| Ultimi arrivi - Saturn: the "Ringed Beauty" and His Moons |
Prometheus-PIA07653.jpgThe Runners in the Ring: Prometheus and Pandora66 visiteThis spectacular image shows Prometheus (at left) and Pandora (at right), with their flock of icy ring particles (the F-Ring) between them. Pandora is exterior to the Ring, and closer to the spacecraft here. Each of the shepherd satellites has an unusual shape, with a few craters clearly visible.
The effect of Prometheus (about 102 Km across) on the F-Ring is visible as it pulls material out of the Ring when it is farthest from Saturn in its orbit. Pandora is about 84 Km across.
The image was taken in polarized green light with the Cassini spacecraft narrow-angle camera on Oct. 29, 2005, at a distance of approx. 459.000 Km (about 285.000 miles) from Pandora and 483.500 Km (roughly 300.500 miles) from Prometheus. The image scale is 3 Km (about 2 miles) per pixel on Pandora and 3 Km (idem) per pixel on Prometheus. The view was acquired from about 1/3 of 1° below the Ring-Plane.Dic 16, 2005
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Saturn-PIA07652.jpgCassini, Encke and Keeler: bright arcs in the shadow of the Rings58 visiteSaturn's Rings throw imposing shadows and relegate parts of the Planet's Northern Regions to darkness. Three thin and bright arcs in this scene represent three well-known gaps in the immense Ring System. From bottom to top here (and widest to thinnest) they are the Cassini Division, the Encke Gap and the Keeler Gap.
The image was taken in infrared light (752 nnmts) using the Cassini spacecraft wide-angle camera on Oct. 29, 2005, at a distance of approximately 446.000 Km (about 277.000 miles) from Saturn.
The image scale is 23 Km (roughly 14 miles) per pixel.
The image was contrast enhanced to improve visibility of features in the atmosphere.Dic 14, 2005
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Saturn-PIA07650.jpgCirrus-like clouds in the upper atmosphere of Saturn55 visiteA gorgeous close-up look at the Saturnian (upper) atmosphere reveals small, bright and puffy clouds with long filamentary streamers that are reminiscent of the anvil-shaped Earthly cirrus clouds that extend downwind of thunderstorms. Dark ring shadows hang over the scene while the Planet rotates beneath.
The image was taken in infrared light (939 nnmts) with the Cassini spacecraft wide-angle camera on Oct. 29, 2005, at a distance of approximately 388.000 Km (roughly 241.000 miles) from Saturn.
The image scale is 20 Km (about 12 miles) per pixel.
The image was contrast enhanced to improve visibility of features in the atmosphere.
Dic 14, 2005
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The Rings-Bulge-PIA07651.jpgA "bulge" in the F-Ring?!?54 visiteViewing Saturn's Rings very close to edge-on produces some puzzling effects, as these 2 images of the F-Ring demonstrate: the upper image was acquired from less than 1/10th of 1° beneath the RingPlane and shows a mysterious bulge. Such a feature has not been seen previously by the Cassini spacecraft from this angle. It is possible that, because of the very shallow viewing angle, the Cassini spacecraft's view takes a long path through the Ring, making very faint material visible. It also may be that an embedded object of about 1 Km stirs up the neighboring ring particles to create a bulge. Alternatively, an impact into an embedded moonlet that was covered with debris could produce a cloud like this. Images taken by the Voyager spacecrafts showed clumps that might have been produced in these ways. Cassini's investigations will help to determine the vertical extent of such clumps and understand their origins.
The lower image was obtained from less than a hundredth of a degree beneath the ringplane. Across the center of the rings is a dark lane, giving them an appearance not unlike that of a spiral galaxy, seen edge-on.Dic 14, 2005
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Rhea and Dione-PIA07649.jpgSpheres...57 visiteOriginal caption:"Saturn's sibling moons, Rhea and Dione, pose for the Cassini spacecraft in this view.
Even at this distance, it is easy to see that Dione (below) appears to have been geologically active in the more recent past, compared to Rhea.
Dione's smoother surface and linear depressions mark a contrast with Rhea's cratered terrain.
Sunlit terrain seen on Rhea (1.528 Km, or 949 miles across) is on the moon's Saturn-Facing Hemisphere. Lit terrain on Dione (1.126 Km, or 700 miles across) is on that moon's Leading Hemisphere. North is up.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 1, 2005, at a distance of approx. 1,8 MKM (about 1,1 MMs) from Rhea and 1,2 MKM (approx. 800.000 miles) from Dione. The image scale is 11 Km (about 7 miles) per pixel on Rhea and 7 Km (about 4 miles) per pixel on Dione".Dic 12, 2005
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EnceladusFountains-PIA07762.gifThe "Fountains" of Enceladus124 visiteJets of icy particles burst from Enceladus in this GIF sequence of 4 images taken on Nov. 27, 2005. The sensational discovery of active eruptions on a third outer Solar System body (after Jupiter's moon, Io, and Neptune's moon, Triton) is one of the great highlights of the Cassini mission.
Images taken in January 2005, appeared to show the plume originating from the fractured South Polar Region of Enceladus, but the visible plume was only slightly brighter than the background noise in the image because the lighting geometry was not suitable to reveal the true details of the feature. This potential sighting, in addition to the detection of the icy particles in the plume by other Cassini instruments, prompted imaging scientists to target Enceladus again with exposures designed to confirm the validity of the earlier plume sighting.
The new views show individual jets, or plume sources, that contribute to the plume with much greater visibility than the earlier images.
The full plume towers over the 505-kilometer-wide (314-mile) moon, and is at least as tall as the moon's diameter.
The four, 10-second exposures were taken over the course of about 36 minutes at approximately 12-minute intervals. Enceladus rotates about 7.5 degrees in longitude over the course of the frames, and most of the observed changes in the appearances of the jets are likely due to changes in the viewing geometry. However, some of the changes may be due to actual variation in the flow from the jets on a time scale of tens of minutes.
Additionally, the shift of the sources seen here should provide information about their location in front of and behind the visible limb (edge) of Enceladus.
These images were obtained using the Cassini spacecraft narrow-angle camera at distances between 144,350 and 149,520 kilometers (89,695 and 92,907 miles) from Enceladus and at a phase angle of about 161 degrees. Image scale is about 900 meters (2,950 feet) per pixel on Enceladus.
Dic 08, 2005
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Pandora-PIA07647.jpgPandora and the F-Ring69 visiteThis dramatic image shows Saturn's craggy (---> rocciosa, colma di dirupi) moon Pandora skimming (to skim---> rasentare, sfiorare) along the F-Ring's outer edge.
Pandora orbits about 1.000 Km (approx. 620 miles) exterior to the Ring, but, in this view, is projected onto the Ring.
The moderately high-resolution of the image reveals the moonlet's odd shape.
The image was acquired from less than 1 degree below the Ring-Plane and taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 29, 2005, at a distance of approx. 455.000 Km (roughly 283.000 miles) from Pandora. The image scale is 3 Km (about 2 miles) per pixel.Dic 08, 2005
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Rhea-PIA07769.jpgRhea and Dione (false colors)59 visiteOriginal caption:"Saturn's cratered, icy moons, Rhea and Dione, come alive with vibrant color that reveals new information about their surface properties. To create these false-color views, ultraviolet, green and infrared images were combined into a single black and white picture that isolates and maps regional color differences. This "color map" was then superimposed over a clear-filter image of each moon. The combination of color map and brightness image shows how the colors vary across the moon's surface in relation to geologic features. The origin of the color differences is not yet understood, but may be caused by subtle differences in the surface composition or the sizes of grains making up the icy soil. (...) The images have not been scaled to show the moons' proper relative sizes".Dic 08, 2005
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Saturn-N00044405.jpgPhotographic Defect, Photo-Artifact or UFO in-transit? (3)58 visitevedi il commento al frame precedenteDic 08, 2005
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Saturn-N00044403.jpgPhotographic Defect, Photo-Artifact or UFO in-transit? (1)61 visitevedi il commento al frame successivoDic 08, 2005
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Saturn-N00044404~0.jpgPhotographic Defect, Photo-Artifact or UFO in-transit? (2)62 visiteQuesto frame (dal seriale N. 00044404) contiene un piccolo enigma che, presumibilmente, susciterà una nuova, modesta (e fuggevole) vampata di interesse per la Missione Cassini. Che cosa c'è di così "curioso"? Una striscia (un "bright streak") che taglia - letteralmente - l'immagine e che può ricordare le tracce lasciate da un oggetto in movimento rapido (tipo un satellite o un aereo) quando scattiamo una fotografia del cielo usando un'esposizione non brevissima (ma neppure - necessariamente - lunga). Ci sono elementi per ritenere che questa "linea bianca" sia solo un mero difetto dell'immagine (causato, p.e., da una perdita di dati durante la trasmissione da Saturno), e ci sono elementi - diremmo evidenti - per escludere l'ipotesi del "raggio cosmico" o del "riflesso".
Il frame precedente e quello successivo (anche se non conosciamo il tempo intercorso fra le diverse riprese) non evidenziano l'Anomalìa la quale rimane quindi confinata solo su questa immagine.
Conclusioni? Nessuna, naturalmente...Dic 08, 2005
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Janus-N00044721.jpgJanus and Epimetheus (4)58 visitenessun commentoDic 08, 2005
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