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| Piú votate - Saturn: the "Ringed Beauty" and His Moons |
Rhea.jpgRhea in "strange" colors72 visiteAbbiamo intitolato questa immagine "Rhea in colori strani" ma, a ben vedere, avremmo forse fatto meglio a scrivere "Rhea falsa". Questa ripresa di Rhea è, in effetti - ed a quanto ci è dato sapere - completamente unica. Il colorito azzurrino e quelle formazioni frastagliate bianche che attraversano l'intero Pianeta (e che assomigliano a nuvole) non sono visibili in nessun altra fotografia di questa Luna di Saturno. Si tratta dunque di un falso? O forse di un errore occorso durante l'attività di processo del frame originale? Cattivi abbinamenti cromatici? Potremmo andare avanti per pagine, senza arrivare a nulla. L'unica cosa che si può dire, ad oggi, è che Rhea, agli occhi di Voyager o di Cassini/Huygens (ed ai nostri occhi), appare - di regola! - in maniera completamente differente. L'unica cosa che possiamo fare è aspettare nuove immagini a colori per tentare di vederci più chiaramente.
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Tethys.pngTethys and the Sun (possible Natural Colors; credits for the additional process. and color.: Marco Faccin and E. Bonora)108 visitenessun commentoMareKromium
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Epimetheus-PIA21335.jpgEpimetheus117 visitenessun commentoMareKromium
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Saturn-PIA21899.gifPolar Lights (Auroral Emissions from the North Pole of Saturn)115 visiteCaption NASA Originale:"On Sept. 14, 2017, one day before making its final plunge into Saturn's Atmosphere, NASA's Cassini Spacecraft used its Ultraviolet Imaging Spectrograph, or UVIS, instrument to capture this final view of Ultraviolet Auroral Emissions over the Planet's North Polar Regions.
The view is centered on the North Pole of Saturn, with lines of Latitude visible for 80, 70 and 60°. Lines of Longitude are spaced 40° apart. The Planet's Day-Side is at the bottom of the picture, while the Night-Side is at the top. A sequence of images from this observation has also been assembled into a movie sequence. The last image in the movie was taken about an hour before the still image, which was the actual final UVIS auroral image.
Auroral Emissions are generated by charged particles traveling along the invisible lines of Saturn's Magnetic Field. These particles (then) precipitate into the Atmosphere, releasing light when they strike (the) Gas Molecules (that are present) there.
Several individual auroral structures are visible here, despite that this UVIS view was acquired at a fairly large distance from the Planet (such as about 424.000 miles or approx. 682.361,856 Km). Each of these features is connected to a particular phenomenon (occurring) in the Saturnian Magnetosphere. For instance, it is possible to identify Auroral "signatures" here that are related to the injection of "Hot Plasma" from the Day-Side Magnetosphere, as well as Auroral Features associated with a change in the Magnetic Field's shape (existing) on the Magnetosphere's Night-Side.
Several possible scenarios have been postulated over the years to explain Saturn's changing Auroral Emissions, but researchers are still far from a complete understanding of this complicated puzzle. Researchers will continue to analyze the hundreds of image sequences UVIS obtained of Saturn's auroras during Cassini's 13-year mission, with many new discoveries likely to be made.
This image and movie sequence were produced by the Laboratory for Planetary and Atmospheric Physics (LPAP) of the STAR Institute of the University of Liege in Belgium, in collaboration with the UVIS Team".MareKromium
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Saturn-PIA12825.jpgSaturnian Storm (False Colors; credits: NASA/JPL-Caltech/Space Science Institute)67 visiteCaption NASA:"These false-color images from NASA's Cassini Spacecraft chronicle a day in the life of a huge storm that developed from a small spot that appeared 12 weeks earlier in Saturn's Northern Mid-Latitudes.
This storm is the largest and most intense observed on Saturn by NASA's Voyager or Cassini Spacecraft. The storm is still active. As seen in these and other Cassini images, the storm encircles the Planet - whose circumference at these latitudes is approx. 186.000 miles (about 300.000 Km).
From North to South, it covers a distance of about 9000 miles (approx. 15.000 Km), which is one-third of the way around the Earth. It encompasses an area of about 1,5 BSMs (Billion Square Miles - such as approx. 4 BSKM), or eight times the surface area of Earth. This storm is about 500 times the area of the biggest of the Southern Hemisphere storms observed by Cassini.
The highest clouds in the image are probably around 100 millibars pressure, or 60 miles (approx. 100 Km) above the regular undisturbed clouds. These false colors show clouds at different altitudes. Clouds that appear blue here are the highest and are semitransparent, or optically thin. Those that are yellow and white are optically thick clouds at high altitudes. Those shown green are intermediate clouds. Red and brown colors are clouds at low altitude unobscured by high clouds, and the deep blue color is a thin haze with no clouds below. The base of the clouds, where lightning is generated, is probably in the water cloud layer of Saturn's Atmosphere. The storm clouds are likely made out of Water Ice covered by crystallized Ammonia.
Taken about 11 hours -- or one Saturn day -- apart, the two mosaics in the lower half of this image product consist of 84 images each. The mosaic in the middle was taken earlier than the mosaic at the bottom. Both mosaics were captured on Feb. 26, 2011, and each of the two batches of images was taken over about 4,5 hours.
Two enlargements from the earlier, middle mosaic are shown at the top of this product. The white lines below the middle mosaic identify those parts of the mosaic that were enlarged for these close-up views. The enlargement on the top left shows the head of the storm, and that on the top right shows the turbulent middle of the storm. Cassini observations have shown the head of the storm drifting West at a rate of about 2,8° of Longitude each Earth day (28 meters per second, or 63 miles per hour). The central latitude of the storm is the site of a Westward jet, which means that the clouds to the North and South are drifting Westward more slowly or even drifting eastward. In contrast, clouds at Saturn's Equator drift Eastward at speeds up to 450 meters per second (about 1000 miles per hour).
Both of the long mosaics cover an area ranging from about 30° to 51° North Latitude. The views stretch from about 138° (on the left) to 347° West Longitude (on the right), passing through 360/0° West Longitude near the far right of the mosaics.
The images were taken with the Cassini Spacecraft narrow-angle camera using a combination of spectral filters sensitive to wavelengths of Near-InfraRed light. The images filtered at 889 nanometers are projected as blue. The images filtered at 727 nanometers are projected as green, and images filtered at 750 nanometers are projected as red.
The views were acquired at a distance of approx. 1,5 MMs (such as about 2,4 MKM) from Saturn and at a Sun-Saturn-Spacecraft Angle (i.e.: Phase Angle) of 62°. Both the top and bottom images are simple cylindrical map projections, defined such that a square pixel subtends equal intervals of Latitude and Longitude. At higher Latitudes, the pixel size in the North-South direction remains the same, but the pixel size in the East-West direction becomes smaller. The pixel size is set at the Equator, where the distances along the sides are equal. The images of the long mosaics have a pixel size of 33 miles (53,108 Km) at the Equator, and the two close-up views have a pixel size of 6 miles (9,656 Km) per pixel at the equator".MareKromium
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Saturn-PIA12826.jpgSaturnian Storm (Natural Colors; credits: NASA/JPL-Caltech/Space Science Institute)71 visitenessun commentoMareKromium
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Saturn-PIA14119.jpgLarge Ammonia Crystals in Saturn Storm (False Colors; credits: NASA/JPL-University of Arizona)67 visiteCaption NASA:"This false-color InfraRed image, obtained by NASA's Cassini Spacecraft, shows clouds of large Ammonia ice particles dredged up by a powerful storm in Saturn's Northern Hemisphere. Large updrafts dragged Ammonia gas upward more than 30 miles (approx. 50 Km) from below. The Ammonia then condensed into large crystals in the frigid Upper Atmosphere. This storm is the most violent ever observed at Saturn by an orbiting Spacecraft.
Cassini's Visual and InfraRed Mapping Spectrometer obtained these images on Feb. 24, 2011. Scientists colorized the image by assigning red to brightness detected from the 4.08-micron wavelength, green to brightness from the 0.90-micron wavelength, and blue to brightness from the 2.73-micron wavelength. Large particles (red) reflect Sunlight well at 4.08 microns. Particles at high altitude (green) reflect Sunlight well at 0.9 microns. Particles comprised of Ammonia -- especially large ones -- do not reflect 2.73-micron sunlight well, but instead absorb light at this wavelength.
The storm here shows up as yellow, demonstrating that it has a large signal in both red and green colors. This indicates the cloud has large particles and extends upward to relatively high altitude. In addition, the lack of blue in the feature indicates that the storm cloud has a substantial component of Ammonia Crystals. The head of the storm is particularly rich in such particles, as created by powerful updrafts of Ammonia gas from depth in the throes of Saturn's thunderstorm".MareKromium
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Saturn-PIA08823~0.jpgCrescent Saturn (Natural Colors; credits: NASA/JPL/Space Science Institute)63 visiteFrom Norther than the North Pole...
Caption NASA originale:"The Cassini spacecraft gazes down at the marvelous Rings and swirling clouds of giant Saturn from above the Planet's North Pole.
Such views are possible as the spacecraft performs its "180°-transfer," a key navigation maneuver that quickly raises the inclination of Cassini's orbit and shifts the orbital ellipse around to a different side of the Planet, before quickly lowering the inclination again.
The image was taken in visible light with the Cassini spacecraft wide-angle camera on Oct. 30, 2006. Cassini was then at a distance of approx. 1,2 MKM (about 700.000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 142°.
Image scale is roughly 67 Km (about 41 miles) per pixel".MareKromium
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Saturn-PIA08826.jpgVanishing Pan... (Natural Colors; credits: NASA/JPL/Space Science Institute)59 visiteCaption NASA originale:"The Cassini spacecraft looks down at the unlit side of the Rings as Pan heads into Saturn's shadow. The moon is accompanied by faint ringlets in the Encke Gap. At bottom, the bright F-Ring core fades slowly into darkness. This view looks toward the unlit side of the Rings from about 20° above the Ring-Plane.
The image was taken in visible light with the Cassini spacecraft wide-angle camera on Nov. 15, 2006. Cassini was then at a distance of approx. 1,7 MKM (about 1,1 MMs) from Saturn and at a Sun-Saturn-Spacecraft, or Phase, Angle of 163°. Image scale is roughly 10 Km (approx. 6 miles) per pixel".MareKromium
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Saturn-PIA08838~0.jpgIn the Night of Saturn (Natural Colors; credits: NASA/JPL/Space Science Institute)61 visiteCaption NASA:"Only Cassini could provide this enchanting, Natural Color view of crescent Saturn, which gazes down onto the unlit side of the Planet's spectacular Rings. The robotic ship plies the peaceful black seas around the Ringed Giant, searching for answers to the many questions posed by the inquisitive minds of Earth.
This view looks toward the unlit side of the Rings from about 19° above the Ring-Plane. The view of Saturn is through the dark Rings at bottom; the Rings cast shadows onto the Northern Hemisphere at top. Images taken using red, green and blue spectral filters were combined to create this Natural Color view.
The images were taken with the Cassini Spacecraft wide-angle camera on Nov. 4, 2006 at a distance of approx. 1,7 MKM (a little more than 1 MMs) from Saturn and at a Sun-Saturn-Spacecraft, or Phase, Angle of 162°. Image scale is roughly 97 Km (about 61 miles) per pixel". MareKromium
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Saturn-Storm.jpgSaturnian Storm94 visiteCaption NASA:"Late last year, a new, remarkably bright storm erupted in Saturn's Northern Hemisphere. Amateur astronomers first spotted it in early December, with the Ringed Gas Giant rising in Planet Earth's predawn Sky.
Orbiting Saturn, the Cassini Spacecraft was able to record this close-up of the complex disturbance from a distance of about 1,8 MKM on December 24th, 2010.
Over time, the storm has evolved, spreading substantially in longitude, and now stretches far around the Planet. Saturn's thin Rings are also seen slicing across this space-based view, casting broad shadows on the Planet's Southern Hemisphere".MareKromium
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Enceladus-PIA12713-PCF-LXTT.jpgThe "Fountains" of Enceladus at "High Phase" (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)89 visiteCaption NASA:"Saturn's moon Enceladus, imaged at High Phase, shows off its spectacular Water Ice Plumes emanating from its South Polar Region.
This image was captured at a Phase, or Sun-Enceladus-Spacecraft, Angle of 159° so that Sunlight would reveal the backlit plumes.
Sunlight brightly illuminates Terrain on the left. Light reflected off Saturn illuminates the rest of the moon more dimly. This view looks toward the Trailing Hemisphere of Enceladus. North is down. Background stars, elongated by the movement of the Spacecraft during the exposure, are also visible.
The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera on Oct. 13, 2009. The view was obtained at a distance of approx. 431.000 Km (about 268.000 miles) from Enceladus.
Image scale is roughly 3 Km (about 1,9 miles) per pixel".MareKromium
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