Time on Earth is taken for granted. People do not think that the interval by which time is measured is relative. For example, the measurement of days and years is based on physical factors: the distance from the planet to the Sun is taken into account. One year is equal to the time for which the planet goes around the Sun, and one day is the time for a complete rotation around its axis. By the same principle, time is calculated on other celestial bodies of the solar system. Many people are interested in how long a day lasts on Mars, Venus and other planets?
On our planet, a day lasts 24 hours. It takes this many hours for the Earth to rotate on its axis. The length of the day on Mars and other planets is different: somewhere it is short, and somewhere very long.
Definition of time
To find out how long a day lasts on Mars, you can use solar or sidereal days. The last measurement option is the period during which the planet makes one rotation around its axis. A day measures the time it takes for the stars to be in the same position in the sky from which the countdown began. Earth's star path is 23 hours and almost 57 minutes.
A solar day is a unit of time it takes for a planet to rotate on its axis relative to sunlight. The principle of measuring with this system is the same as when measuring the day of a sidereal day, only the Sun is used as a guide. Sidereal and solar days can be different.
And how long does a day last on Mars according to the star and solar system? A sidereal day on the red planet is 24 and a half hours. A solar day lasts a little longer - 24 hours and 40 minutes. A day on Mars is 2.7% longer than a day on Earth.
When sending vehicles to explore Mars, the time on it is taken into account. The devices have a special built-in clock, diverging from the earth by 2.7%. Knowing how long a day lasts on Mars allows scientists to create special rovers that are synchronized with the Martian day. The use of special clocks is important for science, as rovers are solar-powered. As an experiment, a clock was developed for Mars that takes into account the solar day, but they could not be applied.
The zero meridian on Mars is the one that passes through the crater called Airy. However, there are no time zones on the red planet like there are on Earth.
martian time
Knowing how many hours there are in a day on Mars, you can calculate how long the year is. The seasonal cycle is similar to Earth's: Mars has the same inclination as the Earth (25.19°) with respect to its own orbital plane. From the Sun to the red planet, the distance fluctuates in different periods from 206 to 249 million kilometers.
Temperature readings are different from ours:
- average temperature -46 °С;
- during the period of removal from the Sun, the temperature is about -143 ° С;
- in summer - -35 ° С.
Water on Mars
An interesting discovery was made by scientists in 2008. The rover discovered water ice at the poles of the planet. Prior to this discovery, it was believed that only carbonic ices existed on the surface. Even later, it turned out that precipitation in the form of snow falls on the red planet, and carbon dioxide snow falls near the south pole.
Throughout the year, storms are observed on Mars, spreading over hundreds of thousands of kilometers. They make it difficult to track what is happening on the surface.
A year on Mars
Around the Sun, the red planet makes a circle in 686 Earth days, moving at a speed of 24 thousand kilometers per second. A whole system of designation of Martian years has been developed.
When studying the question of how long a day on Mars lasts in hours, mankind has made many sensational discoveries. They show that the red planet is close to Earth.
Length of a year on Mercury
Mercury is the planet closest to the Sun. It rotates around its axis in 58 Earth days, that is, one day on Mercury is 58 Earth days. And to fly around the Sun, the planet needs only 88 Earth days. This amazing discovery shows that on this planet, a year lasts almost three Earth months, and while our planet flies one circle around the Sun, Mercury makes more than four revolutions. And how long does a day last on Mars and other planets when compared with Mercury time? It's amazing, but in just one and a half Martian days, a whole year passes on Mercury.
Time on Venus
Unusual is the time on Venus. One day on this planet lasts 243 Earth days, and a year on this planet lasts 224 Earth days. It seems strange, but such is the mysterious Venus.
Time on Jupiter
Jupiter is the largest planet in our solar system. Based on its size, many people think that the day on it lasts a long time, but this is not so. Its duration is 9 hours 55 minutes - less than half the length of our earthly day. The gas giant rotates rapidly around its axis. By the way, because of him, constant hurricanes and severe storms rage on the planet.
Time on Saturn
A day on Saturn lasts about the same as on Jupiter, and is 10 hours 33 minutes. But a year lasts approximately 29,345 Earth years.
Time on Uranus
Uranus is an unusual planet, and it is not so easy to determine how long a day of light will last on it. A sidereal day on the planet lasts 17 hours and 14 minutes. However, the giant has a strong axial tilt, which is why it rotates around the Sun almost on its side. Because of this, at one pole, summer will last 42 Earth years, while at the other pole it will be night at that time. When the planet rotates, the other pole will be illuminated for 42 years. Scientists have come to the conclusion that a day on the planet lasts 84 Earth years: one Uranian year lasts almost one Uranian day.
Time on other planets
Dealing with the question of how long a day and a year last on Mars and other planets, scientists have found unique exoplanets where a year lasts only 8.5 Earth hours. This planet is called Kepler 78b. Another planet KOI 1843.03 was also discovered, with a shorter period of rotation around its sun - only 4.25 Earth hours. Every day a person would become three years older if he lived not on Earth, but on one of these planets. If people could adjust to the planetary year, it would be best to go to Pluto. On this dwarf, a year is 248.59 Earth years.
Mercury is the planet closest to the Sun. There is practically no atmosphere on Mercury, the sky there is dark as night and the Sun always shines brightly. From the planet's surface, the Sun would look 3 times larger than Earth's. Therefore, temperature differences on Mercury are very pronounced: from -180 o C at night to unbearably hot +430 o C during the day (lead and tin melt at this temperature).
This planet has a very strange account of time. On Mercury, you will have to adjust the clock so that the day lasts approximately 6 Earth months, and the year is only 3 (88 Earth days). Although the planet Mercury has been known since ancient times, for thousands of years, people had no idea how it looks (until NASA sent the first pictures in 1974).
Moreover, the ancient astronomers did not immediately realize that they see the same star in the morning and in the evening. The ancient Romans considered Mercury the patron of trade, travelers and thieves, as well as the messenger of the gods. It is not surprising that a small planet, rapidly moving across the sky following the Sun, was named after him.
Mercury is the smallest planet after Pluto (which was stripped of planet status in 2006). The diameter is no more than 4880 km and quite a bit larger than the moon. Such a modest size and constant proximity to the Sun create difficulties for studying and observing this planet from Earth.
Mercury is also distinguished by its orbit. It is not circular, but more elongated elliptical, when compared with other planets of the solar system. The minimum distance to the Sun is approximately 46 million kilometers, the maximum is approximately 50% more (70 million).
Mercury receives 9 times more sunlight than Earth's surface. The lack of an atmosphere to protect against the burning sun's rays causes the surface temperature to rise to 430oC. It is one of the hottest places in the solar system.
The surface of the planet Mercury is the personification of antiquity, timeless. The atmosphere here is very rarefied, and there has never been water at all, so erosion processes were practically absent, except for the consequences of the fall of rare meteorites or collisions with comets.
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Do you know...
Although Mars and Venus are the closest orbits to Earth, Mercury is more often than not the closest planet to Earth, as the others move away to a greater extent without being as "attached" to the Sun.
There are no such seasons on Mercury as there are on Earth. This is due to the fact that the axis of rotation of the planet is at almost a right angle to the plane of the orbit. As a result, there are areas near the poles that the sun's rays never reach. This suggests that there are glaciers in this cold and dark zone.
Mercury moves faster than any other planet. The combination of its movements causes the Sun to rise on Mercury for a short time, after which the Sun sets and rises again. At sunset, this sequence is reversed.
For its size, Mercury is very heavy - apparently, it has a huge iron core. Astronomers believe that the planet was once larger and had thicker outer layers, but billions of years ago it collided with a protoplanet, and part of the mantle and crust scattered into outer space.
Here on Earth, people take time for granted. But in fact, at the heart of everything is an extremely complex system. For example, the way people calculate days and years follows from the distance between the planet and the Sun, from the time it takes the Earth to make a complete revolution around a gas star, and also the time it takes to complete a 360-degree movement around its own planet. axes. The same method applies to the rest of the planets in the solar system. Earthlings are used to believing that there are 24 hours in a day, but on other planets, the length of the day is much different. In some cases they are shorter, in others they are longer, sometimes significantly. The solar system is full of surprises and it's time to explore it.
Mercury
Mercury is the planet closest to the Sun. This distance can be from 46 to 70 million kilometers. Considering the fact that Mercury takes about 58 Earth days to turn around 360 degrees, it is worth understanding that on this planet you will only see a sunrise every 58 days. But in order to describe a circle around the main star of the system, Mercury needs only 88 Earth days. This means that a year on this planet lasts about one and a half days.
Venus
Venus, also known as the Earth's twin, is the second planet from the Sun. The distance from it to the Sun is from 107 to 108 million kilometers. Unfortunately, Venus is also the slowest rotating planet, which can be seen when looking at its poles. While absolutely all the planets in the solar system have experienced flattening at the poles due to the speed of their rotation, Venus does not show signs of it. As a result, Venus needs about 243 Earth days to go around the main body of the system once. It may seem strange, but it takes the planet 224 days to complete a complete rotation on its axis, which means only one thing: a day on this planet lasts longer than a year!
Earth
When talking about a day on Earth, people usually think of it as 24 hours, when in fact the rotation period is only 23 hours and 56 minutes. Thus, one day on Earth is equal to about 0.9 Earth days. It looks strange, but people always prefer simplicity and convenience over accuracy. However, everything is not so simple, and the length of the day can change - sometimes it is even actually equal to 24 hours.
Mars
In many ways, Mars can also be called Earth's twin. In addition to having snow poles, changing seasons, and even water (albeit in a frozen state), a day on the planet is extremely close in duration to a day on Earth. It takes Mars 24 hours, 37 minutes and 22 seconds to rotate around its axis. Thus, here the day is slightly longer than on Earth. As mentioned earlier, the seasonal cycles here are also very similar to those on Earth, so the options for the length of the day will be similar.
Jupiter
Given the fact that Jupiter is the largest planet in the solar system, one would expect that the day on it would be incredibly long. But in reality, everything is completely different: a day on Jupiter lasts only 9 hours, 55 minutes and 30 seconds, that is, one day on this planet is about a third of an Earth day. This is due to the fact that this gas giant has a very high rotation speed around its axis. It is because of this that very strong hurricanes are also observed on the planet.
Saturn
The situation on Saturn is very similar to that observed on Jupiter. Despite its large size, the planet has a slow rotation rate, so Saturn takes only 10 hours and 33 minutes to complete one 360-degree rotation. This means that one day on Saturn is less than half the length of an Earth day. And, again, the high speed of rotation leads to incredible hurricanes and even a constant swirling storm at the south pole.
Uranus
When it comes to Uranus, the issue of calculating the length of the day becomes difficult. On the one hand, the time of rotation of the planet around its axis is 17 hours, 14 minutes and 24 seconds, which is slightly less than a standard Earth day. And this statement would be true if not for the strongest axial tilt of Uranus. The angle of this slope is more than 90 degrees. This means that the planet is moving past the main star of the system, actually on its side. Moreover, in this scenario, one pole looks towards the Sun for a very long time - as much as 42 years. As a result, we can say that a day on Uranus lasts 84 years!
Neptune
Last on the list is Neptune, and here also the problem of measuring the length of the day arises. The planet makes a complete rotation around its axis in 16 hours, 6 minutes and 36 seconds. However, there is a catch here - given the fact that the planet is a gas-ice giant, its poles rotate faster than the equator. Above, the time of rotation of the planet's magnetic field was indicated - its equator turns around in 18 hours, while the poles complete a circular rotation in 12 hours.
As soon as the automatic station "Mariner-10" sent from the Earth finally reached the almost unexplored planet Mercury and began photographing it, it became clear that big surprises awaited earthlings here, one of which is the extraordinary, striking similarity of the surface of Mercury with the Moon. The results of further research plunged researchers into even greater amazement it turned out that Mercury has much more in common with the Earth than with its eternal satellite.
Illusory kinship
From the first images transmitted by Mariner 10, scientists were really looking at the Moon so familiar to them, or at least its twin on the surface of Mercury, there were many craters that at first glance looked completely identical to the moon. And only careful studies of the images made it possible to establish that the hilly areas around the lunar craters, composed of material ejected during a crater-forming explosion, are one and a half times wider than the Mercurian ones with the same size of craters. This is explained by the fact that the large force of gravity on Mercury prevented a more distant expansion of the soil. It turned out that on Mercury, as well as on the Moon, there are two main types of terrain - analogues of the lunar continents and seas.
Continental regions are the most ancient geological formations of Mercury, consisting of cratered areas, intercrater plains, mountainous and hilly formations, as well as ruled areas covered with numerous narrow ridges.
The analogues of the lunar seas are the smooth plains of Mercury, which are younger than the continents and somewhat darker than the continental formations, but still not as dark as the lunar seas. Such sites on Mercury are concentrated in the region of the Zhara Plain, a unique and largest ring structure on the planet with a diameter of 1,300 km. The plain got its name not by chance - the meridian 180 ° W passes through it. etc., it is he (or the opposite meridian 0 °) located in the center of that hemisphere of Mercury, which is facing the Sun, when the planet is at a minimum distance from the Sun. At this time, the surface of the planet heats up the most in the areas of these meridians, and in particular in the area of the Zhara plain. It is surrounded by a mountainous ring that encloses a huge circular depression formed at an early stage in Mercury's geologic history. Subsequently, this depression, as well as the areas adjacent to it, were flooded with lavas, during the solidification of which smooth plains arose.
On the other side of the planet, exactly opposite the depression in which the Zhara Plain is located, there is another unique formation - a hilly-ruled terrain. It consists of numerous large hills (510 km in diameter and up to 12 km high) and is crossed by several large rectilinear valleys clearly formed along the fault lines of the planet's crust. The location of this area in the area opposite to the Zhara Plain served as the basis for the hypothesis that the hilly-ruled relief was formed due to the focusing of seismic energy from an asteroid impact that formed the Zhara depression. This hypothesis was indirectly confirmed when areas with a similar relief were soon discovered on the Moon, located diametrically opposite the Sea of Rains and the East Sea - the two largest ring formations of the Moon.
The structural pattern of Mercury's crust is determined to a large extent, like that of the Moon, by large impact craters, around which systems of radial-concentric faults are developed, dividing Mercury's crust into blocks. The largest craters have not one, but two annular concentric shafts, which also resembles the lunar structure. On the photographed half of the planet, 36 such craters have been identified.
Despite the general similarity of the Mercury and lunar landscapes, completely unique geological structures have been discovered on Mercury that have not been observed before on any of the planetary bodies. They were called lobed ledges, since their outlines on the map are typical of rounded protrusions - "blades" with a diameter of up to several tens of kilometers. The height of the ledges is from 0.5 to 3 km, while the largest of them reach 500 km in length. These ledges are rather steep, but in contrast to the lunar tectonic ledges, which have a pronounced downward inflection of the slope, the Mercurial lobed ones have a smoothed surface inflection line in their upper part.
These ledges are located in the ancient continental regions of the planet. All their features give reason to consider them as a superficial expression of the compression of the upper layers of the planet's crust.
Calculations of the magnitude of compression, performed according to the measured parameters of all ledges on the photographed half of Mercury, indicate a reduction in the area of the crust by 100 thousand km 2, which corresponds to a decrease in the radius of the planet by 12 km. Such a decrease could be caused by the cooling and solidification of the interior of the planet, in particular its core, which continued after the surface had already become solid.
Calculations showed that the iron core should have a mass of 0.60.7 of the mass of Mercury (for the Earth, the same value is 0.36). If all the iron is concentrated in the Mercury core, then its radius will be 3/4 of the radius of the planet. Thus, if the radius of the core is approximately 1,800 km, then it turns out that inside Mercury there is a giant iron ball the size of the Moon. The share of the two outer stone shells mantle and crust accounts for only about 800 km. Such an internal structure is very similar to the structure of the Earth, although the dimensions of the shells of Mercury are determined only in the most general terms: even the thickness of the crust is unknown, it is assumed that it can be 50100 km, then a layer about 700 km thick remains on the mantle. On Earth, the mantle occupies the predominant part of the radius.
Relief details. The giant Discovery Scarp, 350 km long, crosses two craters 35 and 55 km in diameter. The maximum height of the ledge is 3 km. It was formed when the upper layers of Mercury's crust were pushed from left to right. This was due to the warping of the planet's crust during the compression of the metal core caused by its cooling. The ledge was named after James Cook's ship.
Photomap of the largest ring structure on Mercury, the Zhara Plain, surrounded by the Zhara Mountains. The diameter of this structure is 1300 km. Only its eastern part is visible, while the central and western parts, which are not illuminated in this image, have not yet been studied. Meridian area 180°W e. is the most strongly heated by the Sun region of Mercury, which is reflected in the names of the plains and mountains. The two main types of terrain on Mercury ancient heavily cratered regions (dark yellow on the map) and younger smooth plains (brown on the map) reflect two major periods of the planet's geological history the period of massive fall of large meteorites and the subsequent period of outpouring of highly mobile, presumably basaltic lavas.
Giant craters with a diameter of 130 and 200 km with an additional shaft at the bottom, concentric to the main annular shaft.
The winding Santa Maria escarpment, named after the ship of Christopher Columbus, cuts through ancient craters and later flat terrain.
Hilly-ruled terrain a section of the surface of Mercury that is unique in its structure. There are almost no small craters here, but many clusters of low hills crossed by straight tectonic faults.
names on the map. The names of the details of the relief of Mercury, identified in the images of Mariner 10, were given by the International Astronomical Union. The craters are named after figures of world culture famous writers, poets, artists, sculptors, composers. To designate the plains (except for the Zhara plain), the names of the planet Mercury in different languages were used. Long linear depressions tectonic valleys were named after radio observatories that contributed to the study of the planets, and two ridges large linear hills were named after the astronomers Schiaparelli and Antoniadi, who made many visual observations. The largest blade-like ledges received the names of sea ships on which the most significant voyages in the history of mankind were made.
Iron heart
Other data obtained by Mariner 10, which showed that Mercury has an extremely weak magnetic field, the magnitude of which is only about 1% of the earth's, turned out to be a surprise. This circumstance, insignificant at first glance, was extremely important for scientists, since of all the planetary bodies of the terrestrial group, only the Earth and Mercury have a global magnetosphere. And the only most plausible explanation of the nature of the Mercury magnetic field may be the presence in the bowels of the planet of a partially molten metal core, again similar to the earth's. Apparently, this core of Mercury is very large, as indicated by the high density of the planet (5.4 g / cm 3), which suggests that Mercury contains a lot of iron, the only heavy element widely distributed in nature.
To date, several possible explanations for the high density of Mercury with its relatively small diameter have been put forward. According to the modern theory of planet formation, it is believed that in the pre-planetary dust cloud, the temperature of the region adjacent to the Sun was higher than in its marginal parts, therefore, light (so-called volatile) chemical elements were carried out to remote, colder parts of the cloud. As a result, in the near-solar region (where Mercury is now located), a predominance of heavier elements was created, the most common of which is iron.
Other explanations link the high density of Mercury with the chemical reduction of oxides (oxides) of light elements to their heavier, metallic form under the influence of very strong solar radiation, or with the gradual evaporation and volatilization into space of the outer layer of the planet's original crust under the influence of solar heating, or else with the fact that a significant part of the "stone" shell of Mercury was lost as a result of explosions and ejections of matter into outer space during collisions with smaller celestial bodies, such as asteroids.
In terms of average density, Mercury stands apart from all other planets of the terrestrial group, including the Moon. Its average density (5.4 g / cm 3) is second only to the density of the Earth (5.5 g / cm 3), and if we keep in mind that the earth's density is affected by a stronger compression of matter due to the larger size of our planet, then it turns out that with equal sizes of the planets, the density of the Mercury substance would be the highest, exceeding the earth's by 30%.
Hot Ice
Judging by the available data, the surface of Mercury, receiving a huge amount of solar energy, is a real hell. Judge for yourself the average temperature at the time of Mercury noon is about +350°C. Moreover, when Mercury is at a minimum distance from the Sun, it rises to + 430 ° C, while at the maximum distance it drops to only + 280 ° C. However, it has also been established that immediately after sunset, the temperature in the equatorial region drops sharply to 100°C, and by midnight it generally reaches 170°C, but after dawn the surface quickly warms up to +230°C. Measurements made from the Earth in the radio range showed that inside the soil at a shallow depth the temperature does not depend at all on the time of day. Which indicates the high heat-insulating properties of the surface layer, but since the light day lasts 88 Earth days on Mercury, during this time all parts of the surface have time to warm up well, albeit at a shallow depth.
It would seem that to speak of the possibility of the existence of ice on Mercury under such conditions is at least absurd. But in 1992, during radar observations from the Earth near the north and south poles of the planet, areas were first discovered that reflect radio waves very strongly. It was these data that were interpreted as evidence of the presence of ice in the near-surface Mercury layer. Radar made from the Arecibo radio observatory located on the island of Puerto Rico, as well as from the NASA Deep Space Communications Center in Goldstone (California), revealed about 20 rounded spots with a diameter of several tens of kilometers with increased radio reflection. Presumably, these are craters, in which, due to their proximity to the poles of the planet, the sun's rays fall only in passing or do not fall at all. Such craters, called permanently shadowed, are also found on the Moon, and measurements from satellites revealed the presence of a certain amount of water ice in them. Calculations have shown that in the depressions of permanently shaded craters near the poles of Mercury it can be cold enough (175°C) for ice to exist there for a long time. Even in flat areas near the poles, the calculated daily temperature does not exceed 105°C. Direct measurements of the surface temperature of the polar regions of the planet are still not available.
Despite observations and calculations, the existence of ice on the surface of Mercury or at a shallow depth below it has not yet received unambiguous evidence, since stone rocks containing metal compounds with sulfur and possible metal condensates on the surface of the planet, for example, ions, have increased radio reflection. sodium, which settled on it as a result of the constant "bombardment" of Mercury by particles of the solar wind.
But here the question arises: why is the distribution of areas that strongly reflect radio signals precisely confined to the polar regions of Mercury? Maybe the rest of the territory is protected from the solar wind by the planet's magnetic field? Hopes for clarifying the riddle of ice in the realm of heat are associated only with the flight to Mercury of new automatic space stations equipped with measuring instruments that make it possible to determine the chemical composition of the planet's surface. Two such stations "Messenger" and "Bepi-Colombo" are already being prepared for flight.
The fallacy of Schiaparelli. Astronomers call Mercury a difficult object to observe, since in our sky it moves away from the Sun by no more than 28 ° and it is always necessary to observe it low above the horizon, through atmospheric haze against the background of dawn (in autumn) or in the evenings immediately after sunset (in spring ). In the 1880s, the Italian astronomer Giovanni Schiaparelli, based on his observations of Mercury, concluded that this planet makes one revolution around its axis in exactly the same time as one revolution in orbit around the Sun, that is, “days” on it are equal " year." Consequently, the same hemisphere always faces the Sun, the surface of which is constantly hot, but on the opposite side of the planet eternal darkness and cold reign. And since the authority of Schiaparelli as a scientist was great, and the conditions for observing Mercury were difficult, for almost a hundred years this position was not questioned. And only in 1965, using radar observations with the help of the largest Arecibo radio telescope, American scientists G. Pettengill and R. Dyes for the first time reliably determined that Mercury makes one revolution around its axis in about 59 Earth days. This was the largest discovery in planetary astronomy of our time, which literally shook the foundations of ideas about Mercury. And after it was followed by another discovery Professor of the University of Padua D. Colombo noticed that the time of rotation of Mercury around the axis corresponds to 2/3 of the time of its revolution around the Sun. This was seen as a resonance between the two rotations, which was due to the Sun's gravitational influence on Mercury. In 1974, the American automatic station Mariner 10, flying for the first time around the planet, confirmed that a day on Mercury lasts more than a year. Today, despite the development of space and radar studies of the planets, observations of Mercury by traditional methods of optical astronomy continue, albeit with the use of new tools and computer methods of data processing. Recently, at the Abastumani Astrophysical Observatory (Georgia), together with the Space Research Institute of the Russian Academy of Sciences, a study was made of the photometric characteristics of the surface of Mercury, which provided new information about the microstructure of the upper soil layer.
In the vicinity of the sun. The planet Mercury closest to the Sun moves in a highly elongated orbit, either approaching the Sun at a distance of 46 million km, or moving away from it by 70 million km. The strongly elongated orbit differs sharply from the almost circular orbits of the other terrestrial planets Venus, Earth and Mars. The axis of rotation of Mercury is perpendicular to the plane of its orbit. One revolution in orbit around the Sun (Mercurian year) lasts 88, and one revolution around the axis 58.65 Earth days. The planet rotates around its axis in the forward direction, that is, in the same direction in which it moves in orbit. As a result of the addition of these two movements, the duration of a solar day on Mercury is 176 Earth days. Among the nine planets of the solar system, Mercury, whose diameter is 4,880 km, is in the penultimate place in size, only Pluto is smaller than it. The force of gravity on Mercury is 0.4 of that of the earth, and the surface area (75 million km 2) is twice that of the moon.
Coming Heralds
The launch of the second in the history of the automatic station directed to Mercury, "Messenger" NASA plans to carry out as early as 2004. After the launch, the station must fly twice (in 2004 and 2006) near Venus, the gravitational field of which will bend the trajectory so that the station goes exactly to Mercury. The studies are scheduled to be carried out in two phases: first, familiarization from the flyby trajectory during two encounters with the planet (in 2007 and 2008), and then (in 20092010) detailed from the orbit of the artificial satellite of Mercury, on which work will take place during one earth year.
When flying near Mercury in 2007, the eastern half of the unexplored hemisphere of the planet should be photographed, and a year later, the western half. Thus, for the first time, a global photographic map of this planet will be obtained, and this alone would be enough to consider this flight quite successful, but the Messenger program is much more extensive. During the two planned flybys, the gravitational field of the planet will "slow down" the station so that at the next, third, meeting, it could go into the orbit of an artificial satellite of Mercury with a minimum distance of 200 km from the planet and a maximum distance of 15,200 km. The orbit will be at an 80° angle to the planet's equator. The low section will be located above its northern hemisphere, which will allow a detailed study of both the largest Zhara plain on the planet and the alleged "cold traps" in craters near the North Pole, which are not exposed to the sun's light and where the presence of ice is assumed.
During the operation of the station in orbit around the planet, it is planned for the first 6 months to perform a detailed survey of its entire surface in various spectral ranges, including color images of the terrain, determination of the chemical and mineralogical composition of surface rocks, measurement of the content of volatile elements in the near-surface layer to search for places of ice concentration.
In the next 6 months, very detailed studies of individual terrain objects, the most important for understanding the history of the geological development of the planet, will be carried out. Such objects will be selected based on the results of the global survey carried out at the first stage. Also, a laser altimeter will measure the heights of surface details to obtain survey topographic maps. The magnetometer, located far from the station on a pole 3.6 m long (to avoid interference from instruments), will determine the characteristics of the planet's magnetic field and possible magnetic anomalies on Mercury itself.
The BepiColombo joint project of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) "BepiColombo" is called to take over from Messenger and start studying Mercury in 2012 with the help of three stations at once. Here, survey work is planned to be carried out using two artificial satellites simultaneously, as well as a lander. In the planned flight, the planes of the orbits of both satellites will pass through the poles of the planet, which will make it possible to cover the entire surface of Mercury with observations.
The main satellite in the form of a low prism with a mass of 360 kg will move in a slightly elongated orbit, either approaching the planet up to 400 km, or moving away from it by 1,500 km. This satellite will host a whole range of instruments: 2 television cameras for survey and detailed survey of the surface, 4 spectrometers for studying the chi-bands (infrared, ultraviolet, gamma, X-ray), as well as a neutron spectrometer designed to detect water and ice. In addition, the main satellite will be equipped with a laser altimeter, which should be used for the first time to map the heights of the surface of the entire planet, as well as a telescope to search for asteroids that are potentially dangerous for colliding with the Earth, which enter the inner regions of the solar system, crossing the earth's orbit.
Overheating by the Sun, from which 11 times more heat comes to Mercury than to the Earth, can lead to failure of electronics operating at room temperature, one half of the Messenger station will be covered with a semi-cylindrical heat-insulating screen made of Nextel special ceramic fabric.
An auxiliary satellite in the form of a flat cylinder with a mass of 165 kg, called a magnetospheric one, is planned to be launched into a highly elongated orbit with a minimum distance from Mercury of 400 km and a maximum distance of 12,000 km. Working in tandem with the main satellite, it will measure the parameters of remote regions of the planet's magnetic field, while the main one will observe the magnetosphere near Mercury. Such joint measurements will make it possible to build a three-dimensional picture of the magnetosphere and its changes in time when interacting with fluxes of charged particles of the solar wind that change their intensity. A camera will also be installed on the auxiliary satellite to take pictures of the surface of Mercury. The magnetospheric satellite is being created in Japan, and the main one is being developed by scientists from European countries.
The research center named after G.N. Babakin at the NPO named after S.A. Lavochkin, as well as companies from Germany and France. The launch of BepiColombo is scheduled for 20092010. In this regard, two options are being considered: either a single launch of all three vehicles by the Ariane-5 rocket from the Kourou cosmodrome in French Guiana (South America), or two separate launches from the Baikonur cosmodrome in Kazakhstan by Russian SoyuzFregat rockets (on onethe main satellite, on the other the lander and the magnetospheric satellite). It is assumed that the flight to Mercury will last 23 years, during which the device should fly relatively close to the Moon and Venus, the gravitational influence of which will "correct" its trajectory, giving the direction and speed necessary to reach the immediate vicinity of Mercury in 2012.
As already mentioned, research from satellites is planned to be carried out within one Earth year. As for the landing block, it will be able to work for a very short time - the strong heating it must undergo on the surface of the planet will inevitably lead to the failure of its electronic devices. During an interplanetary flight, a small disc-shaped lander (diameter 90 cm, weight 44 kg) will be "on the back" of the magnetospheric satellite. After their separation near Mercury, the lander will be launched into an artificial satellite orbit with a height of 10 km above the surface of the planet.
Another maneuver will put him on a descent trajectory. When the surface of Mercury remains 120 m, the speed of the landing block should decrease to zero. At that moment, it will begin a free fall onto the planet, during which plastic bags will be filled with compressed air they will cover the device from all sides and soften its impact on the surface of Mercury, which it will touch at a speed of 30 m / s (108 km / h).
To reduce the negative impact of solar heat and radiation, it is planned to land on Mercury in the polar region on the night side, not far from the dividing line between the dark and illuminated parts of the planet, so that after about 7 Earth days the device will “see” the dawn and rise above the horizon Sun. In order for the onboard television camera to be able to obtain images of the area, it is planned to equip the landing block with a kind of searchlight. With the help of two spectrometers, it will be determined which chemical elements and minerals are contained at the landing point. And a small probe, nicknamed the "mole", will penetrate deep to measure the mechanical and thermal characteristics of the soil. They will try to register possible “mercuryquakes” with a seismometer, which, by the way, are very likely.
It is also planned that a miniature planetary rover will descend from the lander to the surface to study the properties of the soil in the adjacent territory. Despite the grandiosity of the plans, a detailed study of Mercury is just beginning. And the fact that earthlings intend to spend a lot of effort and money on this is by no means accidental. Mercury is the only celestial body whose internal structure is so similar to that of the earth, and therefore it is of exceptional interest for comparative planetology. Perhaps the study of this distant planet will shed light on the mysteries lurking in the biography of our Earth.
The BepiColombo mission over the surface of Mercury: in the foreground the main orbiting satellite, in the distance the magnetospheric module.
Lonely guest. Mariner 10 is the only spacecraft to explore Mercury. The information he received 30 years ago is still the best source of information about this planet. The flight of "Mariner-10" is considered exceptionally successful instead of the planned one time, he conducted research on the planet three times. All modern maps of Mercury and the vast majority of data on its physical characteristics are based on the information received by him during the flight. Having reported all possible information about Mercury, Mariner-10 has exhausted the resource of "life activity", but still continues to silently move along the previous trajectory, meeting with Mercury every 176 Earth days - exactly after two revolutions of the planet around the Sun and after three revolutions of its around its axis. Because of this synchronicity of movement, it always flies over the same region of the planet, illuminated by the Sun, at exactly the same angle as during its very first flyby.
Solar dances. The most impressive sight in the Mercury sky is the Sun. There it looks 23 times larger than in the earth's sky. The peculiarities of the combination of the speeds of rotation of the planet around its axis and around the Sun, as well as the strong elongation of its orbit, lead to the fact that the apparent movement of the Sun across the black Mercury sky is not at all the same as on Earth. At the same time, the path of the Sun looks different at different longitudes of the planet. So, in the regions of the meridians 0 and 180 ° W. e. early in the morning in the eastern part of the sky above the horizon, an imaginary observer could see a “small” (but 2 times larger than in the Earth’s sky), very quickly rising above the horizon Luminary, whose speed gradually slows down as it approaches the zenith, and itself it becomes brighter and hotter, increasing in size by 1.5 times this is Mercury coming closer to the Sun in its highly elongated orbit. Having barely passed the zenith point, the Sun freezes, moves back a little for 23 Earth days, freezes again, and then begins to go down at an ever-increasing speed and noticeably decreasing in size this is Mercury moving away from the Sun, moving into an elongated part of its orbit and with great speed disappears over the horizon in the west.
The daytime course of the Sun near 90 and 270° W looks completely different. e. Here Svetilo writes out absolutely amazing pirouettes there are three sunrises and three sunsets per day. In the morning, a bright luminous disk of enormous size (3 times larger than in the earth's firmament) appears very slowly from behind the horizon in the east, it rises slightly above the horizon, stops, and then goes down and briefly disappears behind the horizon.
Soon a second sunrise follows, after which the Sun begins to slowly crawl up the sky, gradually accelerating its course and at the same time rapidly decreasing in size and dimming. This “small” Sun flies past the zenith point at high speed, and then slows down its run, grows in size and slowly disappears behind the evening horizon. Shortly after the first sunset, the Sun rises again to a low altitude, briefly freezes in place, and then again descends to the horizon and finally sets.
Such "zigzags" of the solar cycle occur because in a short segment of the orbit, when passing perihelion (the minimum distance from the Sun), the angular velocity of Mercury in orbit around the Sun becomes greater than the angular velocity of its rotation around the axis, which leads to the movement of the Sun in the sky of the planet within a short period of time (about two Earth days) back to its usual course. But the stars in the sky of Mercury move three times faster than the Sun. A star that appeared simultaneously with the Sun above the morning horizon will set in the west before noon, that is, before the Sun reaches the zenith, and will have time to rise again in the east before the Sun has set.
The sky above Mercury is black day and night, and all because there is practically no atmosphere there. Mercury is surrounded only by the so-called exosphere, a space so rarefied that its constituent neutral atoms never collide. Helium atoms (they predominate), hydrogen, oxygen, neon, sodium and potassium were found in it, according to observations through a telescope from the Earth, as well as during the passage of the Mariner-10 station around the planet. The atoms that make up the exosphere are "knocked out" from the surface of Mercury by photons and ions, particles arriving from the Sun, as well as micrometeorites. The absence of an atmosphere leads to the fact that there are no sounds on Mercury, since there is no elastic medium air that transmits sound waves.
George Burba, candidate of geographical sciences
