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021-The Moon from Clem-Aristachus-PIA00090.jpg042 - Aristarchus Crater (false colors)54 visiteThe Aristarchus region is one of the most diverse and interesting areas on the Moon. About 500 Clementine images acquired through three spectral filters (415, 750, and 1000 nm) were processed and combined into a multispectral mosaic of this region. Shown here is a color-ratio composite, in which the 750/415 ratio controls the red-channel brightness, it inverse (415/750) controls the blue, and the 750/1000 ratio controls the green. Color ratios serve to cancel out the dominant brightness variations and topographic shading, thus isolating the color differences related to composition or mineralogy. The Aristarchus plateau is a rectangular, elevated crustal block about 200 km across, surrounded by the vast mare lava plains of Oceanus Procellarum. Clementine altimetry shows that the plateau is a tilted slab sloping down to the northwest, that rises more than 2 km above Oceanus Procellarum on its southeastern margin. The plateau was probably uplifted, tilted, and fractured by the Imbrium basin impact, which also deposited hummocky ejecta on the plateau surface. The plateau has experienced intense volcanic activity, both effusive and explosive. It includes the densest concentration of lunar sinuous rilles, including the largest known, Vallis Schroteri, which is about 160 km long, up to 11 km wide, and 1 km deep. The rilles in this area begin at 'cobra-head' craters, which are the apparent vents for low-viscosity lavas that formed vents for 'dark mantling' deposit covering the plateau and nearby areas to the north and east. This dark mantling deposit probably consists primarily of iron-rich glass spheres (pyroclastics or cinders), and has a deep red color on this image. Rather than forming cinder cones as on Earth, the lower gravity and vacuum of the Moon allows the pyroclastics to travel much greater heights and distances, thus depositing an extensive regional blanket. The Aristarchus impact occurred relatively recently in geologic time, after the Copernicus impact but before the Tycho impact. The 42 km diameter crater and its ejecta are especially interesting because of its location on the uplifted southeastern corner of the Aristarchus plateau. As a result, the crater ejecta reveal two different stratigraphic sequences: that of the plateau to the northwest, and that of the portion of Oceanus Procellarum to the southwest. This asymmetry is apparent in the colors of the ejecta as seen in this image, which is reddish to the southeast, dominated by excavated mare lava, and bluish to the northwest, caused by the excavation of highland materials in the plateau. The extent of the continuous ejecta blanket also appears asymmetric: it extends about twice as far to the north and east than in other directions, approximately following the plateau margins. These ejecta lobes could be caused by an oblique impact from the southeast, or it may reflect the presence of the plateau during ejecta emplacement. Two dark blue spots in the center of Aristarchus represent tan especially interesting discovery. The infrared spectral properties measured by Clementine are consistent with a composition of almost pure anorthosite, the primitive rock type produced by the lunar magma ocean. This is the first discovery of a major exposure of anorthosite in this region of the Moon, well within the boundary of the hypothetical Procellarum basin. Don Wilhelms (Geologic History of the Moon, USGS Professional Paper, 1984) proposed that the giant Procellarum basin entirely removed the upper anorthositic crust from the north-central nearside of the Moon.
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033-The Moon from Clem-Aristarchus-3.jpg041 - Aristarchus and Vallis Schroteri55 visiteThe plateau of the Aristarchus Crater has experienced intense volcanic activity, both effusive and explosive.
It includes the densest concentration of Lunar "sinuous rilles" ("snake-like" valleys) including the largest known, Vallis Schroteri, which is about 160 km long, up to 11 km wide and 1 km deep.
The rilles in this area begin at cobra-head craters, which are the apparent vents for a dark mantling deposit covering the plateau and nearby areas to the North and East.
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15-S-Aristarchus Crater-3D.jpgAristarchus Crater, from Lunar Orbiter 5 (3D)86 visiteUno splendido frame, arricchito dalla tridimensionalità, per uno dei crateri più belli e misteriosi della nostra Luna.
Da vedere con attenzione.
Original caption:"Stereoscopic view of the crater Aristarchus, 40 km across and about 3.6 km deep. The floor is partially covered with material that slumped down the walls; its eastern portion (toward the top of the page), being least covered by this material, is the lowest and smoothest part. A long narrow central peak rises 300 meters above the floor. Note the terracing of the inner crater walls and also the elevation of the rim crest above the outer ejecta blanket".
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APOLLO 15 AS 15 82-11086~0.jpgAS 15-82-11086 - Sphere and Star-like Object (1)361 visiteSu segnalazione dell'Amico Lettore Lorenzo Leone - il quale ha dato prova di aver esaminato con attenzione non solo il frame in HR proposto sulle nostra pagine, ma anche la versione "raw-LR" degli Archivi NASA - siamo andati a rivedere il frame in oggetto alla ricerca di due possibili Anomalìe: una (forse) di superficie, ed una orbitale. Ebbene, dopo aver visionato il frame AS 82-11806 nella sua versione "non restaurata" - che ora pubblichiamo - dobbiamo che dire che il Sig. Leone, a nostro parere, ha visto giusto.
C'è qualcosa che "brilla", infatti, sulla superficie della Luna (o in "volo radente"?!?) sulla Sx del frame e c'è uno star-like object di notevoli dimensioni all'estrema Dx. Si tratta di photo-artifacts, poi eliminati dal processo di pulizia e restauro del frame NASA Originale (pulizia e restauro operati da Kipp Teague), oppure sono oggetti reali che l'opera di raffinazione del frame originale ha finito con il "lavar via", come si dice in gergo (wash-away)?
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APOLLO 15 AS 15 82-11086~1.jpgAS 15-82-11086 - Sphere and Star-like Object (2)684 visiteInutile dire che non è ci possibile dare risposte assolute ad un simile quesito e che l'unica strada percorribile, a nostro parere, è quella del buon senso e dell'esperienza.
Come sapete, la visione migliore di quanto ripreso dagli Astronauti è negli Original Uncompressed Frames (che sono diventati difficilissimi da ottenere da quando i Responsabili LPI - Lunar and Planetary Institute - hanno deciso (li citiamo) di "...non perdere più tempo per assecondare le richieste (di frames NASA-Apollo originali non compressi) che arrivano da Ricercatori Indipendenti...").
La versione restaurata ed in HR dei frames NASA-Apollo originali, spesso, è ingannevole e volta alla cancellazione del dettaglio. D'altra parte, i frames originali ma ultra-compressi, sono - purtroppo - autentiche fucìne di photoartifacts. Ciò premesso, facciamo un grande complimento al Sig. Leone per l'attenzione, il metodo e l'acutezza dimostrata; relativamente a quello che si vede in questo frame, perdonateci, ma siamo immersi nei dubbi. Ad ogni modo, sia per esperienza, sia "d'istinto", diremmo che lo star-like object di Dx può essere un photo-artifact, mentre la sfera sulla Sx sembra proprio un oggetto reale...
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APOLLO 15-0326.jpgAPOLLO 15-0326 - Aristarchus61 visiteAristarchus is a large crater on the edge of a plateau within Northern Oceanus Procellarum. In this scene the crater is viewed obliquely from the North. One of the brightest and youngest craters of its size on the Near-Side of the Moon, Aristarchus is believed to be younger even than Copernicus. The general appearance of Aristarchus and of parts of the plateau around it led Alfred Worden, the Apollo 15 CMP, to describe this part of the Moon as "... probably the most volcanic area that I've seen anywhere on the surface". For many years before the Apollo Missions, Earth-based viewers had reported telescopic sightings of TLP's centered on Aristarchus. These brief, subtle changes in color or in sharpness of appearance have been suggested as evidence for volcanic activity or the venting of gases from the lunar interior. The sightings are controversial, but Aristarchus remains a center of interest.
About 39 Km in diameter, Aristarchus is on the borderline between medium-sized and large- sized craters. We have included it among the large craters because its welldeveloped concentric terraces are characteristic of most large craters that have not been too severely degraded. Its terraced walls, as well as its arcuate range of central peaks, are particularly well shown in this view. The walls and parts of the crater floor are extremely rough and cracked, a characteristic feature of other young impact craters of this size range, such as Tycho and Copernicus. The rough deposits in the floor are probably made up largely of shockmelted material formed at the time of the impact. The inner, rougher portions of the rim show a series of channels, lobate flows, and smooth puddlelike deposits that may represent shock-melted material deposited on the crater rim. The outer, smoother portions show the rhomboidal pattern characteristic of crater ejecta blankets.
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APOLLO_15_AS_15-88-12002_(True_Colors).jpgAS 15-88-12002 - Aristarchus and Herodotus (True Colors; credits: Dr Marco Faccin)78 visiteUna elaborazione in Colori Veri della Regione dei grandi Crateri Aristarco ed Erodoto realizzata dal Dr Faccin. Un solo commento: FANTASTICA!MareKromium
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APOLLO_15_AS_15-96-13050.jpgAS 15-96-13050 - Aristarchus (natural colors; credits: Lunexit)95 visitenessun commentoMareKromium
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APOLLO_15_AS_15-M-R71-2611.jpgAS 15-M-R71-2611 - Aristarchus and Herodotus Crater (the NASA/Lunar & Planetary Institute Original Frame)54 visiteCoord.: 25,5° North Lat. and 50,5° West Long.
Lens Focal Length: 3"
Camera Tilt: 40°
Camera Azimuth: 180
Camera Altitude: 107 Km
Sun Elevation (on local horizon): 15°
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LRO-2500-Aristarchus_Crater_Wall-LROC_2000-PCF-LXTT.jpgFeatures of Aristarchus Crater (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)154 visiteAristarchus is a prominent Lunar Impact Crater that lies in the North/Western portion of the Moon's Near Side. It is considered the brightest of the large formations on the Lunar Surface, with an Albedo that is nearly two times brighter that the one of most of the Lunar Features. In fact, Aristrachus is bright enough to be visible to the naked eye, and it becomes dazzling in a large telescope. It is also relatively easy to identify when most of the Lunar Surface is illuminated by the Earthshine.
This Crater lies at the South/Eastern Edge of the Aristarchus Plateau: an elevated rocky rise located within the Oceanus Procellarum and that contains a number of Volcanic Features and that is also well known for the occurrence of a large number of reported Transient Lunar Phenomena (or TLP), as well as for very recent emissions of Radon Gas (emission which were duly registered and measured by the Lunar Prospector Spacecraft). As additional reference points, we remind you that Aristarchus Crater is located just to the East of the Crater Herodotus and the Vallis Schröteri, and South of a system of narrow Sinuous Rilles named Rimae Aristarchus. Probably, the main reason for Aristarchus' brightness is that it is a (relatively, of course) young formation (such as approximately 450 Million Years old) and so the Solar Wind has not yet had enough time to darken the excavated material via the process known as "Space Weathering". The impact which created Aristarchus likely occurred after the creation of the Rayed Crater Copernicus, but some time before the appearance of the Crater Tycho.
Aristarchus was originally named after the Greek Astronomer Aristarchus of Samos, by the Italian map maker Giovanni Riccioli. His work "Almagestum Novum", published in 1651, gave to the, in that time known "spot-shaped telescopic features" (such as the Impact Craters) the eponyms of famous Astronomers and Philosophers. Although the name of Aristarchus Crater has always been widely accepted and adopted, it actually did not become "official" (from an International point of view), until the International Astronomical Union (IAU) so decided to name it, during a General Assembly that was taken in the AD 1935.
As we already wrote hereabove, the Region of the Aristarchus Plateau (and the Crater Aristarchus in particular) has been (and still is) the site of many reported Transient Lunar Phenomena, with a total of 122 reports by the AD 2007: the highest recorded for any Lunar Feature.
Such a TLPs include, among others, Temporary Obscurations and Colorations of the Surface; the appearence of Star-like Shinings (either fixed or slightly moving) as well as isolated Flashes of Red, Blue or even Green light. Official Catalogues mentioning these TLPs show that more than one-third of the most reliable observations came from Aristarchus Crater and its immediate surroundings.
In 1971, when the NASA Apollo 15 Spacecraft passed at about 110 Km from the Surface of the Aristarchus Plateau, a significant rise in Alpha Particles was detected and these particles are thought to be caused by the presence of huge amounts, in the area, of Radon-222: a radioactive and colorless Noble Gas that forms naturally during and as part of the normal Decay Chain of Uranium or Thorium; the Radon -222 possesses a so-called "half-life" of only 3,8 days.
The Lunar Prospector Mission later confirmed Radon-222 emissions from Aristarchus. Some of these fascinating (and still not totally understood) observations could be explained by the occurrence of discrete Explosive Events (Outgassings).MareKromium
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ORIGINAL NASA - APOLLO 15 - AS 15-88-12005.JPGAS 15-88-12005 - Aristarchus and Herodotus54 visite
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SOL643-PIA03613_fig1.jpgSpirit's search for meteors - Sol 64362 visiteSi vedano i commenti (nonchè la Original Caption) riportati nelle note al frame relativo al Sol 668.
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