Mercury data

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The symbol of mercury

orbit parameter

Half-length diameter 0.38709893 astronomical unit

Eccentricity 0.20563069

The inclination angle is 7.00487 degrees.

Period of revolution 87.9693 days

The rotation period is 58.6462 days.

physical parameter

The mass is 3.302× 1023kg.

The average radius is 2440 1 km.

The average density is 5.427 g/cm3.

Ground gravity (equator) 3.70 1m/s2

The escape speed is 4.435 km/s.

Mercury is one of the nine planets in the solar system, ranking first from near to far from the sun.

catalogue

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* 1 overview

* 2 Physical properties

O 2. 1 atmospheric pressure

O 2.2 Temperature and sunshine conditions

O 2.3 topography

O 2.4 internal material composition

O 2.5 revolution

O 2.6 rotation

O 2.7 magnetic field

O 2.8 Iron on Mercury

O 2.9 Ice on Mercury

* 3 Mercury exploration

O 3. 1 prophase

O 3.2 National Aeronautics and Space Administration

O 3.3 Japan and the European Space Agency

O 3.4 Possibility of becoming a human colony

* 4 science fiction novels about Mercury

* 5 Please refer to

* 6 references

* 7 external links

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abstract

Mercury is the second smallest planet in the solar system, larger than the moon 1/3, and the closest planet to the sun. Mercury's visual magnitude is between 0.4 and 5.5; Mercury is so close to the sun that it is often submerged by fierce sunlight, so telescopes can rarely observe it carefully. Mercury has no natural satellites. The only satellite that has ever been close to Mercury is the American probe Mariner 10. When exploring Mercury from 1974 to 1975, only about 45% of the surface was photographed (see the right). Mercury is the fastest moving planet in the solar system.

The English name of Mercury comes from the Roman god Mercury. Above the symbol is a circle, and below it is a short vertical line and a semicircle (Unicode:? This is the shape of mercury's wand. In the 5th century, Mercury was actually considered as two different planets, because it often appeared alternately on both sides of the sun. When it appears in the evening, it is called mercury; But when it appeared in the morning, it was called Apollo to commemorate Apollo, the sun god. Pythagoras later pointed out that they were actually the same planet. In ancient China, Mercury was called the "morning star".

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physical features

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atmosphere

Mercury has only a small amount of atmosphere. Mercury has an extremely thin atmosphere. In fact, gas molecules in Mercury's atmosphere collide with the surface of Mercury more frequently than with each other. For these reasons, Mercury should be considered as having no atmosphere. The atmosphere is mainly composed of oxygen, potassium and sodium.

The atoms that make up Mercury's atmosphere are constantly disappearing into space, because the average "lifetime" of potassium or sodium atoms on a Mercury Day (a Mercury Day-half of its perihelion time) is about 3 hours. The lost atmosphere is constantly replaced by some mechanisms, such as being captured by planetary gravitational fields, volcanic steam, degassing of polar ice sheets and so on.

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Temperature and sunshine conditions

The average surface temperature of Mercury is about 452K, ranging from 90 K to 700K, and it is the planet with the largest temperature difference. Comparing with the earth, the temperature change on the earth is only11k. (This is only solar radiation energy, regardless of "season" and "weather") The sunshine intensity on the surface of Mercury is 8.9 times that of the Earth, and the total * * * irradiance is 9 126.6W/m2.

Surprisingly, the radar observation of 1992 shows that there is ice at the North Pole of Mercury. It is generally believed that ice exists at the bottom of the crater that the sun never shines, and it is accumulated due to the impact of gas from the inner surface of comets and/or planets.

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topography

Mercury's crater is very similar to the moon. One of the most striking features on the surface of Mercury (including only the photographed part) is an impact crater with a diameter of 1350km: Calorie Basin, which is the highest temperature area on Mercury. Mercury's topography is marked as undulating, because the cooling and contraction of Mercury's core caused the shell to wrinkle billions of years ago. Most mercury surfaces include two different age groups; Younger ones are relatively flat, probably because lava is immersed in earlier terrain. In addition, Mercury has "remarkable" and "periodic expansion".

The surface of Mercury is much like the moon, covered with craters, great plains, basins, radiation patterns and cliffs. 1976, the international astronomical union began to name craters on mercury.

The topographical features of Mercury are as follows:

* Craters-Please refer to the list of Mercury craters.

* albedo characteristics (indicating the reflection of different areas)

* Mountains-please refer to the list of Mercury Mountains.

* Mountains

* Great Plains-View a list of Mercury Plains.

* Cliffs-please refer to the list of Mercury Cliffs.

* Grand Canyon-please refer to the list of Mercury Canyon.

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Internal material composition

This planet has a relatively large iron core (even compared with the earth); Mercury is composed of about 70% metal and 30% silicate, so its density is very high. The average density is 5430 kg/m3; The density is slightly less than that of the earth, but greater than that of Venus. The reason for the high density of the earth is that its mass has compressed its volume. The mass of Mercury is only 5.5% of the Earth's-the iron core accounts for 42% of the planet's volume (the core only accounts for 17%), and the planet's mantle is 600km thick around the core. The total weight of mercury is about 3 trillion tons.

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Rotate around (a larger celestial body)

Mercury's orbit is eccentric, with a radius ranging from 46 meters to 70 meters. The slow precession around the sun cannot be completely explained by Newton's classical mechanics, so that many people use another planet closer to the sun (sometimes called Vulcan) to explain the chaos during this period. This is called "Mercury perihelion precession". In any case, Einstein's general theory of relativity later provided an explanation that could eliminate this small mistake.

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Radial

From 65438 to 0889, Italian astronomer Shapari observed that the rotation time and revolution time of Mercury were both 88 days. It was not until 1965 that American astronomers measured the exact period of Mercury's rotation as 58.646 days.

At some time, in some places on the surface of mercury, on the same mercury day, when the observer observes (when the sun rises), he can see that the sun rises first, then goes backwards and finally sets, and then rises again. This is because during the perihelion of about four days, the orbital speed of Mercury is completely equal to its rotation speed, so the apparent motion of the sun stops. At perihelion, Mercury's orbital speed exceeds its rotation speed. So the sun seems to be retrograde, and after four days of perihelion, the sun returns to normal visual movement.

It was not until 1965 that the observation data denied Mercury's view that the sun tide was fixed: its rotation made Mercury always face the sun. Mercury's orbital speed is 3:2, which means it takes three times to go around the sun; The eccentricity of mercury's orbit keeps this resonance stable. At first, astronomers thought it had a fixed tide because Mercury was in the best observation position. It always shows the same side at the same moment of 3:2 resonance, as if it were completely fixed. Mercury rotates 59 times slower than the earth.

Because the orbital speed ratio of Mercury is 3:2, a sidereal day (rotation period) is about 58.7 Earth days, and a solar day (the time when the sun crosses two meridians) is about 65,438+076 Earth days.

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magnetic field

Regardless of the slow rotation, Mercury has a relatively strong magnetosphere, which is 1% of the magnetic force generated by the earth. This magnetic field is produced in a way similar to that of the earth, which is an electric field generated by the flow of metal liquid in the core; At present, it is estimated that the core of Mercury is not hot enough to liquefy nickel-iron alloy, but it should be able to liquefy some low-melting substances, such as sulfur or matte. It is also possible that Mercury's magnetic field is the residual product of the early generator effect that has stopped now, and the magnetic field is "frozen (preserved)" in solid magnetic substances.

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Iron on mercury

Mercury contains more iron than any other known galactic planet. Several theories have been proposed to explain the high metallicity of mercury.

One theory holds that mercury's initial ratio of metallosilicates is similar to that of ordinary chondrites. At that time, its mass was about 2.25 times that of today, but at some point in the history of the early solar system, an asteroid knocked out 1/6 of Mercury. As a result, the crust and mantle of Mercury disappeared. Another similar theory is used to explain the formation of the earth and the moon. See the Great Influence Theory. On the other hand, mercury may have stabilized in the early modeling stage of the so-called solar nebula before the solar burst energy. In this theory, the mass of mercury is about twice that of that time; However, due to the contraction of the protostar, the temperature of Mercury reached about 2500K to 3500K; Even as high as 10000K, many rocks on the surface of mercury evaporate at this temperature, forming "rock vapor", which is then taken away by interstellar storms. The third theory, similar to the second one, holds that the shell of Mercury has been eroded by the solar wind for a long time.

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Ice on Mercury

The radar observation of 1992 shows that Mercury contains frozen water ice. This is thought to exist only at the bottom of the eternal dark crater, erupted by comets and/or from the interior of the planet, and accumulated there.

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Mercury exploration

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early stage

Mercury was first discovered by Semu people (3000 BC), who called it Ubud-Idim-Gude-Ude. The earliest people who recorded the observation data in detail were Babylonians, who called them gu-ad or gu-utu. The Greeks gave it two ancient names, Apollo when it appeared in the morning and Hermes when it appeared in the evening, but Greek astronomers knew that the two names had the same meaning. The Greek philosopher Heraclitus even thought that Mercury and Venus revolved around the sun, not the earth. The observation of mercury is very complicated because it is too close to the sun; The only time you can observe it on earth is at sunrise or sunset.

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National Aeronautics and Space Administration (NASA)

The only capsule close to Mercury is Mariner 10. Recently, a project approved by NASA was named "MESSENGER" (short for Mercury Surface, Space Environment, Geochemistry and Ranging, meaning "Mercury Surface, Space Environment, Geochemistry and Omni-directional Telemetry"), which was launched in June 2004 and arrived at Mercury in March 201year.

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Japan and the European Space Agency

Japan plans to join a project of the European Space Agency called BepiColombo, which will launch two spacecraft orbiting Mercury, one for mapping Mercury and the other for studying its magnetic field. The lander included in the original plan has been abandoned. The Russians sent their spacecraft by Soyuz rocket between 20 1 1 and 20 12, and the spacecraft will arrive at Mercury four years later.

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The possibility of becoming a human colony

The craters in Mercury's north and south poles are probably suitable for human settlements outside the earth, because the temperature there is constant all the year round (about -200℃). This is because the weak axis of Mercury is inclined and there is basically no atmosphere, so it is difficult to carry heat from the part where the sun shines here, even if the bottom of the crater at the shallow poles of Mercury is always dark. Proper human activities will heat the ant colony to a comfortable temperature, which is more comfortable around than most parts of the earth.

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Science fiction about mercury

Mercury is a subject of interest to science fiction writers. The main topics include the dangers of exposure to solar radiation; Staying on the dividing line between light and dark of Mercury (the dividing line between day and night) and moving slowly may be damaged by excessive radiation and authoritarian government (probably because of the high surface temperature of Mercury).

* Eric Rucker Eddison's series of fantasy novels starting with the serpent worm (1922) is set in Mercury, but the name is used purely for its singular value, without considering the known facts about it at that time.

* H. P. Lovecraft's "The Shadow Out of Time" briefly mentioned this planet: "Later, with the end of the earth's span, the transferred ideas (the great Yi Si race) will travel through time and space again-reaching another stop in the physical body of Mercury spherical plants."

* Only Kurt Vonnegut Jr.'s novel Sai Ren of Titan (1959) is more realistic, in which brainless creatures called symphonies live in the caves of Mercury.

* isaac asimov's short story "The First Series, Robots" (1950) takes place on Mercury and involves a robot specially designed to deal with the planet's intense solar radiation.

* Asimov's juvenile novels Lucky Star and Mercury Sun (1956) also took place there.

Asimov's short story Night of the Dead is a murder mystery, in which astronomers from Mercury, the Moon and a fictional space station are suspected of murder. The dynamics and living conditions in these places are the key to finding out which astronomer is guilty.

* Arthur C. Clarke's "Island in the Sky" (1952) describes a terrible creature, who lives in the dark side that was considered to be forever dark at that time, but occasionally goes to the twilight zone.

* In Arthur C. Clarke's novel Meet Rama (1973), Mercury is ruled by a grumpy metal miner's government, which tries to destroy the alien spaceship Rama. This novel shares with several other novels the background of a colonial solar system, especially the Imperial Earth.

* In several novels and short stories by Kim Stanley Robinson, especially "Mercury" in Planet on the Table (1986) and Blue Mars (1996), Mercury is the location of a huge city called Terminator. The city rolls in orbit around the equator of the earth, keeping pace with the rotation of the earth, so the sun will never rise completely on the horizon, and the city can avoid dangerous solar radiation; Power comes from the heat of the sun, which expands the rails during the day. The city was ruled by an autocratic dictator called the Lion of Mercury.

* Alan E. Nourse's short story "Brightside Crossing" tells the survivors of such an attempt, which has become the ultimate sports feat.

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See.

:: Transit of mercury

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refer to

* Neil Cummins's Discovery of the Basic Universe (200 1)

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external links

* "Bepicolombo", the Mercury mission of ESA.

Messenger, NASA's Mercury mission.

* SolarViews.Com

solar system

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Satellites/Asteroids: List of Asteroid Belt, Kuiper Belt, Oort Cloud, Comet and Star Distance.

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Page Classification: Solar System | Planets | Planets in the Solar System | Mercury