| Piú viste - Neptune and His Moons |
t Neptune Space.jpgNeptune's System55 visiteUn magnifico e realistico collage che ci mostra Nettuno e le sue Lune maggiori, insieme, per una "Foto Ricordo" di un viaggio indimenticabile...
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Triton-PIA02234.jpgTriton, from 530.000 Km!55 visiteCaption NASA:"Voyager 2 was 530.000 Km (330,000 miles) from Neptune's largest satellite, Triton, when this photo was taken, Aug. 24, 1989. With a resolution of 10 Km (about 6 miles), this is the first photo of Triton to reveal surface topography. The South Pole, continuously illuminated by sunlight at this season, is at bottom left. The boundary between the bright Southern Hemisphere and the darker Northern Hemisphere is clearly visible. Both the darker regions to the north and the very bright sub-equatorial band show a complex pattern of irregular topography that somewhat resembles "fretted terrain" on parts of Venus and Mars.
The pattern of dark and light Regions over most of the Southern Hemisphere will require HR images for interpretation. Also evident are long, straight lines that appear to be surface expressions of internal, tectonic processes. No large impact craters are visible, suggesting that the crust of Triton has been renewed relatively recently that is, within the past billion years or less".MareKromium
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Triton-PIA02213-moe-ELEI.jpgThe limb of Triton (natural colors - elab. Lunexit)55 visitenessun commentoMareKromium
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Neptune-PIA02220.jpgSouth Polar Clouds and Shadows (Natural Colors; credits: Lunexit)55 visiteCaption NASA:"This image of Neptune shows the discovery of shadows in Neptune's Upper Atmosphere, shadows cast onto a deep cloud band by small elevated clouds. They are the first cloud shadows ever seen by Voyager on any Planet. Estimates of the height of these discrete clouds above the underlying cloud bank can be obtained by careful analysis of this data".MareKromium
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Neptune-PIA01995.jpgSouth Polar Clouds and Shadows (Natural Colors; credits: Lunexit)55 visiteCaption NASA:"This image of Neptune's South Polar Region was obtained by the NASA Voyager 2 Probe narrow-angle camera on Aug. 23, 1989, when it was at a distance of about 25 MKM (about 1,6 MMs).
The smallest cloud features are 45 Km (about 28 miles) in diameter. Also this image shows the discovery of shadows in Neptune's Atmosphere, shadows cast onto a deep cloud bank by small elevated clouds. Located at about 68° South Lat., they are the first cloud shadows ever seen by the Voyager on any Planet.
The dark regions adjacent to the small bright clouds are believed to be shadows, because they are on the side of the cloud that is opposite to the incoming Sunlight and also because they lengthen in places where the Sun lies closer to the horizon".MareKromium
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Triton-PIA12187.jpgTritonian Terminator55 visitenessun commentoMareKromium
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ZA-Triton-PIA02247_modest.jpgFarewell Triton...54 visiteCaption NASA originale:"Voyager 2 obtained this parting shot of Triton, Neptune's largest satellite, shortly after closest approach to the moon and passage through its shadow on the morning of Aug. 25, 1989. The distance to Triton was 90.000 Km and the phase angle was 155°, so that only a thin crescent of Triton's south polar region can be seen. Because of the high phase angle, and perhaps because of scattering sunlight in Triton's hazy atmosphere, few surface features are also easily discernible". Un piccolo commento: non sembra anche a Voi di intuire una sottile somiglianza fra Tritone e Titano?...
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Triton-PIA02212_modest.jpgTriton from Voyager 2 (false colors?)54 visiteCaption NASA originale:"The smallest features that can be seen in this false color image of Neptune's largest satellite, Triton, are about 47 Km across. The image, taken by Voyager 2 early in the morning of Aug. 23, 1989, is a composite of three images taken through ultraviolet, green, and violet filters. The image offers an example of the kinds of puzzles scientists face on the eve of an encounter: mottling in the bright southern hemisphere may be the result of topography, if Triton's crust is predominantly water ice, which is rigid at Triton's surface temperature. Alternatively, the mottling could be due to markings on a smooth surface, if the crust is composed of nitrogen, carbon monoxide, or methane ice, since they are soft at the same temperature". Nota: in questo frame la NASA parla chiaramente di "false colors" mentre nel successivo dice "natural colors". Ora a noi i "colors" di Tritone, nei due frames, sembrano identici.
Sono dunque entrambi "natural" o "false"? Dov'è la verità?
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Neptune-clouds-PIA01982_modest.jpgThe clouds of Neptune (b/w) - 254 visiteAncora i "cirri" di Nettuno, ripresi dalla Sonda Voyager 2, mentre si spostano rapidamente nei pressi - e lungo i bordi, in particolare- della Grande Macchia Scura (o GDS, come dicono alla NASA).
E' curioso pensare che i mutamenti del clima, su Nettuno, possano in qualche modo essere simili ai mutamenti di clima che possiamo riscontrare nel cielo della nostra Terra.
Già, ma in fondo - a pensarci bene - le nuvole ed il vento devono essere fenomeni assolutamente universali.
Certo, le nuvole di Nettuno non sono costituite da cristalli d'acqua, bensì da cristalli di metano ghiacciato ed i venti di Nettuno superano i 2000 Km orari. Ma le nuvole restano nuvole ed il vento - per quanto forte possa essere - rimane vento. Forse queste considerazioni sono banali, ma noi siamo convinti che, di tanto in tanto, sia una cosa giusta quella di pensare a quanto diversi, eppure quanto simili, possano essere i fenomeni della Natura qui, sulla Terra, o su Marte, o su Nettuno od ovunque - probabilmente - nell'Universo.
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Neptune-PIA01286_modest.jpgA new "dark spot" on Neptune, as seen by HST54 visiteCaption NASA originale:"NASA's HST has discovered a new Great Dark Spot, located in the Northern Hemisphere of Neptune. Because the planet's Northern Hemisphere is tilted away from Earth, the new feature appears near the limb of the planet.
The Spot is a near mirror-image to a similar Southern Hemisphere Dark Spot that was discovered in 1989 by the Voyager 2. In 1994, HST showed that the Southern Dark Spot had gone. Like its predecessor, the new Spot has high altitude clouds along its edge, caused by gasses that have been pushed to higher altitudes where they cool to form methane ice crystal clouds. The Dark Spot may be a zone of clear gas that is a window to a cloud deck lower in the atmosphere. Planetary scientists do not know how long this new feature might live. HST's HR images will allow astronomers to follow the spot's evolution and other unexpected changes in Neptune's dynamic atmosphere. This image was taken on 2.11-'94 with HST's Wide Field Planetary Camera 2, when Neptune was 4,5 BKMs from Earth".
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Neptune-PIA01998.jpgNeptune, from FAR away...54 visiteCaption NASA originale:"This image of Neptune was taken through the clear filter of the narrow-angle camera, when the Voyager 2 spacecraft was at a range of 57 MKM (about 35 MMs). The image was processed by computer to show the newly resolved dark oval feature embedded in the middle of the dusky southern collar. The large dark spot nearer the equator is also prominent on the left edge of the disk. The new small dark spot rotates faster than the large dark spot indicating that the winds on Neptune have different velocities at different latitudes as is the case for Jupiter, Saturn and Uranus".
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Proteus-vg2_1138920.jpgProteus (HR)54 visitenessun commento
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