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| IT TASTES LIKE CHEESE UMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM HAHA YOU BEEN FUCKED IN THE ASS!!!!!!!!!!!!!!!!!! | |||
| {{featured article}} | |||
| {{two other uses|Earth's moon|moons in general|Natural satellite}} | |||
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| {{Infobox Planet | |||
| |bgcolour = #dddddd | |||
| |name = Moon | |||
| |symbol = ] | |||
| |image = ] | |||
| |caption = The Moon as seen by an observer on ] | |||
| |apogee = 405,696 ] (0.0027 AU) | |||
| |perigee = 363,104 km (0.0024 ]) | |||
| |semimajor = 384,399 km (0.00257 AU) <!--Wieczorek et al. 2006--> | |||
| |orbital_circ = <br />2,413,402 km (0.016 AU) | |||
| |eccentricity = 0.0549 <!--Wieczorek et al. 2006--> | |||
| |sidereal_month = 27.321 582 d {{nowrap|(27 d 7 h 43.1 min)}} <!--Wieczorek et al. 2006--> | |||
| |synodic_month = 29.530 588 d {{nowrap|(29 d 12 h 44.0 min)}} | |||
| |anomalistic_month = 27.554 550 d | |||
| |draconic_month = 27.212 221 d | |||
| |tropical_month = 27.321 582 d | |||
| |avg_speed = 1.022 km/s (2286 ]) | |||
| |max_speed = 1.082 km/s (2420 mph) | |||
| |min_speed = 0.968 km/s (2165 mph) | |||
| |inclination = 5.145° to ] <!--Wieczorek et al. 2006; 18.29° when the longitude of the Moon's ascending node is 180°, 28.58° when it is 0°--><br/>(between 18.29° and 28.58° to Earth's equator) | |||
| |asc_node = regressing,<br/>1 revolution in 18.6 years | |||
| |arg_perigee = progressing,<br/>1 revolution in 8.85 years | |||
| |satellite_of = ] | |||
| |physical_characteristics = yes | |||
| |oblateness = 0.00125 <!--Calculated from data below--> | |||
| |equatorial_radius = 1,738.14 km (0.273 Earths) <!--Smith et al. 1997 --> | |||
| |polar_radius = 1,735.97 km (0.273 Earths) <!-- Smith et al. 1997--> | |||
| |mean_radius = 1,737.103 km (0.273 Earths) <!--Wieczorek et al. 2006--> | |||
| |equatorial_circ = <br />10,921 km | |||
| |surface_area = 3.793{{e|7}} km² (0.074 Earths) | |||
| |volume = 2.1958{{e|10}} km³ (0.020 Earths) | |||
| |mass = 7.3477{{e|22}} kg (0.0123 Earths) <!--Wieczorek et al. 2006--> | |||
| |density = 3,346.4 kg/m³ <!--Wieczorek et al. 2006--> | |||
| |surface_grav = <br />1.622 m/s² (0.1654 ]) | |||
| |escape_velocity = 2.38 km/s (5324 mph) | |||
| |sidereal_day = <br />27.321 582 d (]) | |||
| <!--Wieczorek et al. 2006--> | |||
| |rot_velocity = <br />4.627 m/s (10.349 mph) | |||
| |axial_tilt = 1.5424° (to ecliptic)<!--Inclination is 5.145° to ecliptic; + 1.5424° = 6.687° difference. See also e.g. http://www.mars-lunar.net/Reality.or.Fantasy/Polar.Ice.on%20Moon.pdf--> | |||
| |obliquity = 6.687° (to orbit plane) <!--http://www.spds.nasa.gov/planetary/factsheet/moonfact.html--> | |||
| |albedo = 0.12 | |||
| |magnitude = up to −12.74 | |||
| |angular_size = from 29′to 33′ | |||
| |adjectives = lunar | |||
| |temperatures = yes | |||
| |temp_name1 = equator <!--Vasavada et al. 1999--> | |||
| |min_temp_1 = 100 ] | |||
| |mean_temp_1 = 220 K | |||
| |max_temp_1 = 390 K | |||
| |temp_name2 = 85°N | |||
| |min_temp_2 = 70 K | |||
| |mean_temp_2 = 130 K | |||
| |max_temp_2 = 230 K | |||
| |atmosphere = yes | |||
| |atmosphere_density = 10<sup>7</sup> particles cm<sup>−3</sup> (day)<br/>10<sup>5</sup> particles cm<sup>−3</sup> (night) | |||
| <!--Lucey et al. 2006--> | |||
| }} | |||
| The '''Moon''' ({{lang-la|Luna}}) is ]'s only permanent ]. It is the ] in the ]. The average centre-to-centre distance from the Earth to the Moon is {{convert|384403|km|mi|0}}, which is about 30 times the diameter of the Earth. The Moon has a diameter of {{convert|3474|km|mi|0}}<ref name="worldbook">{{cite web | last = Spudis | first = P.D. | date = 2004 | url = http://www.nasa.gov/worldbook/moon_worldbook.html | title = Moon | publisher = World Book Online Reference Center, ] | accessdate = 2007-04-12}}</ref>—slightly more than a quarter that of the Earth. This means that the volume of the Moon is close to 1/50<sup>th</sup> that of Earth. The ]al pull at its surface is about 1/6<sup>th</sup> of Earth's. The Moon makes a complete ] around the Earth every 27.3 days, and the periodic variations in the geometry of the Earth–Moon–] system are responsible for the ]s that repeat every 29.5 days. | |||
| The gravitational, ]s generated by the rotation of the Moon and Earth around a common axis, the ], are largely responsible for the ]s on Earth.<!--The following sentence is quite unclear.--> The energy dissipated in generating tides is directly responsible for the reduction in potential energy in the Moon-Earth orbit around the barycentre, resulting in a 3.8 cm yearly increase in the distance between the two bodies.<ref>{{cite web | url = http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/ApolloLaser.html | title = Apollo Laser Ranging Experiments Yield Results | publisher = NASA | date = ] | accessdate = 2007-05-30}}</ref> The Moon will continue to move slowly away from the Earth until the tidal effects between the two are no longer of significance, whereupon the Moon's orbit will stabilise. | |||
| The Moon is the only ] to which humans have travelled and upon which humans have landed. The first artificial object to escape Earth's gravity and pass near the Moon was the ]'s ], the first artificial object to impact the lunar surface was ], and the first photographs of the normally occluded ] were made by ], all in ]. The first spacecraft to perform a successful lunar soft landing was ], and the first unmanned vehicle to orbit the Moon was ], both in ].<ref name="worldbook" /> The ] (U.S.) ] achieved the only manned missions to date, resulting in six landings between ] and ]. Human exploration of the Moon ceased with the conclusion of the Apollo program, although, as of 2007, several countries have announced plans to send either people or robotic spacecraft to the Moon. | |||
| ==Name and etymology== | |||
| Unlike the moons of other planets, the moon of the Earth has no proper ] name other than "the Moon" (capitalized). | |||
| The word ''moon'' is a ], related to Latin {{lang|la|''mensis''}}; it is ultimately a derivative of the ] root ''me-'', also represented in ''measure''<ref name="etymonline" /> (time), with reminders of its importance in measuring time in words derived from it like Monday, month and menstrual. In English, the word ''moon'' exclusively meant "the Moon" until 1665, when it was extended to refer to the recently-discovered ]s of other planets.<ref name="etymonline">{{cite web |url = http://www.etymonline.com/index.php?l=m&p=21 | last = Harper | first = D. | title = Moon | publisher = Online Etymology Dictionary | date = November 2001 | accessdate = 2007-08-17}}</ref> The Moon is occasionally referred to by its Latin name, {{lang|la|''Luna''}}, in order to distinguish it from other natural satellites, with a related adjective ''lunar'', and an adjectival prefix ''seleno-'' or suffix ''-selene'' (from the ] ]<!-- The word usually came before the naming of the deity "in the beginning was the word" -->). | |||
| ==Lunar surface== | |||
| {{main|Geology of the Moon}} | |||
| ===Two sides of the Moon=== | |||
| The Moon is in ], meaning that it keeps nearly the same face turned towards the Earth at all times. Early in the Moon's history, its rotation slowed and became ] in this configuration as a result of ]al effects associated with tidal deformations caused by the Earth.<ref>{{cite journal | last = Alexander | first = M. E. | title = The Weak Friction Approximation and Tidal Evolution in Close Binary Systems | journal = Astrophysics and Space Science | date = 1973 | volume = 23 | pages = 459–508 | url = http://adsabs.harvard.edu/abs/1973Ap&SS..23..459A| accessdate = 2007-04-12}}</ref> Nevertheless, small variations resulting from the eccentricity of the lunar orbit, termed ], allow about 59% of the lunar surface to be viewed from Earth.<ref name="worldbook" /> | |||
| {| class="toccolours" align="center" | |||
| | ] | |||
| | | |||
| | ] | |||
| |- | |||
| | style="text-align:center;"|] | |||
| | | |||
| | style="text-align:center;"|] | |||
| |} | |||
| The side of the Moon that faces Earth is called the ], and the opposite side the ]. The far side should not be confused with the dark side, which is the hemisphere that is not being illuminated by the ] at a given moment (this may be the side facing the Earth, as it is once a month during the New Moon phase). The far side of the Moon was first photographed by the Soviet probe ] in 1959. One distinguishing feature of the far side is its almost complete lack of ]. | |||
| ]]] | |||
| ===Maria=== | |||
| {{Main|Lunar mare}} | |||
| The dark and relatively featureless lunar plains humans can clearly see when the Moon is full are called '']'' (singular ''mare''), Latin for seas, since they were believed by ancient ]s to be filled with water. These are now known to be vast solidified pools of ancient ]ic lava. The majority of these lavas erupted or flowed into the depressions associated with ] that formed by the collisions of meteors and comets with the lunar surface. (] is a major exception in that it does not correspond to a known impact basin). Maria are found almost exclusively on the near side of the Moon, with the far side having only a few scattered patches covering only about 2% of its surface,<ref>{{cite journal | last = Gillis | first = J.J. | coauthors = Spudis, P.D. | title = The Composition and Geologic Setting of Lunar Far Side Maria | journal = Lunar and Planetary Science | date = 1996 | volume = 27 | pages = 413–404 | url = http://adsabs.harvard.edu/abs/1996LPI....27..413G| accessdate = 2007-04-12}}</ref> compared with about 31% on the near side.<ref name="worldbook" /> The most likely explanation for this difference is related to a higher concentration of heat-producing elements on the near-side hemisphere, as has been demonstrated by geochemical maps obtained from the ] gamma-ray spectrometer.<ref name="S06">{{cite journal | last = Shearer | first = C. | coauthors = et al. | title = Thermal and magmatic evolution of the Moon | journal = Reviews in Mineralogy and Geochemistry | volume = 60 | pages = 365–518 | date = 2006}}</ref><ref>{{cite web | url = http://www.psrd.hawaii.edu/Aug00/newMoon.html | title = A New Moon for the Twenty-First Century | last = Taylor | first = G.J. | publisher = Hawai'i Institute of Geophysics and Planetology | date = ] | accessdate = 2007-04-12}}</ref> Several provinces containing ]es and volcanic ]s are found within the near side maria.<ref>{{cite journal | last = Head | first = L.W.J.W. | title = Lunar Gruithuisen and Mairan domes: Rheology and mode of emplacement | journal = Journal of Geophysical Research | date = 2003 | volume = 108 | url = http://www.agu.org/pubs/crossref/2003/2002JE001909.shtml | accessdate = 2007-04-12}}</ref> | |||
| ===Terrae=== | |||
| The lighter-colored regions of the Moon are called ''terrae'', or more commonly just ''highlands'', since they are higher than most maria. Several prominent mountain ranges on the near side are found along the periphery of the giant ], many of which have been filled by mare basalt. These are believed to be the surviving remnants of the impact basin's outer rims.<ref>{{cite web |first = W. | last = Kiefer | date = ] | url = http://www.lpi.usra.edu/expmoon/orbiter/orbiter-basins.html | title = Lunar Orbiter: Impact Basin Geology | publisher = Lunar and Planetary Institute | accessdate = 2007-04-12}}</ref> In contrast to the Earth, no major lunar mountains are believed to have formed as a result of tectonic events.<ref>{{cite web | last = Munsell | first = K. | publisher = NASA | work = Solar System Exploration | title = Majestic Mountains | url = http://sse.jpl.nasa.gov/educ/themes/display.cfm?Item=mountains | date = ] | accessdate = 2007-04-12}}</ref> | |||
| From images taken by the ], it appears that four mountainous regions on the rim of the 73 km-wide (45 mi-wide) ] at the Moon's north pole remain illuminated for the entire lunar day. These ] are possible because of the Moon's extremely small axial tilt to the ecliptic plane. No similar regions of eternal light were found at the south pole, although the rim of ] is illuminated for about 80% of the lunar day. Another consequence of the Moon's small axial tilt is regions that remain in permanent shadow at the bottoms of many polar craters.<ref name="M03">{{cite web | url = http://www.psrd.hawaii.edu/June03/lunarShadows.html | title = The Moon's Dark, Icy Poles | last = Martel | first = L. | publisher = Hawai'i Institute of Geophysics and Planetology | date = ] | accessdate = 2007-04-12}}</ref> | |||
| ===Impact craters=== | |||
| ] on the Moon's far side]] | |||
| The Moon's surface shows obvious evidence of having been affected by ]ing.<ref>{{cite book | title = Impact cratering: A geologic process | last = Melosh | first = H. J. | publisher = Oxford Univ. Press | date = 1989}}</ref> Impact craters form when asteroids and comets collide with the lunar surface, and globally about half a million craters with diameters greater than {{convert|1|km|mi|1}} can be found. Since impact craters accumulate at a nearly constant rate, the number of craters per unit area superposed on a geologic unit can be used to estimate the age of the surface (see ]). The lack of an atmosphere, weather and recent geological processes ensures that many of these craters have remained relatively well preserved in comparison to those found on Earth. | |||
| The largest crater on the Moon, which also has the distinction of being the largest known crater in the Solar System, is the ]. This impact basin is located on the far side, between the South Pole and equator, and is some {{convert|2240|km|mi|0}} in diameter and {{convert|13|km|mi|1}} in depth.<ref>{{cite web | url = http://www.psrd.hawaii.edu/July98/spa.html | title = The biggest hole in the Solar System | last = Taylor | first = G.J. | date = ] | publisher = Hawai'i Institute of Geophysics and Planetology | accessdate = 2007-04-12}}</ref> Prominent impact basins on the near side include ], ], ], and ]. | |||
| ===Regolith=== | |||
| Blanketed atop the Moon's crust is a highly ] (broken into ever smaller particles) and "impact gardened" surface layer called ]. Since the regolith forms by impact processes, the regolith of older surfaces is generally thicker than for younger surfaces. In particular, it has been estimated that the regolith varies in thickness from about 3–5 m (10–15 ft) in the maria, and by about 10–20 m (30–70 ft) in the highlands.<ref>{{cite book | last = Heiken | first = G. | coauthors = Vaniman, D.; French, B. (eds.) |date = 1991 |title = Lunar Sourcebook, a user's guide to the Moon | publisher = Cambridge University Press | location = New York | pages = 736}}</ref> Beneath the finely comminuted regolith layer is what is generally referred to as the ''megaregolith''. This layer is much thicker (on the order of tens of kilometres) and comprises highly fractured bedrock.<ref>{{cite journal | last = Rasmussen | first = K.L. | coauthors = Warren, P.H. | title = Megaregolith thickness, heat flow, and the bulk composition of the moon | journal = Nature | date = 1985 | volume = 313 | pages = 121–124 | url = http://adsabs.harvard.edu/abs/1985Natur.313..121R | accessdate = 2007-04-12}}</ref> | |||
| ===Presence of water=== | |||
| {{main|Lunar ice}} | |||
| The continuous bombardment of the Moon by ]s and ]s has most likely added small amounts of water to the lunar surface. If so, sunlight would split much of this water into its constituent elements of hydrogen and oxygen, both of which would ordinarily escape into space over time, because of the Moon's weak gravity. However, because of the slightness of the axial tilt of the Moon's spin axis to the ecliptic plane—only 1.5°—some deep craters near the poles never receive direct light from the Sun and are thus in permanent shadow (see ]). Water molecules that ended up in these craters could be stable for long periods of time. | |||
| Clementine has mapped craters at the lunar south pole<ref>{{cite web| url = http://www.lpi.usra.edu/publications/slidesets/clem2nd/slide_32.html| title = Lunar Polar Composites | publisher = Lunar and Planetary Institute | accessdate = 2007-04-12}}</ref> that are shadowed in this way, and computer simulations suggest that up to 14,000 km² (5,500 mi²) might be in permanent shadow.<ref name="M03"/> Results from the ] bistatic radar experiment are consistent with small, frozen pockets of water close to the surface, and data from the ] neutron spectrometer indicate that anomalously high concentrations of hydrogen are present in the upper metre of the regolith near the polar regions.<ref>{{cite web | url = http://lunar.arc.nasa.gov/results/ice/eureka.htm | title = Eureka! Ice found at lunar poles | publisher = Lunar Prospector (NASA) | date = ] | accessdate = 2007-04-12}}</ref> Estimates for the total quantity of water ice are close to one cubic kilometre (0.25 cubic mile). | |||
| Water ice can be mined and then split into its constituent hydrogen and oxygen atoms by means of nuclear generators or electric power stations equipped with solar panels. The presence of usable quantities of water on the Moon is an important factor in rendering ] cost-effective, since transporting water from Earth would be prohibitively expensive. However, recent observations made with the ] planetary radar suggest that some of the near-polar Clementine radar data that were previously interpreted as being indicative of water ice might instead be a result of rocks ejected from young impact craters.<ref>{{cite web| last= Spudis | first = P. | title = Ice on the Moon | url = http://www.thespacereview.com/article/740/1 | publisher = The Space Review | date = ] | accessdate = 2007-04-12}}</ref> The question of how much water there is on the Moon has not been resolved. | |||
| ==Physical characteristics== | |||
| ===Internal structure=== | |||
| {{main|Internal structure of the Moon}} | |||
| ] | |||
| The Moon is a ] body, being composed of a geochemically distinct ], ], and ]. This structure is believed to have resulted from the ] of a ] shortly after its formation about 4.5 billion years ago. The energy required to melt the outer portion of the Moon is commonly attributed to a ] event that is postulated to have formed the Earth-Moon system, and the subsequent reaccretion of material in Earth orbit. Crystallization of this magma ocean would have given rise to a ] mantle and a ]-rich crust (see ''Origin and geologic evolution'' below). | |||
| Geochemical mapping from orbit implies that the crust of the Moon is largely ] in composition,<ref name="L06">{{cite journal | last = Lucey | first = P. | coauthors = et al. |title = Understanding the lunar surface and space-Moon interactions | journal = Reviews in Mineralogy and Geochemistry | volume = 60 | pages = 83–219 | date = 2006}}</ref> consistent with the magma ocean hypothesis. In terms of elements, the crust is composed primarily of ], ], ], ], ], and ]. Based on geophysical techniques, its thickness is estimated to be on average about {{convert|50|km|mi|0}}.<ref name="W06">{{cite journal | last = Wieczorek | first = M. | coauthors = et al. | title = The constitution and structure of the lunar interior | journal = Reviews in Mineralogy and Geochemistry | volume = 60 | pages = 221–364 | date = 2006 }}</ref> | |||
| Partial melting within the mantle of the Moon gave rise to the eruption of mare basalts on the lunar surface. Analyses of these basalts indicate that the mantle is composed predominantly of the minerals ], ] and ], and that the lunar mantle is more iron rich than that of the Earth. Some lunar basalts contain high abundances of ] (present in the mineral ]), suggesting that the mantle is highly heterogeneous in composition. Moonquakes have been found to occur deep within the mantle of the Moon about {{convert|1000|km|mi|0}} below the surface. These occur with monthly periodicities and are related to tidal stresses caused by the eccentric orbit of the Moon about the Earth.<ref name="W06" /> | |||
| The Moon has a mean density of 3,346.4 kg/m³, making it the second densest moon in the Solar System after ]. Nevertheless, several lines of evidence imply that the core of the Moon is small, with a radius of about 350 km or less.<ref name="W06"/> This corresponds to only about 20% the size of the Moon, in contrast to about 50% as is the case for most other terrestrial bodies. The composition of the lunar core is not well constrained, but most believe that it is composed of metallic iron alloyed with a small amount of ] and ]. Analyses of the Moon's time-variable rotation indicate that the core is at least partly molten.<ref>{{cite journal | last = Williams | first = J.G. | coauthors = Turyshev, S.G.; Boggs, D.H.; Ratcliff, J.T. | title = Lunar laser ranging science: Gravitational physics and lunar interior and geodesy | journal = Advances in Space Research | date = 2006 | volume = 37 | issue = 1 | pages = 6771 | url=http://adsabs.harvard.edu/abs/1987AREPS..15..271S | accessdate = 2007-04-12}}</ref> | |||
| ===Topography=== | |||
| {{main|Topography of the Moon}} | |||
| ] | |||
| The ] of the Moon has been measured by the methods of laser altimetry and stereo image analysis, most recently from data obtained during the ]. The most visible topographic feature is the giant far side ], which possesses the lowest elevations of the Moon. The highest elevations are found just to the north-east of this basin, and it has been suggested that this area might represent thick ] deposits that were emplaced during an oblique South Pole-Aitken basin impact event. Other large impact basins, such as ], ], ], ], and ], also possess regionally low elevations and elevated rims. Another distinguishing feature of the Moon's shape is that the elevations are on average about 1.9 km higher on the far side than the near side.<ref name="W06"/> | |||
| ===Gravity field=== | |||
| {{main|Gravity of the Moon}} | |||
| The gravitational field of the Moon has been determined through tracking of radio signals emitted by orbiting spacecraft. The principle used depends on the ], whereby the spacecraft acceleration in the line-of-sight direction can be determined by means of small shifts in frequency of the radio signal, and the distance from the spacecraft to a station on Earth. However, because of the Moon's ] it is not possible to track spacecraft much over the ]s of the Moon, and the farside gravity field is thus only poorly characterised.<ref>{{cite web | url = http://lunar.arc.nasa.gov/results/dopres.htm | publisher = Lunar Prospector (NASA) | title = Doppler Gravity Experiment Results | date = ] | accessdate = 2007-04-12}}</ref> | |||
| ] | |||
| The major characteristic of the Moon's gravitational field is the presence of ]s, which are large positive gravitational anomalies associated with some of the giant ].<ref>{{cite journal | last = Muller | first = P. | coauthors = Sjogren, W. | title = Masons: lunar mass concentrations | journal = Science | volume = 161 |pages = 680–684 | date = 1968}}</ref> These anomalies greatly influence the orbit of spacecraft about the Moon, and an accurate gravitational model is necessary in the planning of both manned and unmanned missions. The mascons are in part due to the presence of dense mare basaltic lava flows that fill some of the impact basins. However, lava flows by themselves can not explain the entirety of the gravitational signature, and uplift of the crust-mantle interface is required as well. Based on ] gravitational models, it has been suggested that some mascons exist that do not show evidence for mare basaltic volcanism.<ref>{{cite journal | last = Konopliv | first = A. | coauthors = Asmar, S.; Carranza, E.; Sjogren, W.; Yuan, D. | title = Recent gravity models as a result of the Lunar Prospector mission | journal = Icarus | volume = 50 | pages = 1–18 | date = 2001}}</ref> It should be noted that the huge expanse of mare basaltic volcanism associated with ] does not possess a positive gravitational anomaly. | |||
| ===Magnetic field=== | |||
| {{main|Magnetic field of the Moon}} | |||
| ] electron reflectometer experiment]] | |||
| The Moon has an external ] of the order of one to a hundred ]—more than 100 times smaller than the ], which is 30-60 microtesla. Other major differences are that the Moon does not currently have a ] magnetic field (as would be generated by a ] in its core), and the magnetizations that are present are almost entirely crustal in origin.<ref>{{cite web |url = http://lunar.arc.nasa.gov/results/magelres.htm | publisher = Lunar Prospector (NASA) | title = Magnetometer / Electron Reflectometer Results | date = 2001 | accessdate = 2007-04-12}}</ref> One hypothesis holds that the crustal magnetizations were acquired early in lunar history when a geodynamo was still operating. The small size of the lunar core, however, is a potential obstacle to this theory. Alternatively, it is possible that on an airless body such as the Moon, transient magnetic fields could be generated during large impact events. In support of this, it has been noted that the largest crustal magnetizations appear to be located near the ] of the giant impact basins. It has been proposed that such a phenomenon could result from the free expansion of an impact generated plasma cloud around the Moon in the presence of an ambient magnetic field.<ref>{{cite journal |last = Hood | first = L.L. | coauthors = Huang, Z. | title = Formation of magnetic anomalies antipodal to lunar impact basins: Two-dimensional model calculations | journal = J. Geophys. Res. | volume = 96 | pages = 9837–9846 | date = 1991}}</ref> | |||
| ===Atmosphere=== | |||
| {{main|Atmosphere of the Moon}} | |||
| The Moon has an atmosphere so thin as to be almost negligible, with a total atmospheric mass of less than 10<sup>4</sup> kg.<ref>{{cite web| last = Globus | first = Ruth | title = Impact Upon Lunar Atmosphere | url = http://www.nas.nasa.gov/About/Education/SpaceSettlement/75SummerStudy/5appendJ.html| year = 2002|accessdate=2007-08-29}}</ref> One source of its atmosphere is ]—the release of gases such as ] that originate by ] processes within the crust and mantle. Another important source is generated through the process of ], which involves the bombardment of micrometeorites, solar wind ions, electrons, and sunlight.<ref name="L06"/> Gases that are released by sputtering can either reimplant into the regolith as a result of the Moon's gravity, or can be lost to space either by solar radiation pressure or by being swept away by the solar wind magnetic field if they are ionised. The elements ] (Na) and ] (K) have been detected using earth-based spectroscopic methods, whereas the element ]–222 and ]–210 have been inferred from data obtained from the ] ] spectrometer.<ref>{{cite journal | last = Lawson | first = S. | coauthors = Feldman, W.; Lawrence, D.; Moore, K.; Elphic, R.; Belian, R. | title = Recent outgassing from the lunar surface: the Lunar Prospector alpha particle spectrometer | journal = J. Geophys. Res. | volume = 110 | pages=1029 | date = 2005}}</ref> Argon–40, He–4, O and/or CH<sub>4</sub>, N<sub>2</sub> and/or CO, and CO<sub>2</sub> were detected by in-situ detectors placed by the Apollo astronauts.<ref>{{cite journal | last = Stern | first = S.A. | title = The Lunar atmosphere: History, status, current problems, and context | journal = Rev. Geophys. | volume = 37 | date = 1999 | pages = 453–491}}</ref> | |||
| ==Origin and geologic evolution== | |||
| ===Formation=== | |||
| Several mechanisms have been suggested for the Moon's formation. Early speculation proposed that the Moon broke off from the Earth's crust because of ]s, leaving a basin (presumed to be the Pacific Ocean) behind as a scar.<ref>{{cite journal | last = Binder | first = A.B. | title = On the origin of the moon by rotational fission | journal = The Moon | date = 1974 | volume = 11 | issue = 2 | pages = 53–76 | url = http://adsabs.harvard.edu/abs/1974Moon...11...53B | accessdate = 2007-04-12}}</ref> This ''fission'' concept, however, requires too great an initial spin of the Earth. Others speculated that the Moon formed elsewhere and was captured into Earth's orbit.<ref>{{cite journal | last = Mitler | first = H.E. | title = Formation of an iron-poor moon by partial capture, or: Yet another exotic theory of lunar origin | journal = Icarus | date = 1975 | volume = 24 | pages = 256–268 | url = http://adsabs.harvard.edu/abs/1975Icar...24..256M | accessdate = 2007-04-12}}</ref> However, the conditions required for this ''capture'' mechanism to work (such as an extended atmosphere of the Earth for dissipating energy) are improbable. The ''coformation'' hypothesis posits that the Earth and the Moon formed together at the same time and place from the primordial ]. In this hypothesis, the Moon formed from material surrounding the proto-Earth, similar to the formation of the planets around the Sun. Some suggest that this hypothesis fails to adequately explain the depletion of metallic iron in the Moon. A major deficiency with all of these hypotheses is that they cannot easily account for the high ] of the Earth–Moon system.<ref>{{cite journal | last = Stevenson | first = D.J. | title = Origin of the moon – The collision hypothesis | journal = Annual review of earth and planetary sciences | date = 1987 | volume = 15 | pages = 271–315 | url = http://adsabs.harvard.edu/abs/1987AREPS..15..271S | accessdate = 2007-04-12}}</ref> | |||
| Today, the ] for forming the Earth–Moon system is widely accepted by the scientific community. In this hypothesis, the impact of a Mars-sized body on the proto-Earth is postulated to have put enough material into circumterrestrial orbit to form the Moon.<ref name="worldbook" /> Given that planetary bodies are believed to have formed by the hierarchical accretion of smaller bodies to larger ones, giant impact events such as this are thought to have affected most planets. Computer simulations modelling this impact are consistent with measurements of the angular momentum of the Earth–Moon system, as well as the small size of the lunar core.<ref>{{cite journal | last = Canup | first = R. | coauthors = Asphaug, E. | title = Origin of the Moon in a giant impact near the end of the Earth's formation | journal = Nature | volume = 412 | pages = 708–712 | date = 2001}}</ref> Unresolved questions regarding this theory have to do with determining the relative sizes of the proto-Earth and impactor, and with determining how much material from the proto-Earth and impactor ended up in the Moon. The formation of the Moon is believed to have occurred 4.527 ± 0.01 billion years ago, about 30–50 million years after the origin of the solar system.<ref>{{cite journal | url = http://www.sciencemag.org/cgi/content/abstract/310/5754/1671 | journal = Science | date = 2005 | volume = 310 | issue = 5754 | pages = 1671–1674 | title = Hf–W Chronometry of Lunar Metals and the Age and Early Differentiation of the Moon | last = Kleine | first = T. | coauthors = Palme, H.; Mezger, K.; Halliday, A.N. | accessdate = 2007-04-12}}</ref> | |||
| ===Lunar magma ocean=== | |||
| As a result of the large amount of energy liberated during both the giant impact event and the subsequent reaccretion of material in Earth orbit, it is commonly believed that a large portion of the Moon was once initially molten. The molten outer portion of the Moon at this time is referred to as a ], and estimates for its depth range from about 500 km to the entire radius of the Moon.<ref name="S06"/> | |||
| As the magma ocean cooled, it ] and ], giving rise to a geochemically distinct crust and mantle. The mantle is inferred to have formed largely by the precipitation and sinking of the minerals ], ], and ]. After about three-quarters of magma ocean crystallisation was complete, the mineral ] is inferred to have precipitated and floated to the surface because of its low density, forming the crust.<ref name="S06"/> | |||
| The final liquids to crystallise from the magma ocean would have been initially sandwiched between the crust and mantle, and would have contained a high abundance of incompatible and heat-producing elements. This geochemical component is referred to by the acronym ], for ] (K), ] (REE), and ] (P), and appears to be concentrated within the ], which is a small geologic province that encompasses most of ] and ] on the near side of the Moon.<ref name="W06"/> | |||
| ===Geologic evolution=== | |||
| {{seealso|Geology of the Moon}} | |||
| A large portion of the Moon's post–magma-ocean geologic evolution was dominated by impact cratering. The ] is largely divided in time on the basis of prominent basin-forming impact events, such as ], ], and ]. These impact structures are characterised by multiple rings of uplifted material, and are typically hundreds to thousands of kilometres in diameter. Each multi-ring basin is associated with a broad apron of ejecta deposits that forms a regional stratigraphic horizon. While only a few multi-ring basins have been definitively dated, they are useful for assigning relative ages on the basis of ] grounds. The continuous effects of impact cratering are responsible for forming the ]. | |||
| The other major geologic process that affected the Moon's surface was ]. The enhancement of heat-producing elements within the ] is thought to have caused the underlying mantle to heat up, and eventually, to partially melt. A portion of these magmas rose to the surface and erupted, accounting for the high concentration of mare basalts on the near side of the Moon.<ref name="S06"/> Most of the Moon's ] erupted during the Imbrian period in this geologic province 3.0–3.5 billion years ago. Nevertheless, some dated samples are as old as 4.2 billion years,<ref name = "Papike">{{cite journal | last = Papike | first = J. | coauthors = Ryder, G.; Shearer, C. | title = Lunar Samples | journal = Reviews in Mineralogy and Geochemistry | volume = 36 | pages = 5.1–5.234 | date = 1998}}</ref> and the youngest eruptions, based on the method of ], are believed to have occurred only 1.2 billion years ago.<ref name = "Hiesinger">{{cite journal | last = Hiesinger | first = H. | coauthors = Head, J.W.; Wolf, U.; Jaumanm, R.; Neukum, G. | title = Ages and stratigraphy of mare basalts in Oceanus Procellarum, Mare Numbium, Mare Cognitum, and Mare Insularum | journal = J. Geophys. Res. | volume = 108 | pages = 1029 | date = 2003}}</ref> | |||
| There has been controversy over whether features on the Moon's surface undergo changes over time. Some observers have claimed that craters either appeared or disappeared, or that other forms of transient phenomena had occurred. Today, many of these claims are thought to be illusory, resulting from observation under different lighting conditions, poor ], or the inadequacy of earlier drawings. Nevertheless, it is known that the phenomenon of ] does occasionally occur, and these events could be responsible for a minor percentage of the reported ]. Recently, it has been suggested that a roughly 3 km diameter region of the lunar surface was modified by a gas release event about a million years ago.<ref>{{cite web |url = http://www.psrd.hawaii.edu/Nov06/MoonGas.html | last = Taylor | first = G.J. | title = Recent Gas Escape from the Moon | publisher = Hawai'i Institute of Geophysics and Planetology | date = ] | accessdate = 2007-04-12}}</ref><ref>{{cite journal | last = Schultz | first = P.H. | coauthors = Staid, M.I.; Pieters, C.M. | date = 2006 | title = Lunar activity from recent gas release | journal= Nature |volume = 444 |pages = 184–186}}</ref> | |||
| ===Moon rocks=== | |||
| {{main|Moon rocks}} | |||
| Moon rocks fall into two main categories, based on whether they underlie the lunar highlands (terrae) or the maria. The lunar highlands rocks are composed of three suites: the ''ferroan anorthosite suite'', the ''magnesian suite'', and the ''alkali suite'' (some consider the alkali suite to be a subset of the mg-suite). The ferroan anorthosite suite rocks are composed almost exclusively of the mineral ] (a calic ]), and are believed to represent plagioclase flotation cumulates of the lunar magma ocean. The ferroan anorthosites have been dated using radiometric methods to have formed about 4.4 billion years ago.<ref name = "Papike" /><ref name = "Hiesinger" /> | |||
| The mg- and alkali-suite rocks are predominantly mafic plutonic rocks. Typical rocks are ]s, ]s, ]s, alkali ]s, and more rarely, ]. In contrast to the ferroan anorthosite suite, these rocks all have relatively high Mg/Fe ratios in their mafic minerals. In general, these rocks represent intrusions into the already-formed highlands crust (though a few rare samples appear to represent extrusive lavas), and they have been dated to have formed about 4.4–3.9 billion years ago. Many of these rocks have high abundances of, or are genetically related to, the geochemical component ]. | |||
| The lunar maria consist entirely of mare basalts. While similar to terrestrial basalts, they have much higher abundances of iron, are completely lacking in hydrous alteration products, and have a large range of titanium abundances.<ref>{{cite web | url = http://www.psrd.hawaii.edu/April04/lunarAnorthosites.html | title = The Oldest Moon Rocks | last = Norman | first = M. | publisher = Hawai'i Institute of Geophysics and Planetology | date = ] | accessdate = 2007-04-12}}</ref><ref>{{cite book | last = Varricchio | first = L. | title = Inconstant Moon | publisher = Xlibris Books | date = 2006 | isbn = 1-59926-393-9}}</ref> | |||
| Astronauts reported that the dust from the surface felt like snow and smelled like spent ].<ref> from ]</ref> The dust is mostly made of ] glass (SiO<sub>2</sub>), most likely created from the meteors that have crashed into the Moon's surface. It also contains ] and ]. | |||
| ==Orbit and relationship to Earth== | |||
| {{main|Orbit of the Moon}} | |||
| ] as viewed from the Moon during the ] mission, ], 1968]] | |||
| The Moon makes a complete orbit around the Earth with respect to the fixed stars (its ]) about once every 27.3 days. However, since the Earth is moving in its orbit about the Sun at the same time, it takes slightly longer for the Moon to show its same ] to Earth, which is about 29.5 days (its ]).<ref name="worldbook" /> Unlike most satellites of other planets, the Moon orbits near the ] and not the Earth's ]. It is the largest moon in the solar system relative to the size of its planet. (] is larger relative to the ] ].) The ]s orbiting other planets are called "moons", after Earth's Moon. | |||
| Most of the tidal effects seen on the Earth are caused by the Moon's gravitational pull, with the Sun making only a small contribution. Tidal effects result in an increase of the mean Earth-Moon distance of about {{convert|3.8|m|ft|1}} per century, or {{convert|3.8|cm|in|1}} per year.<ref>{{cite web | url = http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/ApolloLaser.html | title = Apollo Laser Ranging Experiments Yield Results | publisher = NASA | date = ] | accessdate = 2007-05-30}}</ref> As a result of the ], the increasing semimajor axis of the Moon is accompanied by a gradual slowing of the Earth's rotation by about 0.002 seconds per day per century.<ref>{{cite web | last = Ray | first = R. | date = ] | url = http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html | title = Ocean Tides and the Earth's Rotation | publisher = IERS Special Bureau for Tides | accessdate = 2007-04-12}}</ref> | |||
| The Earth–Moon system is sometimes considered to be a ] rather than a planet–moon system. This is due to the exceptionally large size of the Moon relative to its host planet; the Moon is a quarter the diameter of Earth and 1/81 its mass. However, this definition is criticised by some, since the common centre of mass of the system (the ]) is located about {{convert|1700|km|mi|0}} beneath the surface of the Earth, or about a quarter of the Earth's radius. The surface of the Moon is less than 1/10<sup>th</sup> that of the Earth, and only about a quarter the size of the Earth's land area (or about as large as Russia, Canada, and the U.S. combined). | |||
| In 1997, the asteroid ] was found to have an unusual Earth-associated ]. However, astronomers do not consider it to be a second moon of Earth, and its orbit is not stable in the long term.<ref>{{cite web | url = http://www.captaincosmos.clara.co.uk/cruithne.html | last = Vampew | first = A | title = No, it's not our "second" moon!!! | accessdate = 2007-04-12}}</ref> Three other ]s, (54509) 2000 PH5, (85770) 1998 UP1 and ], which exist in orbits similar to Cruithne's, have since been discovered.<ref>{{cite journal | last = Morais | first = M.H.M. | coauthors = Morbidelli, A. | title = The Population of Near-Earth Asteroids in Coorbital Motion with the Earth | journal = Icarus | date = 2002 | volume = 160 | pages = 1–9 | url = http://adsabs.harvard.edu/abs/2002Icar..160....1M | accessdate = 2007-04-12}}</ref> | |||
| ] | |||
| ] | |||
| ==Eclipses== | |||
| {{main|Solar eclipse|Lunar eclipse}} | |||
| ] | |||
| ]]] | |||
| Eclipses can occur only when the Sun, Earth, and Moon are all in a straight line. ]s occur near a ], when the Moon is between the Sun and Earth. In contrast, ]s occur near a ], when the Earth is between the Sun and Moon. | |||
| Because the Moon's orbit around the Earth is inclined by about 5° with respect to the ], eclipses do not occur at every full and new moon. For an eclipse to occur, the Moon must be near the intersection of the two orbital planes.<ref name="eclipse">{{cite web | last = Thieman | first = J. | coauthors = Keating, S. | date = ] | url = http://eclipse99.nasa.gov/pages/faq.html | title = Eclipse 99, Frequently Asked Questions | publisher = NASA | accessdate = 2007-04-12}}</ref> | |||
| The periodicity and recurrence of eclipses of the Sun by the Moon, and of the Moon by the Earth, is described by the ], which has a period of approximately 6,585.3 days (18 years 11 days 8 hours).<ref>{{cite web |url = http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros.html | last = Espenak | first = F |title = Saros Cycle | publisher = NASA | accessdate = 2007-04-12}}</ref> | |||
| The angular diameters of the Moon and the Sun as seen from Earth overlap in their variation, so that both ] and ] solar eclipses are possible.<ref>{{cite web | first = F | last = Espenak | date = 2000 | url = http://www.mreclipse.com/Special/SEprimer.html | title = Solar Eclipses for Beginners | publisher = MrEclipse | accessdate = 2007-04-12}}</ref> In a total eclipse, the Moon completely covers the disc of the Sun and the solar ] becomes visible to the ]. Since the distance between the Moon and the Earth is very slightly increasing over time, the angular diameter of the Moon is decreasing. This means that hundreds of millions of years ago the Moon could always completely cover the Sun on solar eclipses so that no annular eclipses were possible. Likewise, about 600 million years from now (assuming that the angular diameter of the Sun will not change), the Moon will no longer cover the Sun completely and only annular eclipses will occur.<ref name="eclipse" /> | |||
| A phenomenon related to eclipse is ]. The Moon is continuously blocking our view of the sky by a 1/2 degree-wide circular area. When a bright star or planet ''passes behind'' the Moon it is ''occulted'' or hidden from view. A solar eclipse is an occultation of the Sun. Because the Moon is close to Earth, occultations of individual stars are not visible everywhere, nor at the same time. Because of the precession of the lunar orbit, each year different stars are occulted.<ref>{{cite web | url = http://occsec.wellington.net.nz/total/totoccs.htm | title = Total Lunar Occultations | publisher = Royal Astronomical Society of New Zealand | accessdate = 2007-04-12}}</ref> | |||
| The last total lunar eclipse took place on ], ]. It was visible from the Americas, the Pacific Ocean, eastern Asia and Oceania. The next solar eclipse takes place on ], ], visible from southern South America and parts of Antarctica. The next total solar eclipse, on ], ], will have a path of totality beginning in northern Canada and passing through Russia and China.<ref name="Espenak">{{cite web | last = Espenak | first = F. | date = 2007 | url = http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html |title = NASA Eclipse Home Page | publisher = NASA | accessdate = 2007-04-12}}</ref> | |||
| ==Observation== | |||
| {{see also|Lunar phase|Earthshine|Observing the Moon}} | |||
| During the brightest full moons, the Moon has an ] of about −12.6. By comparison, the Sun has an apparent magnitude of −26.8. When the Moon is in a quarter phase, its brightness is not half of a full moon, but only about a tenth. This is because the lunar surface is not a perfect ]. When the Moon is full the ] makes it appear brighter, but away from full there are shadows projected onto the surface which diminish the amount of reflected light. | |||
| The Moon appears larger when close to the horizon. This is a purely psychological effect (see ]). The angular diameter of the Moon from Earth is about a half a degree, and is actually about 1.5% smaller when the Moon is near the horizon than when it is high in the sky (because it is farther away by up to one Earth radius). | |||
| The moon appears as a relatively bright object in the sky, however it is worth noting that it reflects only about 7% of the light incident upon it (about as dark as a lump of coal). It has a very low ], and in fact the Moon is about the poorest ] in the ].<ref>{{cite web | url = http://liftoff.msfc.nasa.gov/Academy/UNIVERSE/MOON.HTML | publisher = NASA | title = Exploration: The Moon | date = ] | accessdate = 2007-08-28}}</ref> | |||
| ] in the ] recalibrates the relations between the colours of an object and its surroundings, and since the surrounding sky is comparatively dark the sunlit Moon is perceived as a bright object. | |||
| ] around the Moon]] | |||
| The highest ] of the Moon on a day varies and has nearly the same limits as the Sun. It also depends on the Earth season and lunar phase, with the full moon being highest in winter. The orientation of the Moon's crescent also depends on the latitude of the observation site. Close to the equator, an observer can see a ''boat'' Moon.<ref>{{cite web | url = http://curious.astro.cornell.edu/question.php?number=393 | publisher = Curious About Astronomy | title = Is the Moon seen as a crescent (and not a "boat") all over the world? | date = ] | first = K.| last = Spekkens | accessdate = 2007-04-12}}</ref> | |||
| Like the Sun, the Moon can give rise to atmospheric effects, including a 22° ] ring, and the smaller ] seen more often through thin clouds. For more information on how the Moon appears in Earth's sky, see ]. | |||
| ==Exploration== | |||
| {{main|Exploration of the Moon|Apollo program|Moon landing}} | |||
| {{see also|Robotic exploration of the Moon|Future lunar missions|Colonization of the Moon}} | |||
| The first leap in lunar observation was prompted by the invention of the telescope. ] made good use of this new instrument and observed mountains and craters on the Moon's surface. | |||
| The ]-inspired ] between the Soviet Union and the U.S. led to an acceleration of interest in the Moon. Unmanned probes, both flyby and impact/lander missions, were sent almost as soon as launcher capabilities would allow. The Soviet Union's ] was the first to reach the Moon with unmanned ]. The first man-made object to escape Earth's gravity and pass near the Moon was ], the first man-made object to impact the lunar surface was ], and the first photographs of the normally occluded far side of the Moon were made by ], all in 1959. The first spacecraft to perform a successful lunar soft landing was ] and the first unmanned vehicle to orbit the Moon was ], both in 1966.<ref name="worldbook" /> Moon samples have been brought back to Earth by three Luna missions (], ], and ]) and the Apollo missions 11 to 17 (except ], which aborted its planned lunar landing). | |||
| ] taken from ]]] | |||
| The landing of the first humans on the Moon in 1969 is seen as the culmination of the space race.<ref name=CNN>{{cite news | last = Coren | first = M | title = 'Giant leap' opens world of possibility | publisher = CNN.com | date = ] | url = http://edition.cnn.com/2004/TECH/space/07/16/moon.landing/index.html | accessdate = 2007-04-12}} | |||
| </ref> ] became the first person to walk on the Moon as the commander of the American mission ] by first setting foot on the Moon at 02:56 UTC on ], ] . The last person, as of 2007, to stand on the Moon was ], who, as part of the mission ], walked on the Moon in December 1972. The American ] and return was enabled by considerable technological advances, in domains such as ] chemistry and ] technology, in the early 1960s. | |||
| Scientific instrument packages were installed on the lunar surface during all of the ''Apollo'' missions. Long-lived ] stations (Apollo lunar surface experiment package) were installed at the ], ], ], ], and ] landing sites, whereas a temporary station referred to as EASEP (Early Apollo Scientific Experiments Package) was installed during the Apollo 11 mission. The ALSEP stations contained, among others, heat flow probes, seismometers, magnetometers, and corner-cube retroreflectors. Transmission of data to Earth was terminated on ], ] because of budgetary considerations<ref>{{cite press release | title = NASA news release 77-47 page 242| date = ] | url = http://www.nasa.gov/centers/johnson/pdf/83129main_1977.pdf | accessdate = 2007-08-29 }}</ref><ref>{{cite news | url = http://www.ast.cam.ac.uk/~ipswich/Miscellaneous/Archived_spaceflight_news.htm | accessdate = 2007-08-29 | location = NASA Turns A Deaf Ear To The Moon | date = 1977 | title = OASI Newsletters Archive | last = Appleton | first = James | coauthors = Charles Radley, John Deans, Simon Harvey, Paul Burt, Michael Haxell, Roy Adams, N Spooner and Wayne Brieske }}</ref>. Since the ] (LLR) corner-cube arrays are passive instruments, they are still being used. Ranging to the LLR stations is routinely performed from earth-based stations with an accuracy of a few centimetres, and data from this experiment are being used to place constraints on the size of the lunar core.<ref>{{cite journal | last = Dickey | first = J. | coauthors = et al. | date = 1994 | title = Lunar laser ranging: a continuing legacy of the Apollo program | journal = Science | volume = 265 |pages = 482–490}}</ref> | |||
| ] ] photographed by ] during the ]]] | |||
| From the mid-1960s to the mid-1970s, there were 65 instances of artificial objects reaching the Moon (both manned and robotic, with ten in 1971 alone), with the last being ] in 1976. Only 18 of these were controlled ], with nine completing a round trip from Earth and returning samples of ]. The Soviet Union then turned its primary attention to ] and ]s, and the U.S. to ] and beyond. In 1990, Japan orbited the Moon with the '']'' spacecraft, becoming the third country to place a spacecraft into lunar orbit. The spacecraft released a smaller probe, ''Hagormo'', in lunar orbit, but the transmitter failed, thereby preventing further scientific use of the mission. | |||
| In 1994, the U.S. finally returned to the Moon, robotically at least, sending the Joint Defense Department/NASA spacecraft ]. This mission obtained the first near-global topographic map of the Moon, and the first global ] images of the lunar surface. This was followed by the '']'' mission in 1998. The ] ] on ''Lunar Prospector'' indicated the presence of excess hydrogen at the lunar poles, which is likely to have been caused by the presence of water ice in the upper few metres of the regolith within permanently shadowed craters. The European spacecraft '']'' was launched ], ] and was in lunar orbit from ], ] to ], ]. | |||
| On ], ], U.S. President ] called for a plan to return manned missions to the Moon by 2020 (see ]).<ref>{{cite press release|url = http://www.nasa.gov/missions/solarsystem/bush_vision.html| title = President Bush Offers New Vision For NASA | date = ] | publisher = NASA | accessdate = 2007-04-12}}</ref> NASA is now planning for the construction of a permanent outpost at one of the lunar poles.<ref>{{cite press release | title = | |||
| NASA Unveils Global Exploration Strategy and Lunar Architecture | publisher = NASA | date = ] | url = http://www.nasa.gov/home/hqnews/2006/dec/HQ_06361_ESMD_Lunar_Architecture.html | accessdate = 2007-04-12}}</ref> The People's Republic of China has expressed ambitious plans for exploring the Moon and has started the ] for lunar exploration, with a launch of its first spacecraft, ], slated for September 2007. Japan has one planned lunar mission, '']'' that is also scheduled for launch in September 2007. ] intends to launch several unmanned missions, beginning with '']'' in February 2008, followed by ''Chandaryaan II'' in 2010 or 2011; the latter is slated to include a robotic lunar rover. India also has expressed its hope for a manned mission to the Moon by 2030.] | accessdate = 2007-08-28}}</ref>] The U.S. will launch the '']'' in 2008. Russia also announced to resume its previously frozen project '']'', consisting of an unmanned lander and orbiter, which is slated to land in 2012.<ref>{{cite web | url = http://www.aviationnow.com/avnow/news/channel_awst_story.jsp?id=news/aw060506p2.xml | title = Russia Plans Ambitious Robotic Lunar Mission | last = Covault | first = C. | publisher = Aviation Week | date = ] | accessdate = 2007-04-12}}</ref> | |||
| ==Human understanding== | |||
| {{see also|The Moon in mythology|Moon in art and literature|Lunar effect|Artemis}} | |||
| ] (1647)]] | |||
| The Moon has been the subject of many works of art and literature and the inspiration for countless others. It is a motif in the visual arts, the performing arts, poetry, prose and music. A 5,000-year-old rock carving at ], ] may represent the Moon, which would be the earliest depiction discovered.<ref name=spacetoday>{{cite web | url = http://www.spacetoday.org/SolSys/Earth/OldStarCharts.html | title = Carved and Drawn Prehistoric Maps of the Cosmos | publisher = Space Today Online | date = 2006 | accessdate = 2007-04-12}}</ref> In many prehistoric and ancient cultures, the Moon was thought to be a ] or other ] phenomenon, and ] of the Moon continue to be propagated today. | |||
| Among the first in the Western world to offer a scientific explanation for the Moon was the Greek philosopher ], who reasoned that the Sun and Moon were both giant spherical rocks, and that the latter reflected the light of the former. His atheistic view of the heavens was one cause for his imprisonment and eventual exile.<ref>{{cite web | last = O'Connor | first = J.J. | coauthors = Robertson, E.F. | date = February 1999 | url = http://www-history.mcs.st-andrews.ac.uk/Biographies/Anaxagoras.html | title = Anaxagoras of Clazomenae | publisher = University of St Andrews | accessdate = 2007-04-12}}</ref> | |||
| In ]'s 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. This separation was held to be part of physics for many centuries after.<ref>{{cite book | last = ] | title = The Discarded Image | pages = 108 | publisher = Cambridge University Press | date = 1964 | location = Cambridge | isbn = 0-521047735-2}}</ref> | |||
| ]]] | |||
| By the ], before the invention of the telescope, more and more people began to recognise the Moon as a sphere, though they believed that it was "perfectly smooth".<ref>{{cite web | last = Van Helden | first = A. | date = 1995 | url = http://galileo.rice.edu/sci/observations/moon.html | title = The Moon | publisher = Galileo Project | accessdate = 2007-04-12}}</ref> In 1609, ] drew one of the first telescopic drawings of the Moon in his book {{lang|la|'']''}} and noted that it was not smooth but had mountains and craters. Later in the 17th century, ] and ] drew a map of the Moon and gave many craters the names they still have today. | |||
| ]}}'' (1902) by ]]] | |||
| On maps, the dark parts of the Moon's surface were called ''maria'' (singular ''mare'') or seas, and the light parts were called ''terrae'' or continents. | |||
| The possibility that the Moon contains vegetation and is inhabited by selenites was seriously considered by major astronomers even into the first decades of the 19th century. The contrast between the brighter highlands and darker maria create the patterns seen by different cultures as the ], the rabbit and the buffalo, among others. | |||
| In 1835, the ] fooled some people into thinking that there were exotic animals living on the Moon.<ref>{{cite web|url = http://www.museumofhoaxes.com/moonhoax.html | title = The Great Moon Hoax | last = Boese | first = A. | publisher = Museum of Hoaxes | date = 2002 | accessdate = 2007-04-12}}</ref> Almost at the same time however (during 1834–1836), ] and ] were publishing their four-volume {{lang|la|''Mappa Selenographica''}} and the book {{lang|de|''Der Mond''}} in 1837, which firmly established the conclusion that the Moon has no bodies of water nor any appreciable atmosphere. | |||
| The far side of the Moon remained completely unknown until the ] probe was launched in 1959, and was extensively mapped by the ] in the 1960s. | |||
| ==Legal status== | |||
| {{main|Space law}} | |||
| Although several flags of the Soviet Union (scattered by ] in 1959 and by later landing missions) and the U.S. have been symbolically planted on the Moon, no nation currently claims ownership of any part of the Moon's surface. Russia and the U.S. are party to the ], which places the Moon under the same jurisdiction as ] ({{lang|la|'']''}}). This treaty also restricts the use of the Moon to peaceful purposes, explicitly banning military installations and ] (including ]).<ref>{{cite web | title = International Space Law | publisher = United Nations Office for Outer Space Affairs | url = http://www.unoosa.org/oosa/en/SpaceLaw/index.html | date = 2006 | accessdate = 2007-04-12}}</ref> | |||
| A second treaty, the ], was proposed to restrict the exploitation of the Moon's resources by any single nation, but it has not been signed by any of the ]. Several individuals have made ] to the Moon in whole or in part, although none of these are generally considered credible.<ref>{{cite web | title = It's illegal for private enterprise to go into space | publisher = Artemis Society International | url = http://www.asi.org/adb/j/02/legal-roadblocks.html | date = 2004 | accessdate = 2007-04-12}}</ref> | |||
| In August 2007, NASA stated that all future missions and explorations of the moon will be done entirely using the ]. This was done to improve cooperation with space agencies of other countries which already use the metric system: | |||
| {{Quotation|Emergencies aside, a metric standard will make it easier for countries to form new partnerships and collaborations after their lunar operations are already in place. All data will be in compatible units, whether it's scientific data or operational data -- such as how far a rover must travel to reach the edge of a crater. A single measurement system will make sharing this data and merging operations more seamless.|http://science.nasa.gov/headlines/y2007/08jan_metricmoon.htm}} | |||
| ==See also== | |||
| {{portal|Solar System|Solar system.jpg}} | |||
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| ==References== | |||
| ;Cited | |||
| {{Reflist|2}} | |||
| ;General | |||
| <div class="references-small"> | |||
| * {{cite book| title=The Clementine Atlas of the Moon | last = Bussey | first = B. | coauthors = ] | publisher = Cambridge University Press | date = 2004 | isbn = 0-521-81528-2}} | |||
| * {{cite journal | last = Jolliff | first = B. | coauthors = Wieczorek, M.; Shearer, C.; Neal, C. (eds.) | title = New views of the Moon | journal = Rev. Mineral. Geochem. |publisher = Min. Soc. Amer. | location = Chantilly, Virginia | pages = 721 | date = 2006 | volume = 60 | url = http://www.minsocam.org/msa/RIM/Rim60.html | accessdate = 2007-04-12}} | |||
| * {{cite book| title = On the Moon | last = ] | publisher = Sterling Publishing Co. | location = Tucson, Arizona | date = 2001 | isbn = 0-304-35469-4}} | |||
| * {{cite book| title = The Once and Future Moon | last = Spudis | first = P.D. | publisher = Smithsonian Institution Press | date = 1996 | isbn = 1-56098-634-4}} | |||
| * {{cite book | last = Taylor | first = S.R. | title = Solar system evolution | publisher = Cambridge Univ. Press | pages = 307 | date = 1992}} | |||
| * {{cite journal | last = Wilhelms | first = D.E. | title = Geologic History of the Moon | journal = U.S. Geological Survey Professional paper | date = 1987 | volume = 1348 | url = http://ser.sese.asu.edu/GHM/ | accessdate = 2007-04-12}} | |||
| * {{cite book| title = To a Rocky Moon: A Geologist's History of Lunar Exploration | last = Wilhelms | first = D.E. | publisher = University of Arizona Press | location = Tucson, Arizona | date = 1993}} | |||
| </div> | |||
| ==External links== | |||
| {{sisterlinks|Moon}} | |||
| ;Images and maps | |||
| * {{cite web | last = Constantine | first = M. | title = Apollo Panoramas | publisher = moonpans.com | date = 2004 | url = http://moonpans.com/missions.htm | accessdate = 2007-04-12}} | |||
| * {{cite web | title = Clementine Lunar Image Browser 1.5 | publisher = U.S. Navy | date = ] | url = http://www.cmf.nrl.navy.mil/clementine/clib/ | accessdate = 2007-04-12}} | |||
| * {{cite web | title = Digital Lunar Orbiter Photographic Atlas of the Moon | publisher = Lunar and Planetary Institute | url = http://www.lpi.usra.edu/resources/lunar_orbiter/ | accessdate = 2007-04-12}} | |||
| * {{cite web | title = Google Moon | publisher = Google | date = 2007 | url = http://moon.google.com | accessdate = 2007-04-12}} | |||
| * {{cite web | title = Lunar Atlases | publisher = Lunar and Planetary Institute | url = http://www.lpi.usra.edu/resources/lunar_atlases/ | accessdate = 2007-04-12}} | |||
| * {{cite web | last = Aeschliman | first = R. | title = Lunar Maps | work = Planetary Cartography and Graphics | url = http://ralphaeschliman.com/id26.htm | accessdate = 2007-04-12}} | |||
| * {{cite web | title = Lunar Photo of the Day | date = 2007 | url = http://www.lpod.org/ | accessdate = 2007-04-12}} | |||
| * {{cite web | title = Moon | work = World Wind Central | publisher = NASA | date = 2007 | url = http://www.worldwindcentral.com/Moon | accessdate = 2007-04-12}} | |||
| ;Exploration | |||
| * {{cite web | last = Jones | first = E.M. | title = Apollo Lunar Surface Journal | publisher = NASA | date = 2006 | url = http://www.hq.nasa.gov/office/pao/History/alsj/ | accessdate = 2007-04-12}} | |||
| * {{cite web | title = Exploring the Moon | publisher = Lunar and Planetary Institute | url = http://www.lpi.usra.edu/expmoon/ | accessdate = 2007-04-12}} | |||
| * {{cite web | last = Teague | first = K. | title = The Project Apollo Archive | date = 2006 | url = http://www.apolloarchive.com/apollo_archive.html | accessdate = 2007-04-12}} | |||
| ;Moon phases | |||
| * {{cite web | title = Current Moon Phase | date = 2007 | url = http://www.moonphaseinfo.com/ | accessdate = 2007-04-12}} | |||
| * {{cite web | title = NASA's SKYCAL - Sky Events Calendar | publisher = NASA Eclipse Home Page | url = http://sunearth.gsfc.nasa.gov/eclipse/SKYCAL/SKYCAL.html | accessdate = 2007-08-27}} | |||
| * {{cite web | title = Virtual Reality Moon Phase Pictures | publisher = U.S. Naval Observatory | url = http://tycho.usno.navy.mil/vphase.html | accessdate = 2007-04-12}} | |||
| ;Others | |||
| * {{cite web | title = All About the Moon | publisher = Space.com | date = 2007 | url = http://www.space.com/moon/ | accessdate = 2007-04-12}} | |||
| * by | |||
| * {{cite web | title = Archive of Moon Articles | publisher = Planetary Science Research Discoveries | date = 2007 | url = http://www.psrd.hawaii.edu/Archive/Archive-Moon.html | accessdate = 2007-04-12}} | |||
| * {{cite web | last = Williams | first = D.R. | title = Moon Fact Sheet | publisher = NASA | date = 2006 | url = http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html | accessdate = 2007-04-12}} | |||
| {{Moon footer}} | |||
| {{Natural satellites of the Solar System (compact)}} | |||
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Revision as of 17:04, 30 August 2007
IT TASTES LIKE CHEESE UMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM HAHA YOU BEEN FUCKED IN THE ASS!!!!!!!!!!!!!!!!!!