| Piú viste - Saturn: the "Ringed Beauty" and His Moons |
Saturn.jpgSaturn in real colors58 visitenessun commento
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Enceladus-PIA06547_modest.jpgEnceladus in visible light58 visiteCaption NASA originale:"Hints of the curving linear grooves that crisscross bright, icy Enceladus are just discernible in this image captured by the Cassini spacecraft. Enceladus is almost entirely composed of water ice and has a surface as bright as snow. Its diameter is 499 Km (310 miles).
This view shows principally the leading hemisphere of Enceladus. The image was taken in visible light with the Cassini spacecraft narrow angle camera on Nov. 1, 2004, at a distance of 1,8 MKMs from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 108°. North is up. The image scale is about 11 Km (or 7 miles) per pixel. The image has been magnified by a factor of two and contrast enhanced to aid visibility of surface features".
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Rhea-PIA06555_modest.jpgRhea's craters58 visiteCaption NASA originale: "The sunlight angle in this sharp view of Saturn's second-largest moon, Rhea, highlights the moon's crater-strewn surface. Cassini will fly past Rhea on Nov. 26, 2005, at a distance of only 500 Km (such as 311 miles) and will obtain very high resolution images at that time. Rhea's diameter is 1.528 Km(or 949 miles).
This view shows mainly the hemisphere of Rhea that faces away from Saturn. The image was taken in visible light with the Cassini spacecraft narrow angle camera on Nov. 1, 2004, at a distance of 1,6 MKM (or 994.000 miles) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 102°. North is up. The image scale is about 10 Km (6 miles) per pixel. The image has been slightly contrast enhanced to aid visibility of surface features.
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Japetus-PIA06167_modest.jpgJapetus in "near-true" color58 visiteCaption NASA originale:"This near-true color view from Cassini reveals the colorful and intriguing surface of Saturn's moon Iapetus in unrivaled clarity. The images taken with different spectral filters and used for this composite were taken at the same time as the clear frames used in PIA06166. The use of color on Iapetus is particularly helpful for discriminating between shadows (which appear black) and the intrinsically dark terrain (which appears brownish). This image shows the northern part of the dark Cassini Regio and the transition zone to a brighter surface at high northern latitudes. Within the transition zone, the surface is stained by roughly north-south trending wispy streaks of dark material. The absence of an atmosphere on Iapetus means that the material was deposited by some means other than precipitation, such as ballistic placement from impacts occurring elsewhere on Japetus, or was captured from elsewhere in the Saturn system".
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Mimas-N00026522.jpgMimas: the Ring-Master58 visitenessun commento
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Mimas-N00026566.jpgThe "Eye" of Mimas58 visiteCaption NASA originale:"Whatever hit Mimas nearly destroyed it. What remains is one of the largest impact craters on one of Saturn's smallest moons. The crater, named Herschel after its discoverer, spans about 130 Km and is pictured above in the dramatic light of its terminator. Mimas' low mass produces a surface gravity just strong enough to create a spherical body but weak enough to allow such relatively large surface features. Mimas is made of mostly water ice with a smattering of rock - so it is accurately described as a big dirty snowball".
Una descrizione accurata ed interessante, in linea con le più recenti correnti di pensiero scientifico relative alla struttura ed alla composizione di Mimas.
Tuttavia, assumendo come vere queste informazioni, ci chiediamo come abbia fatto una "palla di neve sporca" a resistere senza disintegrarsi del tutto a seguito dell'impatto che generò il cratere Herschel.
Deduzione: forse Mimas non è solo ghiaccio d'acqua ed un pò di roccia, come ci stanno insegnando...
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Saturn-N00027024.jpgSomething is moving: is it a moon or a spaceship? (3)58 visitevedi i commenti ai frames che precedono
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Mimas and Saturn-PIA06574.jpgMimas and Saturn58 visiteCaption NASA originale:"In a dazzling and dramatic portrait painted by the Sun, the long thin shadows of Saturn's rings sweep across the planet's northern latitudes. Within the shadows, bright bands represent areas where the ring material is less dense, while dark strips and wave patterns reveal areas of denser material. The shadow darkens sharply near upper right, corresponding to the boundary of the thin C-Ring with the denser B-Ring. A wide-field, natural color view of these shadows can be seen in PIA06164.
The globe of Saturn's moon Mimas (398 Km or 247 miles across) has wandered into view near the bottom of the frame. A few of the large craters on this small moon are visible. The image was taken with the Cassini spacecraft narrow angle camera on Jan. 18, 2005, at a distance of 1,4 MKM (889.000 miles) from Saturn using a filter sensitive to wavelengths of infrared light centered at 752 nanometers. The image scale is 9 Km (approx 5,5 miles) per pixel".
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Enceladus-N00028181.jpgEnceladus: from VERY close! (1)58 visiteUna serie di 4 immagini ravvicinate (riprese da una distanza media di circa 1200 Km dalla superficie di questa "Luna di ghiaccio" la quale - a detta degli Scienziati - riflette la luce come se fosse "neve fresca") che ci mostrano lo stupefacente volto di Encelado.
In tutte le 4 immagini che Vi proponiamo sono chiaramente visibili delle lunghissime (ed intricate!) reti di crepacci ("cracks" e/o "chasmas") i quali, nel caratterizzare questa piccola Luna, la rendono, in qualche maniera, piuttosto simile - visivamente - alla Luna Gioviana "Europa".
In questo primissimo frame, inoltre, si può notare una sostanziale mancanza di crateri; una mancanza che, talvolta, può essere indice di una (relativa) 'gioventù geologica' della superficie!
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Enceladus-PIA06191.jpgEnceladus: photomosaic58 visiteCaption NASA originale:"The view is about 300 Km across and shows the myriad of faults, fractures, folds, troughs and craters that make this Saturnian Satellite especially intriguing to planetary scientists. More than 20 years ago, NASA's Voyager spacecraft gave hints of a surface cut by tectonic features and subsequent images of other icy moons have revealed many different ways that stresses have acted on icy moon crusts. The new close-up images of Enceladus, which has a diameter of 505 Km, show some familiar-looking features and others that are brand new. Extending downward from the top center of the mosaic for hundreds of kilometers is a broad belt of complex, interwoven fractures. A huge rift 5 Km-wide dissects this belt and extends into several older-looking, distinct regions or "cells" of terrain that themselves exhibit distinct fracture patterns. The work required to unravel their origins, their formation sequence, and the implications for the evolution of icy Solar System bodies is just beginning...".
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Rings-PIA06588.jpgThe "rings" and a "string" of Moons...58 visiteCaption NASA originale:"Moons visible in this image: Mimas (398 Km, or 247 miles across) at right, Pandora (84 Km, or 52 miles across) near center and Janus (181 Km, or 113 miles across) in the lower left corner. Mimas' orbit inclination of 1,6° relative to Saturn's equator is enough to make it appear as if it orbits just beyond the F-Ring when viewed from this vantage point of 5° below the Rings. In fact, it is 34.000 Km (such as approx. 21.000 miles) more distant than Janus".
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Mimas-N00028766.jpgMimas and the Rings, from approx. 1.378.000 Km58 visiteUna splendida immagine, che non serve commentare.
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