From space, the Moon looks like a whitish-gray sphere, with craters of various sizes.
|Stellar distance||356 565 kilometers|
|Derived orbital elements|
|Periastro o perihelio||405 500 kilometers|
|Apoastro o afelio||363 300 kilometers|
|Sidereal orbital period||27 d 7 h 43,1 m|
|Orbital period sinódico||29 d 12 h 44 m 2.9 s|
|Radio orbital medio||384 403 km|
|Time||7,349 × 1022 kg|
|Volume||2,1958 × 1010 km³|
|Area surface||38 million km²|
|Radio||1 737.1 kilometers|
|Angular diameter|| |
|Escape velocity||2.38 km/s|
|Rotation period||27 d 7 h 43,7 min|
|Bark composition|| |
|Pressure||3 × 10-10 Pa|
The Moon is the only natural satellite of the Earth . With an equatorial diameter of 3476 km, it is the fifth largest satellite in the solar system , while in terms of proportional size with respect to its planet it is the largest satellite: a quarter of the diameter of Earth and 1/81 of its mass. After Io , it is also the second densest satellite. It is in synchronous relationship with the Earth, always showing the same face towards the planet. The visible hemisphere is marked with dark lunar seas of volcanic origin between the bright ancient mountains and the prominent astroblems .
Despite apparently being the brightest object in the sky after the Sun, its surface is actually very dark, with a reflection similar to that of coal . Its prominence in the sky and its regular cycle of phases have made the Moon an object with important cultural influence since ancient times in language, calendar , art or mythology. The gravitational influence of the Moon produces the tides and increases the length of the day. The orbital distance of the Moon, about thirty times the diameter of the Earth, makes it appear in the sky the same size as the Sun and allows the Moon to cover exactly the Sun in total solar eclipses .
The Moon is the only celestial body in which the human being has made a manned descent . Although the Moon program of the Soviet Union was the first to reach the Moon with a spacecraft unmanned, the Apollo program of the United States made the only manned missions to the Earth 's satellite to date, starting with the first lunar orbit manned by Apollo 8 in 1968 , and six manned moon landings between 1969 and 1972 , the first being Apollo 11 in 1969, and the last being Apollo 17. These missions returned with more than 380 kg of lunar rock , which has allowed us to reach a detailed geological understanding of the origins of the Moon (it is believed that it was formed 4.5 billion years ago after a great impact ), the formation of its internal structure. and its subsequent history .
In 1970, the Soviet Union brought to the surface the first robotic vehicle controlled from the ground: Lunojod 1 . The rover was sending photographs and videos of the surface that it traveled (10 km) for almost a year. [ 1 ]
Since the mission of the Apollo 17 in 1972, it has been visited only by space probes unmanned, particularly by the rover Soviet Lunokhod 2 . Since 2004 , Japan , China , India , the United States, and the European Space Agency have sent orbiters . These spacecraft have confirmed the discovery of icy water attached to the regolithlunar craters that are in the permanent shadow zone and are located at the poles. Future manned missions to the Moon have been planned, but have not yet been launched.
The Moon remains, under the Outer Space Treaty , free for any nation to explore for peaceful purposes.
The word for the Earth's satellite, "moon," comes from Latin . In this language it was originally the feminine form of an adjective in -no- * leuk-s-no, 'luminous'. Therefore, the word 'moon' means 'luminous', 'the one that illuminates'. This Latin adjective derives from the root * lūc- / lŭc- ('to shine', 'to be luminous'), from which luceo ('to shine'), lumen ('light'), lux ('light'), etc. also come. . In turn, this root comes from the Indo-European root * leuk-, which is found in other languages in terms related to light, such as the Greek λύχνος, lýkhnos(lýjnos), 'lamp'. Probably, the epithet * leuksno- / * louksno-, 'the luminous one', was already used to designate the moon in Proto-Indo-European .
In Proto-Indo-European there was also a masculine name for the Moon, formed on the root * mēns-, of which forms are preserved in several languages, such as the Greek μηνός, menós , 'moon', and even with the primitive sense in Italic languages , such as the Umbrian (ablative singular) "menzne", 'Moon'. In Latin this form * mēns- has evolved semantically to designate the 'month'. From "moon" comes the term "Monday", which already in Latin designated the "day of the moon" ( dies lunae ). [ 2 ]
Likewise, the Greek term Selene (in ancient Greek , Σελήνη Selếnê , name of the mythological goddess associated with the Moon) has survived in Spanish and in other languages as a cultured way to express certain concepts related to the Moon (such as the words " selenography ", which designates the lunar cartography, or " selenite ", the name of the supposed inhabitants of the satellite and " selenium ", chemical element).
The Moon is exceptionally large compared to its planet Earth: a quarter of the planet's diameter and 1/81 of its mass. [ 3 ] It is the second largest satellite in the Solar System in relation to the size of its planet, Charon being the largest in relation to the dwarf planet Pluto . The surface of the Moon is less than a tenth that of the Earth, which represents about a quarter of the continental area of the Earth. However, the Earth and the Moon are still considered a planet-satellite system, rather than a double planetary system, since their center of gravity is located about 1700 km (about a quarter of the radius of the Earth) below the surface of the earth.
Several mechanisms have been proposed to explain the formation of the Moon 4527 ± 10 million years ago. This age has been calculated according to the dating of the isotope of lunar rocks, between 30 and 50 million years after the origin of the solar system. [ 5 ] These include the fission of the Moon from the Earth's crust due to centrifugal forces , [ 6 ] which should have also required an initial spin of the Earth; [ 7 ] the gravitational attraction of the Moon in a state of formation, [ 8 ] which would have required an unfeasible extension of the atmosphereto dissipate the energy of the Moon, which was passing; [ 7 ] and the co-formation of the Moon and the Earth together in the primordial accretion disk , which does not explain the depletion of iron in the metallic state. [ 7 ] These hypotheses also cannot explain the strong angular momentum in the Earth-Moon system. [ 9 ]
The general hypothesis today is that the Earth-Moon system was formed as a result of a large impact : a celestial body the size of Mars collided with the young Earth, flying material in orbit around it, which merged to form the Moon. . [ 10 ] It is believed that gigantic impacts like this were frequent in the early Solar System. The modeling of a large impact by computer simulations agrees with the measurements of the angular momentum of the Earth-Moon system, and the small size of the lunar nucleus; in turn, they show that most of the matter on the Moon comes from the impacted object, not from the young Earth. [ 11 ] In addition, certainMeteorites show that the isotopic compositions of oxygen and tungsten in other bodies in the inner Solar System such as Mars and (4) Vesta are very different from those of Earth, while Earth and the Moon have practically identical isotopic compositions. The mixture of matter evaporated after the impact between the Earth and the Moon could have matched the compositions, [ 12 ] although this is debated. [ 13 ]
The significant amount of energy released in the large impact and subsequent melting of the material in Earth's orbit may have melted the Earth's surface layer, forming an ocean of magma. [ 14 ] [ 15 ] The newly formed Moon may also have had its own lunar magma ocean ; estimates of its depth vary between 500 km and the entire radius of the Moon.
Distance to the Moon
In astronomy , a lunar distance (LD) is the measure of the distance from the Earth to the Moon. The average distance between the Earth and the Moon is 384,400 kilometers . [ 16 ] The actual distance varies along the Moon's orbit .
The Moon is moving away from Earth at an average rate of 3.8 cm per year, as detected by the lunar laser measurement experiment . [ 17 ] [ 18 ] [ 19 ] The rate of the recession is considered abnormally high. [ 20 ] By coincidence, the diagonal of the retroreflector cubes on the Moon is also 3.8 cm. [ 21 ] [ 22 ]
The first person to measure the distance to the Moon was the astronomer and geographer Hipparchus in 150 BC. C. It was based on the data of the diameter of the Earth, calculated by Eratosthenes 100 years before. He obtained a distance of 348,000 km . For this calculation he used the curvature of the shadow that the Earth casts on the Moon in a lunar eclipse, a method devised by Aristarco de Samos . [ 23 ] The small error is notable, given the limitations of the time, being only about 36,000 km , which represents less than 10%.
Revolutions of the Moon
It takes the Moon to go around the Earth 27 d 7 h 43 min if the rotation is considered with respect to the stellar background (sidereal revolution), but 29 d 12 h 44 min if it is considered with respect to the Sun (synodic revolution) and this is because in this period the Earth has revolved around the Sun (see month ). This last revolution governs the phases of the Moon , eclipses and lunisolar tides . As the Moon takes the same time to turn around itself as it does around the Earth, it always has the same face. This is because the Earth, by an effect called the gravitational gradient, has completely stopped the Moon. Most of the regular satellites present this phenomenon with respect to their planets. Thus, until the time of space research ( Luna 3 ) it was not possible to see the hidden lunar face, which is asymmetrical with respect to the visible face. The Sun always illuminates half of the Moon (except in lunar eclipses), which does not have to coincide with the visible side, producing the phases of the Moon . The apparent immobilization of the Moon with respect to the Earth has occurred because the Earth's gravity acts on the irregularities of the lunar globe in such a way that in the course of time the visible part has 4 km more radius than the non-visible part, being the center serious lunar displaced from the lunar center 1.8 km towards Earth.
- Synodic revolution : it is the time interval necessary for the Moon to return to an analogous position with respect to the Sun and the Earth. Its duration is 29 d 12 h 44 min 2.78 s. It is also called lunation or lunar month.
- Sidereal revolution : it is the time interval that it takes for the Moon to return to an analogous position with respect to the stars. Its duration is 27 d 7 h 43 min 11.5 s.
- Tropic Revolution: it is the time necessary for the Moon to return to the same celestial length. Its duration is 27 d 7 h 43 min 4.7 s.
- Draconic Revolution : it is the time it takes for the Moon to pass through the ascending node twice in a row. Its duration is 27 d 5 h 5 min 36 s.
- Anomalistic revolution : it is the time interval that elapses between 2 consecutive steps of the Moon through the perigee. Its duration is 27 d 13 h 18 min 33 s.
Moon translation movement
The fact that the Moon rises about an hour later each day is explained by knowing the orbit of the Moon around the Earth. The Moon completes one revolution around the Earth in approximately 28 days. If the Earth did not rotate on its own axis, it would be very easy to detect the movement of the Moon in its orbit. This movement causes the Moon to move about 12 ° in the sky each day. If the Earth did not rotate, what would be seen would be the Moon crossing the celestial vault from west to east for two weeks, and then it would be two weeks away (during which the Moon would be visible on the opposite side of the Globe).
However, the Earth completes one revolution each day (the direction of rotation is also due east). Thus, each day it takes Earth about 50 more minutes to face the Moon again (which means that you can see the Moon in the sky). The spin of the Earth and the orbital motion of the Moon combine, in such a way that the rise of the Moon is delayed on the order of 50 minutes each day.
Taking into account that the Moon takes approximately 28 days to complete its orbit around the Earth, and it takes 24 hours to complete one revolution around its axis, it is easy to calculate the daily "lag" of the Moon.
While in 24 hours the Earth will have made a complete revolution, the Moon will only have traveled 1/28 of its orbit around the Earth, which expressed in degrees of arc gives:
If we now calculate the time that the Earth takes in its rotation to travel this arc,
It gives the approximately 50 minutes that the Moon delays its rise each day.
To notice the movement of the Moon in its orbit, one must take into account its location at the time of sunset for a few days. Its orbital motion will take it one point further east in the sky at twilight each day.
The Moon rotates on an axis of rotation that has an inclination of 88.3 ° with respect to the plane of the ecliptic of the Earth, therefore almost perpendicular. Since the duration of the two movements is the same, the Moon constantly presents the same hemisphere to the Earth. The Moon takes 27.32 days to turn around on itself.
Translation of the Moon around the Sun
As it moves around the Sun, the Earth drags its satellite and the shape of the path that it describes is a curve of such a nature that it always directs its concavity towards the Sun. The speed with which the Moon moves in its orbit around Earth is 1 km / s.
Due to the eccentricity of the lunar orbit, the inclination of the axis of rotation of the Moon with respect to the plane of the ecliptic and the rotational movement of the Earth in the course of a sidereal revolution, it is possible to see, from the Earth, a 59% of the Moon's surface - instead of 50% -, as if it were animated by slight swaying from east to west and north to south. These apparent movements are known as hovers.
Libration in length
It is because the Moon's rotational motion is uniform while its angular velocity is not. It is maximum in the perigee and minimum in the apogee . Due to this Libration, the satellite has a rolling from east to west, thanks to which it is possible to see the convex surface corresponding to that of a 7 ° spindle .
Libration in latitude
It is due to the inclination of the axis of rotation of the Moon with respect to the plane of its orbit and the ecliptic. This axis forms an angle of 88 ° 30 'with the plane of the ecliptic and since that of the lunar orbit is 5 ° with respect to the ecliptic, then the angle formed with the axis of rotation of the Moon with the plane of its orbit is 6 ° 30 '. Therefore, not only can the North Pole and South Pole of the Moon be seen, but 6 ° 30 'beyond the South Pole can be seen. This hover is a kind of pitch from north to south in a time that is not equal to a sidereal revolution because it is 27.2 days.
It is due to the fact that the terrestrial radius is not negligible with respect to the distance to the Moon. The value of this hover is almost one degree, approximate value to its degree of parallax.
The Moon by its size is the fifth satellite in the Solar System . However, if the mass ratio with its planet is adopted as a comparison criterion, it turns out that Ganymede is 1/12500 the mass of Jupiter , Titan is 1/4700 the mass of Saturn and the Moon is 1 / 81.3 the mass of the Earth . In this way, the Earth-Moon system could be considered as a binary system.
It is the name that some scientists give to the Earth-Moon system due to the disproportionate size that the satellite presents in relation to the planet, of only 81 times less mass, that is, only 3.6 times less than the Earth in diameter (if the planet were the size of a basketball, the Moon would be like a tennis ball).
This statement is supported by the existing relationships between the different planets of the Solar System and their satellites, these varying between 3.6 / 1 times smaller than the Moon and 8924/1 of the XIII Leda satellite in relation to Jupiter.
This name is also supported by the non-existence of more natural satellites that orbit the Earth, since it is usual that there are none (in the case of Mercury or Venus ) or that there are many of them as in the planets of the Jovian type.
Thus, when it is said that the Earth describes an ellipse around the Sun, in reality it must be said that the orbit is described by the center of the Earth-Moon system. Both stars, joined by an invisible axis, form something like a dissymmetrical barbell that revolves around its center of gravity.
Because the mass of the Earth is much higher than that of the Moon, this center, called the center of gravity , which divides the common mass into two equal parts, is located inside the terrestrial globe, about 4683 km from its center. . Thus, 26 times a year, the Moon alternately passes from one side of the Earth's orbit to the other.
From these considerations, it follows that the movements of the Moon are much more complex than is supposed, being necessary to accurately determine the real movements of the Moon to take into account no less than 1,475 irregularities in the different lunar movements and that they include the disturbances of its orbit due to the attraction exerted by the other stars of the solar system, especially Venus (the closest) and Jupiter (the one with the greatest mass), as well as, among others, the secular acceleration of the Moon's movement.
Orbit of the Moon
The Moon describes an elliptical path of low eccentricity around the Earth , at an average distance of 384,400 kilometers and in a counterclockwise direction. The distance between the Earth and its natural satellite varies, as does the speed in orbit. [ 25 ]
Since the lunar rotation is uniform and its translation is not, as it follows Kepler's laws , a Libration in longitude is produced that allows a little more of the lunar surface to be seen to the east and west, which otherwise would not be seen. The plane of the lunar orbit is inclined with respect to the ecliptic about 5 ° so that a Libration is produced in latitude that allows to see alternately a little beyond the North or South Pole. For both movements, the total lunar surface seen from Earth reaches 59% of the total. Every time the Moon crosses the ecliptic, if the Earth and the Sun are sensibly aligned ( full moon or new moon ), a lunar eclipse will occuror a solar eclipse .
The orbit of the Moon is especially complex. The reason is that the Moon is far enough from the Earth and the force of gravity exerted by the Sun is significant. Given the complexity of the movement, the nodes of the Moon are not fixed, but they go around in 18.6 years. The axis of the lunar ellipse is not fixed and the apogee and perigeethey make a complete turn in 8.85 years. The inclination of the orbit varies between 5 ° and 5 ° 19 '. In fact, to calculate the position of the Moon accurately it is necessary to take into account at least several hundred terms. In addition, the Moon-Earth orbit is inclined with respect to the plane of the Earth-Sun orbit, so that only in two points of its trajectory, called nodes, can solar or lunar eclipses occur.
Likewise, the Moon moves away about four centimeters a year from the Earth, [ 26 ] at the same time that it slows down the Earth's rotation - which will cause total eclipses of the Sun to cease to occur in the distant future as there is no Moon. large enough to completely cover the sun disk. In theory, this separation should last until the Moon takes 47 days to complete an orbit around our planet, at which point it would take our planet 47 days to complete a rotation around its axis, similar to what happens in the Pluto-Charon system. However, the future evolution of our Sun can disrupt this process. It is possible that by turning our star into a red giantSeveral billion years from now, the proximity of its surface to the Earth-Moon system will cause the lunar orbit to close until the Moon is around 18,000 kilometers from Earth - the Roche limit -, at which time which Earth's gravity will destroy the Moon turning it into rings similar to those of Saturn . In any case, the end of the Earth-Moon system is uncertain and depends on the mass that the Sun loses in these final stages of its evolution. [ 27 ]
A study by the European Space Agency carried out in 2019, with data collected by the SOHO observatory , establishes that the Moon orbits within the Earth's atmosphere since the most distant region of this extends beyond the orbit of the Moon and has a radius of 630,000 km, 50 times the diameter of the Earth. [ 28 ]
A lunar eclipse is an astronomical event that happens when the Earth gets between the Sun and the Moon, generating a cone of shadow that obscures the Moon. The diameter of the Sun is 400 times larger than that of the Moon, but it is also 400 times farther away, so they both span roughly the same solid angle for an observer on Earth. The Moon in a lunar eclipse can contain up to three times its diameter within the cone of shadow caused by the Earth. Lunar eclipses are classified into 3 types. These are
- Penumbralesː the full Moon passes only through the twilight zone of the Earth's shadow cone. Its relative luminosity very little, therefore a simple view is not perceived.
- Partialː the full Moon does not completely enter the Earth's shadow cone, that is, part remains in the penumbra and part in the umbra, it will then be partial.
- Totalː the full Moon completely enters the cone of earth's shadow acquiring different colors from a yellowish, orange, light copper to a dark one.
On the contrary, in a solar eclipse , the dark silhouette of the Moon completely obscures the bright one of the Sun (total eclipse) and in a certain part of its orbit, when it is more distant, it does not completely hide it, leaving an annular strip (annular eclipse) or it is not exactly in line with the Earth and the Moon only partially obscures the Sun (partial eclipse).
The complexity of the lunar movement makes it difficult to calculate eclipses and the periodicity with which they occur must be taken into account ( Saros Period ).
Luna azul (translation from English blue moon ) is called the second full moon that occurs during the same month of the Gregorian calendar (the one usually used in the West ), which happens approximately (on average) every 2.5 years [ 29 ] and Originally, at the third full moon when in any season of the year there are four full moons instead of three. The "Blue Moon" phenomenon became popular when it occurred twice in 1999 (January and March). The media widely reported the event, little known until then. Naturally, in February 1999 there was no full moon.
Based on the origin of the term in the Gregorian calendar, its use spread during medieval times . The Spanish translation is not entirely complete, since the expression comes from the English blue ("blue"), which in turn comes from a deformation of Old English belewe , which actually means "traitor", since an additional moon in the spring it involved extending the fast of Lent . [ 30 ] Between three and seven times in each century there are two blue moons in the same year. Because the month of February is the only one whose duration is less than the lunar cycle, the first always occurs in January and the second, in decreasing order of probability, in March, April or May. [ 31 ] Two blue moons were observed on December 2 and 31, 2009, coinciding that on December 31, 2009 there was a partial lunar eclipse, whose full moon was in December.The term belewe was abbreviated as blwe and later it became blue , and thus it passed into the Latin culture translated as "blue". Thus, according to the meaning of belewe it would be a traitorous moon , although what would really be traitorous is the Gregorian month of 31 days in the sense that its duration is 1.5 days longer than the natural month marked by the moon, of 29.5 days . The English word month itself is rooted moonand in fact means "lunar", but eight of the "months" of the Gregorian (Christian Roman) calendar are not lunar, and when it happens that the beginning of a 31-day month coincides with the full phase, a mes belewe or belewe month , blwe month , and from there it evolves by sonic analogy as blue month and blue moon . As it is not an astronomical event but a cultural curiosity of the Christian calendar, it is also called belewe month.or traitorous month, less popular name but more consistent with the original meaning. The traitorous month does not exist in cultures that use lunar calendars, such as the Jewish and Muslim, for which the calendar is sacred, creation of God (Yahweh, Allah), and therefore perfect and part of religion.
In reality, the Moon does not revolve around the Earth, but rather the Earth and the Moon revolve around the center of mass of both. However, since the Earth is a large body, the gravity that the Moon exerts on it is different at each point.
At the closest point it is much greater than at the Earth's center of mass, and greater at this than at the farthest point from the Moon.
Thus, while the Earth revolves around the center of gravity of the Earth-Moon system, a force appears at the same time that tries to deform it, giving it the appearance of an egg.
This phenomenon is called a gravitational gradient , which produces the tides.
As the Earth is solid, the deformation affects the waters and the atmosphere more and is what gives the effect that they rise and fall twice a day (it rises at the closest and furthest points from the Moon).
An associated effect is that the tides slow the Earth in its rotation (it loses energy due to the friction of the oceans with the seabed), and since the Earth-Moon system has to conserve angular momentum, the Moon compensates for it. currently receding 38 mm [ 34 ] each year, as laser distance measurements have shown , made possible by retro-reflectors left by astronauts on the Moon.
Water on the moon
Until 2009 , the possible existence of water on the Moon was debated in the scientific community . The selenite environment makes the presence of water almost impossible: except in a microscopic crystallized form in the rocks, the existence of liquid water is practically impossible, since in most of the lunar surface, at times the temperature rises a lot.
This and the lack of an atmosphere mean that all water exposed to the typical lunar environment becomes sublime and its molecules escape into space. However, two discoveries, one in 1996 by the Clementine probe , [ 35 ] and another in 1998 due to the Lunar Prospector detected unforeseen hydrogen presences at the lunar poles. [ 36 ]
One hypothesis to explain this phenomenon is that this hydrogen is in the form of water and that some comets , when impacting the polar areas, may have created craters where sunlight does not reach. In such craters perhaps frozen water of cometary origin (ie exogenous water) could be found. The interior of the polar craters never gets sunlight, they remain in eternal darkness and never rise above −240 ° C. In these icy hollows there is frozen water or a hydrogen compound such as methane (CH 4 ). On September 24, 2009, India reported that its first lunar exploration spacecraft the Chandrayaan-1 using the Moon Mineralogy Mapper.(Lunar Mineralogical Tracer) from NASA , has found evidence of a significant amount of endogenous water (not from other stars) below the surface of the Moon, such water would be largely the product of chemical reactions triggered by strong radiation that the aforementioned satellite receives, more specifically: the solar wind during the lunar day would cause the hydrogen ions present in the selenite surface materials to originate hydroxyl (OH) and water (H 2 O), [ 37 ] as far as possible lunar icesome scientists suggest that there may be as much as 300 million tons in polar craters that never receive sunlight or heat. [ 38 ] [ 39 ] [ 40 ]
Discovery of water on the Moon
The 13 of November of 2009 , the US space agency NASA announced the discovery of water on the moon. When, on October 9, NASA crashed the LCROSS probe and its Centauro propeller at the bottom of the Cabeus crater at the south pole of the Moon, in an operation that sought to confirm the presence of water on Earth's natural satellite. The collision lifted a column of material from the bottom of a crater that has not received sunlight in billions of years.
The water that was lifted by the impact of the probe could fill a dozen eight-liter buckets, said scientist Anthony Colaprete. Preliminary data obtained from the analysis of these materials "indicates that the mission successfully discovered water (...) and this discovery opens a new chapter in our understanding of the Moon," said NASA .
"The concentration and distribution of water and other substances require further analysis, but we can safely say that (the crater) Cabeus contains water," Colaprete said. [ 41 ]
In October 2020, NASA revealed that the SOFIA observatory had managed to detect the presence of water molecules - in the form of small deposits located between the ground or trapped in crystals - in the lunar Clavius crater . The telescope captured infrared light at a wavelength that only water can emit and the discovery, which confirms the presence of this element in the illuminated area of the Moon, was published in Nature Astronomy . Another study published in the same journal affirms that the cold water deposits (in areas where sunlight does not reach) of this satellite would occupy about 40,000 square kilometers. [ 42 ]
Atmosphere of the Moon
The Moon has a negligible atmosphere due to its low gravity and the absence of an electromagnetic field, unable to retain gas molecules on its surface. The entirety of its composition is still unknown. Apollo program identified atoms helium and argon , and later (in 1988), observations from Earth added ions of sodium and potassium . Most of the gases on its surface come from its interior.
The thermal agitation of gas molecules is induced by solar radiation and by random collisions between the atmospheric particles themselves. In the earth's atmospherethe molecules usually have speeds of hundreds of meters per second, but exceptionally some manage to reach speeds of 2000 to 3000 m / s. Since the escape velocity is approximately 11,200 m / s, they never escape into space. On the Moon, on the other hand, since gravity is six times less than on our planet, the escape velocity is also lower, of the order of 2,400 m / s. We can then deduce that if the Moon once had an atmosphere, the fastest molecules were able to escape from it to, according to a law of the kinetic theory of gases, induce the rest to increase their speed, thus accelerating the process of atmospheric loss. It is estimated that the complete disappearance of the hypothetical lunar atmosphere must have been made over several hundred million years.
The practically total absence of atmosphere on our satellite forces astronauts to have autonomous gas supply equipment, known as PLSS, on their walks on the surface. Likewise, since there is no protective mantle, the ultraviolet radiation and the gamma rays emitted by the Sun bombard the lunar surface, making it necessary to have special protective suits to avoid their harmful effects.
For the tenuous lunar atmosphere, any small change can be important. The mere presence of astronauts locally alters their pressure and composition by enriching it with the gases exhaled by them and by those that escape from the lunar module each time an EVA is carried out . There is a fear that the gases emitted by the ships that landed on the Moon in the 1970s have created pollution or contamination of equal mass to that of their native atmosphere. Although these gases must have mostly disappeared by now, there is still a concern that debris remains that prevent research on the real atmosphere of the Moon.
The lunar atmosphere also receives contributions from solar particles during the day, which ceases at night. During the lunar night, the pressure can drop to no more than two billionths of the Earth's atmosphere, rising to eight billionths during the day, thus demonstrating that the lunar atmosphere is not a permanent atmosphere, but a concentration of particles. dependent on the exolunar environment.
The ionosphere that surrounds our satellite differs from the terrestrial one in the low number of ionized particles, as well as the presence of low-energy electrons that, torn from the soil of the Moon, are emitted into space by the impact of the solar rays. Currently, it has been possible to determine the existence of a sodium tail composed of vapors that are released from our satellite in a similar way to how the gases of comets do .
The absence of air, and consequently of winds, prevents the surface from eroding and transporting dirt and sand, smoothing and covering its irregularities. Due to the absence of air, sound is not transmitted . The lack of atmosphere also means that the Moon's surface has no protection from sporadic bombardment by comets and asteroids . In addition, once the impacts of these occur, the resulting craters do not degrade practically over time due to the lack of erosion.
Origin of the Moon
When discovering that the composition of the Moon was the same as that of the Earth's surface, it was assumed that its origin had to come from the Earth itself. Such a large body in relation to our planet could hardly have been captured, nor was it likely to have formed alongside Earth. Thus, the best explanation for the formation of the Moon is that it originated from the pieces left behind after a cataclysmic collision with a protoplanet the size of Mars at the dawn of the Solar System ( the Great Impact Hypothesis ). This theory also explains the large axial inclination of the axis of rotation.terrestrial that would have been caused by the impact. In 2018, a study by the universities of California Davis and Harvard offered a version in which the Moon had arisen inside the Earth, when our planet was a seething cloud of vaporized rock revolving around itself. [ 43 ]
The enormous energy supplied by the crash melted the entire earth's crust and threw a large quantity of incandescent debris into space. Over time, a ring of rock formed around our planet until, by accretion , the Moon formed. Its initial orbit was much closer than the current one and the Earth day was much shorter since the Earth rotated faster. For hundreds of millions of years, the Moon has been moving slowly away from the Earth, at the same time that the speed of the Earth's rotation has decreased due to the transfer of angular momentum that occurs between the two stars. This process of distancing currently continues at the rate of 38 mm per year.
After its formation, the Moon underwent a cataclysmic period, dating from around 3800-4000 million years ago, in which the Moon and the other bodies of the inner Solar System were violently impacted by large asteroids. This period, known as late heavy bombardment , formed most of the craters seen on the Moon, as well as on Mercury . Analysis of the Moon's surface yields important data on this final period in the formation of the Solar System. Later there was a period of volcanism consisting of the emission of large amounts of lava, which filled the largest impact basins forming the lunar seas and which ended 3 billion years ago. Since then, little more has happened on the lunar surface than the formation of new craters due to the impact of asteroids, although reports (both historical and current) that report the presence of occasional luminous phenomena on the moon are not uncommon. called transient lunar phenomena .
When Galileo Galilei pointed his telescope at the Moon in 1610, he was able to distinguish two different types of surface regions. He called the dark regions " seas, " and although it was soon learned that they contain no water, they have retained names such as the Sea of Serenity or the Sea of Fertility; they are plains with few craters . The rest of the lunar surface is brighter, and features higher regions with a high density of craters, such as Tycho and Clavius. On the lunar surface there are also mountain ranges that bear names like the Alps and Apennines, just like on Earth .
|Tycho crater on the lunar surface.||Tsiolkovski Crater photographed from Apollo 15 .||Sea of Tranquility photographed from Apollo 8 .||Mar Imbrium and the Copernicus crater , the mountain range at the top are the Carpathian mountains.|
- Meteorite impacts on the lunar surface
Around 1830, leading selenographers (such as the German astronomer Johann Heinrich von Mädler ) had concluded that the satellite contains neither atmosphere nor water, and that the relief of the Moon does not change. However, being this true in general lines in the short term (due to the current absence of volcanic, hydrological or atmospheric phenomena in conditions of modeling the lunar surface), the lack of atmosphere does not mitigate meteoritic impacts, which by simple accumulation in Spaces of time on a geological scale, it implies a considerable effect on its relief (proof of this are the many impact craters that cover its surface).
In fact, there is some historical evidence about meteorite impacts on the moon:
- On June 18, 1178, the British monk Gervasio of Canterbury observed the impact of an asteroid on the crescent moon, a fact that is reflected in the chronicles of Canterbury Cathedral .
- In 1866, the Irish astronomer John Birmingham wrote an essay on the disappearance of a crater on the moon's surface and the subsequent appearance of a vast luminous cloud in its place.
- On March 17, 2013, a meteoroid the size of a small rock impacted on the lunar surface in Mare Imbrium and caused an explosion ten times brighter than those observed up to that moment. [ 45 ]
- On September 11, 2013, a meteoroid with a diameter between 0.6 and 1.4 meters and a weight of 400 kg collided in the Mare Nubium (Sea of Clouds) at about 65,000 km / h, causing the brightest lunar explosion ever recorded. [ 46 ]
From time immemorial the Moon surprised humanity with its great size, its orbital cycles and its phases. It was one of the two most important bodies along with the Sun and its periodicity served as a calendar in many cultures. A 5000-year-old rock has been found in Ireland that appears to be the earliest representation of the Moon discovered to date.
In many prehistoric and ancient cultures, the Moon was a deity or other supernatural phenomenon (for example, the Kiliwa believe that the Moon is a male power, and according to their own mythology the Moon god Meltí? Ipá jalá (u) was the creator of the entire universe).
One of the first times that an attempt was made to offer a rational and scientific view of what the moon was was in Ancient Greece . It was proposed by the philosopher Anaxagoras who reasoned that both the Sun and the Moon were two giant, rocky and spherical bodies and that the light emitted by the Moon was nothing more than light reflected from the Sun. His atheistic idea of the sky was one of the causes of his imprisonment and subsequent exile.
In 1609 , Galileo Galilei observed the Moon for the first time with a telescope and stated, in his book Sidereus Nuncius ( The Celestial Messenger ), that it was not smooth as it had craters . Later, also in the 17th century , Giovanni Battista Riccioli and Francesco Maria Grimaldi drew a map of the Moon and named many of these craters, names that remain today.
The Moon Program of the former Soviet Union (1959-1976) aimed to reach the Moon with unmanned spacecraft. The Luna 3 able to photograph the hidden face, Luna 9 achieved perching gently, and Luna 10 orbited first moon. Two Lunojod vehicles managed to land and move on its surface and after the manned Apollo 11 moon landing, the Luna 16 , Luna 20 and Luna 24 spacecraft brought about 300 grams of lunar dust to Earth.
The American Ranger program (1961-1965) launched a series of photographic reconnaissance ships directly against the Moon. Only Ranger 7, 8 and 9 achieved their goal. The Lunar Orbiter program put five unmanned spacecraft in lunar orbit between the years 1966-1967 to map it and help the Apollo Program to put a person on the Moon, a historic milestone that was achieved with the arrival of Apollo 11 on July 20 , 1969 and that it was broadcast to the entire planet from the different facilities of the Deep Space Network . The MDSCC in Robledo de Chavela ( Madrid ,Spain ) belonging to her, served as support throughout the round trip. [ 47 ] [ 48 ] A Ranger program the program happened Surveyor that after Luna 9 achieved soft landings of unmanned spacecraft.
The American ships Clementine and Lunar Prospector , the Japanese Hiten and Selene , the European Smart 1 , the Chinese Chang'e 1 and the Hindu Chandrayaan-1 represented a return to the Moon, abandoned since 1973 . Its mission was to detect the presence of water vapor mixed with lunar dust and coming from comets that have crashed near the lunar poles in craters where they are never illuminated by the Sun.
The different forms that the moon takes during its 28-day cycle (especially the recognizable silhouette that recalls a letter "C" called the crescent ) have a wide presence in various manifestations, ranging from mythology to art , through heraldry. or its symbolic association with Islam . This last link (especially in the eyes of non-Muslims) has its origin in the 16th century, when the crescent was adopted by the Turks as a heraldic symbol, and it would not acquire its current connotation as a religious symbol until much later. [ 49 ]Its presence is common on the spiers of mosques , and is part of the flag of some countries (generally of Islamic tradition).
In heraldry, the crescent can acquire different names depending on how it is oriented; the silhouette formed by four linked crescents (reminiscent of a four-leaf clover) is called a "lunel". [ 50 ]
Its presence in art dates back to the time of cave paintings (with examples in Tassili n'Ajjer , Algeria ) [ 51 ] and its appearance is omnipresent in all cultures of antiquity, from Egypt to Rome. The visual arts (from literary illustrations to cinema) have produced numerous more or less anthropomorphic images of the Moon, some of them turned into authentic icons of 20th century culture (such as the historic images in the 1902 film Journey to the Moon , by Georges Méliès ).
Finally, as an example of the uses varied given to the shape of the growing , we recall the relationship of the form of the croissant with the moon half, circumstances linked to the siege of Vienna by Turkish troops in 1683. [ 52 ]
The Moon in international law
|Flags that include the image of the Moon:|
Activities that directly affect outer space (which includes the Moon) are regulated by an international treaty initially signed in 1967 by the United States, the United Kingdom, and the Soviet Union. In 2015, 103 countries are party to the treaty, while another 89 have signed the agreement but have not yet ratified it.
However, this fact has not prevented the emergence of some initiatives of more than doubtful legal legitimacy, which periodically claim ownership of the Moon before official bodies, and which are reflected by the newspapers due to their striking anecdotal nature:
- In 1953 , the Chilean lawyer Jenaro Gajardo Vera registered the property of the Moon paying 42,000 pesos of the time, and the deed became official on September 25 , 1954 at the Real Estate Custodian of the city of Talca . The story that President Richard Nixon fulfilled the formality of requesting permission for the Apollo 11 moon landing in 1969 has become a popular false myth associated with the original story. [ 53 ]
- In 1980, after the signing of the international treaty, the American Dennis Hope once again formalized in a San Francisco registry office the "purchase" of the Moon, dedicating himself ever since to sell "parcels" on lunar soil. [ 54 ]
Influence on human behavior
This is the name given to the widespread belief that the cycles of the Moon have some influence on human behavior. However, there is no statistically significant scientific evidence that minimally confirms this assertion. Not even the human menstrual cycle (whose duration of 28 days coincides sensibly with the lunar cycle), presents the least statistical correlation in its distribution in the female population with the phases of the Moon. [ 55 ] Along the same lines, disciplines such as biodynamic agriculture have also spread , which seek to obtain supposed benefits in harvests by coordinating the planting or harvesting moments with certain phases of the Moon.
Influence on physiological rhythms during sleep
It has been scientifically confirmed, after many years of speculation in this regard, that there is a correlation between the phases of the moon and the biological rhythms of the human being during sleep . A group of Swiss scientists observed that around the full moon, the delta waves of the EEG decreased by 30 percent during NMOR sleep , an indicator of deep sleep , so it took participants five minutes longer to fall asleep and , in general, they slept twenty minutes less . Volunteer participants felt they slept poorly ( subjective sleep quality) during the full moon, a phase during which lower levels of melatonin , a hormone that regulates sleep-wake cycles, were observed in them . It is perhaps a circalunar rhythm that has remained as a vestige of antiquity, "when the moon was responsible for the synchronization of human behavior." This is considered to be the first reliable evidence that a lunar rhythm can modulate the structure of sleep in humans when measured under the highly controlled conditions of a circadian laboratory study protocol without the presence of time cues . [ 56 ] [ 57 ]
- Moons of Mars · Jupiter · Saturn · Uranus · Neptune · Pluto · Eris · Haumea
- Natural satellite
- Moon exploration
- Lunar water
- Colonization of the Moon
- Apolo XI
- Moon phase
- Lunar mythology
- Annex: Artificial objects on the Moon
- Annex: Artificial satellites of the Moon
- Annex: Fictional Moon Trips in Literature
- Tourism on the Moon
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- Eureka! Ice found at the Moon's poles (NASA report) | 04-24-2006
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- "Wet" soil detected on the moon
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- Lunar volcanism lasted longer than expected
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- Wikimedia Commons hosts a multimedia category on Luna .
- Wikiquote hosts famous quotes from or about Luna .
- Lunar calendars
- Online lunar calendar and eclipse predictor
- Movements of the Moon (includes forecast of the lunar phases from January 100 to December 2300)
- Record of the current moon phase
- Interactive educational resource on the phases of the Moon
- Scientific information
- On the Moon (in Spanish)
- The Moon on the AstronoMía website
- Theories of lunar formation
- Technical Moon tab on the NASA website (English)
- Interactive simulation of lunar orbit (requires Firefox 1.5) (in English)
- Inconstant moon - by Kevin Clarke (English)
- Geological history of the Moon by Don Wilhelms (English)
- Formation of the Moon
- Chinese scientists create the most complete map of the Moon (in Spanish)
- Lunar space missions
- Moon version of GoogleMaps
- More about the Moon
- More links on cartography and lunar observation
- The big moon near the horizon (ponzo effect)
- Luna: Why does it look so big?
- Lunar libration: Why on Earth does one look at a little more than 50% of the lunar surface?
- Lunar browser: Interactive maps of the Moon (English)
- Distance from the moon to Earth illustrated (in English)
- Lunar dimensional globe (English)
- Links on the Moon - UCM