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Nereid-V2-PIA00054.jpgNereid55 visiteUn'immagine certo non magnifica, ma di grande valore e molto rara: si tratta di Nereide, la seconda delle due Lune Maggiori di Nettuno. I dettagli che possono percepirsi da questa fotografia ottenuta dal Voyager 2 sono troppo indefiniti per poter azzardare delle valutazioni, ma l'ipotesi più probabile relativamente alle fattezze di Nereide, è che si tratti di un piccolo mondo fatto di roccia e ghiaccio, dalla forma irregolare, ricoperto di crateri da impatto e costellato da crepacci che ne rendono la superficie completamente inospitale.
Forse, come sostengono alcuni Scienziati, si potrebbe trattare di un KBO catturato da Nettuno in tempi assai remoti.
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Nereid-vg2_1138148.jpgNereid (HR)54 visitenessun commento
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PROTEUS.jpgProteus75 visiteUna luna minore del Sistema di Nettuno: Proteus.
Caratterizzata da una forma solo vagamente sferica, questa luna presenta un gigantesco - e facilmente visibile - cratere da impatto in prossimità del suo Polo Nord (fotografico).
Forse è proprio questo cratere la "cicatrice" generata dall'urto che ha spinto "Proteus" al di fuori dalla Fascia di Kuiper e poi verso Nettuno, dalla cui gravità è stato infine catturato.
Un probabilissimo KBO, dunque, o - come dicono alcuni - un Trans Neptunian Object.
O forse una cometa mancata.
Forse.
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Proteus-vg2_1138920.jpgProteus (HR)54 visitenessun commento
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Proteus2.jpgProteus (HR)55 visitenessun commento
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TRITON.jpgTriton from Voyager 2 (enhanced real colors)101 visiteLa superficie di Tritone, come ripresa dal Voyager 2, in colori reali ma con esaltazione dei contrasti.
Canali, crepacci, montagne e grandi crateri da impatto sono facilmente visibili, al pari di una strana distesa semi-pianeggiante che interrompe nettamente e bruscamente il paesaggio del pianeta, facendolo passare dall'estremamente accidentato e montuoso al (relativamente) liscio e pianeggiante. Forse questo paesaggio così affascinante ed "alieno" è il prodotto di eventi sismici aventi carattere planetario e risalenti alla "gioventù" del corpo celeste.
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TRITON2.jpgTriton from Voyager 2 (enhanced real colors)78 visiteUn dettaglio della superficie di Tritone, sempre ripresa dal Voyager 2 (da notare che le gradazioni di colore e, conseguentemente, la qualità del dettaglio e dei particolari, sono state artificiosamente accentuate/i).
Una curiosità: a quanto è stato possibile accertare sino ad ora, le caratteristiche morfologiche superficiali di Tritone sembrano davvero molto simili a quelle di Plutone. Due mondi simili (due KBOs?) con un comune passato remoto e che, magari, sono destinati ad un comune lontano futuro...
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Triton-PEI.jpgMoments of Triton...56 visiteThis set of images shows the best views of Neptune's moon Triton taken by Voyager 2 as the spacecraft withdrew from the Neptune system on August 25, 1989. The top four images were constructed from various color image bands as Voyager receded from Triton.
The third image from the left is sharper than the other four, because it was taken with the Narrow Angle Camera, with Triton filling two thirds of the frame. The thin crescent first image, while much closer, spanned about a quarter of the frame. The second image was somewhat smaller, and the last was very small. The first of the four images was composed of Blue, Green, and Orange filter images. The second utilized Violet, Green, and Orange Filtered images. In both composites, the Orange image was of poorer quality. In the fourth image, no orange was available, and the green and blue images were badly smeared, though somewhat salvageable. A clear filtered image (also smeared) was substituted for orange. They were combined and used as a color overlay for a slightly overexposed, but sharp clear filtered view. The third image is composed of a Violet and a Green wide-angle image. Like all the images in the first and second composites, and like the images used to color the fourth composite, these images were underexposed. However, they were very sharp. The orange image came from a poor quality wide angle orange image. The resulting color image was combined with a well exposed clear filter image to provide the detail
The Narrow Angle images used in these mosaics were the first obtained after closest approach, with the exception of a single clear filter image obtained while the disk was about twice as big as what could be framed in the camera's field of view. It is very noisy, and by far the worst underexposure of them all, and could not be processed to the point in which the whole image could be made presentable. However, a few sections were salvaged. The first (lower left) was binned to make up for noisiness and sharpened. It was then merged with the color data from the third image above. A cloud can be seen near the limb. To its right is an image of the cloud that has not been as heavily processed. The cloud itself is better presented, as it was far brighter than the surrounding area and hence more securely detected. Its shadow can be faintly made out to its right.
The next two images are the same, but one to the right was merged with color data. The image is towards the center of the crescent, the brightest area, in which white spots can be seen. Although a few of them may be impact craters, this area, as most of the crescent, is over the south polar cap, and thus frost covered, and the appearance of this area most closely resembles the cantaloupe terrain seen on the other hemisphere before closest approach. The final image (lower right) hints of surface topography near the terminator. It seems it is one of the more rugged parts of Triton. The large, foreshortened circular feature slightly below the center of the image is a dimple similar those found in the cantaloupe terrain. The other features are too ambiguous to determine whether or not they are of the same nature.
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Triton-PIA00056_modest.jpgTriton's limb56 visiteCaption NASA originale:"Voyager 2 acquired this black and white image of Triton, Neptune's largest satellite, during the night of Aug. 24-25, 1989. Triton's limb cuts obliquely across the middle of the image. The field of view is about 1.000 Km (600 miles) across. Three irregular dark areas, surrounded by brighter material, dominate the image. Low-lying material with intermediate albedo occupies the central area, and fresh craters occur along the right margin. Sub-parallel alignment of linear patches of dark material shown in the lower and left part of the image suggests that the patches are structurally controlled".
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Triton-PIA00059_modest.jpgThe South Polar Region of Triton: "dark plumes" and "seasonal winds"55 visiteCaption NASA originale:"This image of the South Polar terrain of Triton, taken on Aug. 25, 1989 reveals about 50 dark plumes or 'wind streaks' on the icy surface. The plumes originate at very dark spots generally a few miles in diameter and some are more than 100 miles long. The spots which clearly mark the source of the dark material may be vents where gas has erupted from beneath the surface and carried dark particles into Triton's nitrogen atmosphere. Southwesterly winds then transported the erupted particles, which formed gradually thinning deposits to the northeast of most vents. It is possible that the eruptions have been driven by seasonal heating of very shallow subsurface deposits of volatiles and the winds transporting particles similarly may be seasonal winds. The polar terrain, upon which the dark streaks have been deposited, is a region of bright materials mottled with irregular, somewhat dark patches. The pattern of irregular patches suggests that they may correspond to lag deposits of moderately dark material that cap the bright ice over the polar terrain".
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Triton-PIA00061_modest.jpgTriton's Northern Hemisphere in HR55 visiteCaption NASA originale:"This is one of the most detailed views of the surface of Triton taken by Voyager 2 on its flyby of the large satellite of Neptune early in the morning of Aug. 25, 1989. The picture was stored on the tape recorder and relayed to Earth later. Taken from a distance of only 40.000 Km (25.000 mi), the frame is about 220 Km (140 miles) across and shows details as small as 750 meters (0.5 miles). Most of the area is covered by a peculiar landscape of roughly circular depressions separated by rugged ridges. This type of terrain, which covers large tracts of Triton's Northern Hemisphere, is unlike anything seen elsewhere in the Solar System. The depressions are probably not impact craters: they are too similar in size and too regularly spaced. Their origin is still unknown, but may involve local melting and collapse of the icy surface. A conspicuous set of grooves and ridges cuts across the landscape, indicating fracturing and deformation of Triton's surface. The rarity of impact craters suggests a young surface by solar system standards, probably less than a few billion years old".
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Triton-PIA00317-PCF-LXTT-IPF.jpgThe Southern Regions of Triton (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)76 visiteThis wonderful and highly detailed global Absolute Natural Color image mosaic of Triton was obtained in the AD 1989 by the NASA - Voyager 2 Spacecraft during its Fly-By of the Neptunian System.
With a radius of approx. 1350 Km (such as a little more than 838 miles) and therefore some 22% smaller than Earth's Moon, Triton is by far the largest Natural Satellite of Neptune. Furthermore, Triton is one of the only 3 (three) objects in the Solar System known to have a Nitrogen-dominated Atmosphere (the others are our Home Planet Earth and the Saturnian giant moon, Titan). Triton has the coldest Surface known anywhere in the Solar System (38 K, or about - 391 degrees Fahrenheit, or - 235° Celsius): it is so cold that most of Triton's Nitrogen is condensed as Frost, making it the only Celestial Body in the whole Solar System that is known to have a Surface mainly composed of Nitrogen Ice.
The pinkish deposits constitute a vast South Polar Cap, that is believed to contain Methane Ice, which somehow reacted under Sunlight so to form pink or red Compounds. The Dark Streaks overlying these pink ices are believed to be an Icy and - perhaps - Carbonaceous Dust deposited from huge Geyser-like Plumes, some of which were found to be active during the Voyager 2 Fly-By. The light gray colored band visible in this image extends all the way around Triton, near the Equator and it may consist of relatively fresh Nitrogen Frost Deposits. The vaguely greenish areas of Triton (central and upper right side) include what is known as "The Cantaloupe Terrain", whose origin is still unknown, and a set of "Cryovolcanic" Landscapes apparently produced by Icy-cold Liquids (now totally frozen) that were erupted from Triton's interior.
This frame (which is the Original NASA - Voyager 2 color image mosaic published on the NASA - Planetary Photojournal with the ID n. PIA 00317) has been additionally processed and then re-colorized, according to an educated guess carried out by Dr Paolo C. Fienga (LXTT-IPF), in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Voyager 2 Spacecraft and then looked outside, towards the Neptunian moon Triton), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among others, the existence of different Elements present on the Surface of Triton, each having a different Albedo (---> Reflectivity) and Chemical Composition.MareKromium
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