| Piú votate - Saturn: the "Ringed Beauty" and His Moons |
Enceladus_cassini_full.jpgEnceladus: the Paradise of "Interplanetary Skiers"54 visiteDa "NASA - Picture of the Day" del 24.02.2005:"Small, icy, inner moon of Saturn, Enceladus is only about 500 Km in diameter. But the distant world does reflect over 90% of the received sunlight, giving its surface about the same reflectivity as fresh snow. Seen here in a sharp view from the Cassini spacecraft's recent flyby, Enceladus shows a variety of surface features and very few impact craters - indicating that it has been an active world even though this tiny moon should have completely cooled off long ago. In fact, the resurfaced appearance of Enceladus could be the result of liquid water geysers or water volcanos. Since Enceladus orbits within the outer E-Ring of Saturn, the moon's surface may be kept snow-bright as it is continuously bombarded with icy ring particles. Eruptions on Enceladus itself would in turn supply material to the E-Ring. Would you like to ski there? Why not, but take note: Enceladus has only about 1/100th the surface gravity of Earth and a surface temperature of approx. - 200°C!".
(9 voti)
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F-Enceladus-N00028770.jpgEnceladus from approx. 1.784.000 Km55 visiteUn'immagine davvero spettacolare di Encelado e (supponiamo...) Epimeteo, apparentemente "divisi" dagli Anelli di Saturno: una sorta di 'pentagramma spaziale" fatto di sottili filamenti luminosi i quali sembrano 'tagliare' il Cielo circostante.
(9 voti)
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RHEA~0.jpgRhea: a Moon made of "frozen water"! (possible ANOMALY)55 visiteDa "NASA - Picture of the Day" del 15 Febbraio 2005:"Rhea, Saturn's second largest moon behind Titan, shows unusual wisps (wisp---> piccola striscia), visible above as light colored streaks. HR images of the wisps show them to be made of long braided fractures. Rhea is composed mostly of water ice, but likely has a small rocky core. Rhea's rotation and orbit are locked together, just like Earth's Moon, so that one side always faces Saturn; a consequence of this is that one side always leads the other. Rhea's leading surface is much more heavily cratered than the above pictured trailing surface".
Vi segnaliamo inoltre una possibile "Anomalia" (e non crediamo che si tratti di un photo-artifact o di un difetto del frame derivante da un'incompleta trasmissione dei dati): se osservate il lato Sn di Rhea, in prossimità del bordo e circa ad ore 8, vedrete un "disco scuro" stagliarsi contro il grigio della sua superficie. Noi crediamo che sia un "corpo in transito" (magari una "luna di Rhea!).
(9 voti)
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Mimas-PIA06176.jpgBlue Saturn and Mimas56 visiteCaption NASA originale:"Mimas drifts along in its orbit against the azure backdrop of Saturn's northern latitudes in this true color view. The long, dark lines on the atmosphere are shadows cast by the planet's rings.
Saturn's northern hemisphere is presently relatively cloud-free, and rays of sunlight take a long path through the atmosphere. This results in sunlight being scattered at shorter (bluer) wavelengths, thus giving the northernmost latitudes their bluish appearance at visible wavelengths.
At the bottom, craters on icy Mimas (398 Km or 247 miles across) give the moon a dimpled appearance.
Images taken using infrared (930 nanometers), green (568 nanometers) and ultraviolet (338 nanometers) spectral filters were combined. The colors have been adjusted to match closely what the scene would look like in natural color. The images were obtained using the Cassini spacecraft narrow angle camera on Jan. 18, 2005, at a distance of approx. 1,4 MKM from Saturn".
(9 voti)
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Saturn-PIA07008.jpgSaturn's temperature emissions (upper troposphere)56 visiteCaption NASA originale:"This is the sharpest image of Saturn's temperature emissions taken from the ground; it is a mosaic of 35 individual exposures made at the W.M. Keck I Observatory, Mauna Kea, Hawaii on Feb. 4, 2004.
The images to create this mosaic were taken with infrared radiation. The mosaic was taken at a wavelength near 17,65 microns and is sensitive to temperatures in Saturn's upper troposphere. The prominent hot spot at the bottom of the image is right at Saturn's South Pole. The warming of the Southern Hemisphere was expected, as Saturn was just past Southern Summer Solstice, but the abrupt changes in temperature with latitude were NOT expected. The tropospheric temperature increases toward the pole abruptly near 70° latitude from 88° to 89° Kelvin (-301° to -299° Fahrenheit) and then to 91° Kelvin (-296° degrees Fahrenheit) right at the Pole. Ring particles are not at a uniform temperature: they are obviously coldest just after having cooled down in Saturn's shadow (lower left)".
(9 voti)
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Mimas-N00026588.jpgOne half of Mimas56 visitenessun commento
(9 voti)
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Japetus-PIA07002_modest.jpgJapetus' surface composition (organic material?!?)55 visiteCaption NASA originale:"The three colors used in the mosaic correspond to 1.01, 3.21, and 3.80 microns. The different colors represent vastly different surface compositions. The upper bright blue region is rich in water ice, while the lower, dark brown region is composed mainly of a substance rich in organic material. The yellow region consists of a mixture of ice and organics, suggesting a gradual change in composition on the surface. This pattern suggests Iapetus swept up the dark material, which may have come from debris created from meteoritic impacts onto the small, outer satellites of Saturn".
(9 voti)
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Japetus-PIA06170_modest.jpgJapetus in HR55 visiteCaption NASA originale:"This oblique view of Saturn's moon Japetus from high latitude shows how the dark, heavily cratered terrain of Cassini Regio transitions to a bright, icy terrain at high latitudes. In this mosaic of 2 HR images taken during Cassini's New Year's Eve 2004 flyby of Japetus, the direction toward the north pole is approximately 15° below the horizontal on the right. At the equator terrains are uniformly covered with a dark mantle of material that has a reflectivity of about 4%. At latitudes toward the pole of about 40°, the dark deposits become patchy and diffuse as the surface transitions to a much brighter, icy terrain near the pole. The brightest icy materials exhibit visual reflectivity over 60%. Superimposed on the bright terrain is a subtle, ghostly pattern of crudely parallel, north-south trending wispy streaks. The streaks, which were discovered during this flyby of Iapetus, are typically a few kilometers wide and sometimes tens of kilometers long. Their appearance and orientation may be connected with the emplacement of dark materials that cover Cassini Regio. The dark materials might represent the gradual accumulation of dark debris falling from space, or alternatively, may represent fallout from plume-style eruptions that may have accompanied the formation of Iapetus's enigmatic equatorial ridge (see PIA 06166)".
(9 voti)
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Rhea-PIA06555_modest.jpgRhea's craters54 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.
(9 voti)
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Japetus-N00026373.jpgANOMALY - Japetus and a "streak" of light72 visiteNon ci vuole certo un "Cacciatore di Anomalie" per notare la ENORME Anomalia riscontrabile in questo frame: c'è un oggetto luminoso, infatti, in movimento sostanzialmente lineare e che emana una luce costante il quale sta transitando nelle vicinanze di questo pianetino. Molte immagini di Giapeto, come Voi stessi potrete constatare, contengono phographic artifacts di varia natura e che vanno dai "dead pixels" alle "strisciature" da raggi cosmici ad imperfezioni vere e proprie dell'immagine causate da un vizio nella trasmissione dei dati. Però, a nostro modo di vedere, questa "striscia" di luce è qualcosa di diverso. Ne abbiamo già incontrata una, nello Spazio di Saturno, qualche mese fa...ve ne ricordate? Era identica a questa!
(9 voti)
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Japetus-N00026216.jpgJapetus (and the "Pentagon") from about 180.000 Km (1)114 visiteUna serie di immagini ravvicinate di Giapeto, la "Luna Nera" di Saturno: un corpo celeste strano, per una metà simile a tante altre lune (sia di Saturno, sia di altri Pianeti del Sistema Solare) e per un'altra metà completamente diverso: nero, buio, indefinibile. Non sappiamo da che cosa dipenda l'oscurità che domina su una metà abbondante della superficie di questo gelido mondo, anche se sono state formulate tante ipotesi al riguardo.
La più verosimile, a nostro avviso, è quella che fa risalire la mancanza di riflessione della luce che colpisce questo mondo al materiale che lo forma e/o lo ricopre in buona parte. Carbone, molto probabilmente (o polveri carbonifere) oppure qualche altro minerale dalle caratteristiche simili. La luce, se osservate le fotografie di Giapeto (in particolar modo quelle riprese da una certa distanza), sembra "affogare" sulla superficie di questa luna: essa viene - semplicemente - catturata da Giapeto e non riflessa. Un altro mistero da esaminare, dunque...
(9 voti)
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Saturn-W00002927.jpgSaturn from approx. 1.600.000 Km53 visiteUna splendida ripresa di Saturno che ci permette di familiarizzare con il "Signore degli Anelli". Il particolare di maggiore interesse, secondo noi (ed anche se non siamo certi che si tratti di un oggetto reale), è costituito dal corpuscolo luminoso, dalla forma vagamente allungata, visibile sul margine superiore degli anelli, verso la Sn dell'Osservatore. Si tratta di una Luna minore, di un "clump", o di un difetto dell'immagine (e cioè un "artifact")?...
(9 voti)
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