Crater characteristics
Aristarchus (center) and Herodotus (right) from Apollo 15. NASA photo.
Coordinates	23.7° N, 47.4° W
Diameter	40 km
Depth	3.7 km
Colongitude	48° at sunrise
Eponym	Aristarchus of Samos

Aristarchus is a prominent lunar impact crater that lies in the northwest part of the Moon's near side. It is considered the brightest of the large formations on the lunar surface, with an albedo nearly double that of most lunar features. The feature is bright enough to be visible to the naked eye, and is dazzling in a large telescope. It is also readily identified when most of the lunar surface is illuminated by earthshine. Image File history File links Size of this preview: 666 × 599 pixelsFull resolution‎ (750 × 675 pixels, file size: 120 KB, MIME type: image/jpeg) This is a view of the Aristarchus and Herodotus craters taken from orbit during the Apollo 15 mission. ... Apollo 15 was the ninth manned mission in the Apollo program and the fourth mission to land on the Moon. ... The National Aeronautics and Space Administration (NASA) (IPA [ˈnæsə]) is an agency of the United States government, responsible for the nations public space program. ... Selenographic coordinates are used to refer to locations on the surface of Earths moon. ... DIAMETER is a computer networking protocol for AAA (Authentication, Authorization and Accounting). ... The depth of any crater in a solid planet or moon - whether it is an impact crater, a volcanic crater, or a subsidence crater - may be measured from the local surface to the bottom of the crater, or from the rim of the crater to the bottom. ... Selenographic coordinates are coordinates that refer to locations on the surface of the Moon. ... An eponym is the name of a person, whether real or fictitious, who has (or is thought to have) given rise to the name of a particular place, tribe, discovery, or other item. ... For other uses of this name, including the grammarian Aristarchus of Samothrace, see Aristarchus Statue of Aristarchus at Aristotle University in Thessalonica, Greece Aristarchus (Greek: Ἀρίσταρχος; 310 BC - ca. ... This article is about Earths moon. ... Tycho crater on Earths moon. ... This article is about Earths moon. ... For other uses, see Albedo (disambiguation). ... This article does not cite any references or sources. ... The lunar surface (or the surface of the moon) differs greatly from that of Earth. ... Saturns moon Iapetus lit by Saturnshine. ...

The crater is located at the southeastern edge of the Aristarchus plateau, an elevated area that contains a number of volcanic features, such as sinuous rilles. This area is also noted for the large number of reported transient lunar phenomena, as well as recent emissions of radon gas as measured by the Lunar Prospector spacecraft. It is pronounced the same as a second name of a river in Normandy in France, see Risle A rille is used to describe any of the long, narrow depressions in the lunar surface that resemble channels. ... This map, based on a survey of 300 TLPs by Barbara Middlehurst and Patrick Moore, shows the approximate distribution of observed events. ... For other uses, see Radon (disambiguation). ... NASAs Lunar Prospector The Lunar Prospector mission was the third selected by NASA for full development and construction as part of the Discovery Program. ...

Aristarchus was originally named after the Greek astronomer Aristarchus of Samos by the Italian map maker Giovanni Riccioli. His work Almagestum novum ("New Almagest"), published in 1651, gave the spot-shaped telescopic features (later called craters) eponyms of noted astronomers and philosophers. Although widely adopted, the name only became an official international standard by a vote of the IAU General Assembly in 1935.^[1] For other uses of this name, including the grammarian Aristarchus of Samothrace, see Aristarchus Statue of Aristarchus at Aristotle University in Thessalonica, Greece Aristarchus (Greek: Ἀρίσταρχος; 310 BC - ca. ... Giovanni Battista Riccioli (b. ... An eponym is the name of a person, whether real or fictitious, who has (or is thought to have) given rise to the name of a particular place, tribe, discovery, or other item. ... IAU redirects here. ...

Selenography

The Aristarchus crater is located on an elevated rocky rise, known as the Aristarchus plateau, in the midst of the Oceanus Procellarum, a large expanse of lunar mare. This is a tilted crustal block, about 200 km across, that rises to a maximum altitude of 2 km above the mare in the southeastern section.^[2] Aristarchus crater is just to the east of the Herodotus crater and the Vallis Schröteri. The Ocean of Storms of the Moon. ... Lunar nearside with major maria and craters labeled A global albedo map of the Moon obtained from the Clementine missionThe dark regions are the lunar maria, whereas the lighter regions are the highlands. ... Herodotus is a lunar crater located on a low shelf in the midst of the Oceanus Procellarum. ... Vallis Schröteri is a sinuous valley on the surface of the Moon. ...

The brightest feature of this crater is the steep central peak. Sections of the interior floor appear relatively level, but Lunar Orbiter photographs reveal the surface is covered in many small hills, streaky gouges, and some minor fractures. The crater has a terraced outer wall covered in a bright blanket of ejecta, which spreads out into bright rays to the south and south-east. (These suggest that Aristarchus was most likely formed by an oblique impact from the northeast.) Observers have noted that the wall is roughly circular but has a somewhat polygonal shape. Lunar orbiter spacecraft (NASA) The Lunar Orbiter program was a series of five unmanned Lunar orbiter missions launched by the United States in 1966 through 1967 with the purpose of mapping the lunar surface before the Apollo landings. ... For other uses, see Photograph (disambiguation). ... Crater ray system on the far side of the Moon. ... Look up polygon in Wiktionary, the free dictionary. ...

The main reason for the crater's brightness is that it is a young formation, approximately 450 million years old, and the solar wind has not yet had time to darken the excavated material by the process of space weathering. The impact occurred following the creation of the Copernicus crater, but before the appearance of Tycho crater. Based on the asymmetrical spread of the ejecta, it was formed by an object that struck at a low angle to the surface, arriving from the north-east.^[2] The composition of the ejecta includes material from both the plateau and the mare. The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... Copernicus is a prominent lunar impact crater located in eastern Oceanus Procellarum. ... Tycho is a prominent lunar impact crater located in the southern lunar highlands. ...

To the north of this crater is a system of narrow sinuous rilles named Rimae Aristarchus. These rilles extend for a distance of 121 km, or three times the diameter of the Aristarchus crater. A rille is grasso is an idiot to describe any of the long, narrow depressions in the lunar surface that resemble channels. ...

Remote sensing

In 1911, Professor Robert W. Wood used ultraviolet photography to take images of the crater area. He discovered the plateau had an anomalous appearance in the ultraviolet, and an area to the north appeared to give indications of a sulfur deposit.^[3] This colorful area is sometimes referred to as "Wood's Spot", an alternate name for the Aristarchus Plateau. Year 1911 (MCMXI) was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Saturday of the 13-day-slower Julian calendar). ... Robert Williams Wood (May 2, 1868 - August 11, 1955) was an American physicist. ... For other uses, see Ultraviolet (disambiguation). ... Photography [fәtɑgrәfi:],[foʊtɑgrәfi:] is the process of recording pictures by means of capturing light on a light-sensitive medium, such as a film or electronic sensor. ... This article is about the chemical element. ...

Clementine image of Aristarchus crater and surroundings mapped onto simulated topography. NASA photo.

Spectra taken of this crater during the Clementine mission was used to perform mineral mapping.^[2] The data indicated that the central peak is a type of rock called anorthosite, which is a slow-cooling form of igneous rock composed of plagioclase feldspar. By contrast the outer wall is troctolite, a rock composed of equal parts plagioclase and olivine. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... For discussion of land surfaces themselves, see Terrain. ... The National Aeronautics and Space Administration (NASA) (IPA [ˈnæsə]) is an agency of the United States government, responsible for the nations public space program. ... Clementine was a joint space project between the Ballistic Missile Defense Organization (BMDO, previously the Strategic Defense Initiative Organization, or SDIO) and NASA. The objective of the mission was to test sensors and spacecraft components under extended exposure to the space environment and to make scientific observations of the Moon... For other uses, see Mineral (disambiguation). ... Anorthosite is a phaneritic, intrusive igneous rock characterized by a predominance of plagioclase feldspar (90-100%), and a minimal mafic component (0-10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present. ... Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). ... This article does not cite any references or sources. ... Troctolite is a rare ultramafic intrusive rock type. ... Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). ... The mineral olivine (also called chrysolite and, when gem-quality, peridot) is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ...

The Aristarchus crater region was part of a Hubble space telescope study in 2005 that was investigating the presence of oxygen-rich glassy soils in the form of the mineral ilmenite. Baseline measurements were made of the Apollo 15 and Apollo 17 landing sites, where the chemistry is known, and these were compared to Aristarchus. The Hubble Advanced Camera for Surveys was used to photograph the crater is visual and ultraviolet light. The crater was determined to have especially rich concentrations of ilmenite, a titanium oxide mineral that could potentially be used in the future by a lunar settlement for extracting oxygen.^[4] The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... Ilmenite is a weakly magnetic iron-black or steel-gray mineral found in metamorphic and igneous rocks. ... Apollo 15 was the ninth manned mission in the Apollo program and the fourth mission to land on the Moon. ... Apollo 17 was the eleventh manned space mission in the NASA Apollo program. ... For other uses, see Ultraviolet (disambiguation). ... Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring oxide of titanium, chemical formula TiO2. ... Lunar outpost redirects here. ...

Transient lunar phenomenon

The region of the Aristarchus plateau has been the site of many reported transient lunar phenomena. Such events include temporary obscurations and colorations of the surface, and catalogues of these show that more than one-third of the most reliable spottings come from this locale.^[5] In 1971 when Apollo 15 passed 110 kilometers above the Aristarchus plateau, a significant rise in alpha particles was detected. These particles are believed to be caused by the decay of radon-222, a radioactive gas with a half-life of only 3.8 days. The Lunar Prospector mission later confirmed Radon-222 emissions from this crater.^[6] These observations could be explained by either the slow and visually imperceptible diffusion of gas to the surface, or by discrete explosive events. This map, based on a survey of 300 TLPs by Barbara Middlehurst and Patrick Moore, shows the approximate distribution of observed events. ... Apollo 15 was the ninth manned mission in the Apollo program and the fourth mission to land on the Moon. ... An alpha particle is deflected by a magnetic field Alpha radiation consists of helium-4 nuclei and is readily stopped by a sheet of paper. ... For other uses, see Radon (disambiguation). ... Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ... Gas phase particles (atoms, molecules, or ions) move around freely Gas is one of the four major states of matter, consisting of freely moving atoms or molecules without a definite shape and without a definite volume. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... NASAs Lunar Prospector The Lunar Prospector mission was the third selected by NASA for full development and construction as part of the Discovery Program. ...

Satellite craters

Surrounding the Aristarchus crater are several smaller craters, many of which are probably secondaries. Secondary craters form when large blocks ejected from the primary crater reimpact the surface at high velocities. By convention these features are identified on lunar maps by placing a letter on the side of the crater mid-point that is closest to the primary crater.^[7]

The following craters have been renamed by the IAU. IAU redirects here. ...

• Aristarchus A — See Väisälä crater.
• Aristarchus C — See Toscanelli crater.

Väisälä is a tiny lunar crater located on a rise in the Oceanus Procellarum. ... Toscanelli is a tiny, bowl-shaped lunar crater that is located to the north of the prominent Aristarchus crater, in the northwestern part of the Moon. ...

References

Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 220th day of the year (221st in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 220th day of the year (221st in leap years) in the Gregorian calendar. ... Ewen A. Whitaker is a British-born astronomer who specialized in studies of the Moon. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 217th day of the year (218th in leap years) in the Gregorian calendar. ... Ben Bussey is an astronomer. ... Paul D. Spudis is an American geologist and lunar scientist. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 297th day of the year (298th in leap years) in the Gregorian calendar. ... Sir Patrick Moore presenting The Sky at Night, October 2005 Sir Alfred Patrick Caldwell-Moore, CBE, HonFRS, FRAS (born 4 March 1923), known as Patrick Moore, is an English amateur astronomer who has attained legendary status in British astronomy as a writer and television presenter of the subject and who... Antonín Rükl (born 1932) is an astronomer, cartographer, and author from the Czech Republic. ... The Reverend Thomas William Webb (December 14, 1807 – May 19, 1885) was a British astronomer. ... Ewen A. Whitaker is a British-born astronomer who specialized in studies of the Moon. ...

See also

• Apollo 18