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| Ultimi arrivi - Saturn: the "Ringed Beauty" and His Moons |
Tethys-PIA10547.jpgPenelope's still waiting... (possible True Colors; credits: Lunar Explorer Italia)57 visiteCaption NASA:"The Terminator encroaches upon Penelope, one of the largest craters on Saturn's moon Tethys. Two other large craters, Polyphemus and Phemius, are visible near the Limb in this view of the southern portions of Tethys' Trailing Hemisphere.
The far Rim of Phemius disrupts the smooth profile of the icy moon's limb. (Features on Tethys are named from characters and places mentioned in "The Odyssey")
The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera on Nov. 24, 2008 at a distance of approximately 62,000 kilometers (38,000 miles) from Tethys and at a Sun-Tethys-Spacecraft, or Phase, Angle of 94°. Image scale is 366 meters (about 1200 feet) per pixel".MareKromiumGen 02, 2009
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The_Rings-PIA11144.jpgSpokes (natural - but enhanced - colors; credits: Lunar Explorer Italia)103 visiteCaption NASA:"Dark Spokes dance around Saturn's B-Ring in this image taken with Cassini's wide-angle camera.
As Saturn nears Equinox (which will occur in August 2009) and the Sun angle on the Ring-Plane decreases, Spokes become common sights in Cassini images, just as they were in Voyager images. The Planet's orbital period is 29,5 years, so Saturn has nearly made one complete trip around the Sun since the flybys of the two Voyager Spacecraft (1980 and 1981), allowing Cassini to closely match Voyager's viewing geometry.
The Spokes appear dark against Saturn's B-Ring at low phase angles because the particles within them scatter light more efficiently in the forward direction (meaning away from Cassini) than the surrounding larger ring particles. In the opposite viewing geometry, at high phase angles, spokes appear bright relative to surrounding ring particles (See PIA07807).
MareKromiumGen 01, 2009
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The_RingsPIA11142.jpgSaturn's Rings: the whole System (natural colors; credits: NASA)58 visiteCaption NASA:"Details of Saturn's icy Rings are visible in this sweeping view from Cassini of the Planet's glorious Ring System.
This natural color mosaic, taken from 10° below the illuminated side of the Rings, shows, from left to right, radially outward from Saturn, the C-Ring (with its Colombo and Maxwell Gaps); the B-Ring and the Cassini Division beyond, with the intervening Huygens Gap; the A-Ring (with its Encke and Keeler Gaps); and, on the far right, the narrow F-Ring. The total span covers approx. 65.700 Km (such as about 40.800 miles).
Although it is too faint to be seen here, the D-Ring is located just to the left of the C-Ring.
It is interesting to compare this view with PIA08389, which shows the unilluminated side of the Rings. The difference in brightness of the B-Ring relative to the other Rings is striking. When illuminated directly by the Sun, the B-Ring appears brighter than the adjacent A and C-Rings; however, when viewing the unlit side of the B-Ring, the A and C-Rings appear brighter.
This phenomenon occurs because the density of the B-Ring is greater than that of the A or C-Rings.
The mosaic was constructed from 45 narrow-angle-camera images — 15 separate sets of red, green and blue images — taken over the course of about four hours, as Cassini scanned across the Rings. The images in this view were obtained by NASA's Cassini Spacecraft on Nov. 26, 2008, at a distance of approx. 1,1 MKM (such as about 700.000 miles) from Saturn and at a Phase Angle of 28°.
Image scale in the radial (horizontal) direction is about 7 Km (4,3 miles) per pixel".MareKromiumDic 31, 2008
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Saturn-PIA11141.jpgThe Lord of the Rings (natural colors; credits: NASA)60 visiteCaption NASA:"As Saturn advances in its orbit toward Equinox and the Sun gradually moves Northward on the Planet, the motion of Saturn's Ring shadows and the changing colors of its atmosphere continue to transform the face of Saturn as seen by Cassini.
This captivating natural color view was created from images collected shortly after Cassini began its extended Equinox Mission in July 2008. It can be contrasted with earlier images from the Spacecraft's four-year Prime Mission that show the shadow of Saturn's Rings first draped high over the Planet's Northern Hemisphere, then shifting Southward as Northern Summer changed to Spring.
During this time, the colors of the Northern Hemisphere have evolved from azure/blue to a multitude of muted-colored bands.
This mosaic combines 30 images — 10 each of red, green and blue light — taken over the course of approximately two hours as Cassini panned its wide-angle camera across the entire Planet and Ring System on July 23, 2008, from a southerly elevation of 6°.
Six moons complete this constructed panorama: Titan, Janus, Mimas, Pandora, Epimetheus and Enceladus.
NASA's Cassini Spacecraft captured these images at a distance of approx. 1,1 MKM (such as about 690.000 miles) from Saturn and at a Sun-Saturn-Spacecraft, or phase, angle of 20°. Image scale is roughly 70 Km (about 43,6 miles) per pixel".MareKromiumDic 31, 2008
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The_Rings-PIA11142.jpgSaturn's Rings: the whole System68 visitenessun commentoMareKromiumDic 31, 2008
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Rhea-PIA11143.jpgRhea (possible True Colors credits: Lunar Explorer Italia)58 visiteCaption NASA:"The Cassini Spacecraft's narrow-angle camera captured Saturn's moon Rhea as it gradually slipped into the Planet's (i.e.: Saturn) shadow — an event known as "ingress" — on Aug. 19, 2008.
This image was acquired by NASA's Cassini Spacecraft at a Solar Phase, or Sun-Rhea-Spacecraft, angle of about 28° and at a distance from Rhea of approx. 450.000 Km (about 280.000 miles). Image scale is roughly 2,7 Km (about 1,7 miles) per pixel".MareKromiumDic 31, 2008
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Saturn-W00052086.jpgUnusual Saturn Image60 visiteSapreste spiegare, in un massimo di tre righe, il contenuto visivo di questo frame?... Provateci, se volete, utilizzando la funzione "commenti"!MareKromiumDic 29, 2008
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Saturn-PIA10539-M.jpgSpokes (natural - but enhanced - colors; credits: Lunar Explorer Italia)69 visiteCaption NASA:"A large group of Spokes emerges from Saturn's shadow in this image taken of the morning side of the Rings. Such groupings may hold clues to the manner in which these features are formed.
The image was taken in visible light with the Cassini spacecraft wide-angle camera on Nov. 2, 2008 at a distance of approx. 869.000 Km (such as about 540.000 miles) from Saturn and at a Phase angle of 37°.
Image scale is approx. 48 Km (such about 30 miles) per pixel".MareKromiumDic 28, 2008
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Saturn-N00126685.jpgSaturnian Swirls (False Colors; credits: Lunar Explorer Italia)75 visiteCaption NASA:"N00126685.jpg was taken on December 16, 2008 and received on Earth December 17, 2008. The camera was pointing toward Saturn that, at the time, was approximately 655.610 Km away; the image was taken using the CL1 and CB2 filters.
This image has not been validated or calibrated".MareKromiumDic 26, 2008
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Enceladus-PIA11139.jpgAxial Discontinuity on Enceladus57 visiteCaption NASA:"These two side-by-side images compare a "twisted" sea-floor spreading feature on Earth, known as an Offset Spreading Center (OSC), to a very similar looking twisted break, or Axial Discontinuity, in the Damascus Sulcus "Tiger Stripe" on Saturn’s moon Enceladus. The image of Enceladus was acquired by NASA’s Cassini Spacecraft imaging science sub-system during one of its four close targeted flybys of Enceladus in March, August and October 2008.
The image on the left shows a shaded relief map of bathymetry (or sonar-like topography) data along a spreading ridge on the East Pacific Rise near 9,5° North Lat. and 104° West Long.
On Earth, OSC's occur only along fast-spreading ridges - ones that spread faster than about 100 mm (such as 4") per year. They do not occur on slow-spreading ridges, like the famous Mid-Atlantic Ridge where spreading rates are often less than 20 mm (0,7") per year.
The Axial Discontinuity on Enceladus’ Damascus Sulcus, shown in the image on the right, twists in the same helical way that the OSC does on Earth. However, the morphological resemblance is no guarantee that both features are caused by fast spreading.
On Earth OSCs form when two nearly parallel spreading ridges lengthen along their ridge (or long) axes. As the lengthening tips of the ridges pass each other side-by-side in opposite directions, shear forces caused by tectonic spreading between them force the two tips to twist around each other. The twisting tip of each one eventually merges with the "neck" of the other in a "yin-yang" shaped pattern.
The result is an oval shaped basin that is surrounded by the twisted ridge tips.
On Enceladus, the twisted features have not produced an oval basin, but the pattern of the twist is very similar to the terrestrial OSC and probably similar tectonic shear forces, perhaps even tectonic spreading, resulted in this twisted shape. Note that the Enceladus image has been flipped right-to-left to make comparison to the sea-floor feature easier to see".MareKromiumDic 23, 2008
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EncelalusPIA11137.jpgRelict Tiger Stripe57 visitenessun commentoMareKromiumDic 23, 2008
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Enceladus-PIA11133.jpgCrescent Enceladus (possible True Colors; credits: Lunar Explorer Italia)60 visiteCaption NASA:"On Oct. 5, 2008, just after coming within 25 kilometers (15.6 miles) of the surface of Enceladus, NASA's Cassini captured this stunning mosaic as the Spacecraft sped away from this geologically active moon of Saturn.
Craters and cratered terrains are rare in this view of the Southern Region of the moon's Saturn-facing Hemisphere. Instead, the surface is replete with fractures, folds, and ridges — all hallmarks of remarkable tectonic activity for a relatively small world. In this True Colors view, regions that appear blueish are thought to be coated with larger grains than those that appear white or gray.
Portions of the Tiger Stripe Fractures, or Sulci, are visible along the Terminator at lower right, surrounded by a circumpolar belt of mountains. The icy moon's famed jets emanate from at least 8 distinct Source Regions, which lie on or near the Tiger Stripes. However, in this view, the most prominent feature is Labtayt Sulci, the approximately one-kilometer (such as 0,6 miles) deep Northward-trending chasm located just above the center of the mosaic.
Near the top, the conspicuous ridges are Ebony and Cufa Dorsae. This mosaic was created from 28 images obtained at seven footprints, or pointing positions, by Cassini's narrow-angle camera. At each footprint, 4 images using filters sensitive to UltraViolet (UV), Visible (V) and InfraRed light (IR) - spanning wavelengths from 338 to 930 nanometers) were combined to create the individual frames. The mosaic is an orthographic projection centered at 64,49° South Lat. and 283,87° West Long., and it has an image scale of 196 Km (about 122,5 miles) per pixel. The original images ranged in resolution from 180 meters (594 feet) to 288 meters (950 feet) per pixel and were acquired at distances ranging from 30.000 to 48.000 Km (such as from about 18.750 to 30.000 miles) as the Spacecraft receded from Enceladus.
The view was acquired at a Sun-Enceladus-spacecraft, or phase, angle of 73°".MareKromiumDic 16, 2008
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