| Piú votate - Uranus and His Moons |
ZA-Uranus-LP-PIA00143.jpgFarewell Uranus... (2)85 visiteCaption NASA originale:"This view of Uranus was recorded by Voyager 2 on Jan 25, 1986, as the spacecraft left the planet behind and set forth on the cruise to Neptune. Voyager was 1 MKM (about 600.000 miles) from Uranus when it acquired this wide-angle view. The picture - a color composite of blue, green and orange frames - has a resolution of 140 Km (90 mi) per pixel". 
(17 voti)
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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".
(14 voti)
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Uranus-HST-CJH.jpgUranus, from HST65 visitenessun commento
(13 voti)
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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".
(12 voti)
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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".
(12 voti)
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AAA-Uranus&Co..jpgThe Uranus' "Family"82 visitenessun commento
(11 voti)
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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".
(11 voti)
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A - Uranus.jpgUranus from Voyager 287 visiteUranus Data and Statistics
Discovered by William Herschel
Date of discovery = AD 1781
Mass (kg) = 8.686e+25
Mass (Earth = 1) = 1,4535e+01
Equatorial radius = 25.559 Km
Equatorial radius (Earth = 1) = 4,0074
Mean density (gm/cm^3) = 1,29
Mean distance from the Sun = 2.870.990.000 Km
Mean distance from the Sun (Earth = 1) = 19,1914
Rotational period (hours) = - 17,9
Orbital period (years) = 84,01
Mean orbital velocity = 6,81 Km per second
Tilt of axis = 97,86°
Orbital inclination = 0,774°
Equatorial surface gravity (m/sec^2) = 7,77
Equatorial escape velocity = 21,30 Km per second
Magnitude (Vo) = 5,52
Mean cloud temperature = - 193°C
Atmospheric pressure (bars) = 1,2
Atmospheric composition: Hydrogen 83%; Helium 15%; Methane 2%
(11 voti)
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Miranda-V2-PIA00141_modest.jpgMiranda's limb from Voyager 2 - January 24, 198675 visiteEd ecco ora Miranda, la Luna più interna di Urano. Essa ha una forma decisamente irregolare ed evidenzia molto chiaramente - come in questo frame - delle profonde "cicatrici" superficiali le quali rivelano, come dicono alla NASA, una "complessa storia geologica". EccoVi parte della caption originale NASA per questa foto:"...At least 3 terrain types of different age and geologic style are evident at this resolution of about 700 (2.300 feet) meters. Visible in this clear-filter, narrow-angle image are, from left: (1) an apparently ancient, cratered terrain consisting of rolling, subdued hills and degraded medium-sized craters (2) a grooved terrain with linear valleys and ridges developed at the expense of, or replacing, the first terrain type and (3) a complex terrain seen along the terminator, in which intersecting curvilinear ridges and troughs are abruptly truncated by the linear, grooved terrain. Voyager scientists believe this third terrain type is intermediate in age between the first two".
(11 voti)
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AB-Ariel-V2-PIA01534_modest.jpgBright Ariel!66 visiteSe osservata da una certa distanza (come in questa fotografia, ripresa da circa 150.000 Km), Ariel si dimostra essere una Luna decisamente luminosa, in particolar modo in alcune sue aree: a ridosso del Polo Sud ed in prossimità di alcuni dei suoi "Mari". L'elevatissima albedo di queste aree (ben visibili in questo frame) ci fa supporre che si possa trattare di una conseguenza della presenza di ghiaccio il quale, come sapete, assieme alle nuvole (laddove esistono), è causa dell'elevatissima albedo di alcuni corpi celesti (p.e.: Venere, Giove, Saturno ed alcune delle loro Lune maggiori).
(11 voti)
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AB-Ariel-V2-PIA01356_modest.jpgAriel (detail mgnf)104 visiteIn questo terzo frame potete vedere davvero bene un dettaglio, rilevabile quasi a ridosso della Linea del Terminatore, di alcuni dei crepacci che avevamo intravisto nella prima immagine. Questa ripresa ravvicinata ci permette - con l'aiuto delle ombre che si sono formate sui rilievi - di percepire non solo la profondità, ma anche l'estremo intreccio di questa rete di solchi.
(11 voti)
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UMBRIEL-vg2_p29502-B.jpgUmbriel's extremely unusual surface feature: Wunda Crater (HR - detail mgnf)57 visitenessun commento
(10 voti)
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