The existence of the planet Mercury has been known for thousands of years. Since ancient times, with its rapid movement across the starry sky. Therefore, it got its name in honor of the fleet-footed god Mercury. This planet is best visible in the morning and evening. It can be observed with the naked eye, without a special telescope. Thanks to this, the planet Mercury has been presenting interesting facts about itself since time immemorial.

Is Mercury a former satellite?

There is an opinion that Mercury was once a satellite of Venus. But as a result of a cosmic catastrophe, Mercury separated from it and acquired a new orbit. Such interesting facts about the planet Mercury appeared in the middle of the 19th century. The impetus for this was the launch of the Mariner-10 spacecraft into outer space. At the same time, photographs of the Moon and Mercury were obtained. Scientists carefully studied the images and came to the conclusion that both cosmic bodies have a striking similarity in relief. A hypothesis arose that as a result of the collision of protoplanets, the Earth received the Moon as a satellite, and Venus received Mercury. Why Mercury subsequently “escaped” from Venus is explained by several theories:

Mercury collided with a large asteroid or comet and was blown towards the Sun.
Mercury was captured by the sun's gravity, as a result of which it acquired its own orbit.

It is not yet possible to prove whether this was actually the case. But astronomers suggest that inside Mercury contains a gigantic core the size of three-quarters the radius of the planet itself. And if this is so, then Mercury could never have been a satellite.

Educational and interesting facts about the planet Mercury

Mercury is particularly bright because it is closest to the Sun. The planet can deviate from the solar disk by no more than 28̊̊. And it is on such days that it can be seen in the starry sky without special equipment. You can still look at this planet through a telescope for an infinitely long time. Why is Mercury so attractive, and what individual characteristics does it have:

Mercury is the least studied terrestrial planet. Collecting and processing the information received is a rather labor-intensive process. It becomes obvious that the planet Mercury will reveal even more of its existence.

Mercury is the planet closest to the Sun in the Solar System, the smallest of the terrestrial planets. Named after the ancient Roman god of trade - fast Mercury, because it moves across the celestial sphere faster than other planets.

The average distance of Mercury from the Sun is slightly less than 58 million km (57.91 million km). The planet revolves around the Sun in 88 Earth days. Mercury's apparent magnitude ranges from −1.9 to 5.5, but it is not easily visible due to its proximity to the Sun.

Mercury belongs to the terrestrial planets. In its physical characteristics, Mercury resembles the Moon. It has no natural satellites, but has a very rarefied atmosphere. The planet has a large iron core, which is the source of a magnetic field whose strength is 0.01 of the Earth's magnetic field. Mercury's core makes up 83% of the planet's total volume. The temperature on the surface of Mercury ranges from 80 to 700K (−190 to +430°C). The solar side heats up much more than the polar regions and the far side of the planet.

The radius of Mercury is only 2439.7±1.0 km, which is smaller than the radius of Jupiter's moon Ganymede and Saturn's moon Titan (the two largest planetary moons in the solar system). But despite its smaller radius, Mercury surpasses Ganymede and Titan in mass. The mass of the planet is 3.3⋅1023 kg. The average density of Mercury is quite high - 5.43 g/cm³, which is only slightly less than the density of Earth. Considering that the Earth is much larger in size, the density value of Mercury indicates an increased content of metals in its depths. The acceleration of gravity on Mercury is 3.70 m/s². The second escape velocity is 4.25 km/s. Relatively little is known about the planet yet. It was only in 2009 that scientists compiled the first complete map of Mercury, using images from Mariner 10 and Messenger.

After Pluto was deprived of its planetary status in 2006, Mercury acquired the title of the smallest planet in the solar system.

Astronomical characteristics

Mercury's apparent magnitude ranges from −1.9m to 5.5m, but it is not easily visible due to its small angular distance from the Sun (maximum 28.3°).

The most favorable conditions for observing Mercury are at low latitudes and near the equator: this is due to the fact that the duration of twilight there is shortest. In mid-latitudes, finding Mercury is much more difficult and is possible only during the period of its best elongations. At high latitudes, the planet is almost never (except during eclipses) visible in the dark night sky: Mercury is visible for a very short period of time after dusk.

The most favorable conditions for observing Mercury in the middle latitudes of both hemispheres occur around the equinoxes (the duration of twilight is minimal). The optimal time for observing the planet is morning or evening twilight during periods of its elongations (periods of Mercury's maximum distance from the Sun in the sky, occurring several times a year).

Celestial mechanics of Mercury

Mercury revolves in its orbit around the Sun with a period of about 88 Earth days. The duration of one sidereal day on Mercury is 58.65 Earth days, and the duration of a solar day is 176 Earth days. Mercury moves around the Sun in a fairly elongated elliptical orbit (eccentricity 0.205) at an average distance of 57.91 million km (0.387 AU). At perihelion, Mercury is located 45.9 million km from the Sun (0.3 AU), at aphelion - 69.7 million km (0.46 AU), thus, 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 ecliptic plane is 7°. Mercury spends 87.97 Earth days on one orbital revolution. The average speed of the planet's orbit is 48 km/s (at aphelion - 38.7 km/s, and at perihelion - 56.6 km/s). The distance from Mercury to Earth varies from 82 to 217 million km. Therefore, when observed from Earth, Mercury changes its position relative to the Sun from the west (morning visibility) to the east (evening visibility) over several days.

There are no seasons on Mercury like there are on Earth. This occurs because the planet's rotation axis is almost perpendicular to the orbital plane. As a result, there are areas near the poles that are not illuminated by the sun's rays. Research carried out using the Arecibo radio telescope suggests that glaciers exist in this cold and dark zone. The layer of water ice can reach 2 m; it is probably covered with a layer of dust.

Atmosphere

When the Mariner 10 spacecraft flew past Mercury, it was established that the planet had an extremely rarefied atmosphere, the pressure of which was 5⋅1011 times less than the pressure of the Earth’s atmosphere. Under such conditions, atoms collide more often with the surface of the planet than with each other. The atmosphere is made up of atoms captured from the solar wind or knocked out from the surface by the solar wind - helium, sodium, oxygen, potassium, argon, hydrogen. The average lifetime of an individual atom in the atmosphere is about 200 days.

Mercury's magnetic field and gravity are not sufficient to preserve atmospheric gases from dissipation and maintain a dense atmosphere. Proximity to the Sun entails powerful solar wind and high temperatures (with strong heating, gases leave the atmosphere more actively). At the same time, Mars, which has a gravity almost equal to Mercury, but is located 4-5 times farther from the Sun, even without a magnetic field, did not completely lose its atmosphere to dissipate into space.

Mercury is one of the smallest planets in the solar system, located at the closest distance from the Sun. The Moon is a celestial body that is located relatively close to the Earth. In total, in the entire history of mankind, 12 people have visited the Moon. Up flies for six months. Today it takes only three days to get to the moon. Why are both of these celestial bodies interesting for astronomers and other scientists?

Why do earthlings need the Moon and Mercury?

The most frequently asked question regarding them is: “Which celestial body is larger - the Moon or Mercury?” Why does this mean so much to scientists? The fact is that Mercury is the closest candidate for colonization. Like the Moon, Mercury is not surrounded by an atmosphere. A day here lasts a very long time and amounts to as much as 59 Earth days.

The planet rotates around its axis very slowly. But not only the question of which celestial body is larger - the Moon or Mercury - is of interest to scientists in connection with possible colonization. The fact is that the exploration of Mercury may be hampered by its proximity to the main luminary of our system. But scientists suggest that there may be ice caps at the planet's poles that could facilitate the colonization process.

The closest planet to the Sun

On the other hand, close proximity to the star can guarantee a constant supply of solar energy, if scientists still manage to colonize the planet and build energy stations on it. Researchers believe that due to Mercury's slight tilt, there may be areas called "eternal light peaks" on its territory. They are of main interest to scientists. Mercury's soil contains large deposits of ore that can be used to create space stations. And its soils are rich in the element Helium-3, which could also become a source of inexhaustible energy.

Difficulties in studying Mercury

Mercury has always been very difficult for astronomers to study. Primarily due to the fact that the planet is obscured by the bright rays of the system’s main star. That is why scientists for a very long time could not determine which celestial body is larger - the Moon or Mercury. A planet rotating in the vicinity of the Sun always turns out to be facing the same side towards the star. Despite this, scientists have tried to map the far side of Mercury in the past. But she was not very popular, and she was treated with skepticism. For a very long time it was extremely difficult to determine which celestial body was larger - the Moon or Mercury. Photos of these planets allowed us to conclude that they were approximately the same.

and Mercury

Some of the first astronomical discoveries were the discovery of craters on Mars and the Moon. Then scientists expected that there would be plenty of them on Mercury. After all, this planet is located between the Moon and Mars in size. Moon or Mercury - which is larger and what does this have to do with craters? All this became known after an interplanetary station called Mariner 10 flew around Mercury twice. She took a huge number of photographs, and detailed maps of Mercury were also compiled. Now there was as much knowledge about the planet as there was about the Earth’s satellite.

It turned out that there are as many craters on the territory of Mercury as on the Moon. And a surface of this kind had exactly the same origin - countless meteorite showers and powerful volcanoes were to blame for everything. Even a scientist could not distinguish the surface of Mercury from the surface of the Earth's satellite from photographs.

Meteorite pits on these celestial bodies are formed due to the lack of an atmosphere that could soften impacts from the outside. Previously, scientists believed that Mercury still has an atmosphere, only a very rarefied one. The planet's gravity cannot maintain an atmosphere on its surface that could be similar to Earth's. But still, the instruments of the Mariner 10 station showed that the concentration of gases near the surface of the planet is greater than in space.

Is it possible

The first obstacle that stands in the way of those who dream of populating the Earth's satellite is its constant susceptibility to meteorite bombardment. Meteorite attacks, as scientists have found, occur a hundred times more often than previously thought. Various changes are constantly occurring on the surface of the Moon. Meteorite craters can range in diameter from a few centimeters to 40 meters.

However, in 2014, Roscosmos made a statement that by 2030 Russia would begin a program for mining minerals on the Moon. With regard to such programs, the question of which celestial body is larger - the Moon or Mercury - fades into the background. After all, so far this statement has been made only in relation to the Earth’s satellite. Russia has no plans to colonize Mercury yet. Plans for production were announced on Cosmonautics Day in 2014. For this purpose, the RAS is already developing a scientific program.

Moon or Mercury - which is larger and which planet is more advantageous for colonization?

On Mercury the temperature is about 430 °C. And it can drop to -180 °C. At night, the temperature on the surface of the Earth’s satellite also drops to -153 °C, and during the day it can reach +120 °C. In this regard, these planets are still equally unsuitable for colonization. Which celestial body is larger - the Moon or Mercury? The answer will be as follows: the planet is still larger. Mercury is larger than the Moon in size. The diameter of the Moon is 3474 km, and the diameter of Mercury is 4879 km. Therefore, for now, dreams of settling beyond the Earth remain a fantasy for humanity.

Education

Which celestial body is larger - the Moon or Mercury? Why might these celestial bodies be useful to earthlings?

March 23, 2017

Mercury is one of the smallest planets in the solar system, located at the closest distance from the Sun. The Moon is a celestial body that is located relatively close to the Earth. In total, in the entire history of mankind, 12 people have visited the Moon. The satellite flies to Mercury within six months. Today it takes only three days to get to the moon. Why are both of these celestial bodies interesting for astronomers and other scientists?

Why do earthlings need the Moon and Mercury?

The closest planet to the Sun

Difficulties in studying Mercury

Craters on the Moon and Mercury

Is colonization of the Moon possible?

However, in 2014, Roscosmos made a statement that by 2030 Russia would begin a program for mining minerals on the Moon. With regard to such programs, the question of which celestial body is larger - the Moon or Mercury - fades into the background. After all, so far this statement has been made only in relation to the Earth’s satellite. Russia has no plans to colonize Mercury yet. Plans for mining on the Moon were announced on Cosmonautics Day in 2014. For this purpose, the RAS is already developing a scientific program.

Moon or Mercury - which is larger and which planet is more advantageous for colonization?

Planets of the Solar System

According to the official position of the International Astronomical Union (IAU), the organization that assigns names to astronomical objects, there are only 8 planets.

Pluto was removed from the planet category in 2006. because There are objects in the Kuiper belt that are larger/equal in size to Pluto. Therefore, even if we take it as a full-fledged celestial body, then it is necessary to add Eris to this category, which has almost the same size as Pluto.

By MAC definition, there are 8 known planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

All planets are divided into two categories depending on their physical characteristics: terrestrial planets and gas giants.

Schematic representation of the location of the planets

Terrestrial planets

Mercury

The smallest planet in the solar system has a radius of only 2440 km. The period of revolution around the Sun, equated to an earthly year for ease of understanding, is 88 days, while Mercury manages to rotate around its own axis only one and a half times. Thus, his day lasts approximately 59 Earth days. For a long time it was believed that this planet always turned the same side to the Sun, since periods of its visibility from Earth were repeated with a frequency approximately equal to four Mercury days. This misconception was dispelled with the advent of the ability to use radar research and conduct continuous observations using space stations. The orbit of Mercury is one of the most unstable; not only the speed of movement and its distance from the Sun change, but also the position itself. Anyone interested can observe this effect.

Mercury in color, image from the MESSENGER spacecraft

Its proximity to the Sun is the reason why Mercury is subject to the largest temperature changes among the planets in our system. The average daytime temperature is about 350 degrees Celsius, and the nighttime temperature is -170 °C. Sodium, oxygen, helium, potassium, hydrogen and argon were detected in the atmosphere. There is a theory that it was previously a satellite of Venus, but so far this remains unproven. It does not have its own satellites.

Venus

The second planet from the Sun, the atmosphere is almost entirely composed of carbon dioxide. It is often called the Morning Star and the Evening Star, because it is the first of the stars to become visible after sunset, just as before dawn it continues to be visible even when all the other stars have disappeared from view. The percentage of carbon dioxide in the atmosphere is 96%, there is relatively little nitrogen in it - almost 4%, and water vapor and oxygen are present in very small quantities.

Venus in the UV spectrum

Such an atmosphere creates a greenhouse effect; the temperature on the surface is even higher than that of Mercury and reaches 475 °C. Considered the slowest, a Venusian day lasts 243 Earth days, which is almost equal to a year on Venus - 225 Earth days. Many call it Earth's sister because of its mass and radius, the values of which are very close to those of Earth. The radius of Venus is 6052 km (0.85% of Earth's). Like Mercury, there are no satellites.

The third planet from the Sun and the only one in our system where there is liquid water on the surface, without which life on the planet could not have developed. At least life as we know it. The radius of the Earth is 6371 km and, unlike other celestial bodies in our system, more than 70% of its surface is covered with water. The rest of the space is occupied by continents. Another feature of the Earth is the tectonic plates hidden under the planet's mantle. At the same time, they are able to move, albeit at a very low speed, which over time causes changes in the landscape. The speed of the planet moving along it is 29-30 km/sec.

Our planet from space

One revolution around its axis takes almost 24 hours, and a complete passage through the orbit lasts 365 days, which is much longer in comparison with its closest neighboring planets. The Earth's day and year are also accepted as a standard, but this is done only for the convenience of perceiving time periods on other planets. The Earth has one natural satellite - the Moon.

Mars

The fourth planet from the Sun, known for its thin atmosphere. Since 1960, Mars has been actively explored by scientists from several countries, including the USSR and the USA. Not all exploration programs have been successful, but water found at some sites suggests that primitive life exists on Mars, or existed in the past.

The brightness of this planet allows it to be seen from Earth without any instruments. Moreover, once every 15-17 years, during the Confrontation, it becomes the brightest object in the sky, eclipsing even Jupiter and Venus.

The radius is almost half that of Earth and is 3390 km, but the year is much longer - 687 days. He has 2 satellites - Phobos and Deimos .

Visual model of the solar system

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Sun
The Sun is a star that is a hot ball of hot gases at the center of our Solar System. Its influence extends far beyond the orbits of Neptune and Pluto. Without the Sun and its intense energy and heat, there would be no life on Earth. There are billions of stars like our Sun scattered throughout the Milky Way galaxy.
Mercury
Sun-scorched Mercury is only slightly larger than Earth's satellite the Moon. Like the Moon, Mercury is practically devoid of an atmosphere and cannot smooth out the traces of impact from falling meteorites, so it, like the Moon, is covered with craters. The day side of Mercury gets very hot from the Sun, while on the night side the temperature drops hundreds of degrees below zero. There is ice in the craters of Mercury, which are located at the poles. Mercury completes one revolution around the Sun every 88 days.
Venus
Venus is a world of monstrous heat (even more than on Mercury) and volcanic activity. Similar in structure and size to Earth, Venus is covered by a thick and toxic atmosphere that creates a strong greenhouse effect. This scorched world is hot enough to melt lead. Radar images through the powerful atmosphere revealed volcanoes and deformed mountains. Venus rotates in the opposite direction from the rotation of most planets.
Earth is an ocean planet. Our home, with its abundance of water and life, makes it unique in our solar system. Other planets, including several moons, also have ice deposits, atmospheres, seasons and even weather, but only on Earth did all these components come together in a way that made life possible.
Mars
Although details of the surface of Mars are difficult to see from Earth, observations through a telescope indicate that Mars has seasons and white spots at the poles. For decades, people believed that the bright and dark areas on Mars were patches of vegetation, that Mars might be a suitable place for life, and that water existed in the polar ice caps. When the Mariner 4 spacecraft arrived at Mars in 1965, many scientists were shocked to see photographs of the murky, cratered planet. Mars turned out to be a dead planet. More recent missions, however, have revealed that Mars holds many mysteries that remain to be solved.
Jupiter
Jupiter is the most massive planet in our solar system, with four large moons and many small moons. Jupiter forms a kind of miniature solar system. To become a full-fledged star, Jupiter needed to become 80 times more massive.
Saturn
Saturn is the farthest of the five planets known before the invention of the telescope. Like Jupiter, Saturn is composed primarily of hydrogen and helium. Its volume is 755 times greater than that of the Earth. Winds in its atmosphere reach speeds of 500 meters per second. These fast winds, combined with heat rising from the planet's interior, cause the yellow and golden streaks we see in the atmosphere.
Uranus
The first planet found using a telescope, Uranus was discovered in 1781 by astronomer William Herschel. The seventh planet is so far from the Sun that one revolution around the Sun takes 84 years.
Neptune
Distant Neptune rotates almost 4.5 billion kilometers from the Sun. It takes him 165 years to complete one revolution around the Sun. It is invisible to the naked eye due to its vast distance from Earth. Interestingly, its unusual elliptical orbit intersects with the orbit of the dwarf planet Pluto, which is why Pluto is inside the orbit of Neptune for about 20 years out of 248 during which it makes one revolution around the Sun.
Pluto
Tiny, cold and incredibly distant, Pluto was discovered in 1930 and was long considered the ninth planet. But after discoveries of Pluto-like worlds that were even further away, Pluto was reclassified as a dwarf planet in 2006.

Planets are giants

There are four gas giants located beyond the orbit of Mars: Jupiter, Saturn, Uranus, Neptune. They are located in the outer solar system. They are distinguished by their massiveness and gas composition.

Planets of the solar system, not to scale

Jupiter

The fifth planet from the Sun and the largest planet in our system. Its radius is 69912 km, it is 19 times larger than the Earth and only 10 times smaller than the Sun. The year on Jupiter is not the longest in the solar system, lasting 4333 Earth days (less than 12 years). His own day has a duration of about 10 Earth hours. The exact composition of the planet's surface has not yet been determined, but it is known that krypton, argon and xenon are present on Jupiter in much larger quantities than on the Sun.

There is an opinion that one of the four gas giants is actually a failed star. This theory is also supported by the largest number of satellites, of which Jupiter has many - as many as 67. To imagine their behavior in the planet’s orbit, you need a fairly accurate and clear model of the solar system. The largest of them are Callisto, Ganymede, Io and Europa. Moreover, Ganymede is the largest satellite of the planets in the entire solar system, its radius is 2634 km, which is 8% greater than the size of Mercury, the smallest planet in our system. Io has the distinction of being one of only three moons with an atmosphere.

Saturn

The second largest planet and the sixth in the solar system. In comparison with other planets, it is most similar to the Sun in the composition of chemical elements. The radius of the surface is 57,350 km, the year is 10,759 days (almost 30 Earth years). A day here lasts a little longer than on Jupiter - 10.5 Earth hours. In terms of the number of satellites, it is not much behind its neighbor - 62 versus 67. The largest satellite of Saturn is Titan, just like Io, which is distinguished by the presence of an atmosphere. Slightly smaller in size, but no less famous are Enceladus, Rhea, Dione, Tethys, Iapetus and Mimas. It is these satellites that are the objects for the most frequent observation, and therefore we can say that they are the most studied in comparison with the others.

For a long time, the rings on Saturn were considered a unique phenomenon unique to it. Only recently it was established that all gas giants have rings, but in others they are not so clearly visible. Their origin has not yet been established, although there are several hypotheses about how they appeared. In addition, it was recently discovered that Rhea, one of the satellites of the sixth planet, also has some kind of rings.