulation of the liquid core. A very strong tidal effect occurs due to the very pronounced eccentricity of Mercury. This tidal effect keeps the core in liquid state, and this is a necessary condition for the occurrence of the dynamo effect. The planet's magnetic field is so strong that it can change the direction of the solar wind around Mercury, as a result of which its magnetosphere is created. And although it is so small that it would fit inside the Earth, it is powerful enough to catch the plasma of the solar wind. As a result of observations obtained with the help of Mariner 10, it turned out that there is a low-energy plasma in the magnetosphere of the night side of Mercury. Explosions of active particles in the tail of the magnetosphere indicate its inherent dynamic qualities.
On October 6, 2008, the Messenger, flying by Mercury for the second time, recorded a large number of windows in the planet's magnetic field. "Messenger" discovered the phenomenon of magnetic vortices. These are the woven nodes of the magnetic field that connect the spacecraft to the magnetic field of Mercury. The diameter of the vortex was 800 km, which is a third of the radius of the planet. The solar wind creates such a vortex form of the magnetic field. As the solar wind flows around Mercury's magnetic field, it binds and rushes with it, forming into vortex-like structures. Such vortices create windows in the planet's magnetic shield, through which the solar wind penetrates, reaching the surface of the planet. The connection of the interplanetary and planetary magnetic fields (magnetic reconnection) is a common cosmic phenomenon that also occurs near the Earth, at a time when it creates magnetic vortices. But the frequency of Mercury's magnetic reconnection, according to Messenger, is 10 times higher.
Mercury is the first planet in the solar system. Not so long ago, she occupied almost last place among all 9 planets in terms of their size. But, as we know, under the Moon nothing lasts forever. In 2006, Pluto lost its planetary status due to its oversized. It became known as a dwarf planet. Thus, Mercury is now at the end of a series of cosmic bodies that cut innumerable circles around the Sun. But it's about size. In relation to the Sun, the planet is closest - 57.91 million km. This is the average value. Mercury rotates in an overly elongated orbit, the length of which is 360 million km. That is why it is sometimes further from the Sun, then, on the contrary, closer to it. At perihelion (the point of the orbit closest to the Sun), the planet approaches the flaming star at 45.9 million km. And in aphelion ( far point orbit), the distance to the Sun increases and equals 69.82 million km.
Regarding the Earth, here the scale is slightly different. Mercury from time to time approaches us up to 82 million km or diverges up to a distance of 217 million km. The smallest figure does not mean at all that the planet can be carefully and for a long time examined in a telescope. Mercury deviates from the Sun by an angular distance of 28 degrees. From here it emerges that this planet can be observed from the Earth just before dawn or after sunset. You can see it almost at the horizon line. Also, you can not see the whole body as a whole, but only half of it. Mercury is rushing in orbit at a speed of 48 km per second. The planet makes a complete revolution around the Sun in 88 Earth days. The value that shows how different an orbit is from a circle is 0.205. The run-up between the plane of the orbit and the plane of the equator is 3 degrees. This suggests that the planet is characterized by minor seasonal changes. Mercury is a terrestrial planet. This also includes Mars, Earth and Venus. All of them have a very high density. The diameter of the planet is 4880 km. As it is not a shame to realize, but here even some satellites of the planets bypassed it. The diameter of the largest satellite, Ganymede, which revolves around Jupiter, is 5262 km. Titan, a satellite of Saturn, has no less solid appearance. Its diameter is 5150 km. The diameter of Callisto (satellite of Jupiter) is 4820 km. The Moon is the most popular satellite in the solar system. Its diameter is 3474 km.
Earth and Mercury
It turns out that Mercury is not so unpresentable and nondescript. Everything is known in comparison. A small planet loses well in size to the Earth. Compared to our planet, this small cosmic body looks like a fragile creature. Its mass is 18 times less than the earth's, and its volume is 17.8 times. The area of Mercury lags behind the area of the Earth by 6.8 times.
Features of Mercury's orbit
As mentioned above, the planet makes a complete revolution around the Sun in 88 days. It rotates around its axis in 59 Earth days. The average speed is 48 km per second. Mercury moves slower in some parts of its orbit, faster in others. Its maximum speed at perihelion is 59 km per second. The planet tries to skip the closest area to the Sun as soon as possible. At aphelion, Mercury's speed is 39 km per second. The interaction of speed around the axis and speed along the orbit gives a striking effect. For 59 days, any part of the planet is in one position to the starry sky. This section returns to the Sun after 2 Mercurial years or 176 days. From this it turns out that the solar day on the planet is equal to 176 days. An interesting fact is observed at perihelion. Here, the orbital rotation speed becomes greater than the movement around the axis. This is how the effect of Joshua (the leader of the Jews who stopped the Sun) arises at longitudes that are turned towards the luminary.
Sunrise on the planet
The sun stops and then starts moving in the opposite direction. The luminary tends to the East, completely ignoring the western direction destined for it. This continues for 7 days, until Mercury passes the closest part of its orbit to the Sun. Then its orbital speed begins to decrease, and the movement of the Sun slows down. In the place where the speeds coincide, the luminary stops. A little time passes, and it begins to move in the opposite direction - from east to west. Regarding longitudes, the picture is even more surprising. If people lived here, they would watch two sunsets and two sunrises. Initially, the Sun would have risen, as expected, in the east. In a moment it would stop. After the beginning of the movement back and would disappear over the horizon. After 7 days, it would again shine in the east and make its way to highest point in the sky. Such striking features of the planet's orbit became known in the 60s. Previously, scientists believed that it is always turned to the Sun on one side, and moves around the axis at the same speed as around the yellow star.
The structure of Mercury
Until the first half of the 70s, little was known about its structure. In 1974, in March, the interplanetary station Mariner-10 flew 703 km from the planet. She repeated her maneuver in September of the same year. Now its distance to Mercury was equal to 48 thousand km. And in 1975, the station made another orbit at a distance of 327 km. It is noteworthy that the magnetic field was recorded by the equipment. It did not represent a powerful formation, but compared to Venus, it looked quite significant. Mercury's magnetic field is 100 times smaller than Earth's. Its magnetic axis is 2 degrees out of alignment with the axis of rotation. The presence of such a formation confirms that this object has a core, where this very field is created. Today there is such a scheme for the structure of the planet - Mercury has an iron-nickel hot core and a silicate shell that surrounds it. The core temperature is 730 degrees. Core large sizes. It contains 70% of the mass of the entire planet. The core diameter is 3600 km. The thickness of the silicate layer is within 650 km.
planet surface
The planet is littered with craters. In some places they are located very densely, in others there are very few of them. The largest crater is Beethoven, its diameter is 625 km. Scientists suggest that the flat terrain is younger than that dotted with many sinkholes. It was formed due to eruptions of lava, which covered all the craters and made the surface even. Here is the largest formation, which is called the Heat Plain. This is an ancient crater with a diameter of 1300 km. It is surrounded by a mountainous ring. It is believed that lava eruptions flooded this place and made it almost invisible. Opposite this plain there are many hills that can reach a height of 2 km. The lowlands are narrow. Apparently, a large asteroid that fell on Mercury provoked a shift in its bowels. In one place a large dent was left, and on the other side the crust rose and thus formed a displacement of rocks and faults. Something similar can be observed in other parts of the planet. These formations have a different geological history. Their shape is wedge-shaped. The width reaches tens of kilometers. It seems to be rock, which was squeezed out under enormous pressure from the deep bowels.
There is a theory that these creations arose with a decrease in the temperature regimes of the planet. The core began to cool and shrink at the same time. Thus, the top layer also began to decrease. Bark shifts were provoked. This is how this peculiar landscape of the planet was formed. Now temperature conditions Mercury also have certain specifics. Given that the planet is close to the Sun, the conclusion follows: the surface that faces the yellow star has too high a temperature. Its maximum can be 430 degrees (at perihelion). In aphelion, respectively, cooler - 290 degrees. In other parts of the orbit, the temperature fluctuates between 320-340 degrees. It is easy to guess that at night the situation here is completely different. At this time, the temperature is kept at minus 180. It turns out that in one part of the planet there is a terrible heat, and in another at the same time it is a terrible cold. An unexpected fact that the planet has reserves of water ice. It is found at the bottom of large craters at polar points. The sun's rays do not penetrate here. Mercury's atmosphere contains 3.5% water. It is delivered to the planet by comets. Some collide with Mercury as they approach the Sun and stay there forever. The ice melts into water and it evaporates into the atmosphere. At cold temperature it settles on the surface and turns back into ice. If it was at the bottom of the crater or at the pole, it freezes and does not return to the gaseous state. Since temperature differences are observed here, the conclusion follows: the cosmic body has no atmosphere. More precisely, there is a gas cushion available, but it is too rarefied. Main chemical element This planet's atmosphere is helium. It is brought here by the solar wind, a stream of plasma that flows out of the solar corona. Its main constituents are hydrogen and helium. The first is present in the atmosphere, but in a smaller ratio.
Research
Although Mercury is not at a great distance from the Earth, its study is quite difficult. This is due to the peculiarities of the orbit. This planet is very difficult to see in the sky. Only by observing it up close, you can get a complete picture of the planet. In 1974, such an opportunity arose. As already mentioned, this year there was an interplanetary station "Mariner-10" near the planet. She took pictures that mapped nearly half of Mercury's surface. In 2008, the Messenger station honored the planet with attention. Of course, they will continue to study the planet. What surprises it will present, we will see. After all, space is so unpredictable, and its inhabitants are mysterious and secretive.
Facts to know about the planet Mercury:
It is the smallest planet in the solar system.
A day here is 59 days, and a year is 88.
Mercury is the planet closest to the Sun. Distance - 58 million km.
This is a solid planet that belongs to the terrestrial group. Mercury has a heavily cratered, rugged surface.
Mercury has no satellites.
The exosphere of the planet consists of sodium, oxygen, helium, potassium and hydrogen.
There is no ring around Mercury.
There is no evidence of life on the planet. Daytime temperatures reach 430 degrees and drop to minus 180.
From the closest point to the yellow star on the surface of the planet, the Sun appears to be 3 times larger than from Earth.
Planet characteristics:
- Distance from the Sun: 57.9 million km
- Planet Diameter: 4878 km
- Days on the planet: 58 days 16 o'clock*
- Year on the planet: 88 days*
- t° on the surface: -180°C to +430°C
- Atmosphere: almost not present
- Satellites: does not have
* period of rotation around its own axis (in Earth days)
** orbital period around the Sun (in Earth days)
Mercury is the eighth largest planet and the closest to the Sun, with an average distance of 0.387 AU (astronomical units) or 57,910,000 kilometers. The mass of the planet is 3.30e23 kg, and the diameter is 4.880 km (only Pluto is smaller).
Presentation: planet Mercury
Internal structure
In the center of the planet is a metal core, similar to the earth, the difference is only in size. If the earth's core occupies only 17% of the planet's volume, then Mercury has 42% of the volume.
Around the core is a mantle layer - 500-700 kilometers of silicate rock. The next layer is the crust, which is about 100-300 kilometers thick. The upper layer of the planet has a lot of damage, most scientists adhere to the theory that they arose due to the slow cooling of Mercury.
atmosphere and surface
The atmosphere of Mercury is very rarefied and practically equates to a vacuum. Composition:
- hydrogen (70 atoms per 1 cm³);
- helium (4,500 atoms per 1 cm³).
Due to the almost zero atmosphere and proximity to the Sun, the temperature on the planet's surface fluctuates between -180….+440 °C. The surface resembles the lunar one - many craters (from a collision with asteroids), and mountains up to 4 km high (lunar ones can be one and a half times higher).
Unlike the Earth's satellite, on the reverse side of Mercury there are swellings that were formed under the influence of solar tides. There are also high ledges, whose length can reach several hundred kilometers.
The name of the planet was given by the ancient Romans, who revered the god Mercury as the patron of thieves, travelers and merchants. However, it is believed that the first planet from the Sun was known as early as 3000 BC. (from the time of the Samaritans).
IN Ancient Greece she was called immediately by two names - Apollo (god sunlight, patron of the arts and sciences) in the morning and Hermes (nimble messenger of the gods) in the evening. Moreover, the Greeks did not know that they were seeing the same planet.
For a long time, astronomers could not figure out the movement of Mercury across the sky, and all because of the anomalous precession of its orbit. Newtonian mechanics was in no way suitable for explaining an overly elongated orbit: perihelion = 46 million km from the Sun, aphelion = 70 million km. Scientists of the 19th century even believed that some other planet (sometimes called Vulcan) was moving close to Mercury, which influenced its orbit. It became possible to correctly predict the motion of the planet only after the discovery by Einstein of his General Theory of Relativity.
Exploring the planet
The study of Mercury is very complicated due to its close location to the Sun, from the American Hubble telescope impossible to get good quality pictures.
Only one interplanetary station approached the planet - Mariner 10, which made three flybys in 1974-1975. It turned out to make cartography only 45% of the planet.
Radar observations were also carried out, but these data are more of a theory than iron facts. So, a similar study showed the presence of frozen water at the north pole of Mercury (Mariner did not map this area).
First place in the list of planets of our solar system occupied by Mercury. Despite the rather modest size, this planet has an honorable role: to be closest to our star, to be approached by the cosmic body of our luminary. However, this location cannot be called very successful. Mercury is the closest planet to the Sun and is forced to endure the full force of the hot love and warmth of our star.
Astrophysical characteristics and features of the planet
Mercury is the smallest planet in the solar system, belonging together with Venus, Earth and Mars to the terrestrial planets. The average radius of the planet is only 2439 km, and the diameter of this planet at the equator is 4879 km. It should be noted that the size makes the planet not only the smallest among other planets in the solar system. In size, it is even smaller than some of the largest satellites.
Jupiter's satellite Ganymede and Saturn's satellite Titan have a diameter of over 5,000 km. Jupiter's moon Callisto is about the same size as Mercury.
The planet is named after the sly and swift Mercury, the ancient Roman god of trade. The choice of name is not accidental. A small and nimble planet moves the fastest in the sky. The movement and length of the orbital path around our star takes 88 Earth days. This speed is due to the close location of the planet to our star. The planet is at a distance from the Sun within 46-70 million km.
TO small sizes planets, the following astrophysical characteristics of the planet should be added:
- the mass of the planet is 3 x 1023 kg or 5.5% of the mass of our planet;
- the density of a small planet is slightly inferior to that of the earth and equals 5.427 g/cm3;
- gravitational force on it or acceleration free fall is 3.7 m/s2;
- the surface area of the planet is 75 million square meters. kilometers, i.e. only 10% of the earth's surface area;
- the volume of Mercury is 6.1 x 1010 km3 or 5.4% of the volume of the Earth, i.e. 18 such planets would fit in our Earth.
Mercury rotates around its own axis with a frequency of 56 Earth days, while a Mercury day lasts half an Earth year on the surface of the planet. In other words, during a Mercury day, Mercury basks in the rays of the Sun for 176 Earth days. In this situation, one side of the planet is heated to extreme temperatures, while the other side of Mercury at this time cools to a state of cosmic cold.
There are very Interesting Facts the state of the orbit of Mercury and the position of the planet in relation to other celestial bodies. There is practically no change of seasons on the planet. In other words, there is a sharp transition from a hot and hot summer to a fierce cosmic winter. This is due to the fact that the planet has an axis of rotation located perpendicular to the orbital plane. As a result of this position of the planet, there are areas on its surface that the sun's rays never touch. The data obtained from the Mariner space probes confirmed that on Mercury, as well as on the Moon, suitable water was found, which, however, is in a frozen state and is located deep under the surface of the planet. On the this moment it is believed that such areas can be found in areas close to the regions of the poles.
Other interesting property, which characterizes the orbital position of the planet, is the discrepancy between the speed of rotation of Mercury around its own axis with the movement of the planet around the Sun. The planet has a constant frequency of revolution, while it runs around the Sun with different speed. Near perihelion, Mercury moves faster than the angular velocity of the planet itself. This discrepancy is interesting astronomical phenomenon- The sun begins to move across the Mercury sky in the opposite direction, from the West to the east.
Given the fact that Venus is considered to be the closest planet to Earth, Mercury is often much closer to our planet than the “morning star”. The planet has no satellites, so it accompanies our star in splendid isolation.
Atmosphere of Mercury: origin and current state
Despite its close position to the Sun, the surface of the planet is separated from the star by an average of 5-7 tens of millions of kilometers, but the most significant daily temperature drops are observed on it. During the day, the surface of the planet is heated to the state of a hot frying pan, the temperature of which is 427 degrees Celsius. At night, cosmic cold prevails here. The surface of the planet has low temperature, its maximum reaches minus 200 degrees Celsius.
The reason for such extreme temperature fluctuations lies in the state of the Mercury atmosphere. It is in an extremely rarefied state, having no effect on thermodynamic processes on the surface of the planet. Atmospheric pressure here is very low and is only 10-14 bar. The atmosphere has a very weak influence on the climatic conditions of the planet, which is determined by the orbital position in relation to the Sun.
Basically, the atmosphere of the planet consists of molecules of helium, sodium, hydrogen and oxygen. These gases were either captured by the planet's magnetic field from solar wind particles or originated from the evaporation of the Mercury surface. The rarefiedness of the atmosphere of Mercury is evidenced by the fact that its surface is clearly visible not only from the board of automatic orbital stations, but also through a modern telescope. There is no cloudiness above the planet, opening up free access to the Mercury surface for the sun's rays. Scientists believe that this state of the Mercury atmosphere is explained by the close position of the planet to our star, its astrophysical parameters.
For a long time, astronomers had no idea what color Mercury was. However, observing the planet through a telescope and looking at pictures taken from spacecraft, scientists discovered a gray and unattractive Mercury disk. This is due to the lack of an atmosphere on the planet and the rocky landscape.
The strength of the magnetic field is clearly not able to resist the influence of the gravitational force that the Sun exerts on the planet. Solar wind streams supply the planet's atmosphere with helium and hydrogen, but due to constant heating, the heated gases dissipate back into outer space.
Brief description of the structure and composition of the planet
In this state of the atmosphere, Mercury is not able to protect itself from the attack of cosmic bodies falling on the surface of the planet. There are no signs of natural erosion on the planet, the surface is more likely to be affected by cosmic processes.
Like other terrestrial planets, Mercury has its own firmament, but unlike the Earth and Mars, which are mainly composed of silicates, it is 70% metal. This explains the rather high density of the planet and its mass. For many physical parameters Mercury is very much like our satellite. As on the Moon, the surface of the planet is a lifeless desert, devoid of a dense atmosphere and open to cosmic influence. At the same time, the crust and mantle of the planet have thin layer, if compared with terrestrial geological parameters. The inner part of the planet is mainly represented by a heavy iron core. It has a core, which consists entirely of molten iron and occupies almost half of the entire planetary volume and ¾ of the planet's diameter. Only an insignificant mantle, only 600 km thick, represented by silicates, separates the core of the planet from the crust. The layers of the Mercurial crust have different thicknesses, which vary in the range of 100-300 km.
This explains the very high density of the planet, which is uncharacteristic of planets similar in size and origin. celestial bodies. The presence of a molten iron core gives Mercury a magnetic field strong enough to counteract the solar wind by trapping charged plasma particles. Such a structure of the planet is uncharacteristic for most planets in the solar system, where the core accounts for 25-35% of the total planetary mass. Probably, such mercurology is caused by the peculiarities of the origin of the planet.
Scientists believe that the composition of the planet was strongly influenced by the origin of Mercury. According to one version, it is a former satellite of Venus, which subsequently lost its rotational momentum and was forced, under the influence of the Sun's gravity, to move into its own elongated orbit. According to other versions, at the formation stage, more than 4.5 billion years ago, Mercury collided with either Venus or another planetesimal, as a result of which most of the Mercury crust was demolished and dispersed in outer space.
The third version of the origin of Mercury is based on the assumption that the planet was formed from the remnants of cosmic matter left after the formation of Venus, Earth and Mars. Heavy elements, mostly metals, formed the core of the planet. For the formation outer shell the planet of lighter elements was clearly not enough.
Judging by the photos taken from space, the time of Mercury activity is long gone. The surface of the planet is a meager landscape, on which the main decoration are craters, large and small, presented in huge numbers. The Mercury Valleys are vast areas of solidified lava, which testifies to the former volcanic activity of the planet. The bark has no tectonic plates and covers the planet's mantle in layers.
The size of the craters on Mercury is amazing. The largest and largest crater, which was called the Heat Plain, has a diameter of more than one and a half thousand kilometers. The giant caldera of the crater, whose height is 2 km, suggests that the collision of Mercury with a cosmic body of this size had the scale of a universal cataclysm.
The early cessation of volcanic activity led to a rapid cooling of the planet's surface and the formation of an undulating landscape. The cooled layers of the crust crawled onto the lower ones, forming scales, and the impacts of asteroids and the fall of large meteorites only more disfigured the face of the planet.
Spacecraft and equipment involved in the study of Mercury
For a long time, we observed cosmic bodies, asteroids, comets, satellites of the planet and stars through telescopes, not having the technical ability to study our cosmic neighborhood in more detail and in detail. We looked at our neighbors and Mercury in a completely different way, including when it became possible to launch to distant planets space probes and apparatuses. We got a completely different idea of what outer space looks like, the objects of our solar system.
The bulk of scientific information about Mercury was obtained as a result of astrophysical observations. The study of the planet was carried out with the help of new powerful telescopes. Significant progress in the study of the smallest planet in the solar system was made by the flight of the American spacecraft Mariner-10. Such an opportunity appeared in November 1973, when the Atlas rocket with an astrophysical automatic probe was launched from Cape Canaveral.
The American space program "Mariner" assumed the launch of a series of automatic probes to the nearest planets, to Venus and Mars. If the first devices were mainly directed towards Venus and Mars, then the last, tenth probe, having studied Venus along the way, flew away towards Mercury. It was the flight of a small spacecraft that gave astrophysicists the necessary information about the surface of the planet, about the composition of the atmosphere and about the parameters of its orbit.
The spacecraft performed surveys of the planet from a flyby trajectory. The flight of the spacecraft was calculated in such a way that Mariner 10 could pass as many times as possible in close proximity to the planet. The first flight took place in March 1974. The device passed from the planet at a distance of 700 km, taking the first pictures of a distant planet from a close distance. During the second flyby, the distance decreased even more. The American probe swept over the surface of Mercury at an altitude of 48 km. For the third time, Mariner 10 was separated from Mercury by a distance of 327 km. As a result of the flights of the Mariner, it was possible to obtain images of the surface of the planet and draw up an approximate map of it. The planet turned out to be seemingly dead, inhospitable and unsuitable for existing and known to science life forms.
If you have any questions - leave them in the comments below the article. We or our visitors will be happy to answer them.
We also recommend
Loading...