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131-509: It corresponds to: The 30.5 eclipse years means that if there is a solar eclipse (or lunar eclipse ), then after one inex a New Moon (resp. Full Moon) will take place at the opposite node of the orbit of the Moon , and under these circumstances another eclipse can occur. Unlike the saros , the inex is not close to an integer number of anomalistic months so successive eclipses are not very similar in their appearance and characteristics. From

262-526: A lunar eclipse , always illuminated by the Sun, but from Earth the visible illumination shifts during its orbit, producing the lunar phases . The Moon is the brightest celestial object in Earth's night sky . This is mainly due to its large angular diameter , while the reflectance of the lunar surface is comparable to that of asphalt . The apparent size is nearly the same as that of the Sun, allowing it to cover

393-676: A battle between the Medes and the Lydians . Both sides put down their weapons and declared peace as a result of the eclipse. The exact eclipse involved remains uncertain, although the issue has been studied by hundreds of ancient and modern authorities. One likely candidate took place on May 28, 585 BC, probably near the Halys river in Asia Minor . An eclipse recorded by Herodotus before Xerxes departed for his expedition against Greece , which

524-425: A decisive role on local surface temperatures . Parts of many craters, particularly the bottoms of many polar craters, are permanently shadowed, these " craters of eternal darkness " have extremely low temperatures. The Lunar Reconnaissance Orbiter measured the lowest summer temperatures in craters at the southern pole at 35 K (−238 °C; −397 °F) and just 26 K (−247 °C; −413 °F) close to

655-434: A few kilometers wide), shallower, and more irregularly shaped than impact craters. They also lack the upturned rims characteristic of impact craters. Several geologic provinces containing shield volcanoes and volcanic domes are found within the near side maria. There are also some regions of pyroclastic deposits , scoria cones and non-basaltic domes made of particularly high viscosity lava. Almost all maria are on

786-493: A fortuitous combination of circumstances. Even on Earth, the diversity of eclipses familiar to people today is a temporary (on a geological time scale) phenomenon. Hundreds of millions of years in the past, the Moon was closer to Earth and therefore apparently larger, so every solar eclipse was total or partial, and there were no annular eclipses. Due to tidal acceleration , the orbit of the Moon around Earth becomes approximately 3.8 cm more distant each year. Millions of years in

917-503: A global dipolar magnetic field and only has crustal magnetization likely acquired early in its history when a dynamo was still operating. Early in its history, 4 billion years ago, its magnetic field strength was likely close to that of Earth today. This early dynamo field apparently expired by about one billion years ago, after the lunar core had crystallized. Theoretically, some of the remnant magnetization may originate from transient magnetic fields generated during large impacts through

1048-718: A hospitable environment for future astronauts, protecting them from extreme temperatures, solar radiation, and micrometeorites. However, challenges include accessibility and risks of avalanches and cave-ins. This discovery offers potential for future lunar bases or emergency shelters. The main features visible from Earth by the naked eye are dark and relatively featureless lunar plains called maria (singular mare ; Latin for "seas", as they were once believed to be filled with water) are vast solidified pools of ancient basaltic lava. Although similar to terrestrial basalts, lunar basalts have more iron and no minerals altered by water. The majority of these lava deposits erupted or flowed into

1179-429: A hypothesized Mars-sized body called Theia . The lunar surface is covered in lunar dust and marked by mountains , impact craters , their ejecta , ray-like streaks , rilles and, mostly on the near side of the Moon, by dark maria ("seas"), which are plains of cooled lava . These maria were formed when molten lava flowed into ancient impact basins. The Moon is, except when passing through Earth's shadow during

1310-533: A landscape featuring craters of all ages. The Moon was volcanically active until 1.2 billion years ago, which laid down the prominent lunar maria . Most of the mare basalts erupted during the Imbrian period , 3.3–3.7 billion years ago, though some are as young as 1.2 billion years and some as old as 4.2 billion years. There are differing explanations for the eruption of mare basalts, particularly their uneven occurrence which mainly appear on

1441-462: A longer lens is needed (over 500 mm). As with viewing the Sun directly, looking at it through the optical viewfinder of a camera can produce damage to the retina, so care is recommended. Solar filters are required for digital photography even if an optical viewfinder is not used. Using a camera's live view feature or an electronic viewfinder is safe for the human eye, but the Sun's rays could potentially irreparably damage digital image sensors unless

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1572-454: A maximum of a few minutes at any location because the Moon's umbra moves eastward at over 1700 km/h (1100 mph; 470 m/s; 1500 ft/s). Totality currently can never last more than 7 min 32 s. This value changes over the millennia and is currently decreasing. By the 8th millennium, the longest theoretically possible total eclipse will be less than 7 min 2 s. The last time an eclipse longer than 7 minutes occurred

1703-543: A more precise alignment between the centers of the Sun and Moon , and because the Moon's apparent size in the sky is sometimes too small to fully cover the Sun. An eclipse is a natural phenomenon . In some ancient and modern cultures, solar eclipses were attributed to supernatural causes or regarded as bad omens . Astronomers' predictions of eclipses began in China as early as the 4th century BC; eclipses hundreds of years into

1834-595: A partial eclipse at the opposite polar region. A saros series lasts 1226 to 1550 years and 69 to 87 eclipses, with about 40 to 60 of them being central. Between two and five solar eclipses occur every year, with at least one per eclipse season . Since the Gregorian calendar was instituted in 1582, years that have had five solar eclipses were 1693, 1758, 1805, 1823, 1870, and 1935. The next occurrence will be 2206. On average, there are about 240 solar eclipses each century. Total solar eclipses are seen on Earth because of

1965-420: A practically identical eclipse will occur. The most notable difference will be a westward shift of about 120° in longitude (due to the 0.3 days) and a little in latitude (north-south for odd-numbered cycles, the reverse for even-numbered ones). A saros series always starts with a partial eclipse near one of Earth's polar regions, then shifts over the globe through a series of annular or total eclipses, and ends with

2096-428: A radius of about 500 kilometres (310 mi). This structure is thought to have developed through the fractional crystallization of a global magma ocean shortly after the Moon's formation 4.5 billion years ago. Crystallization of this magma ocean would have created a mafic mantle from the precipitation and sinking of the minerals olivine , clinopyroxene , and orthopyroxene ; after about three-quarters of

2227-458: A satellite with similar mass and iron content to the Moon into orbit far outside Earth's Roche limit . Even satellites that initially pass within the Roche limit can reliably and predictably survive, by being partially stripped and then torqued onto wider, stable orbits. On November 1, 2023, scientists reported that, according to computer simulations, remnants of Theia could still be present inside

2358-460: A solar eclipse was taken on July 28, 1851, by Johann Julius Friedrich Berkowski , using the daguerreotype process. Photographing an eclipse is possible with fairly common camera equipment. In order for the disk of the Sun/Moon to be easily visible, a fairly high magnification long focus lens is needed (at least 200 mm for a 35 mm camera), and for the disk to fill most of the frame,

2489-475: A study of Ina , a tiny depression in Lacus Felicitatis , found jagged, relatively dust-free features that, because of the lack of erosion by infalling debris, appeared to be only 2 million years old. Moonquakes and releases of gas indicate continued lunar activity. Evidence of recent lunar volcanism has been identified at 70 irregular mare patches , some less than 50 million years old. This raises

2620-502: A texture resembling snow and a scent resembling spent gunpowder . The regolith of older surfaces is generally thicker than for younger surfaces: it varies in thickness from 10–15 m (33–49 ft) in the highlands and 4–5 m (13–16 ft) in the maria. Beneath the finely comminuted regolith layer is the megaregolith , a layer of highly fractured bedrock many kilometers thick. These extreme conditions are considered to make it unlikely for spacecraft to harbor bacterial spores at

2751-501: A total eclipse and only very briefly; it does not occur during a partial or annular eclipse). Viewing the Sun's disk through any kind of optical aid (binoculars, a telescope, or even an optical camera viewfinder) is extremely hazardous and can cause irreversible eye damage within a fraction of a second. Viewing the Sun during partial and annular eclipses (and during total eclipses outside the brief period of totality) requires special eye protection, or indirect viewing methods if eye damage

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2882-420: A total eclipse occurs. The Moon orbits Earth in approximately 27.3 days, relative to a fixed frame of reference . This is known as the sidereal month . However, during one sidereal month, Earth has revolved part way around the Sun, making the average time between one new moon and the next longer than the sidereal month: it is approximately 29.5 days. This is known as the synodic month and corresponds to what

3013-478: A total eclipse was taken of the solar eclipse of July 28, 1851 . Spectroscope observations were made of the solar eclipse of August 18, 1868 , which helped to determine the chemical composition of the Sun. John Fiske summed up myths about the solar eclipse like this in his 1872 book Myth and Myth-Makers , Moon The Moon is Earth 's only natural satellite . It orbits at an average distance of 384,400 km (238,900 mi), about 30 times

3144-485: A total solar eclipse was made in France in 1706. Nine years later, English astronomer Edmund Halley accurately predicted and observed the solar eclipse of May 3, 1715 . By the mid-19th century, scientific understanding of the Sun was improving through observations of the Sun's corona during solar eclipses. The corona was identified as part of the Sun's atmosphere in 1842 , and the first photograph (or daguerreotype ) of

3275-439: A trans-Atlantic flight, 200 times more than on Earth's surface. For further comparison radiation on a flight to Mars is about 1.84 millisieverts per day and on Mars on average 0.64 millisieverts per day, with some locations on Mars possibly having levels as low as 0.342 millisieverts per day. The Moon's axial tilt with respect to the ecliptic is only 1.5427°, much less than the 23.44° of Earth. Because of this small tilt,

3406-439: A year, when the Sun and Moon are not exactly in line with Earth and the Moon only partially obscures the Sun. This phenomenon can usually be seen from a large part of Earth outside of the track of an annular or total eclipse. However, some eclipses can be seen only as a partial eclipse, because the umbra passes above Earth's polar regions and never intersects Earth's surface. Partial eclipses are virtually unnoticeable in terms of

3537-531: Is 1.2% that of the Earth, and its diameter is 3,474 km (2,159 mi), roughly one-quarter of Earth's (about as wide as the United States from coast to coast ). Within the Solar System , it is the largest and most massive satellite in relation to its parent planet , the fifth largest and most massive moon overall, and larger and more massive than all known dwarf planets . Its surface gravity

3668-461: Is about 400 times the Moon's distance, and the Sun's diameter is about 400 times the Moon's diameter. Because these ratios are approximately the same, the Sun and the Moon as seen from Earth appear to be approximately the same size: about 0.5 degree of arc in angular measure. The Moon's orbit around Earth is slightly elliptical , as is Earth's orbit around the Sun. The apparent sizes of the Sun and Moon therefore vary. The magnitude of an eclipse

3799-407: Is about one sixth of Earth's, about half of that of Mars , and the second highest among all Solar System moons, after Jupiter 's moon Io . The body of the Moon is differentiated and terrestrial , with no significant hydrosphere , atmosphere , or magnetic field . It formed 4.51 billion years ago, not long after Earth's formation , out of the debris from a giant impact between Earth and

3930-489: Is around 3 × 10   atm (0.3  nPa ); it varies with the lunar day. Its sources include outgassing and sputtering , a product of the bombardment of lunar soil by solar wind ions. Elements that have been detected include sodium and potassium , produced by sputtering (also found in the atmospheres of Mercury and Io ); helium-4 and neon from the solar wind; and argon-40 , radon-222 , and polonium-210 , outgassed after their creation by radioactive decay within

4061-532: Is asymmetric, being more dense near the boundary between the Moon's dayside and nightside. Ionizing radiation from cosmic rays , the Sun and the resulting neutron radiation produce radiation levels on average of 1.369 millisieverts per day during lunar daytime , which is about 2.6 times more than on the International Space Station with 0.53 millisieverts per day at about 400 km above Earth in orbit, 5–10 times more than during

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4192-416: Is commonly called the lunar month . The Moon crosses from south to north of the ecliptic at its ascending node , and vice versa at its descending node. However, the nodes of the Moon's orbit are gradually moving in a retrograde motion , due to the action of the Sun's gravity on the Moon's motion, and they make a complete circuit every 18.6 years. This regression means that the time between each passage of

4323-561: Is estimated from about 500 km (300 miles) to 1,737 km (1,079 miles). While the giant-impact theory explains many lines of evidence, some questions are still unresolved, most of which involve the Moon's composition. Models that have the Moon acquiring a significant amount of the proto-earth are more difficult to reconcile with geochemical data for the isotopes of zirconium, oxygen, silicon, and other elements. A study published in 2022, using high-resolution simulations (up to 10 particles), found that giant impacts can immediately place

4454-513: Is horizontal (meaning that after an interval of an inex the moon will be at the same latitude), whereas at the beginning of the panorama around 11,000 BC for the moon to come back to the same latitude at another eclipse required about one saros for every ten inex. This implies that back then 3580+223 or 3803 synodic months equaled 3885+242 or 4127 draconic months. So a synodic month was about 1.0851959 draconic months, as compared to about 1.0851958 today. This decrease by about 0.1 ppm can be compared to

4585-423: Is increasing by about 0.2 seconds (ca 0.08 ppm) per millennium, but doesn't explain why the draconic month is increasing faster. From the data file we can see that eclipses recur with a period of a combination of 15 inex and 1 saros (5593 synodic months, 165164.58 days, or 452.2 tropical years) throughout the whole panorama (26,000 years), for example from the eclipse of saros series −290, inex series 2 (slightly off

4716-448: Is no warning that injury is occurring. Under normal conditions, the Sun is so bright that it is difficult to stare at it directly. However, during an eclipse, with so much of the Sun covered, it is easier and more tempting to stare at it. Looking at the Sun during an eclipse is as dangerous as looking at it outside an eclipse, except during the brief period of totality, when the Sun's disk is completely covered (totality occurs only during

4847-440: Is on average about 1.9 km (1.2 mi) higher than that of the near side. The discovery of fault scarp cliffs suggest that the Moon has shrunk by about 90 metres (300 ft) within the past billion years. Similar shrinkage features exist on Mercury . Mare Frigoris, a basin near the north pole long assumed to be geologically dead, has cracked and shifted. Since the Moon does not have tectonic plates, its tectonic activity

4978-477: Is simply Moon , with a capital M. The noun moon is derived from Old English mōna , which (like all its Germanic cognates) stems from Proto-Germanic *mēnōn , which in turn comes from Proto-Indo-European *mēnsis 'month' (from earlier *mēnōt , genitive *mēneses ) which may be related to the verb 'measure' (of time). Occasionally, the name Luna / ˈ l uː n ə / is used in scientific writing and especially in science fiction to distinguish

5109-574: Is slow and cracks develop as it loses heat. Scientists have confirmed the presence of a cave on the Moon near the Sea of Tranquillity , not far from the 1969 Apollo 11 landing site. The cave, identified as an entry point to a collapsed lava tube, is roughly 45 meters wide and up to 80 m long. This discovery marks the first confirmed entry point to a lunar cave. The analysis was based on photos taken in 2010 by NASA's Lunar Reconnaissance Orbiter . The cave's stable temperature of around 17 °C could provide

5240-473: Is that of archaeologist Bruce Masse, who putatively links an eclipse that occurred on May 10, 2807, BC with a possible meteor impact in the Indian Ocean on the basis of several ancient flood myths that mention a total solar eclipse. Eclipses have been interpreted as omens , or portents. The ancient Greek historian Herodotus wrote that Thales of Miletus predicted an eclipse that occurred during

5371-476: Is the lowest point on the surface of the Moon. The highest elevations of the Moon's surface are located directly to the northeast, which might have been thickened by the oblique formation impact of the South Pole–Aitken basin. Other large impact basins such as Imbrium , Serenitatis , Crisium , Smythii , and Orientale possess regionally low elevations and elevated rims. The far side of the lunar surface

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5502-435: Is the ratio of the apparent size of the Moon to the apparent size of the Sun during an eclipse. An eclipse that occurs when the Moon is near its closest distance to Earth ( i.e., near its perigee ) can be a total eclipse because the Moon will appear to be large enough to completely cover the Sun's bright disk or photosphere ; a total eclipse has a magnitude greater than or equal to 1.000. Conversely, an eclipse that occurs when

5633-455: Is this effect that leads to the difference between total and annular eclipses. The distance of Earth from the Sun also varies during the year, but this is a smaller effect (by up to about 0.85% from its average value). On average, the Moon appears to be slightly (2.1%) smaller than the Sun as seen from Earth, so the majority (about 60%) of central eclipses are annular. It is only when the Moon is closer to Earth than average (near its perigee ) that

5764-481: Is to be avoided. The Sun's disk can be viewed using appropriate filtration to block the harmful part of the Sun's radiation. Sunglasses do not make viewing the Sun safe. Only properly designed and certified solar filters should be used for direct viewing of the Sun's disk. Especially, self-made filters using common objects such as a floppy disk removed from its case, a Compact Disc , a black colour slide film, smoked glass, etc. must be avoided. The safest way to view

5895-474: Is traditionally dated to 480 BC, was matched by John Russell Hind to an annular eclipse of the Sun at Sardis on February 17, 478 BC. Alternatively, a partial eclipse was visible from Persia on October 2, 480 BC. Herodotus also reports a solar eclipse at Sparta during the Second Persian invasion of Greece . The date of the eclipse (August 1, 477 BC) does not match exactly the conventional dates for

6026-399: The 2023 April 20 hybrid eclipse 's totality is over a minute in duration at various points along the path of totality. Like a focal point , the width and duration of totality and annularity are near zero at the points where the changes between the two occur. Central eclipse is often used as a generic term for a total, annular, or hybrid eclipse. This is, however, not completely correct:

6157-492: The Moon passes between Earth and the Sun , thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season in its new moon phase, when the Moon's orbital plane is closest to the plane of Earth's orbit . In a total eclipse , the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses , only part of

6288-438: The darkness described at Jesus's crucifixion was a solar eclipse. This research has not yielded conclusive results, and Good Friday is recorded as being at Passover , which is held at the time of a full moon. Further, the darkness lasted from the sixth hour to the ninth, or three hours, which is much, much longer than the eight-minute upper limit for any solar eclipse's totality. Contemporary chronicles wrote about an eclipse at

6419-452: The Earth and the material accreted and formed the Moon just beyond the Earth's Roche limit of ~ 2.56  R 🜨 . Giant impacts are thought to have been common in the early Solar System. Computer simulations of giant impacts have produced results that are consistent with the mass of the lunar core and the angular momentum of the Earth–Moon system. These simulations show that most of

6550-520: The Earth's moon from others, while in poetry "Luna" has been used to denote personification of the Moon. Cynthia / ˈ s ɪ n θ i ə / is another poetic name, though rare, for the Moon personified as a goddess, while Selene / s ə ˈ l iː n iː / (literally 'Moon') is the Greek goddess of the Moon. The English adjective pertaining to the Moon is lunar , derived from the Latin word for

6681-429: The Earth, due to gravitational anomalies from impact basins. Its shape is more elongated than current tidal forces can account for. This 'fossil bulge' indicates that the Moon solidified when it orbited at half its current distance to the Earth, and that it is now too cold for its shape to restore hydrostatic equilibrium at its current orbital distance. The Moon is by size and mass the fifth largest natural satellite of

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6812-469: The Earth-Moon system might be explained by the post-impact mixing of the vaporized material that formed the two, although this is debated. The impact would have released enough energy to liquefy both the ejecta and the Earth's crust, forming a magma ocean. The liquefied ejecta could have then re-accreted into the Earth–Moon system. The newly formed Moon would have had its own magma ocean ; its depth

6943-530: The Earth. The newly formed Moon settled into a much closer Earth orbit than it has today. Each body therefore appeared much larger in the sky of the other, eclipses were more frequent, and tidal effects were stronger. Due to tidal acceleration , the Moon's orbit around Earth has become significantly larger, with a longer period. Following formation, the Moon has cooled and most of its atmosphere has been stripped. The lunar surface has since been shaped by large impact events and many small ones, forming

7074-459: The Equator, but as the Moon is moving in the same direction as Earth's rotation at about 61 km/min, the umbra almost always appears to move in a roughly west–east direction across a map of Earth at the speed of the Moon's orbital velocity minus Earth's rotational velocity. The width of the track of a central eclipse varies according to the relative apparent diameters of the Sun and Moon. In

7205-504: The Moon approximately 10 minutes, taking 5 minutes to rise, and 5 minutes to fall. On average, 120 kilograms of dust are present above the Moon, rising up to 100 kilometers above the surface. Dust counts made by LADEE 's Lunar Dust EXperiment (LDEX) found particle counts peaked during the Geminid , Quadrantid , Northern Taurid , and Omicron Centaurid meteor showers , when the Earth, and Moon pass through comet debris. The lunar dust cloud

7336-458: The Moon derived from the impactor, rather than the proto-Earth. However, models from 2007 and later suggest a larger fraction of the Moon derived from the proto-Earth. Other bodies of the inner Solar System such as Mars and Vesta have, according to meteorites from them, very different oxygen and tungsten isotopic compositions compared to Earth. However, Earth and the Moon have nearly identical isotopic compositions. The isotopic equalization of

7467-495: The Moon for longer than just one lunar orbit. The topography of the Moon has been measured with laser altimetry and stereo image analysis . Its most extensive topographic feature is the giant far-side South Pole–Aitken basin , some 2,240 km (1,390 mi) in diameter, the largest crater on the Moon and the second-largest confirmed impact crater in the Solar System . At 13 km (8.1 mi) deep, its floor

7598-466: The Moon formed around 50 million years after the origin of the Solar System . Historically, several formation mechanisms have been proposed, but none satisfactorily explains the features of the Earth–Moon system. A fission of the Moon from Earth's crust through centrifugal force would require too great an initial rotation rate of Earth. Gravitational capture of a pre-formed Moon depends on an unfeasibly extended atmosphere of Earth to dissipate

7729-455: The Moon is a crescent\decrescent, [REDACTED] \ [REDACTED] , for example in M ☾ 'lunar mass' (also M L ). The lunar geological periods are named after their characteristic features, from most impact craters outside the dark mare , to the mare and later craters, and finally the young, still bright and therefore readily visible craters with ray systems like Copernicus or Tycho . Isotope dating of lunar samples suggests

7860-399: The Moon is near its farthest distance from Earth ( i.e., near its apogee ) can be only an annular eclipse because the Moon will appear to be slightly smaller than the Sun; the magnitude of an annular eclipse is less than 1. Because Earth's orbit around the Sun is also elliptical, Earth's distance from the Sun similarly varies throughout the year. This affects the apparent size of the Sun in

7991-415: The Moon through the ascending node is slightly shorter than the sidereal month. This period is called the nodical or draconic month . Finally, the Moon's perigee is moving forwards or precessing in its orbit and makes a complete circuit in 8.85 years. The time between one perigee and the next is slightly longer than the sidereal month and known as the anomalistic month . The Moon's orbit intersects with

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8122-508: The Moon's solar illumination varies much less with season than on Earth and it allows for the existence of some peaks of eternal light at the Moon's north pole , at the rim of the crater Peary . The surface is exposed to drastic temperature differences ranging from 120 °C to −171 °C depending on the solar irradiance . Because of the lack of atmosphere, temperatures of different areas vary particularly upon whether they are in sunlight or shadow, making topographical details play

8253-403: The Moon, lūna . Selenian / s ə l iː n i ə n / is an adjective used to describe the Moon as a world, rather than as a celestial object, but its use is rare. It is derived from σελήνη selēnē , the Greek word for the Moon, and its cognate selenic was originally a rare synonym but now nearly always refers to the chemical element selenium . The element name selenium and

8384-494: The Solar System relative to their primary planets. The Moon's diameter is about 3,500 km, more than a quarter of Earth's, with the face of the Moon comparable to the width of either Mainland Australia , Europe or the Contiguous United States (which excludes Alaska , etc.). The whole surface area of the Moon is about 38 million square kilometers, comparable to North and South America combined,

8515-467: The Solar System, categorizable as one of its planetary-mass moons , making it a satellite planet under the geophysical definitions of the term . It is smaller than Mercury and considerably larger than the largest dwarf planet of the Solar System, Pluto . While the minor-planet moon Charon of the Pluto-Charon system is larger relative to Pluto, the Moon is the largest natural satellite of

8646-402: The Sun (the bright disk of the Sun itself), even for just a few seconds, can cause permanent damage to the retina of the eye, because of the intense visible and invisible radiation that the photosphere emits. This damage can result in impairment of vision, up to and including blindness . The retina has no sensitivity to pain, and the effects of retinal damage may not appear for hours, so there

8777-426: The Sun completely during a total solar eclipse . From Earth about 59% of the lunar surface is visible over time due to cyclical shifts in perspective ( libration ), making parts of the far side of the Moon visible. The Moon has been an important source of inspiration and knowledge for humans, having been crucial to cosmography , mythology, religion , art, time keeping , natural science , and spaceflight . In 1959,

8908-402: The Sun is obscured, then an effect can be observed by which the daylight appears to be dim, as if the sky were overcast, yet objects still cast sharp shadows. When the shrinking visible part of the photosphere becomes very small, Baily's beads will occur. These are caused by the sunlight still being able to reach Earth through lunar valleys. Totality then begins with the diamond ring effect ,

9039-400: The Sun is obscured. Unlike a lunar eclipse , which may be viewed from anywhere on the night side of Earth, a solar eclipse can only be viewed from a relatively small area of the world. As such, although total solar eclipses occur somewhere on Earth every 18 months on average, they recur at any given place only once every 360 to 410 years. If the Moon were in a perfectly circular orbit and in

9170-403: The Sun is within about 15 to 18 degrees of a node, (10 to 12 degrees for central eclipses). This is referred to as an eclipse limit, and is given in ranges because the apparent sizes and speeds of the Sun and Moon vary throughout the year. In the time it takes for the Moon to return to a node (draconic month), the apparent position of the Sun has moved about 29 degrees, relative to the nodes. Since

9301-439: The Sun's brightness, as it takes well over 90% coverage to notice any darkening at all. Even at 99%, it would be no darker than civil twilight . A hybrid eclipse (also called annular/total eclipse) shifts between a total and annular eclipse. At certain points on the surface of Earth, it appears as a total eclipse, whereas at other points it appears as annular. Hybrid eclipses are comparatively rare. A hybrid eclipse occurs when

9432-513: The Sun's disk is by indirect projection. This can be done by projecting an image of the disk onto a white piece of paper or card using a pair of binoculars (with one of the lenses covered), a telescope, or another piece of cardboard with a small hole in it (about 1 mm diameter), often called a pinhole camera . The projected image of the Sun can then be safely viewed; this technique can be used to observe sunspots , as well as eclipses. Care must be taken, however, to ensure that no one looks through

9563-482: The apparent size of the Moon is not large enough to completely block out the Sun. Totality thus does not occur; the Sun instead appears as a very bright ring, or annulus , surrounding the dark disk of the Moon. Annular eclipses occur once every one or two years, not annually. The term derives from the Latin root word anulus , meaning "ring", rather than annus , for "year". A partial eclipse occurs about twice

9694-429: The beginning and end of a series, eclipses may fail to occur. However once settled down, inex series are very stable and run for many thousands of years. For example, series 30 has produced eclipses every 29 years since saros series −197 in 8045 BC, including most recently the solar eclipse of February 5, 2000 . An inex also is close to an integer number of days (10,571.95) so solar eclipses on average take place at about

9825-581: The beginning of May 664 that coincided with the beginning of the plague of 664 in the British isles. In the Western hemisphere, there are few reliable records of eclipses before AD 800, until the advent of Arab and monastic observations in the early medieval period. A solar eclipse took place on January 27, 632 over Arabia during Muhammad 's lifetime. Muhammad denied the eclipse had anything to do with his son dying earlier that day, saying "The sun and

9956-413: The combined American landmass having an area (excluding all islands) of 37.7 million square kilometers. The Moon's mass is 1/81 of Earth's, being the second densest among the planetary moons, and having the second highest surface gravity , after Io , at 0.1654  g and an escape velocity of 2.38 km/s ( 8 600  km/h; 5 300  mph) . The Moon is a differentiated body that

10087-433: The crust and mantle. The absence of such neutral species (atoms or molecules) as oxygen , nitrogen , carbon , hydrogen and magnesium , which are present in the regolith , is not understood. Water vapor has been detected by Chandrayaan-1 and found to vary with latitude, with a maximum at ~60–70 degrees; it is possibly generated from the sublimation of water ice in the regolith. These gases either return into

10218-415: The dark silhouette of the Moon completely obscures the bright light of the Sun, allowing the much fainter solar corona to be visible. During an eclipse, totality occurs only along a narrow track on the surface of Earth. This narrow track is called the path of totality. An annular eclipse, like a total eclipse, occurs when the Sun and Moon are exactly in line with Earth. During an annular eclipse, however,

10349-401: The decrease in the length of a tropical year by about 1 ppm in the last 10,000 years (see Tropical year ). (Note that if the length of a sidereal month were constant, then a decrease in the length of a year would cause an increase in the length of a synodic month.) One source states that the draconic month is increasing by about 0.4 seconds (ca 0.16 ppm) per millennium whereas the synodic month

10480-439: The definition of a central eclipse is an eclipse during which the central line of the umbra touches Earth's surface. It is possible, though extremely rare, that part of the umbra intersects with Earth (thus creating an annular or total eclipse), but not its central line. This is then called a non-central total or annular eclipse. Gamma is a measure of how centrally the shadow strikes. The last (umbral yet) non-central solar eclipse

10611-447: The dense mare basaltic lava flows that fill those basins. The anomalies greatly influence the orbit of spacecraft about the Moon. There are some puzzles: lava flows by themselves cannot explain all of the gravitational signature, and some mascons exist that are not linked to mare volcanism. The Moon has an external magnetic field of less than 0.2 nanoteslas , or less than one hundred thousandth that of Earth . The Moon does not have

10742-514: The depressions associated with impact basins , though the Moon's largest expanse of basalt flooding, Oceanus Procellarum , does not correspond to an obvious impact basin. Different episodes of lava flows in maria can often be recognized by variations in surface albedo and distinct flow margins. As the maria formed, cooling and contraction of the basaltic lava created wrinkle ridges in some areas. These low, sinuous ridges can extend for hundreds of kilometers and often outline buried structures within

10873-447: The diameter of Earth. Tidal forces between Earth and the Moon have synchronized the Moon's orbital period ( lunar month ) with its rotation period ( lunar day ) at 29.5 Earth days, causing the same side of the Moon to always face Earth. The Moon's gravitational pull—and, to a lesser extent, the Sun 's—are the main drivers of Earth's tides . In geophysical terms , the Moon is a planetary-mass object or satellite planet . Its mass

11004-457: The duration of a total solar eclipse (in order of decreasing importance): The longest eclipse that has been calculated thus far is the eclipse of July 16, 2186 (with a maximum duration of 7 minutes 29 seconds over northern Guyana). A total solar eclipse is a rare event, recurring somewhere on Earth every 18 months on average, yet is estimated to recur at any given location only every 360–410 years on average. The total eclipse lasts for only

11135-459: The eclipse circumstances will be at any given location. Calculations with Besselian elements can determine the exact shape of the umbra's shadow on Earth's surface. But at what longitudes on Earth's surface the shadow will fall, is a function of Earth's rotation, and on how much that rotation has slowed down over time. A number called ΔT is used in eclipse prediction to take this slowing into account. As Earth slows, ΔT increases. ΔT for dates in

11266-427: The eclipse limit creates a window of opportunity of up to 36 degrees (24 degrees for central eclipses), it is possible for partial eclipses (or rarely a partial and a central eclipse) to occur in consecutive months. During a central eclipse, the Moon's umbra (or antumbra, in the case of an annular eclipse) moves rapidly from west to east across Earth. Earth is also rotating from west to east, at about 28 km/min at

11397-578: The ecliptic at the two nodes that are 180 degrees apart. Therefore, the new moon occurs close to the nodes at two periods of the year approximately six months (173.3 days) apart, known as eclipse seasons , and there will always be at least one solar eclipse during these periods. Sometimes the new moon occurs close enough to a node during two consecutive months to eclipse the Sun on both occasions in two partial eclipses. This means that, in any given year, there will always be at least two solar eclipses, and there can be as many as five. Eclipses can occur only when

11528-499: The end of totality, the same effects will occur in reverse order, and on the opposite side of the Moon. A dedicated group of eclipse chasers have pursued the observation of solar eclipses when they occur around Earth. A person who chases eclipses is known as an umbraphile, meaning shadow lover. Umbraphiles travel for eclipses and use various tools to help view the sun including solar viewing glasses , also known as eclipse glasses, as well as telescopes. The first known photograph of

11659-468: The energy of the passing Moon. A co-formation of Earth and the Moon together in the primordial accretion disk does not explain the depletion of metals in the Moon. None of these hypotheses can account for the high angular momentum of the Earth–Moon system. The prevailing theory is that the Earth–Moon system formed after a giant impact of a Mars -sized body (named Theia ) with the proto-Earth . The oblique impact blasted material into orbit about

11790-422: The expansion of plasma clouds. These clouds are generated during large impacts in an ambient magnetic field. This is supported by the location of the largest crustal magnetizations situated near the antipodes of the giant impact basins. The Moon has an atmosphere so tenuous as to be nearly vacuum , with a total mass of less than 10 tonnes (9.8 long tons; 11 short tons). The surface pressure of this small mass

11921-1182: The exposed ones. Conversely, mare lava has obscured many impact melt sheets and pools. Impact melts are formed when intense shock pressures from collisions vaporize and melt zones around the impact site. Where still exposed, impact melt can be distinguished from mare lava by its distribution, albedo, and texture. Sinuous rilles , found in and around maria, are likely extinct lava channels or collapsed lava tubes . They typically originate from volcanic vents , meandering and sometimes branching as they progress. The largest examples, such as Schroter's Valley and Rima Hadley , are significantly longer, wider, and deeper than terrestrial lava channels, sometimes featuring bends and sharp turns that again, are uncommon on Earth. Mare volcanism has altered impact craters in various ways, including filling them to varying degrees, and raising and fracturing their floors from uplift of mare material beneath their interiors. Examples of such craters include Taruntius and Gassendi . Some craters, such as Hyginus , are of wholly volcanic origin, forming as calderas or collapse pits . Such craters are relatively rare, and tend to be smaller (typically

12052-510: The first human-made objects to leave Earth and reach another body arrived at the Moon, with the flyby of the Soviet Union 's Luna 1 and the intentional impact of Luna 2 . In 1966, the Moon became the first extraterrestrial body with a soft landing by Luna 9 and a orbital insertion by Luna 10 were achieved . On July 20, 1969, humans for the first time landed on the Moon and any extraterrestrial body, at Mare Tranquillitatis with

12183-427: The flood lavas that erupted onto the surface from partial melting in the mantle confirm the mafic mantle composition, which is more iron-rich than that of Earth. The crust is on average about 50 kilometres (31 mi) thick. The Moon is the second-densest satellite in the Solar System, after Io . However, the inner core of the Moon is small, with a radius of about 350 kilometres (220 mi) or less, around 20% of

12314-446: The future can only be roughly estimated because Earth's rotation is slowing irregularly. This means that, although it is possible to predict that there will be a total eclipse on a certain date in the far future, it is not possible to predict in the far future exactly at what longitudes that eclipse will be total. Historical records of eclipses allow estimates of past values of ΔT and so of Earth's rotation. The following factors determine

12445-434: The future may now be predicted with high accuracy. Looking directly at the Sun can lead to permanent eye damage, so special eye protection or indirect viewing techniques are used when viewing a solar eclipse. Only the total phase of a total solar eclipse is safe to view without protection. Enthusiasts known as eclipse chasers or umbraphiles travel to remote locations to see solar eclipses. The Sun's distance from Earth

12576-405: The future, the Moon will be too far away to fully occlude the Sun, and no total eclipses will occur. In the same timeframe, the Sun may become brighter, making it appear larger in size. Estimates of the time when the Moon will be unable to occlude the entire Sun when viewed from Earth range between 650 million and 1.4 billion years in the future. Looking directly at the photosphere of

12707-722: The globe (although at the same node and hence at about the same geographical latitude). The significance of the inex cycle is not in the prediction, but in the organization of eclipses: any eclipse cycle, and indeed the interval between any two eclipses, can be expressed as a combination of saros and inex intervals. The following fourteen eclipses from part of inex series 52, which has been yielding eclipses every 29 years since saros series −115 in 5275 BC and will continue to do so beyond 15,000 AD. These eclipses are part of Lunar Inex Series 40. A saros-inex panorama has been produced by Luca Quaglia and John Tilley. It shows 61775 solar eclipses from −11000 ( 11001 BC ) to +15000. Each column of

12838-400: The graph is a complete Saros series which progresses smoothly from partial eclipses into total or annular eclipses and back into partials. Each graph row represents an inex series. The lifetime of each inex series is not simple due to long-term period variations in the synodic and draconic month lengths. One can see from the data file that in the future (around saros series 300) the graph

12969-412: The invasion accepted by historians. In ancient China, where solar eclipses were known as an "eating of the Sun" ( rìshí 日食 ), the earliest records of eclipses date to around 720 BC. The 4th century BC astronomer Shi Shen described the prediction of eclipses by using the relative positions of the Moon and Sun. Attempts have been made to establish the exact date of Good Friday by assuming that

13100-471: The lander Eagle of the United States ' Apollo 11 mission. Five more crews were sent between then and 1972, each with two men landing on the surface. The longest stay was 75 hours by the Apollo 17 crew. Since then, exploration of the Moon has continued robotically, and crewed missions are being planned to return beginning in the late 2020s. The usual English proper name for Earth's natural satellite

13231-429: The last bright flash of sunlight. It is safe to observe the total phase of a solar eclipse directly only when the Sun's photosphere is completely covered by the Moon, and not before or after totality. During this period, the Sun is too dim to be seen through filters. The Sun's faint corona will be visible, and the chromosphere , solar prominences , coronal streamers and possibly even a solar flare may be seen. At

13362-429: The latter being favored by most recent authors on the topic. A solar eclipse of June 15, 763 BC mentioned in an Assyrian text is important for the chronology of the ancient Near East . There have been other claims to date earlier eclipses. The legendary Chinese king Zhong Kang supposedly beheaded two astronomers, Hsi and Ho, who failed to predict an eclipse 4000 years ago. Perhaps the earliest still-unproven claim

13493-423: The lens and viewfinder protects the equipment and makes viewing possible. Professional workmanship is essential because of the dire consequences any gaps or detaching mountings will have. In the partial eclipse path, one will not be able to see the corona or nearly complete darkening of the sky. However, depending on how much of the Sun's disk is obscured, some darkening may be noticeable. If three-quarters or more of

13624-428: The lens is covered by a properly designed solar filter. Historical eclipses are a very valuable resource for historians, in that they allow a few historical events to be dated precisely, from which other dates and ancient calendars may be deduced. The oldest recorded solar eclipse was recorded on a clay tablet found at Ugarit , in modern Syria , with two plausible dates usually cited: 3 May 1375 BC or 5 March 1223 BC,

13755-414: The longest total eclipse of the 20th century at 7 min 8 s occurred on June 20, 1955 , and there will be no total solar eclipses over 7 min in duration in the 21st century. It is possible to predict other eclipses using eclipse cycles . The saros is probably the best known and one of the most accurate. A saros lasts 6585.3 days (a little over 18 years), which means that, after this period,

13886-421: The magma ocean had crystallized, lower-density plagioclase minerals could form and float into a crust atop. The final liquids to crystallize would have been initially sandwiched between the crust and mantle, with a high abundance of incompatible and heat-producing elements. Consistent with this perspective, geochemical mapping made from orbit suggests a crust of mostly anorthosite . The Moon rock samples of

14017-424: The magnitude of an eclipse changes during the event from less to greater than one, so the eclipse appears to be total at locations nearer the midpoint, and annular at other locations nearer the beginning and end, since the sides of Earth are slightly further away from the Moon. These eclipses are extremely narrow in their path width and relatively short in their duration at any point compared with fully total eclipses;

14148-521: The mantle could be responsible for prolonged activities on the far side in the Orientale basin. The lighter-colored regions of the Moon are called terrae , or more commonly highlands , because they are higher than most maria. They have been radiometrically dated to having formed 4.4 billion years ago, and may represent plagioclase cumulates of the lunar magma ocean. In contrast to Earth, no major lunar mountains are believed to have formed as

14279-406: The mare. Another result of maria formation is the creation of concentric depressions along the edges, known as arcuate rilles . These features occur as the mare basalts sink inward under their own weight, causing the edges to fracture and separate. In addition to the visible maria, the Moon has mare deposits covered by ejecta from impacts. Called cryptomares, these hidden mares are likely older than

14410-628: The moon do not eclipse because of the death of someone from the people but they are two signs amongst the signs of God." The Cairo astronomer Ibn Yunus wrote that the calculation of eclipses was one of the many things that connect astronomy with the Islamic law , because it allowed knowing when a special prayer can be made. The first recorded observation of the corona was made in Constantinople in AD 968. The first known telescopic observation of

14541-514: The most favourable circumstances, when a total eclipse occurs very close to perigee, the track can be up to 267 km (166 mi) wide and the duration of totality may be over 7 minutes. Outside of the central track, a partial eclipse is seen over a much larger area of Earth. Typically, the umbra is 100–160 km wide, while the penumbral diameter is in excess of 6400 km. Besselian elements are used to predict whether an eclipse will be partial, annular, or total (or annular/total), and what

14672-524: The near side of the Moon, and cover 31% of the surface of the near side compared with 2% of the far side. This is likely due to a concentration of heat-producing elements under the crust on the near side, which would have caused the underlying mantle to heat up, partially melt, rise to the surface and erupt. Most of the Moon's mare basalts erupted during the Imbrian period , 3.3–3.7 billion years ago, though some being as young as 1.2 billion years and as old as 4.2 billion years. In 2006,

14803-440: The near-side. Causes of the distribution of the lunar highlands on the far side are also not well understood. Topological measurements show the near side crust is thinner than the far side. One possible scenario then is that large impacts on the near side may have made it easier for lava to flow onto the surface. The Moon is a very slightly scalene ellipsoid due to tidal stretching, with its long axis displaced 30° from facing

14934-611: The panorama to the left) to the eclipse of saros series 580, inex series 60 on the right-side edge of the panorama. Similar cycles with more or less than 15 inex per saros also cover the whole panorama. Lunar eclipses can also be plotted in a similar diagram, this diagram covering 1000 AD to 2500 AD. The yellow diagonal band represents all the eclipses from 1900 to 2100. This graph immediately illuminates that this 1900–2100 period contains an above average number of total lunar eclipses compared to other adjacent centuries. [REDACTED] Solar eclipse A solar eclipse occurs when

15065-432: The possibility of a much warmer lunar mantle than previously believed, at least on the near side where the deep crust is substantially warmer because of the greater concentration of radioactive elements. Evidence has been found for 2–10 million years old basaltic volcanism within the crater Lowell, inside the Orientale basin. Some combination of an initially hotter mantle and local enrichment of heat-producing elements in

15196-587: The prefix seleno- (as in selenography , the study of the physical features of the Moon) come from this Greek word. Artemis , the Greek goddess of the wilderness and the hunt, came to also be identified as the goddess of the Moon ( Selene ) and was sometimes called Cynthia , after her birthplace on Mount Cynthus . Her Roman equivalent is Diana . The names Luna, Cynthia, and Selene are reflected in technical terms for lunar orbits such as apolune , pericynthion and selenocentric . The astronomical symbol for

15327-514: The projector (telescope, pinhole, etc.) directly. A kitchen colander with small holes can also be used to project multiple images of the partially eclipsed Sun onto the ground or a viewing screen. Viewing the Sun's disk on a video display screen (provided by a video camera or digital camera ) is safe, although the camera itself may be damaged by direct exposure to the Sun. The optical viewfinders provided with some video and digital cameras are not safe. Securely mounting #14 welder's glass in front of

15458-436: The radius of the Moon. Its composition is not well understood, but is probably metallic iron alloyed with a small amount of sulfur and nickel; analyzes of the Moon's time-variable rotation suggest that it is at least partly molten. The pressure at the lunar core is estimated to be 5 GPa (49,000 atm). On average the Moon's surface gravity is 1.62  m/s ( 0.1654  g ; 5.318  ft/s ), about half of

15589-471: The regolith because of the Moon's gravity or are lost to space, either through solar radiation pressure or, if they are ionized, by being swept away by the solar wind's magnetic field. Studies of Moon magma samples retrieved by the Apollo missions demonstrate that the Moon had once possessed a relatively thick atmosphere for a period of 70 million years between 3 and 4 billion years ago. This atmosphere, sourced from gases ejected from lunar volcanic eruptions,

15720-502: The remainder of 0.67351, being near 2 ⁄ 3 , every third eclipse will have a similar position in the moon's elliptical orbit and apparent diameter, so the quality of the solar eclipse (total versus annular) will repeat in these groupings of 3 cycles (87 years minus 2 months), called triads . Inex series last much longer than saros series . For example, inex series 30 started in saros series −245 in 9435 BC and will continue well beyond 15,000 AD. But inex series are not unbroken: at

15851-451: The same geographical longitude at successive events, although variations of the moon's speed at different points of its orbit mask this relation. In addition sequential events occur at opposite geographical latitudes because the eclipses occur at opposite nodes. This is in contrast to the better known saros, which has a period of about 6,585 + 1 ⁄ 3 days, so successive solar eclipses tend to take place about 120° in longitude apart on

15982-449: The same orbital plane as Earth, there would be total solar eclipses once a month, at every new moon. Instead, because the Moon's orbit is tilted at about 5 degrees to Earth's orbit, its shadow usually misses Earth. Solar (and lunar) eclipses therefore happen only during eclipse seasons , resulting in at least two, and up to five, solar eclipses each year, no more than two of which can be total. Total eclipses are rarer because they require

16113-420: The same way, but not as much as does the Moon's varying distance from Earth. When Earth approaches its farthest distance from the Sun in early July, a total eclipse is somewhat more likely, whereas conditions favour an annular eclipse when Earth approaches its closest distance to the Sun in early January. There are three main types of solar eclipses: A total eclipse occurs on average every 18 months when

16244-460: The surface gravity of Mars and about a sixth of Earth's. The Moon's gravitational field is not uniform. The details of the gravitational field have been measured through tracking the Doppler shift of radio signals emitted by orbiting spacecraft. The main lunar gravity features are mascons , large positive gravitational anomalies associated with some of the giant impact basins, partly caused by

16375-449: The time of a new moon, the Moon will usually pass to the north or south of the Sun. A solar eclipse can occur only when a new moon occurs close to one of the points (known as nodes ) where the Moon's orbit crosses the ecliptic. As noted above, the Moon's orbit is also elliptical . The Moon's distance from Earth varies by up to about 5.9% from its average value. Therefore, the Moon's apparent size varies with its distance from Earth, and it

16506-419: The umbra touches Earth's surface is where a total eclipse can be seen. The larger light gray area is the penumbra , in which a partial eclipse can be seen. An observer in the antumbra , the area of shadow beyond the umbra, will see an annular eclipse. The Moon's orbit around Earth is inclined at an angle of just over 5 degrees to the plane of Earth's orbit around the Sun (the ecliptic ). Because of this, at

16637-446: The winter solstice in the north polar crater Hermite . This is the coldest temperature in the Solar System ever measured by a spacecraft, colder even than the surface of Pluto . Blanketed on top of the Moon's crust is a highly comminuted (broken into ever smaller particles) and impact gardened mostly gray surface layer called regolith , formed by impact processes. The finer regolith, the lunar soil of silicon dioxide glass, has

16768-488: Was June 30, 1973 (7 min 3 sec). Observers aboard a Concorde supersonic aircraft were able to stretch totality for this eclipse to about 74 minutes by flying along the path of the Moon's umbra. The next total eclipse exceeding seven minutes in duration will not occur until June 25, 2150 . The longest total solar eclipse during the 11 000 year period from 3000 BC to at least 8000 AD will occur on July 16, 2186 , when totality will last 7 min 29 s. For comparison,

16899-422: Was on April 29, 2014 . This was an annular eclipse. The next non-central total solar eclipse will be on April 9, 2043 . The visual phases observed during a total eclipse are called: The diagrams to the right show the alignment of the Sun, Moon, and Earth during a solar eclipse. The dark gray region between the Moon and Earth is the umbra , where the Sun is completely obscured by the Moon. The small area where

17030-424: Was initially in hydrostatic equilibrium but has since departed from this condition. It has a geochemically distinct crust , mantle , and core . The Moon has a solid iron-rich inner core with a radius possibly as small as 240 kilometres (150 mi) and a fluid outer core primarily made of liquid iron with a radius of roughly 300 kilometres (190 mi). Around the core is a partially molten boundary layer with

17161-401: Was twice the thickness of that of present-day Mars . The ancient lunar atmosphere was eventually stripped away by solar winds and dissipated into space. A permanent Moon dust cloud exists around the Moon, generated by small particles from comets. Estimates are 5 tons of comet particles strike the Moon's surface every 24 hours, resulting in the ejection of dust particles. The dust stays above

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