| Piú votate - Saturn: the "Ringed Beauty" and His Moons |
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.
(4 voti)
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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.
(4 voti)
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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.
(4 voti)
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Rhea-PIA07765.jpgCraters, Slopes and Scarps on Rhea (HR)59 visiteCraters within craters cover the scarred face of Saturn's moon Rhea in this oblique, HR view of terrain on the moon's Western Hemisphere.
A large, degraded crater lies at the center, filled with rolling mounds and many smaller craters. A couple of linear depressions are visible in the terrain (especially at lower right), possibly marking tectonic faults. The crater is about 90 Km-wide (about 56-miles) and is located at 8,5° South Latitude and 154,9 West Longitude. The moon's icy regolith, or loose surface material, has likely been pummeled into a fine powder over the eons.
This is one of the highest-resolution images of Rhea's surface obtained during Cassini's close flyby on Nov. 26, 2005, during which the spacecraft swooped to within 500 Km of the large moon.
The clear filter image was acquired with the wide-angle camera at an altitude of approx. 620 Km above Rhea.
Image scale is about 85 mt (approx. 280 feet) per pixel.
(4 voti)
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Rhea-PIA07764.jpgRhea's "Ray Crater" (alias the "Great White Splat") and scarps from 511 Km59 visite(...) Cassini spacecraft snapped this image of the Eastern rim of Saturn's moon Rhea's bright, Ray Crater. The impact event appears to have made a prominent bright splotch on the Leading Hemisphere of Rhea. Because Cassini was traveling so fast relative to Rhea as the flyby occurred, the crater would have been out of the camera's field of view in any earlier or later exposure. The crater's total diameter is about 50 Km, but this rim view shows details of terrains both interior to the crater and outside its rim. The prominent bright scarp, left of the center, is the crater wall, and the crater interior is to the left of the scarp. The exterior of the crater (right of the scarp) is characterized by softly undulating topography and gentle swirl-like patterns that formed during the emplacement of the large crater's continuous blanket of ejecta material.
Numerous small craters conspicuously pepper the larger crater's floor and much of the area immediately outside of it. However, in some places, such as terrain in the top portion of the image and the bright crater wall, the terrain appears remarkably free of the small impacts. The localized "shot pattern" and non-uniform distribution of these small craters indicate that they are most likely secondary impacts -- craters formed from fallback material excavated from a nearby primary impact site. Because they exist both inside and outside the large crater in this image, the source impact of the secondary impacts must have happened more recently than the impact event that formed the large crater in this scene.
(4 voti)
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Epimetheus&Janus-N00043535.jpgJanus and Epimetheus (2)57 visiteN00043535.jpg was taken on November 29, 2005 and received on Earth November 29, 2005. The camera was pointing toward Epimetheus that, at the time, was approximately 1.103.937 Km away, and the image was taken using the CL1 and CL2 filters.
(4 voti)
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Rhea-N00043374.jpgFeatures on the Terminator58 visiteN00043374.jpg was taken on November 26, 2005 and received on Earth November 27, 2005. The camera was pointing toward Rhea that, at the time, was approximately 70.878 Km away.
The image was taken using the CL1 and IR3 filters.
(4 voti)
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Rhea-N00043395.jpgLittle "White Rayed Splat"61 visiteN00043395.jpg was taken on November 26, 2005 and received on Earth November 27, 2005. The camera was pointing toward Rhea that, at the time, was approximately 65.528 Km away.
The image was taken using the CL1 and CL2 filters.
(4 voti)
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Rhea-N00043426.jpgHills, Knobs and Craters58 visiteN00043426.jpg was taken on November 26, 2005 and received on Earth November 28, 2005. The camera was pointing toward Rhea that, at the time, was approximately 691 Km away.
The image was taken using the CL1 and CL2 filters.
(4 voti)
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Rhea-N00043273.jpgApproaching Rhea (3)59 visiteSpettacolare la nitidezza di alcuni rilievi posti lungo il Terminatore; da notare una sostanziale mancanza di photographic artifacts i quali invece - di regola - caratterizzano questo tipo di immagini. Lo streak di luce che si vede alla Sx di Rhea (circa ore 10 del frame) potrebbe essere un raggio cosmico.
"...Rhea is the largest airless satellite in the Saturnian System. It is an icy body with a low density, which indicates that it is composed of a rocky core taking up less than 1/3rd of the moon's mass, with the rest composed of water-ice. Rhea is somewhat similar to Dione: they both have similar composition, albedo features, varied terrain and synchronous rotations. Rhea is heavily cratered with bright wispy markings. Its surface can be divided into 2 geologically different areas based on crater density. The 1st area contains craters that are larger than 40 Km in diameter while the 2nd area, spanning over parts of the Polar and Equatorial Regions, has craters under 40 Km in diameter and this suggests that a major resurfacing event occurred some time during its formation.
(4 voti)
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Dione-PIA07637.jpgDione: over the clouds of Saturn59 visiteOriginal caption:"Cassini prepared for its rendezvous with Dione on Oct. 11, 2005, capturing the brilliant, cratered iceball in front of its shadow-draped planet. The terrain seen here becomes notably darker toward the West, and is crosscut by the bright, fresh canyons that form wispy markings on Dione's Trailing Hemisphere.
The image was taken in visible light with the Cassini wide-angle camera at a distance of approx. 24.500 Km (about 15.200 miles) from Dione and at a phase angle of 22°. The image scale is about 2 Km (about 1 mile) per pixel".
(4 voti)
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Japetus-N00043109.jpgGeodesic Japetus?57 visiteOriginal caption:"N00043109.jpg was taken on November 15, 2005 and received on Earth November 16, 2005. The camera was pointing toward Japetus at approximately 674.885 kilometers away, and the image was taken using the CL1 and CL2 filters. This image has not been validated or calibrated".
Nota: l'immagine, che mostra le cosiddette "star-trails" ed è quindi indice, assieme al bianco brillante della superficie illuminata di Giapeto, di una sostanziale sovraesposizione del frame, appare molto interessante soprattutto perchè ci consente di apprezzare bene la davvero particolare struttura del "disco" di Giapeto. Un disco-non disco, come aveva a suo tempo notato il Prof. Hoagland: una superficie non "smooth" (liscia) ed arrotondata, bensì squadrata, come fosse "scolpita", in qualche modo. E' evidente che la conclusione di Hoagland ("...Giapeto è una gigantesca nave spaziale...") rimane una boutade, ma l'assoluta peculiarità della forma - in termini globali - di questa luna lontana, resta un fatto.
(4 voti)
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