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| Piú viste - Uranus and His Moons |
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".
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UMBRIEL-PIA00040-PCF-LXTT-IPF.jpgUmbriel (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)71 visiteThe Southern Hemisphere of the Uranian moon Umbriel displays heavy Cratering in this NASA - Voyager 2 image, taken on January 24, 1986, at a distance of approx. 557.000 Km (such as a little less than 346.000 miles) from the Surface of the moon. This frame, taken through the Clear-Filter of Voyager's Narrow-Angle Camera, is the most detailed image of Umbriel that we have, with a resolution of about 10 Km (such as 6,21 miles) per picture element.
Umbriel is the darkest of Uranus' larger moons and the one that appears to have experienced the lowest level of Geological Activity. It has a diameter of about 1200 Km (a little more than 745 miles) and its Surface reflects only 16% of the light that receives; in the latter respect, Umbriel is similar to the Lunar Highland Areas of our own Moon. Umbriel, as we wrote herebefore, is heavily cratered, but it lacks the numerous Bright-Ray Craters that are commonly seen on the other large Uranian Natural Satellites; this fact, among other things, results in a relatively uniform Surface Albedo (---> Reflectivity).
The prominent Impact Crater visible on the Terminator (at about 11 o'clock of Umbriel's disk) is approx. 110 Km (such as 68,3 miles) across and it shows a really bright Central Peak. On the other hand, the strangest Surface Feature visible in this image (on the Limb of Umbriel, right at 12 o'clock of the disk) is a curious-looking Bright Ring which represents the most reflective area seen on Umbriel itself. The Bright Ring is about 140 Km (approx. 87 miles) in diameter and it lies near the moon's Equator. The nature of the Bright Ring is unknown, although it might be a very large Frost Deposit, perhaps associated with (located on top and near) the Rim of a huge Impact Cater. The few white spots that can be barely seen against the black background are not stars, but just just image artifacts, due to 'noise' in the data received on Earth.
This frame (which is the Original NASA - Voyager 2 b/w image published on the NASA - Planetary Photojournal with the ID n. PIA 00040) has been additionally processed and then 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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Miranda-vg2_2684617-B.jpgThe beautiful "Verona Rupes" from a different angle (detail mgnf)68 visiteUn detail mgnf dedicato ad un frame raro e stupendo che ci rammenta (ancora una volta) una delle Meraviglie del Sistema Solare: le Verona Rupes.
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Oberon-PIA01352-PCF-LXTT-IPF.jpgIcy Oberon (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunar Explorer Italia/Italian Planetary Foundation)68 visiteUranus' outermost and largest moon, Oberon, can be very well seen in this NASA - Voyager 2 frame which was obtained January, 22, 1986, from a distance of approx. 2,77 Million KiloMeters (such as a little more than 1,72 Million Miles). The Clear-Filter Image, shuttered by the Voyager's Narrow-Angle Camera, shows us that Oberon displays several distinct Highly Reflective (---> High-Albedo) "Patches" of its Surface which also show - and this circumstance still sounds kind of strange/unusual - very Low-Albedo Centers. Some of the bright Patches are suggestive of Radial Patterns that could represent the visible consequence of powerful Impact Events which occurred on a basically Ice-rich Surface (in other words, we may be looking at Rayed Impact Craters that formed - were excavated - on an extremely hard and frozen Surface) .
On average, Oberon reflects (in all directions) only about 20% (twenty-percent) of the Incident Sunlight and that fact makes it Celestial Body with a (relatively) Low Albedo. The moon is about 1600 Km (such as approx. 993,6 miles) in diameter; the resolution of this image is roughly 51 Km (such as about 31,67 miles) per pixel. This frame was taken 2 (two) days before Voyager's 2 Closest Approach to Oberon (at which point the Spacecraft flew-by Oberon at a distance of approx. 471.000 Km - such as about 292.491 miles - from its frozen Surface).
This frame (which is an Original NASA - Voyager 2 Spacecraft Natural Color image published on the NASA - Planetary Photojournal with the ID n. PIA 01352) has been additionally processed, contrast enhanced, magnified to aid visibility of the Surface details and then re-colorized, according to an educated guess carried out by Dr Paolo C. Fienga/LXTT/IPF, in what they should be its 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 Uranian moon Oberon), 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 Oberon, each having a different Albedo (---> Reflectivity) and Chemical Composition.
Note 1: it is possible (but we, as IPF, have no way to be one-hundred-percent sure of such a circumstance), that the actual luminosity of Oberon - as it is in this frame - would appear, to an average human eye, a little bit lower than it has been shown (or, better yet: interpreted) here.
Note 2: the "squared" feature visible at about 4 o'clock of Oberon's disk (almost on the Limb of the moon and right on the Terminator Line), is just an original image defect.MareKromium
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AAA-vg2_2684726.gifFlying over Uranus...67 visiteOriginal caption:"Image of Uranus taken by Voyager 2 about 21 minutes before closest approach. This image, centered at 4° South, 58° West, was taken with the wide angle camera. The frame is approx. 5.300 km from top to bottom and north is at 1:00. (Voyager 2, 26847.26)".
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AB-Ariel-vg2_p29523.jpgAriel (HR)67 visitenessun commento
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VG-Desdemona-V2.jpgDesdemona - Voyager 266 visitenessun commento
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VH-Juliet-V2.jpgJuliet - Voyager 266 visitenessun commento
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VE-Caliban.jpgCaliban66 visiteUna "Luna Minore" di Urano, Calibano, persa fra le stelle ed individuabile solo grazie alla "cerchiatura" bianca inserita in questa (comunque molto bella) immagine.
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Ariel.jpgAriel (HR)66 visiteLa tormentata superficie di Ariel si rivela in tutto il suo (comunque grande) fascino.
Una serie di impressionanti fratture tettoniche (forse un raffreddamento troppo rapido?) caratterizza l'Est e l'Ovest di questo mondo lontano; svariati mega-canyons, lunghi e profondi, passano attraverso l'equatore di Ariel, frammentandosi e ramificandosi poi in centinaia di crepacci minori; distese simili ai "mari" della Luna contraddistinguono una buona parte della sua superficie la quale, inoltre, sembra avere delle aree (alla Vostra Sx - Eastern limb) la cui albedo (alta) appare molto diversa rispetto al resto del Pianeta.
Da notare che, a differenza di quanto accade per le altre lune di Urano (come per la maggior parte delle lune dei quattro Giganti Gassosi), non riusciamo a distinguere che un modesto numero di crateri da impatto e questa circostanza è sicuramente strana: che Ariel sia passata, magari, attraverso una parziale e "recente" (in senso geologico) ridefinizione della sua superficie?
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VI-Puck-vg2_2683716.jpgPuck (HR)66 visitenessun commento
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UranusfromHST-2.JPGUranus, from HST (Natural, but enhanced, Colors; credits: NASA)66 visitenessun commentoMareKromium
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