| Piú votate - Saturn: the "Ringed Beauty" and His Moons |
Mimas-HerschelCrater.jpgHerschel Crater on Mimas57 visitenessun commento
(8 voti)
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Enceladus-Model2-PIA07726-br500.jpg"Warm" Ice on Enceladus (Model 2)54 visiteOriginal NASA caption:"This graphic represents a second possible 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 venting by plumes".
(8 voti)
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Enceladus-Model1-PIA07725.jpg"Warm" Ice on Enceladus (Model 1)54 visiteOriginal NASA caption:"This graphic represents a possible 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 warmed surface ice. Sublimation is to cause to change directly from a solid to a gas, or from a gas to a solid, without becoming a liquid".
(8 voti)
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Epimetheus.jpgEpimetheus, from approx. 87.000 Km54 visiteOriginal caption:"How did Epimetheus form? No one is yet sure. To help answer that question, this small moon has recently been imaged again in great detail by the robot spacecraft Cassini now orbiting Saturn. Epimetheus sometimes orbits Saturn in front of Janus, another small satellite, but sometimes behind. The above false-color image, taken during mid July, shows a surface covered with craters indicating great age. Epimetheus spans about 115 Km across. Epimetheus does not have enough surface gravity to restructure itself into a sphere".
(8 voti)
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Mimas-PIA06256.jpgMimas: spectacular overview55 visiteThe most detailed images ever taken of Saturn's moon Mimas show it to be one of the most heavily cratered Saturnian moons, with little (if any) evidence for internal activity. Mimas has been so heavily cratered that new impacts can only overprint or even completely obliterate other older craters. Mimas is about 397 Km across.
The moon displays an unexpected array of crater shapes. The highest crater walls tower 6 Km above the floors and show signs of material sliding down slope. Indeed, many of the large craters - more than 15 Km in diameter - appear to be filled in with rough-surfaced material, likely the result of landslides triggered by subsequent impacts elsewhere on Mimas' surface. Some of these deposits have craters superimposed on them, demonstrating that the landslides themselves may be quite old.
Grooves, some of which are over a Km deep, cut across the surface for more than 100 Km. These are some of the only indications that there might have once been internal activity under this ancient, battered surface.
(8 voti)
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Tethys-PIA07557_modest.jpgOdysseus: the Eye of Tethys54 visiteCaption NASA originale:"This richly textured look at Saturn's moon Tethys shows the huge crater Odysseus and its central mountain in relief, as well as many smaller impact sites. Vertical relief on solid Solar System bodies is often most easily visible near the terminator (the line between day and night).
North on Tethys is up in this view. The lit portion of Tethys seen here is on the moon's leading hemisphere as it orbits Saturn.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 27, 2005, at a distance of approximately 490.000 Km (approx 304.000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 117°. The image scale is 3 Km (about 2 miles) per pixel".
(8 voti)
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Hyperion.jpgHyperion: the "sponge-like" moon56 visiteDa "NASA - Picture of the Day" del 26 Luglio 2005:"Recent HR images from the Cassini spacecraft orbiting Saturn show Hyperion to be an even stranger place than thought before. Previously, it was known that the length of a day on Hyperion is unpredictable. The moon's highly elliptical orbit around Saturn, its highly non-spherical shape and its locked 4:3 orbital resonance with Titan torque Hyperion around so much it is hard to predict when the Sun will rise next. The newly imaged craters on the unusually coarse surface are surely the result of impacts, but for some reason have dark centers. The low density of Hyperion indicates it might even be a spelunker's paradise, riddled with tremendous caverns".
Nota: è la prima volta che la NASA dice espressamente che i crateri visibili sono "surely the result of impacts". A parte l'ovvia assurdità di una simile certezza (irraggiungibile per definizione), molti Ricercatori credono che gli impatti ebbero un ruolo MARGINALE nella definizione di questo ed altri mondi...
(8 voti)
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Prometheus_and_the_Rings.jpgPrometheus and the Rings57 visiteCaption NASA originale:"What do Saturn's Rings look like from the other side? From Earth, we usually see Saturn's Rings from the same side of the ring-plane that the Sun illuminates them. Geometrically, in the above picture taken in April by the Cassini Spacecraft, the Sun is behind the camera but on the other side of the ring-plane. Such a vantage point gives a breathtaking views of the most splendid ring system in the Solar System. Strangely, the Rings have similarities to a photographic negative of a front view. For example, the dark band in the middle is actually the normally bright B-Ring. The Ring brightness as recorded from different angles indicates ring thickness and particle density of ring particles. Images like these are also interesting for what they do not show: such as the spokes. The unexpected shadowy regions once recorded by the Voyager missions when they passed Saturn in the early '80s are not, so far, being seen by Cassini. Extra credit: Can you spot the small moon (Prometheus)?
(8 voti)
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Rhea-PIA07517.jpgRhea and the Rings55 visiteCaption NASA originale:"Saturn's brightly sunlit moon Rhea commands the foreground in this image from Cassini; the Gas Giant Planet's Rings are discernible in the background. The spacecraft was just above the Ringplane when it acquired this image, and thus captured the darkened appearance of the dense B-Ring when viewed with sunlight filtered through the Rings. From this perspective, bright areas in the Rings are regions of low density, containing very small particles that effectively scatter light toward Cassini.
North on Rhea is up and rotated about 25° to the left. This view shows principally the anti-Saturn hemisphere on Rhea. It is very clear that the right side of Rhea is highly overexposed.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 18, 2005, at a distance of approx. 540.000 Km (such as approx 340.000 miles) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 110°. The image scale is 3 Km (2 miles) per pixel".
(8 voti)
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Rhea-N00032543.jpgRhea, from approx. 242.000 Km (3)56 visitenessun commento
(8 voti)
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Phoebe-PIA06070.jpgThe "true shape" of Phoebe53 visiteCaption NASA originale:"This colorful graphic illustrates that despite Phoebe's bumpy, irregular topography, the moon has a fairly round shape. A digitally rendered shape model of Phoebe was constructed using Cassini imaging data obtained before and after the spacecraft's close flyby of the Saturnian moon on June 11, 2004.
The average diameter of Phoebe is about 214 Km. The four views of the model are each separated by a 90° rotation; the upper left is centered at 0° West longitude. The others show regions of the moon centered at 90, 180 and 270° West longitude, as labeled. The coloring of the models corresponds to the height of Phoebe's surface, relative to the lowest point - a range of about 16 Km - going from blue (low) to red (high). Interestingly, much of this range in height occurs in 1 large crater, visible in the 180° West view".
(8 voti)
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Mimas and Janus.jpgMimas (from 1,8 MKM) and Janus (from 1,9 MKM)63 visiteCaption NASA originale:"Saturn's icy, impact-riddled moon Mimas slips briefly in front of Saturn's moon Janus in this movie from Cassini. The movie was created from 37 original images taken over the course of 20 minutes as the spacecraft's narrow-angle camera remained pointed toward Janus. Although Mimas moves a greater distance across the field of view, Janus also moved perceptibly during this time. The images were aligned to keep Janus close to the center of the scene. Additional frames were inserted between the 37 Cassini images in order to smooth the appearance of Mimas' movement - a scheme called interpolation. Close-up images from the few minutes surrounding the occultation are arranged into a strip along the bottom of the movie. Contrast on Janus was mildly enhanced to aid the visibility of its surface. The right side of Mimas appears bright because the moon was partly overexposed in this image sequence".
(8 voti)
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