| Piú votate - Saturn: the "Ringed Beauty" and His Moons |
Enceladus~1.jpgEnceladus' "Tiger Stripes"55 visiteDa "NASA - Picture of the Day" del 6 Settembre 2005:"The Tiger Stripes on Saturn's moon Enceladus might be active. Even today, they may be spewing ice from the Moon's icy interior into space, creating a cloud of fine ice particles over the Moon's South Pole and creating Saturn's mysterious E-Ring. Recent evidence for this has come from the Cassini spacecraft. Cassini detected a marked increase in particle collisions during its July flyby only 270 Km over a South Polar Region of Enceladus. Pictured above, a HR image of Enceladus is shown from the close flyby. The unusual surface features dubbed "Tiger Stripes" are visible on the left in false-color blue. Why Enceladus is active remains a mystery, as the neighboring moon Mimas, approximately the same size, appears quite dead".
(9 voti)
|
|
Enceladus-Model3-PIA07727.jpg"Warm" Ice on Enceladus (Model 3)54 visiteOriginal NASA caption:"This graphic represents a possible third model for mechanisms that could generate the water vapor and tiny ice particles detected by Cassini over the Southern Polar terrain on Enceladus.
This model shows sublimation of an "ammonia-water slush" (slush----> fanghiglia costituita da un mix di ammoniaca ed acqua) or "slurry" (slurry---->sin. di slush, ma anche 'combinazione') on the surface".
(9 voti)
|
|
Mimas-PIA07573.jpgMimas in the shadows of the B-Ring54 visiteAs the closest-orbiting of Saturn's intermediate-sized moons, Mimas is occasionally captured against the planet's dim and shadowed northern latitudes. The Moon is seen here next to the shadows cast by the dense B-Ring. The image was taken with the Cassini spacecraft narrow-angle camera on July 18, 2005, at a distance of approx. 1,6 MKM (such as about 1 MMs) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 90°. Image scale is 10 Km (about 6 miles) per pixel.
(9 voti)
|
|
Rhea-PIA07572.jpgRhea, from about 342.000 Km54 visiteCassini looks upward at the South Polar Region on Rhea during a recent distant encounter. Rhea's icy surface is so heavily saturated with impact craters that the moon's limb, or edge, has a rugged, bumpy appearance. The bright splotch seen here near the upper right is impact material (or ejecta) from a relatively fresh crater.
The image was taken with the Cassini spacecraft narrow-angle camera on July 14, 2005, at a distance of approx. 342.000 Km (about 212.000 miles) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 36°. The image was obtained using a filter sensitive to wavelengths of infrared light centered at 298 nnmts. The image scale is 1,6 Km per pixel
(9 voti)
|
|
Mimas-PIA06257.jpgMimas: surface geology through "false colors"54 visiteThe image at the left is a narrow angle clear-filter image, which was separately processed to enhance the contrast in brightness and sharpness of visible features. The image at the right is a color composite of narrow-angle ultraviolet, green, infrared and clear filter images, which have been specially processed to accentuate subtle changes in the spectral properties of Mimas' surface materials. To create this view, 3 color images (ultraviolet, green and infrared) were combined into a single black and white picture that isolates and maps regional color differences. This "color map" was then superimposed over the clear-filter image at the left.
The combination of color map and brightness image shows how the color differences across the Mimas surface materials are tied to geological features.
Shades of blue and violet in the image at the right are used to identify surface materials that are bluer in color and have a weaker infrared brightness than the average Mimas materials (green).
(9 voti)
|
|
Saturn-PIA06436.jpgSaturn's Aurora55 visiteThe Cassini spacecraft has obtained new images of Saturn's auroral emissions, which are similar to Earth's Northern Lights. Images taken on June 21, 2005, with Cassini's UVA Imaging Spectrograph are the first from the mission to capture the entire "oval" of the auroral emissions at Saturn's South Pole.
In the side-by-side, false-color images, blue represents aurora emissions from H gas excited by electron bombardment, while red-orange represents reflected sunlight. The images show that the aurora lights at the Polar Regions respond rapidly to changes in the Solar Wind. Previous images have been taken closer to the Equator, making it difficult to see the Polar Regions. Changes in the emissions inside the Saturn South-Pole aurora are visible by comparing the 2 images, taken about 1 hour apart. The brightest spot in the left aurora fades and a bright spot appears in the middle of the aurora in the second image. Like Earth's aurora, those on Saturn form in an oval at high latitudes around each pole, along with associated spots and streaks. The ultraviolet imaging spectrograph data shows that the Saturn aurora lasts at least one hour, but small changes are visible in that time between the two images.
The same process produces auroras on both planets: variations in the plasma environment release trapped electrons, which stream along the magnetic field lines into the upper atmosphere. There, they collide with atoms and molecules, exciting them to higher energies. The atoms and molecules release this added energy by radiating light at particular characteristic colors and wavelengths. On Earth, this light is mostly from oxygen atoms and nitrogen molecules. On Saturn, it is from emissions of molecular and atomic hydrogen.
(9 voti)
|
|
SaturnandCompanions-PIA07538.jpgSaturn's Space Panorama56 visiteCaption NASA originale:"Three of Saturn's icy moons are seen here, along with the magnificent water-ice rings and the cold gaseous envelope of the Planet's atmosphere. Saturn's dark shadow stretches completely across the rings.
At nine and a half times farther from the Sun than Earth, Saturn inhabits the deep cold of the outer Solar System. The Sun appears only 1% as bright there as it appears at Earth, creating an environment where ice dominates over rock.
The icy Moons visible here, from left to right are: Janus (181 kilometers, or 113 miles, across), Enceladus (505 kilometers, or 314 miles, across), and Epimetheus (116 kilometers, or 72 miles, across).
The image was taken in visible green light with the Cassini spacecraft wide-angle camera on June 1, 2005, at a distance of approximately 2,4 MKM from Saturn. The image scale is 139 Km per pixel".
(9 voti)
|
|
The Rings-N00034670.jpgThe 'clumpy' F-Ring57 visiteUn frame HD che ci mostra, con ampio dettaglio, le 'imperfezioni' (cioè i 'clumps'------> addensamenti, nodi, blocchi et sim.) che caratterizzano questo sottile, ma sempre affascinante, Anello "F".
(9 voti)
|
|
Mimas-PIA06642.jpgMimas, Dione and Rhea57 visiteCaption NASA originale:"A scene straight out of science fiction, this fantastic view shows, from left to right, Saturn's moon's Mimas, Dione and Rhea, on the far side of Saturn's nearly edge-on rings.
The trailing hemispheres of all three moons are sunlit here and wispy markings can be seen on the limbs of both Dione and Rhea. The image was taken in visible blue light with the Cassini spacecraft narrow-angle camera on March 15, 2005, at a distance of approximately 2,4 mkm (approx. 1,5 MMs) from Saturn.
The image scale is 14 Km (approx. 9 miles) per pixel".
(9 voti)
|
|
Pandora-PIA06618~0.jpgPandora at the edge of the Rings64 visiteCaption NASA originale:"Pandora is seen in this dramatic view, orbiting just beyond the outer edge of Saturn's F-Ring. Several bright areas are visible within the F-Ring. In the main Rings, the Keeler gap and the Encke gap - with a bright ringlet - are also visible. Pandora is 84 Km (approx. 52 miles) across. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 18, 2005, at a distance of approximately 1,2 MKM (approx. 746.000 miles) from Pandora and at a Sun-Pandora-spacecraft angle of 108°. The image scale is 7 Km per pixel".
(9 voti)
|
|
Saturn-tilted.jpgTilted Saturn54 visiteCaption NASA originale:"Saturn's whirling vortices and feathery cloud bands are the signs of a restless world. Cassini captured this arresting view of the giant planet scored by bold shadows cast by the rings. The rings are seen edge-on in this dramatic, artfully tilted scene.
The image was taken with the Cassini spacecraft wide-angle camera on March 6, 2005, at a distance of approx. 1,7 MKM (1 MMs) from Saturn through a filter sensitive to wavelengths of infrared light centered at 750 nnmts. The image scale is 10 Km per pixel".
(9 voti)
|
|
Rhea~0.jpgRhea (false colors)63 visiteCaption NASA originale:"This false-color picture of Saturn's moon Rhea from Cassini enhances slight differences in natural color across the moon's face. The extreme north and south latitudes have a notable difference in hue compared to the mid-latitudes.
This view of Rhea is a composite of images taken using filters sensitive to green (centered at 568 nnmts) and infrared light (2 infrared filters, centered at 752 and 930 nnmts) and has been processed to accentuate subtle color differences.
The image was taken with the Cassini spacecraft narrow angle-camera on Feb. 18, 2005, at a distance of approximately 890.000 Km from Rhea and at a Sun-Rhea-spacecraft phase angle of 116°. The image scale is 5 Km per pixel".
(9 voti)
|
|
| 2244 immagini su 187 pagina(e) |
 |
|
|
|
6 | |
|
|
|
|
|
