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| Ultimi arrivi - Uranus and His Moons |
AB-Ariel-V2-PIA01351.jpgAriel, from 2,52 MKM62 visiteCaption NASA originale:"Distinct bright patches are visible on Ariel, the brightest of Uranus' 5 largest satellites. Voyager 2 obtained this image Jan. 22, 1986, from a distance of 2,52 MKM (1,56 MMs). The clear-filter image, obtained with the narrow-angle camera, shows a resolution of 47 Km (approx. 29 miles). This image shows several distinct bright areas that reflect nearly 45% of the incident sunlight; on average, the satellite displays a reflectivity of about 25-30%. The bright areas are probably fresh water ice, perhaps excavated by impacts. The South Pole of Ariel is slightly off center of the disk in this view. Voyager 2 obtained its best views of the satellite on Jan. 24, 1986 at a closest-approach distance of about 127.000 km (approx. 79.000 mi)". Mar 15, 2005
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Miranda-PIA00140.jpgMiranda, from approx. 31.000 Km72 visiteCaption NASA originale:"This Voyager 2 image of Miranda was taken Jan 24, 1986, from a distance of about 31.000 Km (19.000 miles), shortly before the spacecraft's closest approach to the Uranian moon. The HR of 600 meters (2.000 feet) reveals a bewildering variety of fractures, grooves and craters, as well as features of different albedos (reflectancea). This clear-filter, narrow-angle view encompasses areas of older, heavily cratered terrain with a wide variety of forms. The grooves and troughs reach depths of a few Km (or miles) and expose materials of different albedos. The great variety of directions of fractures and troughs, and the different densities of impact craters on them, signify a long, complex geologic evolution of this satellite".Mar 15, 2005
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Miranda-PIA02217.jpgMiranda63 visiteCaption NASA originale:"Mosaic of HR images of Miranda. One wide-angle and eight narrow-angle camera images of Miranda were combined in this view. The controlled mosaic was transformed to an orthographic view centered on the South Pole. The trapezoidal region (about 200 Km on a side) occurs near the South Pole and is located near the center of the mosaic. The trapezoid's outer boundary and its internal patterns of ridges and band of contrasting albedo display numerous sharp corners".Mar 15, 2005
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Uranus-familyportrait-PIA01975_modest.jpgThe 5 major moons of Uranus59 visiteThis "family portrait" of Uranus' 5 largest moons was compiled from images sent back Jan. 20, 1986, by Voyager 2 spacecraft. The pictures were taken through a clear filter from distances of 5 to 6,1 MKM (3,1 to 3.8 MMs). In this comparison, we see the relative sizes and relativities of the satellites. From left, in order of increasing distance from the planet, they are Miranda, Ariel, Umbriel, Titania and Oberon. The 2 largest, Oberon and Titania, are about half the size of Earth's Moon, or roughly, 1.600 Km (1.000 miles) in diameter. Miranda, smallest of the 5, has about one-quarter to one-third the diameter. Even in these distant views, the satellites exhibit distinct differences in appearance. On average, Oberon and Titania reflect about 20% of the sunlight, Umbriel about 12%, Ariel and Miranda about 30%. Ariel shows the largest contrast on its surface, with the brightest areas about 25%. All five satellites show only slight color variations on their surfaces, with their average color being very nearly gray. The best views of the satellites will be obtained Jan. 24, the day of closest approach.Mar 15, 2005
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Miranda-PIA02218.jpgNot only Verona Rupes: more deep scarps on Miranda (HR)63 visiteCaption NASA originale:"View of Miranda showing light and dark banded scarps near the boundary of the banded ovoid and a deep graben that bounds the ovoid in this region".Mar 15, 2005
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Oberon-V2-PIA00034_modest.jpgOberon, from 660.000 Km - Voyager 256 visiteCaption NASA originale:"This Voyager 2 picture of Oberon is the best the spacecraft acquired of Uranus' outermost moon. The picture was taken shortly after 3:30 a.m. PST on Jan. 24, 1986, from a distance of 660.000 Km. The color was reconstructed from images taken through the narrow-angle camera's violet, clear and green filters. The picture shows features as small as 12 Km on the moon's surface. Clearly visible are several large impact craters in Oberon's icy surface surrounded by bright rays similar to those seen on Jupiter's moon Callisto. Quite prominent near the center of Oberon's disk is a large crater with a bright central peak and a floor partially covered with very dark material. This may be icy, carbon-rich material erupted onto the crater floor sometime after the crater formed. Another striking topographic feature is a large mountain (vedi il frame "Oberon's Peak"), about 6 km high, peeking out on the lower left limb".
Feb 10, 2005
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VP-URANUS-PIA01360.jpgUranus in natural colors55 visiteCaption NASA originale"These 2 pictures of Uranus were compiled from images recorded by Voyager 2 on Jan. 1O, 1986, when the NASA spacecraft was 18 MKM (11 MMs) from the Planet. The images were obtained by Voyager 2 narrow-angle camera; the view is toward the planet's pole of rotation, which lies just left of center. The picture on the left has been processed to show Uranus as human eyes would see it from the vantage point of the spacecraft. The second picture is an exaggerated false-color view that reveals details not visible in the true-color view - including indications of what could be a polar haze of smog-like particles. The true-color picture was made by combining pictures taken through blue, green and orange filters. The dark shading of the upper right edge of the disk is the terminator, or day-night boundary. The blue-green appearance of Uranus results from methane in the atmosphere; this gas absorbs red wavelengths from the incoming sunlight, leaving the predominant bluish color seen here".Feb 01, 2005
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VO-Uranus-PIA00032.jpgUranus in natural and false colors56 visiteCaption NASA originale:"These two pictures of Uranus - one in true color (left) and the other in false color - were compiled from images returned Jan. 17, 1986, by the narrow-angle camera of Voyager 2. The spacecraft was 9,1 MKM (5,7 MMs) from the planet, several days from closest approach. The picture at left has been processed to show Uranus as human eyes would see it from the vantage point of the spacecraft. The picture is a composite of images taken through blue, green and orange filters. The darker shadings at the upper right of the disk correspond to the day-night boundary on the planet. Beyond this boundary lies the hidden northern hemisphere of Uranus, which currently remains in total darkness as the planet rotates.
The blue-green color results from the absorption of red light by methane gas in Uranus' deep, cold and remarkably clear atmosphere. The picture at right uses false color and extreme contrast enhancement to bring out subtle details in the polar region of Uranus. Images obtained through ultraviolet, violet and orange filters were respectively converted to the same blue, green and red colors used to produce the picture at left. The very slight contrasts visible in true color are greatly exaggerated here. In this false-color picture, Uranus reveals a dark polar hood surrounded by a series of progressively lighter concentric bands. One possible explanation is that a brownish haze or smog, concentrated over the pole, is arranged into bands by zonal motions of the upper atmosphere. The bright orange and yellow strip at the lower edge of the planet's limb is an artifact of the image enhancement. In fact, the limb is dark and uniform in color around the planet".Feb 01, 2005
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Miranda-PIA00038_modest.jpg"Chevron grooves" on Miranda - HR86 visiteCaption NASA originale:"This image of Miranda, obtained by Voyager 2 on approach, shows an unusual 'chevron' figure and regions of distinctly differing terrain on the Uranian moon. Voyager was 42.000 Km (26.000 miles) away when its narrow-angle camera acquired this clear-filter view. Grooved areas baring light and dark bands, distinct from other areas of mottled terrain, are visible at this resolution of about 600 meters (2.000 feet). The bright V-shaped feature in the grooved areas is the 'chevron' observed in earlier, lower-resolution images. Cutting across the bands are sinuous scarps, probably faults. Superimposed on both types of terrain are many bowl-shaped impact craters less than 5 Km (3 mi) wide. The entire picture spans an area about 220 Km (140 mi) across". Gen 13, 2005
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Miranda-PIA00044_modest.jpgMiranda (super close-up of "Verona Rupes") - HR101 visiteCaption NASA originale:"This HR image of Miranda was acquired by Voyager 2 on Jan. 24, 1986, when the spacecraft was 36.250 Km (22.500 miles) from the Uranian moon. In this clear-filter, narrow-angle image, Miranda displays a dramatically varied surface. Well shown at this resolution of 660 meters (2.160 feet) are numerous ridges and valleys - a topography that was probably produced by compressional tectonics. Cutting across the ridges and valleys are many faults. The largest fault scarp, or cliff, is seen below and right of center; it shows grooves probably made by the contact of the fault blocks as they rubbed against each other (leaving what are known as slickensides). Movement of the down-dropped block is shown by the offset of the ridges. The fault may be 5 Km (3 mi) high, or higher than the walls of the Grand Canyon on Earth. NASA's Voyager 2 probe encountered the planet Uranus and its collection of moons in 1986. The small moon Miranda, with a diameter of 472 km, has a surface made up of a jumble of bizarre geological features. One of the most prominent of these features is an enormous cliff with a vertical relief of about 20 km (12 miles). This cliff, named Verona Rupes, is 10 times higher than the walls of the Grand Canyon on Earth. That this towering cliff is so huge is made even more remarkable by the small size of Miranda itself. The white material exposed in the cliff face is probably mostly water ice". Gen 13, 2005
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Miranda-PIA01354_modest.jpgMiranda (close-up of the Verona Rupes Region) - HR81 visiteCaption NASA originale:"Miranda, innermost of Uranus' large satellites, is seen at close range in this Voyager 2 image, taken Jan. 24, 1986, as part of a HR mosaicing sequence. Voyager was some 36.000 Km (22.000 miles) away from Miranda. This clear-filter, narrow-angle image shows an area about 250 Km (150 mi) across, at a resolution of about 800 meters (2.600 feet). Two distinct terrain types are visible: a rugged, higher-elevation terrain (right) and a lower, striated terrain. Numerous craters on the rugged, higher terrain indicate that it is older than the lower terrain. Several scarps, probably faults, cut the different terrains.
The impact crater in the lower part of this image is about 25 Km (15 mi) across".Gen 13, 2005
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Miranda-PIA00042_modest.jpgMiranda in natural colors (elab. NASA)83 visiteCaption NASA originale:"This color composite of the Uranian satellite Miranda was taken by Voyager 2 on Jan. 24, 1986, from a distance of 147.000 Km (91.000 miles). This picture was constructed from images taken through the narrow-angle camera's green, violet and ultraviolet filters. It is the best color view of Miranda returned by Voyager. Miranda, just 480 Km (300 mi) across, is the smallest of Uranus' 5 major satellites. Miranda's regional geologic provinces show very well in this view of the Southern Hemisphere, imaged at a resolution of 2,7 km (1,7 mi). The dark and bright-banded region with its curvilinear traces covers about half of the image. HR pictures taken later show many fault valleys and ridges parallel to these bands. Near the terminator (at right), another system of ridges and valleys abuts the banded terrain; many impact craters pockmark the surface in this region. The largest of these are about 30 Km in diameter; many more lie in the range of 5 to 10 Km in diameter". Gen 13, 2005
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