| Piú votate - Saturn: the "Ringed Beauty" and His Moons |
EnceladusFountains-PIA07762.gifThe "Fountains" of Enceladus122 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.
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Pandora-PIA07632.jpgBeautiful Pandora (false colors)91 visiteCassini's best close-up view of Saturn's F-Ring shepherd moon, Pandora, shows that this small ring-moon is coated in fine dust-sized icy material.
Craters formed on this object by impacts appear to be covered by debris, a process that probably happens rapidly in a geologic sense. The grooves and small ridges on Pandora suggest that fractures affect the overlying smooth material. The crisp craters on another Saturn moon, Hyperion, provide a contrasting example of craters on a small object.
Cassini acquired infrared, green and ultraviolet images on Sept. 5, 2005, which were combined to create this false-color view. The image was taken with the Cassini spacecraft narrow-angle camera at a distance of approx. 52.000 Km from Pandora and at a phase angle of 54°. Resolution in the original image was about 300 mt per pixel".
Nota: un'immagine stupenda e spettacolare e poi, per i più attenti, come non notare l'incredibile somiglianza (troppo grande per essere casuale...) di questa luna con Phobos?
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Janus-N00041468.jpgJanus and Prometheus55 visiteN00041468.jpg was taken on October 13, 2005 and received on Earth October 14, 2005. The camera was pointing toward JANUS - distant approximately 876.959 Km away - and the image was taken using the CL1 and CL2 filters. This image has not been validated or calibrated.
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RingsStructure-2-PIA03550.jpgThe "Rings' Structure"54 visiteSaturn's Rings make up an enormous, complex structure. From edge-to-edge, the Ring System would not even fit in the distance between Earth and the Moon. The 7 main rings are labeled in the order in which they were discovered. From the planet outward, they are D, C, B, A, F, G and E. The D-Ring is very faint and closest to Saturn. The main Rings are A, B and C. The outermost Ring, easily seen with Earth-based telescopes, is the A-Ring. The Cassini Division is the largest gap in the Rings and separates the B from the A-Ring. Just outside the A-Ring is the narrow F-Ring, shepherded by tiny moons Pandora and Prometheus. Beyond that are 2 much fainter Rings named G and E. Saturn's diffuse E-Ring is the largest planetary ring in our Solar System, extending from Mimas' orbit to Titan's orbit, about 1 MKM.
The particles in Saturn's rings are composed primarily of water ice and range in size from microns to tens of meters. The rings show a tremendous amount of structure on all scales; some of this structure is related to gravitational interactions with Saturn's many moons, but much of it remains unexplained. One moonlet, Pan, actually orbits inside the A ring in a 330-kilometer-wide (200-mile) gap called the Encke Gap. The main rings (A, B and C) are less than 100 meters (300 feet) thick in most places, compared to their radial extent of 62,120 kilometers (38,600 miles). The main rings are much younger than the age of the solar system, perhaps only a few hundred million years old. They may have formed from the breakup of one of Saturn's moons or from a comet or meteor that was torn apart by Saturn's gravity.
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Pandora-PIA07570.jpgPandora, from 1,3 MKM54 visiteWhile close to Saturn in its orbit, Cassini stared directly at the Planet to find Saturn's moon Pandora in the field of view. The F-Ring shepherd moon is gliding towards the right in this scene. The F-Ring is thinly visible just above the main rings. Pandora is 84 Km (about 52 miles) across.
Near the lower left, some variation in the height of Saturn's cloud tops can be detected. This effect is often visible near the terminator (such as the day and night boundary), where the Sun is at a very low angle above Saturn's horizon.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 16, 2005, at a distance of approx. 1,3 MKM (about 800.000 miles) from Saturn.
The image scale is about 8 Km (about 5 miles) per pixel on Saturn and about 6 Km (about 4 miles) per pixel on Pandora.
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Saturn-PIA07563.jpgSaturn or Van Gogh?54 visiteSaturn's turbulent atmosphere is reminiscent of a Van Gogh painting in this view. However, unlike the famous impressionist painter, Cassini records the world precisely as it appears to the spacecraft's cameras.
The feathery band that cuts across from the upper left corner to the right side of this scene has a chevron, or arrow, shape near the right. The center of the chevron is located at the latitude (about 28° South) of an eastward-flowing zonal jet in the atmosphere. Counter-flowing eastward and westward jets are the dominant dynamic features seen in the giant planet atmospheres. A chevron-shaped feature with the tip pointed East means that this is a local maximum in the eastward wind and a region of horizontal wind shear where clouds to the North and South of the jet are being swept back by the slower currents on the sides of the jet.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 6, 2005, at a distance of approx. 2,5 MKM from Saturn using a filter sensitive to wavelengths of infrared light centered at 727 nanometers. The image scale is 14 kilometers (9 miles) per pixel.
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Japetus-PIA07003_modest.jpgJapetus' surface composition (organic material?!?)66 visiteCaption NASA originale:"The polar water ice is relatively dark at this wavelength, so the ice cap is not seen. The next frame shows carbon dioxide on the surface. The carbon dioxide peaks at mid latitudes and shows less strength at the pole and along the equator (the dark band curving near the left edge of the image). The third frame shows the strength of water absorption on Japetus. The brightest regions are due to water ice near the pole. The grayer areas indicate water bound to minerals on the surface. The color composite shows water as blue, carbon dioxide as green, and non-ice minerals as red".
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Tethys-PIA06140-N-HD.jpgTethys in natural colors (HD)56 visiteCommento NASA originale estratto da "NASA - Picture of the Day" del 29 Novembre 2004:"Tethys is one of the larger and closer moons of Saturn. The Cassini spacecraft now orbiting Saturn passed near the frozen moon at the end of October, capturing the most detailed images since the Voyager spacecrafts in the early 1980s. Tethys is composed almost completely of water ice and shows a large impact crater that nearly circles the planet. Because this crater did not disrupt the moon, Tethys is hypothesized to be at least partly liquid in its past. Two smaller moons, Telesto and Calypso, orbit Saturn just ahead of and behind Tethys. Giovanni Cassini discovered Tethys in 1684. The Cassini spacecraft is scheduled for a close fly-by of Tethys in September 2005".
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Saturn-W00003104.jpgSaturn and his shadow (2)56 visite2) vengono pubblicate solo le immagini che non presentano difetti (e quindi quelle mosse, quelle sovra e/o sotto-esposte oppure quelle, semplicemente, che non "mostrano nulla", sono eliminate). Ma non è vero neppure questo perchè nella Galleria (e chiunque lo può verificare) sono pubblicate decine di frames difettosi nel senso dianzi visto!; 3) la mancanza di sequenzialità e, quindi, l'esistenza di "buchi", dipende dal fatto che il sistema di numerazione e catalogazione dei frames prevede che vi siano, di tanto in tanto, dei "salti" (certo, tutto è possibile, ma questa ipotesi, fra le tante, ci sembra davvero la meno plausibile); 4) dopo che si è verificata - presumibilmente per errore (?) o per mancanza di attenzione (??) - la "pubblicazione" in Rete di alcuni frames "ambigui" o "potenzialmente pericolosi" (gli "streaks" in the sky, per esempio) che hanno di certo suscitato grandi interessi e provocato valanghe di domande alle quali non si può nè si deve rispondere, qualcuno ha pensato bene di "oscurare"...
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Saturn-W00002414.jpgSaturn and his Rings from approx. 590.000 Km54 visitenessun commento
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A - Saturn_s sky before the Streak (1).jpgSaturn's Sky just before the "Streak" (1) - N00008768149 visiteOggi, 5 Agosto 2004, inseriamo nella Sezione del Sito Lunar Explorer Italia dedicata a Saturno ed alle sue Lune, una serie di 5 fotogrammi ripresi dalla Sonda Cassini/Huygens che, a nostro parere, rappresenta una prova tangibile della presenza di un Oggetto Volante Non Identificato in transito nello spazio di Saturno.
Si tratta dei frames n. N00008768; N00008769; N00008770; N00008771 ed N00008772.
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The Rings from approx. 24.500.000 Km.jpgThe Rings from app.x 24.500.000 Km53 visitenessun commento
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