Mercury (English: Mercury; Latin : Mercurius), due to rapid movement, Europe Ancient times called it Mercury "Mercury" means Ancient Rome The mythical messenger god who runs at great speed. The ancient Chinese called Chen Xing, the Western Han Dynasty "Shi Ji" Book of Heaven The author of Sima Qian From the actual observation, it is found that the star is gray, which is associated with the theory of five elements, and it is named Mercury after black water.

Mercury is Solar system the Eight planets The smallest and closest planet to the sun. Orbital period It's 87.9691 days, and it meets Earth once every 116 days or so, revolution Far faster than any other planet in our solar system. Mercury has the largest temperature difference between day and night on its surface, atmosphere Too thin to retain heat effectively during the day equator The temperature in the area can reach 437°C and drop to -172°C at night. Mercury has the smallest axial tilt of all the planets in the solar system (approx 1 / 30 Degree), but there is the maximum Orbital eccentricity . Mercury is in aphelion The distance is about perihelion One and a half times. Mercury's surface is covered crater , and seleno Like other moons, its geology has been inactive for billions of years.

Mercury is the only planet with no seasons Sun Orbital resonance . It takes almost as long to rotate three times as it takes to orbit the sun twice. Mercury is seen from the sun only once every two Mercury years, based on its rotation and revolution Solar day .

Mercury's orbit lies inside the Earth (with Venus The same), so it can only appear in the sky at dawn and dusk and during the day, not around midnight. Mercury's brightness varies greatly from Earth, Apparent magnitude From -2.48 to 7.25, but it's with the sun Spur Angle Maximum is only 28.3°. in The northern hemisphere Only in the early morning or at dusk twilight Mercury is seen in the sky. when Long range Occurring at latitudes south of the equator when in the southern hemisphere mid-latitude Mercury can be seen in a completely dark sky.

Chinese name: Mercury
Foreign name: Mercury
alias: Morning star
categorize: planet , Terrestrial planet
Mass and quantity: 3.3011 ✕ 10 23 kg
Mean density: 5.427 g/cm³
Straight diameter: 4880 km
Surface temperature: -190 to 428 ° C
Escape velocity: 4.25 km/s
albedo: 0.088 (Sphere, 0.142 geometry)
Apparent magnitude: -2.48 to 7.25 etc ^[1]
Rotation period: 58.65 days
Ground distance: 150000000 km

Semi-major axis: 0.3871 astronomical units
eccentricity: 0.205630
Period of revolution: 87.9691 days
Flat near point Angle: 174.796 degrees
Orbital inclination: 7.00487 degrees
Longitude of ascending node: 48.331 degrees
volume: 6.083×10¹⁰ cubic kilometers
Surface area: 7.48 x 10 Guess m ²
Conjunctive period: 115.88 days
Perihelion Angle: 29.124 °
perihelion: 0.307499 Astronomical unit
aphelion: 0.466697 astronomical units
Angle of rotation: 0.034 °
Angular diameter: 4.5 "- 13"

catalogue

Human history

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Discovery & Naming

Mercury, a collection of woodcuts edited by Gudbonati in 1550

In ancient China, Mercury was called the "cinnabar". It is the largest with the sun Angular distance Not more than 28°, because the ancient called 30° for one hour, so named. ^[1]

Mercury Craters

In 1976, International Astronomical union Start naming craters on Mercury. Of the more than 310 craters that have been named, 21 are named after Chinese historical figures. For example, Bo Ya : The legend is a musician of the Spring and Autumn Period; CAI Yan : Poetess in the late Eastern Han Dynasty; Li Bai: Great poet in Tang Dynasty; Bai Juyi: Great poet of the Tang Dynasty: Dong Yuan : Painters of the Five Dynasties and Ten kingdoms in the Southern Tang Dynasty; Li Qingzhao: female poet of Southern Song Dynasty; Jiang Kui: musician of the Southern Song Dynasty; Liang Kai : Southern Song Dynasty painter; Guan Hanqing: Yuan Dynasty opera; Ma Zhiyuan: Yuan Dynasty opera; Zhao Mengzhi «¯ : Book of the Yuan Dynasty Wang Meng : Painter at the end of Yuan Dynasty; Zhu Dali: painter in the early Qing Dynasty; Cao Xueqin: literary writer in Qing Dynasty; Lu Xun : Chinese modern writers. ^[5] Qi Baishi: modern painter; Anglophobia : Ming Dynasty painter; Han Gan : Tang Dynasty painter; Du Fu: Tang Dynasty poet; Wen Tianxiang: Song Dynasty poet; bleak : Song Dynasty painter; Silver snake (light spot) ^[13]

Astronomical data

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Motion & Track

revolution

perihelion

Mercury has an orbit of all the planets eccentricity The largest is 0.20563, and its distance from the Sun varies between 46 million and 70 million kilometers. It's 87.969 Earth Day It completes one full orbit around the sun. Mercury's orbital map on the right has the same superposition Semi-major axis The circular track to show Orbital eccentricity The impact. Signs at 5-day intervals are displayed in perihelion It has a large distance and clearly shows a relatively high orbital velocity. The size of the balls, inversely proportional to their distance from the sun, is used to illustrate Heliocentric distance The change. The change in distance to the sun, combined with the planets around Axis of rotation Rotation of Orbital resonance , result in Surface temperature Complex changes. This resonance makes a Mercury day two Mercury years in length, or about 176 Earth days. mercurial Orbital plane The plane of the Earth's orbit (the ecliptic) is tilted by 7 degrees, as shown in the image on the right. A transit of Mercury in front of the Sun occurs only when Mercury crosses the ecliptic plane and is also between the Earth and the Sun. On average, it happens about once every seven years. mercurial Angle of rotation Almost zero, measuring less than 0.027 degrees. This is obviously much smaller Jupiter It is the second smallest planet with a value of 3.1 degrees. This means that at the poles of Mercury observer , the Sun Central point The height will never be higher Horizon line Upper 2.1 Minute of arc .

At certain points on Mercury's surface, observers can see it Sun Halfway up, it reverses back to sunset and then rises again; At all points, this happens on the same Mercury day. This is because about four Earth days before perihelion, the angular speed of Mercury's orbit is almost the same as its rotation speed, so the sun's velocity is the same Apparent motion Will stall; At perihelion, Mercury orbits Angular velocity More than the angular speed of Mercury's rotation. Thus, for a hypothetical observer on Mercury, it would be obvious to see the Sun retrograde. It was observed at these points four days after passing perihelion Apparent solar motion It's back to normal.

Mercury and Earth involution The average period (closest to Earth) is 116 Earth days, but due to Mercury's orbit eccentricity This interval varies from 105 to 129 days. Mercury can come as close as 77.3 million km to Earth, but will not come within 80 million km until 28622, 82.1 million km in 2679, and 82 million km in 4487. The retrograde time that can be seen from Earth is about 8-15 days before and after the endoconjunction, so the wide range of variations is entirely due to its large eccentricity.

Mercury orbit

Diagram of Mercury's revolution

Diagram of Mercury rotation

autorotation

The year 1889 Italy After years of observations, astronomer Giovanni Schiaparelli determined that Mercury's rotation time and orbit time are both 88 days. For many years, Mercury was thought to be in sync with the Sun Tidal locking With the same side facing the sun in every orbit, like seleno Always with the same side facing the earth. During radar observations in 1965, American astronomers measured the precise period of Mercury's rotation to be 58.646 days, proving that Mercury resonates with a rotational orbit of 3:2 per revolution Sun The second time also rotates three times; And the high eccentricity of Mercury's orbit makes this resonance stable - at perihelion, the sun's Tidal force At its strongest, the sun appears calmly (steadily) in the sky closest to Mercury.

At first, astronomers thought the reason it was synchronously locked was that when Mercury was in a position suitable for observation, it was almost always in the same position in the 3:2 resonance and therefore presented the same face. It's also because of Mercury Period of revolution With the earth Conjunctive period Half a coincidence, due to Mercury's 3:2 spin orbital resonance, one Solar day The sun crosses twice culmination the Time interval About 176 Earth days. one Sidereal day ( Rotation period It is about 59 Earth days.

Simulation studies show the orbit of Mercury eccentricity It's chaotic, and over millions of years it will be affected by other planets perturbation Range from near 0 (circular) to over 0.45. This is thought to explain Mercury's 3:2 spin orbital resonance (rather than the more common 1:1), since this state is present during periods of high eccentricity orbits May happen Yes. Numerical simulation Shows future long-term orbital resonance with Jupiter interaction Will cause the perihelion distance to increase, in the next 5 billion years there is a 1% chance that Venus Collision.

Perihelion precession

1859, French mathematician and astronomer Auburn Le Verrier Urbain Jean Joseph Le Verrier reports that Mercury orbits Sun The orbit has Newtonian mechanics And the slowness of the known planetary perturbations cannot be fully explained precession . He suggested dealing with these with "another planet (or a series of smaller bodies) in an orbit closer to the sun than Mercury. perturbation (Other explanations include the sun's slight flattening.) Based on Uranus The orbit was disturbed and found Neptune Its success gave astronomers confidence in the explanation, and the hypothetical planet was named Vulcanization But the planet was never discovered.

The perihelion of a mercury relative to the Earth precession That's 5600 per century Second of arc (1.5556 degrees), or 574.10±0.65 relative to the inertial ICFR per century Second of arc ; But Newtonian mechanics, which takes into account all the influences from the other planets, predicts a precession of only 5557 arcseconds (1.5436 degrees) per century. In the early 20th century, Einstein's General relativity An explanation for the observed precession is provided. This effect is very small: the relativistic precession of Mercury's perihelion is 42.98 arcseconds per century, just enough to be previously inadequate; However, after 12 million revolutions, it still has a slight surplus. Other planets have a very similar situation, but the effects are much smaller: Venus It's 8.62 arcseconds per century, 3.84 arcseconds for Earth, 1.35 arcseconds for Mars, Icarus (1566 Icarus) is 10.05 arcseconds.

Ground observation

Diagram of the inner planets (Mercury, Venus)

mercurial Apparent magnitude Between −2.6 magnitude (brighter than the brightest stars) Sirius Brighter) and +5.7 etc. (close to theory Naked eye visible Limiting value ) between. These two items. Extreme value Both appear as Mercury in the sky Apparent position Close to the sun. Due to its proximity to the sun, it is difficult to observe, spending most of its time lost in sunlight and only visible during the brief twilight hours before sunrise or after sunset. Speaking of the five planets Mercury, since ancient times Macroscopic observation It's the hardest. According to legend, the great astronomer Copernicus Before he died, he lamented that he had never seen Mercury in his life. Mercury, like some other planets and bright stars, can be found in Total solar eclipse The time to be seen.

like seleno and Venus As well, the phases of Mercury can be observed from Earth. Its "new moon" appears in involution The "full moon" appears in Waihe. Due to its relatively close proximity to the Sun, Mercury is not visible from Earth in either of these phases. The best time to observe Mercury is about 50 minutes before sunrise or 50 minutes after sunset.

If necessary Spyglass Looking at Mercury, you can choose whether Mercury is farthest from the Sun on one side of its orbit or the other. Long range ) and search for it before sunrise or after sunset. The astronomical almanac will tell you whether this so-called "great distance" is west (right) or east (left) of the sun. If it is in the west, it can be observed in the early morning. If it is in the east, it can be observed at dusk. You know the date, you know what side of the sun to look for, and you should try to pick a spot where there's nothing blocking the horizon. The search for Mercury should be about one tussah width from where the sun rises or sets. You will see a small star that glows reddish.

On its quilt sunlight You can observe it for about two weeks before it submerges. Six weeks later, it reappears at the opposite distance.

In most parts of China, there are usually only two or three optimal Mercury viewing opportunities a year. When Mercury is the evening star, from late March to early June each year, especially in mid to late May, it has the opportunity to reach a relatively large altitude, which can be found in the evening western sky. When Mercury is the morning star, from early September to early December, especially mid-to-late October, it has the opportunity to reach a relatively large altitude, which can be sought to the east at dawn. It is worth noting that it is not necessary to say that the Mercury in these two periods will be higher, only when the Mercury large distance occurs during this period, the height will be larger, otherwise it can only wait for the next year. For example, there are two large distances in 2021 that are very close to the best observation date. They are the Evening Star on May 17 and the Morning Star on October 25. ^[9]

Mercury isn't as hard to see with the naked eye as you might think. If you want to observe Mercury, it is important to choose its large distance, and for observers at 30, or even 20 degrees north and south latitude, the mercury relative to the Sun declination Extremely important. According to legend, the great astronomer Copernicus Before he died, he lamented that he had never seen Mercury in his life.

Copernicus There are two important objective reasons why Mercury has not been seen: First, in the last 5,000 years, The northern hemisphere Relative to the southern Hemisphere, Mercury is not suitable for observation, because whenever Mercury is at a large distance from it aphelion Observers in the northern hemisphere will notice that Mercury's declination is always lower Solar declination Even though Mercury is away from the sun Spur Angle Near the maximum of 28 degrees, Mercury still rises and sets almost at the same time as the sun. By contrast, when Mercury reaches perihelion, northern hemisphere observers see Mercury higher than the sun's declination. But perihelion is only 18 degrees away, so Mercury is still hard to see. It would take another few thousand years for Mercury's perihelion to precess by 90 degrees to change. Second, Geographical latitude The higher the height, Inner planet The harder it is to see. High latitudes of the region, the sun Dusk and morning For a long time, before sunrise or long after sunset, the sky is still bright, so it is not conducive to observing Mercury, even if Mercury is at least brighter than the sun whenever it is above the sun's declination for a large distance in the northern hemisphere Vega (Vega) Bright, but the bright sky background still makes Mercury difficult to observe.

In the northern Hemisphere, such as China, it is easy to observe Mercury if you choose the right date and the weather is good. The best months of the year to observe Mercury are March, April, September, and October, around the spring and autumn equinox. The differential value of the declination of the ecliptic is the largest in the spring and autumn period, (the declination of the ecliptic changes the most), and the declination of the distance between the sun and Mercury is larger than that of other ecliptic regions when the sun and Mercury are at the same distance Angle. When Mercury's declination is much larger than that of the Sun, the northerly Mercury can be observed long after the sun is below the horizon. The experience is: Vernal equinox The season in the west of Pisces, Aries Looking for, Autumnal equinox The season is in the lion, Virgo Look for Mercury. Mercury is quite bright, in Baby blue The low sky of dawn and dusk glows with an unblinking yellow light.

Usually by binoculars Mercury can even be seen directly with the naked eye, but it is always very close to the sun twilight It's hard to see. Mike Harvey's planet-hunting chart shows Mercury's position in the sky (and the positions of other planets) at this time, which is further customized by the Starry Sky program.

Mercury probe

In order to fully understand Mercury, as of October 2022, humans have sent three probes to Mercury, namely Mariner 10 probe, Messenger Mercury probe and BepiColombo Mercury probe. ^[16-17]

Mariner 10

Mariner 10, the first Mercury probe

The first to probe Mercury spaceship is NASA the Mariner 10 (Mariner 10, 1974-1975). This ship spaceship Using Venus' gravity to adjust its orbital speed allowed it to approach Mercury and make it the first ship to use Gravity assist Effect, and NASA's first visit to multiple planets Space mission . Mariner 10 provided the first close-up images of Mercury's surface, which immediately revealed a large number of ringed mountains, as well as many other types of geological features, such as giant steep slopes, later attributed to a slight contraction of Mercury's iron core as it cooled. Unfortunately, due to the length of Mercury's orbital period, Mariner 10 looked at the same side of the planet every time it approached. This made it impossible for Mariner 10 to observe the full surface of Mercury, and the result was less than 45% of the completed map of Mercury's surface.

A composite image of Mercury's surface taken by Mariner 10 in 1974

On March 27, 1974, two days before the first flyby of Mercury, Mariner 10 instruments unexpectedly discovered a large number of nearby Mercury Ultraviolet radiation This led to the initial belief that Mercury has moons. Soon after, overdose Ultraviolet light Be identified as Colossus 31, and Mercury's moon became a footnote in astronomical history books. The spacecraft flew by Mercury three times, and at its closest approach it was only 327 kilometers from the surface. During the first approach, the instrument detected Mercury's magnetic field, which made the planet geologist Big surprise - because Mercury's rotation is too slow to create a dynamo effect. The second approach was mainly to capture images, but extensive magnetic data were obtained during the third approach. These data show that Mercury's magnetic field is very similar to Earth's, which causes Mercury's surrounding Solar wind Create a deviation. Mercury magnetic field There are still several major competing theories about the origin of the virus. On March 24, 1975, just eight days after its final approach to Mercury, Mariner 10 ran out of fuel. No longer able to accurately control its orbit, mission controllers shut down the probe's instruments. Mariner 10 is thought to still be orbiting the sun, still passing close to Mercury every few months.

Messenger

The Messenger Mercury probe is preparing for launch

Messenger The Messager was NASA's second spacecraft to Mercury, launched on August 3, 2004, using a Boeing Dale He's a Type 2 rocket from Cape Canaveral Air Force Station Launch. It flew by Earth in August 2005, and by Venus in October 2006 and June 2007, adjusting it to the right orbit to orbit Mercury. Messenger made its first flyby of Mercury on January 14, 2008, followed by another flyby on October 6, 2008, and a third flyby on September 29, 2009. During these flybys, the hemispheres that Mariner 10 had not photographed were photographed. The probe successfully entered the orbit around Mercury on March 18, 2011 Elliptical orbit . Messenger is in a Large elliptical orbit It orbits Mercury on a 12-hour cycle, at its closest distance of 200 km and at its farthest of 15,193 km. The lowest point of its orbit is above Mercury's latitude of 60 degrees north, chosen in part so that it can study the giant in detail The Karori Basin . With a diameter of 1,550 km, this basin is the largest on Mercury Surface feature . The first image of Mercury in orbit was obtained on March 29, 2011. The probe has completed one year of mapping and is working on another extended year of exploration scheduled for 2013. In addition to continuing to observe and map Mercury, Messenger will also observe 2012 Solar maximum .

The first and last pictures taken by Messenger

Messenger impact point

The mission will clarify six key questions: Mercury's High density Geological history, the nature of the magnetic field, the structure of the nucleus, the poles Water ice . And how the thin atmosphere formed. To achieve these goals, Messenger carries imaging equipment with much higher resolution than Mariner 10's instruments spectrograph geodesy Abundance of elements , and magnetometer Wait for equipment to measure Charged particle The speed of... Detailed measurements of small changes in the probe's orbital speed are used to infer detailed information about Mercury's internal structure. United States Eastern time April 30, 2015 at 3:26 PM ( Beijing time At 3:26 am on May 1), Messenger ended its exploration mission by crashing into Mercury The North Pole Nearby left an equivalent NBA The size of a basketball court Impact crater (about 15 meters in diameter).

MESSENGER

Messenger probe

The Messenger Mercury probe

The Bepicolumbo

European Space Agency In cooperation with Japan, two spacecraft are planned to orbit Mercury: one to map the planet and the other to study its magnetosphere, called the BepiColombo exploration program. Launched on October 20, 2018, the spacecraft is expected to reach Mercury by 2025. The vehicle will release a magnetometer into the orbit around Mercury Elliptical orbit , and then Chemical rocket Will ignite to allow the mapping probe to enter Circular orbit . Both probes will operate for one Earth year. The mapping probe will carry a spectrometer similar to Messenger's, and study the planet at many different wavelengths, including Infrared ray , ultraviolet light, X-ray and Gamma ray .

The Bepicolumbo

In 2023, Scientists from the French National Center for Scientific Research and other institutions have discovered a mechanism for auroras that may be common throughout the solar system. This discovery comes from the Mercury probe." The Bepicolumbo Data from the first flyby of Mercury. The study revealed that auroras in Mercury's southern magnetosphere are similar to those on Earth and Mars, and the processes that create auroras are similar to those observed on Earth, Jupiter, Saturn, and Uranus. ^[15]

Future colony

At Mercury's north and south poles crater It is a very likely place to become an extraterrestrial human colony, because the temperature there is constant all year round (about -200 ° C). This is because of Mercury's weak axial tilt and because it has little atmosphere, heat from the sunlit part is hard to carry here, even the shallower craters at Mercury's poles are always dark at the base. appropriate Human activity It will be able to heat the colony to a comfortable temperature around a region that is lower than most of the Earth Ambient temperature Will make the lost heat easier to deal with. ^[10]

Salt glacier

In November 2023, the United States Planetary Science Institute (PSI) scientific research team in-depth study of Mercury, that in the North Pole of Mercury around the Laditradi and Emineescu crater, found traces of salt glaciers, speculated that under the hot surface of Mercury, there may be life. ^[14]

Geographical feature

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atmosphere

Due to the lack of atmospheric surrounding, Mercury has a steep temperature difference between the equator and the poles on its surface, ranging from 100K to 700K. The temperature of the subhelion is as high as 700K at perihelion and only 550K at aphelion. On the night side of the planet, the average temperature is 110K. The intensity range of sunlight is Solar constant (1,370W·m 2 - ) 4.59 and 10.61 times.

Although Mercury's surface temperature is very high during the day, observations strongly support the presence of ice (frozen water) on Mercury. in Polar region The bottom of the pit is never exposed to direct sunlight, and the temperature remains below 102K, well below the global average. Water ice is highly reflective of radar, and observations by the 70-meter telescope and the VLA in the early 1990s revealed very high specks of radar reflection near the poles. Although ice is not the likely cause of these reflected areas, astronomers believe that ice is the most likely. ^[6]

In the permanently dark craters of Mercury's North Pole, there is a hidden mass of water ice (yellow)

The area of ice is believed to hold about 10 14 - 10 15 Kilograms of ice, possibly covered in a layer Epiclastic cut Inhibited sublimation. Compare that to the Earth The South Pole The ice sheet is about 4×10 18 Kilograms of ice, from the South Pole of Mars Ice cap There are about 10 16 Kilo of ice. The source of Mercury's ice is unknown, but there are two most likely sources: emissions from the planet's interior, or comet Deposits from the impact. November 29, 2012, Mercury Detection satellite Messenger According to a team spokesman, scientists have found a large amount of frozen ice (possibly weighing up to 10 percent) in a dark crater at Mercury's North Pole that never gets sun 12 Tons).

Radar image of Mercury's North Pole

Mercury is not only too small, but also too hot, so its gravity is not strong enough to hold on to for long atmosphere ; But it does have a thin, superficial one exosphere Contains hydrogen, helium, oxygen, sulfur, calcium, potassium and other elements. This exosphere is not stable, atom It is constantly lost and replenished by different sources. Hydrogen and helium may have come from the solar wind and spread to Mercury before escaping back into space magnetosphere . elemental Radioactive decay It is another source of helium, sodium, and potassium in Mercury's crust. Messenger found calcium, helium, hydroxide High proportions of magnesium, oxygen, potassium, silicon and sodium. As well as steam The combined process of the presence of the comet is described as follows: the comet hits its surface, sputtering to create water, in which hydrogen comes from the solar wind, oxygen comes from rocks, and the sublimation of ice stored in permanent shadow within the polar craters. Many ions released by water, such as O, were detected + , OH - , and H 3 O + It was a surprise. Due to these considerable number of ions are in Mercury Space environment As a result, scientists speculate that the solar wind destroyed the molecules from Mercury's surface or exosphere. ^[7] In the 1980s and 1990s, sodium, potassium, and calcium were found in the atmosphere, believed to be mainly surface rocks micrometeorite Caused by vaporization on impact. In 2008, the Messenger probe discovered magnesium. The study notes that the sodium emissions are regional points that correspond to the planet's magnetic poles. This will show the interaction between the magnetosphere and the planet's surface.

Bombarded by the sun's intense radiation, Mercury atmosphere It is compressed backwards and spreads out, forming a "tail" at the dorsal sun, like a giant comet . What's even weirder, though, is that Mercury is actually losing atmospheric gas. The atoms that make up Mercury's atmosphere are constantly being lost to space, because potassium or sodium atoms have an average "life" of about three hours in a Mercury day (a Mercury day - half the time of its perihelion).

So, as Dr Solomon points out, "you need constant replenishment to keep the atmosphere going." Scientists think Mercury's replenishment is by capture Solar radiation As well as dust particles thrown up by micrometeorite impacts. The lost atmosphere is constantly being replaced by mechanisms such as planets Gravitational field Trapped volcanic steam and at the poles Ice cap the degassing Effect. ^[8]

Surface geography

Topographic map of Mercury's northern hemisphere by Messenger's MLA instrument

The surface of Mercury is very similar to that of the Moon, showing vast plains like oceans and large quantities of water Impact crater It has been inactive for billions of years. Geology of Mercury The early understanding of Mercury was established by the 1975 flyby Mariner 10 and Ground observation This knowledge improved when data from Messenger's flyby of Mercury were processed. For example, scientists have discovered an unusual crater radiation trough called a "spider." Later, it was renamed Apollodorus . The names of features on Mercury's surface come from different sources, from people who have passed away. Potholes use artists, musicians, painters and writers, all of whom have made outstanding or fundamental contributions in their respective fields. Ridges or ridges, named after scientists who contributed to the study of Mercury; A depression or trench is named after an architect. Mountains are named after popular words in various languages; Plains or plain lowlands are named after the god of Mercury in various languages. Cliffs or cliffs are named after scientific expedition ships; Valleys or valleys are named after radio telescopes. ^[2]

albedo Features refer to sites observed with telescopes in different fields, with distinct albedos. Mercury has ridges (sometimes called Furrow ridge Such as the highlands, mountains, Planitiae, rupes and valleys of the Moon. When Mercury formed 4.6 billion years ago, it experienced a brief bombardment of comets and asteroids, which ended 3.8 billion years ago and may have occurred independently Late heavy bombing period . In these violent formation Meteor crater Due to the lack of atmosphere to slow the impact, the entire surface of the planet is covered in craters. During this period, the planet was volcanically active, with basins such as the Karori Basin being covered with magma from within the planet, forming plains similar to the seas found on the Moon.

Topographic map of Mercury

Messenger flew by Mercury on October 28, 2008, giving researchers more information about the planet's chaotic surface. Mercury's surface is more complex than that of Mars and the Moon, and it contains a large number of geology similar to that of both, such as seas and plains.

plain

Mercury has two geologically distinct plains. Between the craters, the gently rolling, hilly plains are the oldest areas visible on Mercury's surface, predating the violent Volcano crater The terrain. These crater-buried plains appear to have obliterated many older craters and lack craters less than 30 km in diameter and smaller ones. It's unclear whether they originated from volcanoes or impacts, but these cratered plains are roughly evenly distributed across the planet's surface.

The so-called "strange topography" of the Antipodes of the Karolis Impact Basin

flat plain It's a wide, flat area filled with depressions, big and small, much like the moon's oceans. Notably, they surround the perimeter of the Karori Basin extensively. Be different from Mare selenis Mercury's flat plains and ancient cratered plains have the same albedo. Despite the lack of clear volcanic features, the geochemical platforms and rounded, split shapes strongly support the volcanic origin of these plains. It is worth noting that all Mercury flat plains formed later than the Karori Basin, and comparing the density of small craters detectable on the Karori eruption cover reveals that the floor of the Karori Basin is filled with distinctive plain geology, broken ridges and rough polygon Shattered. We don't know if it was impact induced Volcanic lava Or the impact caused a large amount of melting.

An unusual feature of the planet's surface is the numerous compression folds, or crags, crisscrossing the plain surface. As the planet's interior cooled, it probably shrank slightly and began to change its surface shape, creating these features. The depressions are also seen at the top of other terrain, such as pits and smooth plains, suggesting that these folds were formed only today. Mercury's surface is also distorted by the sun Sun The tidal forces on Mercury are 17 times stronger than the Moon's on Earth. Messenger is on Mercury Arctic region Discovered one of the largest open areas of volcanic plains on Mercury, covering an area of about 4 million Square kilometer , several thousand meters deep. It helped confirm Volcanic activity Has played a key role in shaping Mercury's crust for most of its history. ^[3-4]

crater

Mercury's surface is much like the Moon's, with craters, great plains, basins, Radial streaks And the cliff. As a result, the craters on Mercury, like those on the Moon, were named. The craters on Mercury's surface are named after literary artists, not scientists, because most of the craters on the moon are named after scientists. The named craters on the surface of Mercury are all over 20 km in diameter and are located on the planet The Western Hemisphere The names of these celebrities will forever shine with the sun and the moon in honor of their contributions to humanity.

The central peak inside the Abedin Ring

Internal structure

Mercury is Solar system Within the 4 similar to Earth Terrestrial planet One, with rocky bodies like the Earth. With a radius of 2,439.7 km at the equator, Mercury is the smallest planet in the solar system, even larger than some Natural satellite Like Ganymede and Titan It's smaller, although it has more mass. Mercury is made of about 70% metal and 30% metal silicate Mercury has a density of 5.427g/cm 3 It is the second highest in the solar system, after Earth's 5.515g/cm 3 . Without considering the effect of gravitational compression on the density of matter, Mercury would have the highest density of matter. Mercury's mass density, uncompressed by gravity, is 5.3g/cm 3 By comparison, the Earth's mass is only 4.4g/cm 3 .

False-color image of Mercury's surface as scanned by the Messenger MASCS spectrometer

Details of Mercury's internal structure can be inferred from its density. The high density of the Earth, especially the high density of the core, is caused by gravitational compression. Mercury's mass and gravity are small, there is no gravitational squeezing effect inside, and its core contains a large amount of iron and has a high density. Geologists estimate that Mercury's core occupies 42% of its volume; The Earth's core makes up only 17 percent of its volume. Mercury's iron-rich core dominates it Gross mass At least 60 percent of Mercury's radius, and its radius is three quarters that of Mercury's. Recent research strongly supports that Mercury has a molten core, surrounded by a core that is 500-700 km thick silicate mantle . Of the terrestrial planets in the solar system, only Mercury and Earth have global magnetic fields. Astronomers think these magnetic fields are generated by electrical currents in the outer layers of their cores. Based on data from the Mariner 10 mission and observations from Earth, Mercury's crust is thought to be only 100-300km thick. The surface of Mercury is characterized by numerous narrow ridges that can extend hundreds of kilometers long, which are believed to have been caused by the cooling of the core and mantle after the planet's crust solidified.

Mercury surface

Mercury's core contains more iron than any other major planet in the solar system, and several theories have been proposed to explain it. The most widely supported theory is that Mercury was originally similar to the common chondrite The core of the metal-silicate ratio, which is considered typical of rocky material within the solar system, is about 2.25 times its current mass. In the early history of the solar System, Mercury may have been hit by an asteroid hundreds of kilometers in diameter and about 1/6 of its mass planetesimal Crash. The impact stripped away much of the original crust and mantle, leaving the core a relatively large part of its composition. This hypothesis was obtained by the Messenger spectrometer on Mercury's surface Element abundance Observational support. A similar hypothesis, called the giant impact hypothesis, has been used to explain the formation of Earth's moon. Another hypothesis is that Mercury was present before the Sun's energy output stabilized Solar nebula Form in. The planet was originally about twice its current mass, but in protoplanet In the process of contraction. At that time, Mercury's temperature may have been between 2500-3500K, and possibly as high as 10,000 K, and much of the rocky composition of Mercury's surface may have vaporized at such high temperatures, becoming "rock vapor" in the atmosphere, which was then blown away by the solar wind. A third hypothesis is that the solar nebula created Mercury accretion This means that lighter material on Mercury's surface is lost from the accreting material. Each hypothesis predicts a different composition of Mercury's surface, and both Messenger and the upcoming Bepicolombo mission are trying to test this theory with observations. Messenger has found that surface potassium and sulfur levels are above predicted levels, and that the vaporization of the crust and mantle of the giant impact hypothesis did not occur because both potassium and sulfur were driven away by the high temperatures of these events. The finding seems to favor lighter planetary material being dragged away, causing heavier ones Metallic material Be condensed. Messenger's spectrometers have measured Mercury's composition, and scientists have found that Mercury's rocks contain far more magnesium than the surface of the Earth or the Moon, and far less aluminum.

Diagram of Mercury's internal structure and magnetic field

Detailed information about Mercury's internal structure can be inferred from its density. The high density of the Earth, especially the high density of the core, is caused by gravitational compression. Mercury is so small that its interior cannot be forcibly squeezed. So for it to have such a high density, its core must be very large.

Impact basin and crater

False-color map showing the highest temperature regions in the Arctic region

Mercury craters range in diameter from small bowl cavities to multi-ring impact craters that span hundreds of kilometers. From relatively fresh and bright to the remains of a highly degraded crater, the phenomenon of all stages of degradation is demonstrated. Mercury's impact craters are subtly different from those on the Moon in that their ejecta covers a much smaller area, suggesting that Mercury has a stronger surface gravity. One of the largest known craters is The Carolis Basin It has a diameter of 1550km. The impact of the impact that created the Karolis Basin was so powerful that it caused the volcanic lava to erupt, leaving concentric rings more than 2 kilometers high around the crater. At the Antipodes of the Karori Basin are large areas of unusual hilly terrain known as "weird terrain". One hypothesis for the origin of the topography is that it was an impact out of the Karolis Basin Shock wave Around the planets, converging in the basin Antipodes (180 degrees apart), resulting in a highly stressed crack surface; Another theory says yes ejecta Direct convergence at the Antipodes of the Karolis basin.

Perspective view of Karolis Basin (red for highlands, blue for lowlands)

Munch,Sander,Poe craters in the volcanic plains of Karolis Basin

Karolis Basin, one of the largest impact basins in the solar system

Overall, about 15 impact basins have been identified in existing images of Mercury. One notable basin is the 400-kilometer-wide, multiple-ringed Tolstoy Basin, whose spray covers a plain that extends for 500 km from the ridges and floors. 625 kilometers in diameter Beethoven The basin has an eruptive covering of similar size. Like the moon, Mercury's surface suffers Space weathering The effects of processes, including solar wind and micrometeorite impacts.

Magnetic field and magnetosphere

Diagram of Mercury's relative magnetic field strength

Although Mercury is small and 59 days old Long period As Mercury rotates, it still has a remarkable global magnetic field. According to Mariner 10, its intensity is only 1.1% of the Earth's. At the equator of Mercury Magnetic field strength It's about 300nT. Like Earth, Mercury's magnetic field is bipolar. Unlike Earth, Mercury's magnetic pole and Mercury's spin axis are almost identical. Measurements from both the Mariner 10 and Messenger spacecraft indicate that the strength and shape of Mercury's magnetic field are stable. This magnetic field may be caused by a dynamo effect, somewhat similar to the Earth's magnetic field. This dynamo effect is caused by the circulation of the planet's iron-rich liquid core, especially because of the strong tidal effects caused by the high eccentricity of the planet's orbit, which is necessary to keep the core liquid.

Mercury's magnetic field is strong enough to deflect the solar wind surrounding the planet, creating magnetosphere . Mercury's magnetosphere, though small, is strong enough to contain Earth and strong enough to deflect the solar wind plasma Trapped inside, it contributes to space weathering on the planet's surface. Observations by the Mariner 10 spacecraft detected low-energy plasma in the interior of the magnetosphere halfway through the starry night Magnetic tail High-energy particle explosions have also been detected, which indicate the dynamics of Mercury's magnetosphere.

During its second flyby of Mercury on October 6, 2008, Messenger found that Mercury's magnetic field was Very high frequency The "leakage". The spacecraft encountered a magnetic" tornado ", twisting the magnetic field with Planetary magnetic field Connect and deepen Interplanetary space It's 800 kilometers wide, or a third of the planet's radius. This tornado formed with the magnetic field of the solar wind attached to Mercury's magnetic field. As the solar wind blows through Mercury's magnetic field, these connected fields are carried away and twisted into swirl-like structures. These twisted flux tubes, technically known as flux transfer events, form open Windows in the planet's magnetic shield, where the solar wind can drive into and directly hit Mercury's surface.

This process of connecting interplanetary and planetary magnetic fields is called Magnetic reconnection Is very common in the universe. It also occurs in the Earth's magnetic field and usually produces tornadoes with magnetic fields as well. Messenger observations show that the reconnection rate is 10 times higher on Mercury. But depending on Mercury's distance from the Sun, Messenger observed only a third of the reconnection.

temperature

Mercury has the largest temperature difference between day and night on the surface of the planet equator There is a steep temperature difference between the two poles, ranging from 100K to 700K. The temperature of the subhelion is as high as 700K at perihelion and only 550K at aphelion. On the night side of the planet, the average temperature is 110K. The intensity of sunlight ranges from the solar constant (1,370W·m) 2 - ) 4.59 and 10.61 times; At the same time, Mercury's atmosphere is so thin that it cannot effectively retain heat, and the temperature at the equator can reach 432°C during the day and drop to -172°C at night. At the bottom of the deep craters of the Arctic and Antarctic craters, which are never directly exposed to sunlight, the temperature remains below 102K all year round, well below the average temperature of Mercury. Although Mercury's surface temperature is very high during the day, radar observations from Messenger strongly support the existence of a large amount of water ice (1 trillion tons) in Mercury's North Pole.

Astronomical phenomenon

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Transit of mercury

Diagram of the transit of Mercury

When Mercury passes between the Sun and Earth, one is seen in the solar circle Little black dot Through. This phenomenon is called Transit of mercury . Reasonable and reasonable Solar eclipse Similar, except Mercury is farther from the Earth than the moon, Apparent diameter It's 1.9 millionth the size of the Sun. The area of Mercury blocking the Sun is too small to dim the Sun's brightness, so it is not visible to the naked eye Transit of mercury It can only be projected through a telescope. Transits of Mercury occur an average of 13 times every 100 years. There was one transit at the end of the 20th century on 16 November 1999 at 5:42 am. In human history, the first predicted transit of Mercury was" Three laws of planetary motion The discoverer of the German astronomer Kepler (1571-1630). In 1629, he predicted that on November 7, 1631, a strange celestial event would take place Transit of mercury . On the same day, French astronomer Gassendi witnessed in Paris a small black dot (Mercury) moving slowly from east to west on the surface of the sun. Between 1631 and 2003, there were 50 transits of Mercury. Of these, 35 occurred in November and only 15 occurred in May. Every 100 years, Mercury transits an average of 13.4 times.

When Mercury transits, the center left dark spot is Mercury, and the center upper sunspot is Mercury

A transit of Mercury occurs in a very similar way to a solar eclipse, and Mercury's orbit is similar to Ecliptic plane There is an inclination, and this inclination is about 7 degrees. This results in two points of intersection between Mercury's orbit and Earth's ecliptic plane. That is Ascending node and Landing node . The ascending node of Mercury is to move from below the Earth's ecliptic plane to above the ecliptic plane, and the descending node is vice versa. A transit of Mercury occurs only when the orbits of Mercury and Earth are in the same plane and the sun, water and earth are in a straight line. If Mercury happens to be near the transversal intersection for two days, it also happens to be Mercury Inferior conjunction Phase, it is possible for a transit of Mercury to occur. Over the course of a dozen centuries, Transit of mercury It could only happen in May or November. The transits of Mercury occur at the descending node in May and at the ascending node in November. The transits of Mercury, which occur in May, are rarer, and Mercury is much closer to Earth. The transit period of Mercury also follows the cycle as follows Eclipse of sun and moon That kind of Charot cycle . Transits of Mercury within the same set of Saros occur on a period of 46 years, 1 day, and 6.5 hours. But if there are 12 leap years in this 46-year cycle. The period is about 46 years and 6.5 hours. The time difference mentioned here is the time difference between two adjacent Mercury transits in the same Saro cycle. Because two transits of Mercury occur at different times in the same Saro period.

Mercury wide distance

In 2022, Mercury will have a total of 7 large distances, of which 3 are in the west and 4 are in the east. On January 7, 2022, Mercury will be far east; October 9, Mercury west wide; On December 21, Mercury will turn east for the last time in 2022. ^[11]

World record

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mercurial perihelion 46 million kilometers from the sun, and aphelion It reaches 69.81 million kilometers (the planet's maximum eccentricity) Guinness World Records ). ^[12]

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