Mercury - the first planet solar system. Not so long ago it ranked almost last among all 9 planets in size. But, as we know, nothing lasts forever under the Moon. In 2006, Pluto lost its status as a planet due to its oversized size. They began to call him dwarf planet. Thus, Mercury is now at the end of a series of cosmic bodies that cut countless circles around the Sun. But this is about sizes. In relation to the Sun, the planet is the closest - 57.91 million km. This 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, sometimes, on the contrary, closer to it. At perihelion (the point of its orbit closest to the Sun), the planet approaches the blazing star at 45.9 million km. And at aphelion (the farthest point of the orbit), the distance to the Sun increases and is equal to 69.82 million km.
Regarding the Earth, the scale is slightly different. Mercury from time to time approaches us up to 82 million km or diverges to a distance of 217 million km. The smallest number does not mean that the planet can be examined carefully and for a long time in a telescope. Mercury deviates from the Sun at an angular distance of 28 degrees. It follows that this planet can be observed from Earth just before dawn or after sunset. You can see it almost at the horizon line. You can also see not the whole body, but only half of it. Mercury rushes through orbit at a speed of 48 km per second. The planet completes a full revolution around the Sun in 88 Earth days. The value that shows how different the orbit is from the circle is 0.205. The takeoff between the orbital plane and the equatorial plane 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. It’s a shame to realize that even some of the planets’ satellites have surpassed it here. The diameter of the largest satellite, Ganymede, which orbits Jupiter, is 5262 km. Titan, the satellite of Saturn, has an equally impressive appearance. Its diameter is 5150 km. The diameter of Callisto (a 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 learned by comparison. The small planet is quite inferior 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 that of the Earth, 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 full revolution around the Sun in 88 days. It rotates around its axis in 59 Earth days. The average speed is 48 km per second. In some parts of its orbit, Mercury moves slower, in others faster. Its maximum speed at perihelion is 59 km per second. The planet is trying to pass the closest part to the Sun as quickly 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 damaging effect. For 59 days, any part of the planet is in the same position to the starry sky. This portion returns to the Sun after 2 Mercury years or 176 days. From this it turns out that a solar day on the planet is equal to 176 days. An interesting fact is observed at perihelion. Here the speed of rotation along the orbit 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 strives to the East, completely ignoring what was destined for it western direction. 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. At the point where the velocities 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. It would have stopped in a moment. Afterwards it began to move backwards and disappear beyond the horizon. After 7 days, it would shine again in the east and make its way to the highest point in the sky without obstacles. Such striking features of the planet’s orbit became known in the 60s. Previously, scientists believed that it is always turned to the Sun with one side, and moves around its axis at the same speed as around the yellow star.
Structure of Mercury
Until the first half of the 70s, people knew little 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 48 thousand km. And in 1975, the station made another orbit at a distance of 327 km. It is noteworthy that the equipment detected a magnetic field. It was not a powerful formation, but compared to Venus it looked quite significant. Mercury's magnetic field is 100 times inferior to Earth's. Its magnetic axis does not coincide with the axis of rotation by 2 degrees. 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 a hot iron-nickel 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 diameter of the core is 3600 km. The thickness of the silicate layer is within 650 km.
Surface of the planet
The planet is dotted 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 the one dotted with many craters. It was formed due to lava emissions, which covered all the craters and made the surface flat. Here is the largest formation, which is called the Plain of Heat. 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 2 km in height. The lowlands are narrow. Apparently, a large asteroid that fell on Mercury provoked a shift in its interior. In one place a large dent was left, and on the other side the crust rose and thus formed rock displacements and faults. Something similar can be observed in other places on the planet. These formations already have a different geological history. Their shape is wedge-like. The width reaches tens of kilometers. It seems that this is a rock that was squeezed out under enormous pressure from the deep bowels.
There is a theory that these creations arose when the temperature conditions of the planet decreased. The core began to cool and at the same time contract. Thus, the top layer also began to decrease. Shifts of the cortex were provoked. This is how this peculiar landscape of the planet was formed. Now temperature conditions Mercury also have certain specifics. Taking into account the fact 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). At aphelion, it is correspondingly 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 remains at minus 180. It turns out that in one part of the planet there is terrible heat, and in another at the same time there is terrible cold. It is an unexpected fact that the planet has reserves of water ice. It is found at the bottom of large craters at polar points. Here Sun rays do not penetrate. Mercury's atmosphere contains 3.5% water. Comets deliver it to the planet. Some collide with Mercury when approaching the Sun, and remain here forever. The ice melts into water, which evaporates into the atmosphere. At cold temperature it settles to the surface and turns into ice again. If it ends up at the bottom of a crater or at a pole, it freezes and never returns to a gaseous state. Since temperature differences are observed here, the conclusion follows: the cosmic body has no atmosphere. More precisely, there is a gas cushion, but it is too rarefied. Main chemical element The atmosphere of this planet is helium. It is brought here by the solar wind, a stream of plasma that flows from the solar corona. Its main components are hydrogen and helium. The first is present in the atmosphere, but in a smaller proportion.
Research
Although Mercury is not at a great distance from 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 can you get a complete picture of the planet. In 1974, such an opportunity arose. As already mentioned, this year the Mariner 10 interplanetary station was near the planet. She took photographs and used them to map almost half of Mercury's surface. In 2008, the Messenger station paid attention to the planet. Of course, the planet will continue to be studied. We'll see what surprises she brings. After all, space is so unpredictable, and its inhabitants are mysterious and secretive.
Facts worth knowing 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 rocky planet that belongs to the terrestrial group. Mercury has a heavily cratered, rugged surface.
Mercury has no satellites.
The planet's exosphere 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 3 times larger than from Earth.
But after it was demoted from the status of “full-fledged” planets, primacy passed to Mercury, which is what our article is about today.
History of the discovery of the planet Mercury
The history of Mercury and our knowledge of this planet goes back to ancient times; in fact, it is one of the first planets known to mankind. This is how Mercury was observed back in ancient Sumer, one of the first developed civilizations on Earth. The Sumerians associated Mercury with the local god of writing, Nabu. Babylonian and ancient Egyptian priests, who were also excellent astronomers of the ancient world, also knew about this planet.
As for the origin of the name of the planet “Mercury”, it comes from the Romans, who named this planet in honor of the ancient god Mercury (in the Greek version Hermes), the patron of trade, crafts and the messenger of others olympian gods. Also, astronomers of the past sometimes poetically called Mercury the morning or evening dawn, according to the time of its appearance in the starry firmament.
God Mercury, after whom the planet was named.
Also, ancient astronomers believed that Mercury and its closest neighbor, the planet Venus, revolved around the Sun, and not around the Earth. But in turn it revolves around the Earth.
Features of the planet Mercury
Perhaps the most interesting feature of this small planet is the fact that it is on Mercury that the largest temperature fluctuations occur: since Mercury is closest to the Sun, during the day its surface warms up to 450 C. But on the other hand, Mercury does not have its own atmosphere and cannot retain heat, as a result, at night the temperature drops to minus 170 C, here the largest temperature difference in our solar system.
Mercury is only slightly larger in size than our Moon. Its surface is also similar to that of the Moon, riddled with craters and traces of small asteroids and meteorites.
Interesting fact: approximately 4 billion years ago, a huge asteroid crashed into Mercury, the force of which can be compared to the explosion of a trillion megaton bombs. This impact left a giant crater on the surface of Mercury, about the size of the modern state of Texas; astronomers called it the crater Basin Caloris.
Also very interesting is the fact that on Mercury there is real ice, which is hidden in the depths of the craters there. Ice could have been brought to Mercury by meteorites, or even formed from water vapor that escaped from the bowels of the planet.
Another interesting feature of this planet is the reduction in its size. The decrease itself, scientists believe, is caused by the gradual cooling of the planet, which occurs over millions of years. As a result of cooling, its surface collapses and lobe-shaped rocks form.
The density of Mercury is high, higher only at our Earth, in the center of the planet there is a huge molten core, making up 75% of the diameter of the entire planet.
With the help of NASA's Mariner 10 research probe sent to the surface of Mercury, an amazing discovery was made - there is a magnetic field on Mercury. This was all the more surprising, since according to the astrophysical data of this planet: the rotation speed and the presence of a molten core, magnetic field shouldn't be there. Despite the fact that the strength of Mercury's magnetic field is only 1% of the strength of the Earth's magnetic field, it is superactive - the magnetic field of the solar wind periodically enters the field of Mercury and from interaction with it strong magnetic tornadoes arise, sometimes reaching the surface of the planet.
The speed of the planet Mercury, at which it revolves around the Sun, is 180,000 km per hour. Mercury's orbit is oval-shaped and highly elongated epileptically, as a result of which it either approaches the Sun by 47 million kilometers, or moves away by 70 million kilometers. If we could observe the Sun from the surface of Mercury, it would appear three times larger from there than from Earth.
One year on Mercury is equal to 88 Earth days.
Mercury photo
We bring to your attention a photo of this planet.
Temperature on Mercury
What is the temperature on Mercury? Although this planet is located closest to the Sun, the championship of the warmest planet in the solar system belongs to its neighbor Venus, whose thick atmosphere, which literally envelops the planet, allows it to retain heat. As for Mercury, due to the lack of an atmosphere, its heat evaporates and the planet both quickly heats up and cools down quickly; every day and every night there are simply huge temperature changes from +450 C during the day to -170 C at night. At the same time, the average temperature on Mercury will be 140 C, but this is not cold, not hot, the weather on Mercury leaves much to be desired.
Is there life on Mercury?
As you probably guessed, with such temperature fluctuations the existence of life is not possible.
Atmosphere of Mercury
We wrote above that there is no atmosphere on Mercury, although one can argue with this statement; the atmosphere of the planet Mercury is not absent, it is simply different and different from what we actually understand by atmosphere.
The original atmosphere of this planet was dissipated 4.6 billion years ago due to the very weak Mercury, which simply could not contain it. In addition, the proximity to the Sun and constant solar winds also did not contribute to the preservation of the atmosphere in the classical sense of the term. However, a weak atmosphere on Mercury remains, and it is the most unstable and insignificant atmosphere in the solar system.
The composition of Mercury's atmosphere includes helium, potassium, sodium, and water vapor. In addition, the planet's current atmosphere is periodically replenished from various sources, such as solar wind particles, volcanic degassing, and radioactive decay of elements.
Also, despite small size and the meager density of Mercury's atmosphere can be divided into as many as four sections: the lower, middle and upper layers, as well as the exosphere. The lower atmosphere contains a lot of dust, which gives Mercury a peculiar red-brown appearance; it warms up to high temperatures due to the heat that is reflected from the surface. The middle atmosphere has a current similar to the earth's. Mercury's upper atmosphere actively interacts with solar winds, which also heat it to high temperatures.
The surface of the planet Mercury is bare rock of volcanic origin. Billions of years ago, molten lava cooled and formed a rocky, gray surface. This surface is also responsible for the color of Mercury - dark gray, although due to the dust in the lower layers of the atmosphere it seems that Mercury is red-brown. Images of the surface of Mercury taken from the Messenger research probe are very reminiscent of the lunar landscape, the only thing is that there are no “lunar seas” on Mercury, while there are no Mercury scarps on the Moon.
Rings of Mercury
Does Mercury have rings? After all, many planets of the solar system, for example, and of course they are present. Alas, Mercury literally has no rings at all. Rings cannot exist on Mercury again due to the proximity of this planet to the Sun, because the rings of other planets are formed from ice debris, pieces of asteroids and other celestial objects, which near Mercury are simply melted by hot solar winds.
Moons of Mercury
Just like Mercury has no satellite rings. This is due to the fact that there are not many asteroids flying around this planet - potential candidates for satellites when they come into contact with the planet’s gravity.
Rotation of Mercury
The rotation of the planet Mercury is very unusual, namely, the orbital period of its rotation is shorter compared to the duration of rotation around its axis. This duration is less than 180 Earth days. While the orbital period is half as long. In other words, Mercury goes through two orbits in three of its revolutions.
How long does it take to fly to Mercury?
At its closest point, the minimum distance from Earth to Mercury is 77.3 million kilometers. How long will it take modern spacecraft to cover such a distance? NASA's fastest spacecraft to date, New Horizons, which was launched to Pluto, has a speed of about 80,000 kilometers per hour. It would take him about 40 days to get to Mercury, which is comparatively not that long.
The first spacecraft, Mariner 10, launched to Mercury back in 1973, was not so fast; it took 147 days to reach this planet. Technology is improving, and perhaps in the near future it will be possible to fly to Mercury in a few hours.
- Mercury is quite difficult to spot in the sky, as it “loves to play hide and seek,” literally “hiding” behind the Sun. However, ancient astronomers knew about it. This is explained by the fact that in those distant times the sky was darker due to the lack of light pollution, and the planet was visible much better.
- The shift in Mercury's orbit helped confirm Albert Einstein's famous theory of relativity. In short, it talks about how the light of a star changes when another planet orbits it. Astronomers reflected a radar signal from Mercury, and the path of this signal coincided with predictions general theory relativity.
- The magnetic field of Mercury, the very existence of which is very mysterious, in addition to everything else, also differs at the poles of the planet. At the south pole it is more intense than at the north.
Mercury, video
And finally interesting documentary about the flight to the planet Mercury.
Mercury is similar in physical characteristics to 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 is heating up significantly more than its back side and polar regions.
Craters of Mercury
On the surface of Mercury there is a large number of craters, this landscape is very reminiscent of the lunar one. The density of craters differs in different parts of Mercury. It is possible that the areas of the planet's surface that are more heavily dotted with craters are more ancient, and those that are less dotted are younger. They were formed as a result of lava flooding the 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 similar on the Moon. For example, scarps are numerous jagged slopes that extend for hundreds of kilometers. When studying the scarps, it was found that they were formed during the compression of the surface that accompanied the cooling of Mercury, during which the surface area of the planet decreased by 1%. Because There are well-preserved large craters on the surface of Mercury, which 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 in the history of Mercury of any some significant atmosphere).
During the research, the Messenger probe obtained photographs of more than 80% of the planet's surface, as a result of which it was determined that it was homogeneous, unlike the surface of Mars or the Moon, in which one hemisphere is very different from the other.
The elemental composition of Mercury's surface, obtained by the Messenger X-ray fluorescence spectrometer, showed that the planet's surface is rich in plagioclase feldspar, characteristic of the continental regions of the Moon, and, in comparison, poor in calcium and aluminum. It is also rich in magnesium and low in iron and titanium, which allows it to fill the gap between ultrabasic rocks, like terrestrial komatiites, and typical basalts. A relative abundance of sulfur has also been discovered - this means that the planet was formed under reducing conditions.
The craters of Mercury differ from each other. They can be small bowl-shaped depressions, or multi-ring impact craters that are hundreds of kilometers in diameter. Mercury's craters to varying degrees destroyed. There are more or less well-preserved ones, with long rays located around them, formed during the release of substance 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 noticeable 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, the collision of which with the surface of Mercury formed a crater, 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 force of the impact is also evidenced by the fact that it provoked the emission of lava, as a result of which the Zhary Mountains, more than 2 km high, were formed around the crater. Kuiper Crater (60 km across) is the point on the planet's surface with the highest albedo. Most likely, Kuiper crater is one of the “last” large craters on Mercury to form.
Another interesting arrangement of craters on the planet was discovered by scientists in 2012: the sequence of crater locations forms the face of Mickey Mouse. Maybe in the future this configuration will be called that way.
Geology of Mercury
More recently, it was believed that in the depths of Mercury there is a metallic core, the radius of which 
Rogo 1800 - 1900 km, it makes up 60% of the mass of the planet, since a weak magnetic field was discovered 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 group took stock in 2007, 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, we can say with almost one hundred percent accuracy that Mercury’s core is liquid.
Compared to any planet in the solar system, Mercury's core has a higher percentage of iron. There are several versions of the explanation for this. The most widely accepted theory in the world of science says that Mercury, while originally 2.25 times as massive as it is today, had the same proportion of silicates and metal as a normal meteorite. But at the very beginning of the history of the Solar System, a planet-like body, several hundred kilometers in diameter and with a mass 6 times less, collided with Mercury. Because of this collision, it was torn away from the planet. most of primary crust and mantle, as a result of which the relative proportion of the core in the composition of 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 obtained during the study of the elemental composition of the surface of Mercury using the AMS Messenger gamma spectrometer (it allows measuring the content radioactive isotopes). It turned out that the planet has a lot of potassium (a volatile element compared to thorium and uranium, which are more refractory). This is not consistent with the inevitable collision high temperatures. 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, to date, is small to explain the high medium density planets.
A silicate mantle (500-600 km thick) surrounds Mercury's core. The thickness of its crust ranges from 100 to 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-Tolstovsky, 2- Tolstoyan, 3- Kalorian, 4- late Kalorian, 5- Mansurian and 6- Kuiper. And the relative geological age of Mercury is divided into periods according to these 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 Plain of Heat) 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 this, 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 planet's time of volcanism ended after the mantle shrank enough to prevent lava from reaching Mercury's surface. It is possible that this happened during the first 700-800 million years since the formation of Mercury. Later changes in the planet's landscape were caused by impacts of cosmic bodies on its surface.
Mercury's magnetic field
The strength of Mercury's magnetic field is approximately one hundred times less than that of Earth and is equal to ~300 nT. Mercury's magnetic field has a dipole structure, is very symmetrical, its axis is only 10 degrees deviated from Mercury's rotation axis. This significantly reduces the number of hypotheses explaining the origin of Mercury's magnetic field. Presumably, Mercury's magnetic field arises as a result of the dynamo effect (the same happens on Earth). Perhaps this effect is a consequence of the circulation of the liquid core. The very strong tidal effect occurs due to the very pronounced eccentricity of Mercury. This tidal effect keeps the core liquid, which is mandatory conditions to create a dynamo effect. The planet's magnetic field is so strong that it can change the direction of the solar wind around Mercury, resulting in the creation of its magnetosphere. 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 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, 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 intertwined magnetic field knots that connect the spacecraft to Mercury's magnetic field. The diameter of the vortex was 800 km, this 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; the solar wind penetrates through them, reaching the surface of the planet. The connection between 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.
To get an idea of how big Mercury is, let's look at it in comparison to our planet.
Its diameter is 4879 km. This is approximately 38% of the diameter of our planet. In other words, we could put three Mercurys side by side and they would be slightly larger than Earth.
What is the surface area
The surface area is 75 million square kilometers, which is approximately 10% of the Earth's surface area.
If you could expand Mercury, it would become almost double more area Asia (44 million square kilometers).
What about volume? The volume is 6.1 x 10*10 km3. This big number, but this is only 5.4% of the Earth's volume. In other words, we could put 18 Mercury-sized objects inside the Earth.
Weight is 3.3 x 10*23 kg. Again, this is a lot, but in terms of ratio it is only equal to 5.5% of the mass of our planet.
Finally, let's look at the force of gravity on its surface. If you could stand on the surface of Mercury (in a good, heat-resistant spacesuit), you would feel 38% of the gravity you feel on Earth. In other words, if you weigh 100 kg, then on Mercury there are only 38 kg.
| · · · · | |
| · | |
Mercury's rotation is very strange compared to Earth's. It rotates around its axis relatively slowly compared to its orbital period.
Orbital characteristics
One revolution of the planet takes 116 Earth days, and the orbital rotation period is only 88 days. Thus, a day is much longer than a year. The planet's equatorial rotation speed is 10.892 km/h.
In some places on the planet, an observer can see a very unusual sunrise. After sunrise, the Sun stops for one Mercury day (that's almost 116 Earth days). This occurs approximately four days before perihelion due to the planet's angular orbital velocity being equal to its angular rotational velocity. This causes the visible stop in the sky of the planet. After Mercury reaches perihelion, its angular orbital velocity exceeds its angular velocity and the star again begins to move in the opposite direction.
Here is another way to explain this in more detail: During one Mercury year, the average speed of the Sun is two degrees per day, due to the fact that the day is longer than the rotation period.
Changes in traffic at different times of the year
As it approaches aphelion, the orbital motion slows down, and its movement across the planet's sky increases by more than 150% of the normal angular velocity (up to three degrees per day). On the other hand, as it approaches perihelion, the movement of the Sun slows down and stops, and then begins to slowly move westward, and then faster and faster. While the star changes its speed across the planet’s horizon, it visible size becomes larger or smaller, depending on how far it is from the planet.
The rotation period was not discovered until 1965. Several decades ago, it was believed that Mercury was always turned to the Sun by the same side due to tidal forces.
But as a result of a radar study of the planet in 1962, with the help of the Arecibo Observatory, it was found that the planet rotates and the sidereal period of rotation of the planet is 58.647 days.
| · · · · | |
