Moon

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.

On July 20, 1969, humans for the first time stepped on an extraterrestrial body, landing on the Moon at Mare Tranquillitatis with the lander Eagle of the United States' Apollo 11 mission.

[56] A study published in 2022, using high-resolution simulations (up to 108 particles), found that giant impacts can immediately place a satellite with similar mass and iron content to the Moon into orbit far outside Earth's Roche limit.

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.

[16][95] 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[96] from the solar wind; and argon-40, radon-222, and polonium-210, outgassed after their creation by radioactive decay within the crust and mantle.

[124] 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)[125] are vast solidified pools of ancient basaltic lava.

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.

[64] In 2006, 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.

[150] The lunar geologic timescale is based on the most prominent impact events, such as multi-ring formations like Nectaris, Imbrium, and Orientale that are between hundreds and thousands of kilometers in diameter and associated with a broad apron of ejecta deposits that form a regional stratigraphic horizon.

[152] The radiometric ages of impact-melted rocks collected during the Apollo missions cluster between 3.8 and 4.1 billion years old: this has been used to propose a Late Heavy Bombardment period of increased impacts.

[169] In May 2011, 615–1410 ppm water in melt inclusions in lunar sample 74220 was reported,[170] the famous high-titanium "orange glass soil" of volcanic origin collected during the Apollo 17 mission in 1972.

Although of considerable selenological interest, this insight does not mean that water is easily available since the sample originated many kilometers below the surface, and the inclusions are so difficult to access that it took 39 years to find them with a state-of-the-art ion microprobe instrument.

[171][173] In October 2020, astronomers reported detecting molecular water on the sunlit surface of the Moon by several independent spacecraft, including the Stratospheric Observatory for Infrared Astronomy (SOFIA).

[h] However, because the Earth–Moon system moves at the same time in its orbit around the Sun, it takes slightly longer, 29.5 days, [i][72] to return to the same lunar phase, completing a full cycle, as seen from Earth.

[183] Measurements from laser reflectors left during the Apollo missions (lunar ranging experiments) have found that the Moon's distance increases by 38 mm (1.5 in) per year (roughly the rate at which human fingernails grow).

[222] Aspects of the Moon were identified and aggregated in lunar deities from prehistoric times and were eventually documented and put into symbols from the very first instances of writing in the 4th millennium BC.

[225] The oldest named astronomer and poet Enheduanna, Akkadian high priestess to the lunar deity Nanna/Sin and pricess, daughter of Sargon the Great (c. 2334 – c. 2279 BCE), had the Moon tracked in her chambers.

[233]: 411 In Aristotle's (384–322 BC) description of the universe, the Moon marked the boundary between the spheres of the mutable elements (earth, water, air and fire), and the imperishable stars of aether, an influential philosophy that would dominate for centuries.

[242] Shen Kuo (1031–1095) of the Song dynasty created an allegory equating the waxing and waning of the Moon to a round ball of reflective silver that, when doused with white powder and viewed from the side, would appear to be a crescent.

Telescopic mapping of the Moon followed: later in the 17th century, the efforts of Giovanni Battista Riccioli and Francesco Maria Grimaldi led to the system of naming of lunar features in use today.

[72] This view gained support in 1892 from the experimentation of geologist Grove Karl Gilbert, and from comparative studies from 1920 to the 1940s,[245] leading to the development of lunar stratigraphy, which by the 1950s was becoming a new and growing branch of astrogeology.

[247] Considered the culmination of the Space Race,[248] an estimated 500 million people worldwide watched the transmission by the Apollo TV camera, the largest television audience for a live broadcast at that time.

Direct transmission of data to Earth concluded in late 1977 because of budgetary considerations,[252][253] but as the stations' lunar laser ranging corner-cube retroreflector arrays are passive instruments, they are still being used.

LCROSS completed its mission by making a planned and widely observed impact in the crater Cabeus on October 9, 2009,[262] whereas LRO is currently in operation, obtaining precise lunar altimetry and high-resolution imagery.

There are several missions by different agencies and companies planned to establish a long-term human presence on the Moon, with the Lunar Gateway as the currently most advanced project as part of the Artemis program.

[300] The lunar soil, although it poses a problem for any moving parts of telescopes, can be mixed with carbon nanotubes and epoxies and employed in the construction of mirrors up to 50 meters in diameter.

In particular the establishment of an international or United Nations regulatory regime for lunar human activity has been called for by the Moon Treaty and suggested through an Implementation Agreement,[267][269] but remains contentious.

This rich history of humans viewing the Moon has been evidenced starting with depictions from 40,000 BP and in written form from the 4th millennium BCE in the earliest cases of writing.

[226] For the representation of the Moon, especially its lunar phases, the crescent (🌙) has been a recurring symbol in a range of cultures since at least 3,000 BCE or possibly earlier with bull horns dating to the earliest cave paintings at 40,000 BP.

It came to represent the selene goddess Artemis, and via the patronage of Hecate, which as triple deity under the epithet trimorphos/trivia included aspects of Artemis/Diana, came to be used as a symbol of Byzantium, with Virgin Mary (Queen of Heaven) later taking her place, becoming depicted in Marian veneration on a crescent and adorned with stars.

The far side of the Moon lacks the near side's characteristic large dark areas of maria. The near side of the Moon might have looked like this early in the Moon's history. [ 34 ] [ 35 ]
Artist's depiction of the Moon as it might have appeared in Earth's sky after the Late Heavy Bombardment around 4 billion years ago. At that time the Moon orbited the Earth at half its current distance, making it appear 2.8 times larger than it does today. [ 60 ]
Size comparison of the main moons of the Solar System with Earth to scale. Nineteen moons are large enough to be round , several having subsurface oceans and one, Titan, having a considerable atmosphere.
Moon's internal structure: solid inner core (iron-metallic), molten outer core, hardened mantle and crust. The crust on the Moon's near side permanently facing Earth is thinner, featuring larger areas flooded by material of the once molten mantle forming today's lunar mare .
Astronaut John Young jumping on the Moon, illustrating that the gravitational pull of the Moon is approximately 1/6 of Earth's. The jumping height is limited by the EVA space suit's weight on the Moon of about 13.6 kg (30 lb) and by the suit's pressurization resisting the bending of the suit, as needed for jumping. [ 81 ] [ 82 ]
The thin lunar atmosphere is visible on the Moon's surface at sunrise and sunset with the lunar horizon glow [ 90 ] and lunar twilight rays, like Earth's crepuscular rays . This Apollo 17 sketch depicts the glow and rays [ 91 ] among the general zodiacal light . [ 92 ] [ 93 ]
Gene Cernan with lunar dust stuck on his suit. Lunar dust is highly abrasive and can cause damage to human lungs and nervous and cardiovascular systems. [ 102 ]
Apollo 17 astronaut Harrison H. Schmitt next to the large Moon boulder nicknamed " Tracy's Rock "
The names of the main volcanic features, the maria (blue), and of some craters (brown) of the near side of the Moon
Old hardened lava flows of Mare Imbrium forming wrinkle ridges
A gray, many-ridged surface from high above. The largest feature is a circular ringed structure with high walled sides and a lower central peak: the entire surface out to the horizon is filled with similar structures that are smaller and overlapping.
A view of a three-kilometer-deep larger crater Daedalus on the Moon's far side
Wide-angle image of a lunar swirl, the 70-kilometer-long Reiner Gamma
In 2008, NASA's Moon Mineralogy Mapper equipment on India 's Chandrayaan-1 discovered, for the first time, water-rich minerals (shown in blue around a small crater from which they were ejected).
A view of the rotating Earth and the far side of the Moon as the Moon passes on its orbit in between the observing DSCOVR satellite and Earth
Minimum, mean and maximum distances of the Moon from Earth with its angular diameter as seen from Earth's surface to scale
Simplified diagram of Earth bulging, being pulled and streched toward the Moon by its gravity, which is the main driver of the tides . The Ocean and Earth are being pulled more where it is closer to the Moon, causing tidal forces to be weaker at the far-side of Earth creating a second bulge and high-tide. The animation shows the change of the Moon's position on its inclined orbit.
Over one lunar month more than half of the Moon's surface can be seen from Earth's surface.
Libration , the slight variation in the Moon's apparent size and viewing angle over a single lunar month as viewed from somewhere on the Earth's northern hemisphere.
Comparison between the Moon on the left, rotating tidally locked (correct), and with the Moon on the right, without rotation (incorrect)
The monthly changes in the angle between the direction of sunlight and view from Earth, and the phases of the Moon that result, as viewed from the Northern Hemisphere . The Earth–Moon distance is not to scale.
The changing apparent color of the Moon, filtered by Earth's atmosphere
The Nebra sky disc ( c. 1800–1600 BCE ), found near a possibly astronomical complex , most likely depicting the Sun or full Moon, the Moon as a crescent, the Pleiades and the summer and winter solstices as strips of gold on the side of the disc, [ 229 ] [ 230 ] with the top representing the horizon [ 231 ] and north .
Galileo 's sketches of the Moon from the ground-breaking Sidereus Nuncius (1610), publishing among other findings the first descriptions of the Moon's topography
First view of the far side of the Moon , taken by Luna 3 , October 7, 1959. Clearly visible is Mare Moscoviense (top right) and a mare triplet of Mare Crisium , Mare Marginis and Mare Smythii (left center).
The small blue-white semicircle of Earth, almost glowing with color in the blackness of space, rising over the limb of the desolate, cratered surface of the Moon.
Earthrise , the first color image of Earth taken by a human from the Moon, during Apollo 8 (1968), the first time a crewed spacecraft left Earth orbit and reached another astronomical body
Artemis II crew, with the first woman , person of color and non–US-citizen astronaut planned to go to the Moon, scheduled for 2025, returning humans to the Moon for the first time since Apollo 17 in 1972. Clockwise from left: Koch , Glover , Hansen and Wiseman .
Map of all the sites of soft landings on the Moon (2024)
Artifacts of human activity, Apollo 17's Lunar Surface Experiments Package [ 283 ]
Earth's exosphere illuminated creating its geocorona , visible in ultraviolet and viewed by the Far Ultraviolet Camera/Spectrograph of Apollo 16 in 1972 from the Moon's surface
Astronaut Buzz Aldrin in life-supporting suit looking back at the first lunar habitat and base , the Lunar Module Eagle of Tranquility Base , during Apollo 11 (1969), the first crewed Moon landing
The Venus of Laussel (c. 25,000 BP ) holding a crescent shaped horn. The 13 notches on the horn may symbolize the average number of days from menstruation to an ovulation , or the approximate number of full menstrual cycles and lunar cycles per year (although these two phenomena are unrelated). [ 321 ] [ 322 ]
The Sun, the planets, their moons, and several trans-Neptunian objects The Sun Mercury Venus The Moon Earth Mars Phobos and Deimos Ceres The main asteroid belt Jupiter Moons of Jupiter Rings of Jupiter Saturn Moons of Saturn Rings of Saturn Uranus Moons of Uranus Rings of Uranus Neptune Moons of Neptune Rings of Neptune Pluto Moons of Pluto Haumea Moons of Haumea Makemake S/2015 (136472) 1 The Kuiper Belt Eris Dysnomia The Scattered Disc The Hills Cloud The Oort Cloud