| Ultimi arrivi - Titan: The "Foggy" Moon |
Titan-Surface-30.jpgOn the surface of Titan57 visiteCaption ESA originale:"This raw image was returned by the ESA Huygens DISR camera after the probe descended through the atmosphere of Titan. It shows the surface of Titan with ice blocks strewn around. The size and distance of the blocks will be determined when the image is properly processed". Dunque Huygens ce l'ha fatta: è scesa su Titano! E la qualità di queste prime immagini supera le nostre più rosee aspettative: la visibilità è buona e questa parte di Titano sembra ricordarci - vagamente - la superficie di Venere, così come ripresa dalle Sonde Sovietiche "Venera".Gen 15, 2005
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Titan-Huygens_Landing_Site-11-PIA07229_modest.jpgHuygens' descent map (3) 60 visiteThe octagons indicate anticipated fields of view of panoramic mosaics of images taken by Huygens' descent imager and spectral radiometer instrument as the probe reaches certain altitudes during its descent. This map shows the footprints for mosaics to be assembled from 36 individual images at each altitude, with the field of view cut off at 75° from straight down although the actual images will extend all the way to the hazy horizon. Each mosaic made this way will be about 1.300 by 1.300 pixels. The largest octagon (in red) is about 1.120 Km across and represents the field of view for the mosaic of images taken at an altitude of 150 Km. From that height, individual pixels in the center of the image will be about 150 mts across, though haze between the ground and the camera at that height will likely degrade the resolution in those images. The location of the anticipated landing site is based on modeling of Titan's winds, and the actual landing site will be different if the actual winds experienced by Huygens during descent differ from this model.
Gen 14, 2005
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Titan-Huygens_Landing_Site-10-PIA06173_modest.jpgHuygens' descent map (2)56 visiteCaption NASA originale:"For about two hours, the probe will fall by parachute from an altitude of 160 Km (99 miles) to Titan's surface. During the descent the DISR and a few other science instruments will send data about the moon's atmosphere and surface back to the Cassini spacecraft for relay to Earth. The DISR will take pictures as the probe slowly spins and some of these will be made into panoramic views of Titan's surface.
The first map (PIA-06172) shows expected coverage by the Descent Imager/Spectral Radiometer side-looking imager and two downward-looking imagers - one providing medium-resolution and the other high-resolution coverage. The planned coverage by the medium- and high-resolution imagers is the subject of this map (PIA-06173)".Gen 12, 2005
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Titan-Huygens_Landing_Site-09-PIA06172_modest.jpgHuygens' descent map (1)57 visiteCaption NASA originale:"This map illustrates the planned imaging coverage for the Descent Imager/Spectral Radiometer (DISR), onboard the Huygens probe during the probe's descent toward Titan's surface on Jan. 14, 2005. The DISR is one of two NASA instruments on the probe. The colored lines delineate regions that will be imaged at different resolutions as the probe descends. On each map, the site where Huygens is predicted to land is marked with a yellow dot. This area is in a boundary between dark and bright regions. This map was made from the images taken by the Cassini spacecraft cameras on Oct. 26, 2004, at image scales of 4 to 6 Km per pixel. The images were obtained using a narrow band filter centered at 938 nanometers - a near-infrared wavelength (invisible to the human eye) at which light can penetrate Titan's atmosphere to reach the surface and return through the atmosphere to be detected by the camera. The images have been processed to enhance surface details".Gen 12, 2005
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Titan-Atmosphere-PIA06160_modest.jpgThe many layers of Titan's Atmosphere56 visiteCaption NASA originale:"Cassini has found Titan's upper atmosphere to consist of a surprising number of layers of haze, as shown in this ultraviolet image of Titan's night side limb, colorized to look like true color. The many fine haze layers extend several hundred kilometers above the surface. Although this is a night side view, with only a thin crescent receiving direct sunlight, the haze layers are bright from light scattered through the atmosphere. The image was taken with the Cassini spacecraft narrow angle camera. About 12 distinct haze layers can be seen in this image, with a scale of 0.7 Km (0.43 miles) per pixel. The limb shown here is at about 10° south latitude, in the equatorial region".Dic 17, 2004
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Titan-PIA06996_modest.jpgDoes Titan have a so-called "weather-pattern"?57 visiteIn the first image (left), obtained on the 1st Titan flyby, from a distance of 200.000 Km, Titan's skies are cloud-free, except for a patch of clouds observed over the South Pole near the bottom of the image. In contrast, the image on the right shows a recent view of this same area of Titan obtained 7 weeks later on the 2nd close Titan flyby, from a distance of 225.000 Km. This image clearly shows that several extensive patches of clouds have formed over temperate latitudes. The appearance of these clouds reveals the existence of weather. Tracking these features is currently underway by scientists, who hope to gain a better understanding of global circulation, regional weather patterns and localized meteorology in Titan's skies. The red color images the surface at a wavelength (2.01 micron) where the surface is relatively bright, making the surface appear reddish in these color images. The green color (2.83 micron) images the surface as well, but due to enhanced absorption of sunlight by the surface and lower atmosphere, the surface is relatively dark here compared to the red. The blue color (2.13 micron) is at a wavelength where sunlight cannot reach the surface at all due to strong absorption by the atmospheric gas methane. In contrast to the reddish surface, bright clouds at a relatively high altitude (here, about 30 kilometers (19 miles) above the ground) residing above most of the atmospheric absorption appear whitish in these representations, as they reflect sunlight effectively in all three near-infrared colors.
Dic 17, 2004
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Titan-PIA06997_modest.jpgHaze Silhouettes Against Titan's Glow56 visite"A high-altitude haze layer residing some 400 Km above the surface of Titan is seen here traced along the limb of Titan as silhouetted against the glow of Titan's atmosphere produced by the fluorescence of methane gas. This detached haze layer can be seen as a dark lane imbedded within the gold-colored fluorescent layers of Titan. This image of Titan's limb and surface was obtained on Dec. 13, 2004 from a vantage point some 158.000 Km above the night side of Titan, at a phase angle of 161°. Beneath the fluorescence, Titan's surface at the extreme limb can be seen in blue color, illuminated by 5-micron wavelength sunlight that penetrates the thick atmosphere and hazes to reflect off the limb of Titan. The darkness of the silhouetted haze layer comprised of relatively small particles suggests that the particles themselves absorb strongly at the fluorescent wavelength and thus are possibly comprised of relatively complex hydrocarbon aerosols generated by photochemical processes in Titan's upper atmosphere".Dic 17, 2004
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Titan-Clouds-PIA06159.jpgTitanian Clouds (December 2004 fly-by)56 visiteCaption NASA originale:"Cutting through the middle of the image is a sharp boundary between the bright region known as Xanadu Regio on the right and dark terrain to the left. This mosaic includes some areas seen at regional scales in October 2004 (see PIA 06124), as well as additional areas to the north and east not seen during that flyby. Among the new features seen in this mosaic is a strangely shaped bright feature near the center of the image as well as clouds near the bottom of the image (see also PIA 06110). The northern portion of the bright/dark boundary appears to be more complex than the arching and sharp boundary seen farther to the south. Cassini scientists continue to examine images such as this to determine the cause of this terrain. The images in this mosaic have been processed to enhance surface features and sharpen brightness variations".Dic 17, 2004
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Titan-Clouds-PIA06158.jpgTitanian Clouds (October 2004 fly-by)56 visiteCaption NASA originale:"Cutting through the middle of the image is a sharp boundary between the bright region known as Xanadu Regio on the right and dark terrain to the left. Several smaller bright features, between 30 and 200 Km across are seen within the dark terrain. These intriguing features are a focus of further research and observations for Cassini scientists. One clue to their origin and history is the presence of bright "trails" within the dark material on the eastern sides of the bright spots. A mottled texture is seen within Xanadu, including dark, crisscrossing lines, suggestive of tectonic activity. No definitive craters have been found in these images, though several bright rings or circular features are seen in the dark terrain. However, without topographic shading, their identification as impact structures can not be confirmed. The images in this mosaic have been processed to enhance surface features and sharpen boundaries".Dic 17, 2004
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Titan-Clouds-PIA06157.jpgTitan: Mid-Latitude Clouds56 visiteCaption NASA originale:"The Clouds seen here are at about 38° South Latitude on Titan. The Clouds across the middle of the frame extend about 250 Km (approx. 155 miles). The image scale is about 0,6 Km (approx. 0,4 miles) per pixel". Dic 17, 2004
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Titan-W00003639.jpgClouds around Titan55 visiteImmagine di Titano ripresa da circa 29.000 Km. Oltre alle nuvole (sempre bianche e vaporose) non si riesce a distinguere alcun dettaglio della superficie di questa luna.Dic 15, 2004
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Titan-PIA06151_modest.jpgTitan from about 810.000 Km54 visiteCaption NASA originale:"The bright and dark regions near the center of the frame are features on Titan's surface. The image has been processed to make features more visible. The surface contrast is degraded toward the edges of the disk due to the effects of Titan's smoggy atmosphere. The region seen here is similar to that seen during Cassini's first close flyby of Titan in October. The bright area toward the bottom of the image is the region dubbed "Xanadu." North is to the upper right.
The image was acquired at a distance of approximately 810.000 Km and the image scale is 4.8 Km per pixel". Ed ora una curiosità: guardate il bordo di Titano, in alto alla Vostra Dx, ad ore 2, c'è un rilievo rotondeggiante (una "cupola scura") perfettamente visibile. Non sembra un difetto della foto o un artifact derivante da vizio di processo e/o di compressione dell'immagine. E allora, secondo Voi, che cos'è? Dic 14, 2004
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