| Piú viste - Titan: The "Foggy" Moon |
Titan-Clouds-PIA06157.jpgTitan: Mid-Latitude Clouds57 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".
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Titan-Clouds-PIA06159.jpgTitanian Clouds (December 2004 fly-by)57 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".
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Titan-PIA06997_modest.jpgHaze Silhouettes Against Titan's Glow57 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".
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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".
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Titan-Huygens_Landing_Site-10-PIA06173_modest.jpgHuygens' descent map (2)57 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)".
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Titan-Shoreline_and_Drainage_Channels-00.jpgShoreline and Drainage Channels' Network on Titan 57 visiteCaption ESA originale:"This is one of the first raw images returned by the ESA Huygens probe during its successful descent. It was taken from an altitude of 16,2 Km with a resolution of approximately 40 metres per pixel. It apparently shows short, stubby drainage channels leading to a shoreline".
Il profilo di un tratto costiero, dunque: montagne (o colline), una fitta rete di canali ed una porzione di "mare" alla vista. Mare.
Già, ma un mare fatto di cosa?...
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Titan-Surface-31.pngFirst real color view of Titan57 visiteCaption ESA originale:"This image was returned yesterday, 14 January 2005, by ESA's Huygens probe during its successful descent to land on Titan. This is the coloured view, following processing to add reflection spectra data, gives a better indication of the actual colour of the surface. Initially thought to be rocks or ice blocks, they are more pebble-sized. The two rock-like objects just below the middle of the image are about 15 cm(left) and 4 cm (centre) across respectively, at a distance of about 85 cm from Huygens. The surface is darker than originally expected, consisting of a mixture of water and hydrocarbon ice. There is also evidence of erosion at the base of these objects, indicating possible fluvial activity".
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Titan-Shoreline_and_Drainage_Channels-04.jpgShoreline and Drainage Channels (Mosaic)57 visiteCaption ESA originale:"This composite was produced from images returned yesterday, 14 January 2005, by ESA's Huygens probe during its successful descent to land on Titan. It shows a full 360-degree view around Huygens. The left-hand side, behind Huygens, shows a boundary between light and dark areas. The white streaks seen near this boundary could be ground 'fog' of methane or ethane vapour, as they were not immediately visible from higher altitudes. As the probe descended, it drifted over a plateau (centre of image) and was heading towards its landing site in a dark area (right). This dark area is possibly a drainage channel which might still contain liquid material. From the drift of the probe, the wind speed has been estimated at around 6-7 mt per second. These images were taken from an altitude of about 8 Km with a resolution of about 20 mt per pixel".
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Titan-Shoreline_and_Drainage_Channels-02a.jpgShoreline and Drainage Channels57 visiteUn'altra istantanea di Titano ripresa durante la quieta discesa di Huygens verso la superficie di questo mondo ritenuto dagli Scienziati e dai Ricercatori di tutto il Mondo come una "versione gelida" (temperatura media di superficie: circa -180°C) di quello che era la Terra ai suoi albori.
L'atmosfera di Titano è prevalentemente costituita da azoto, con l'aggiunta di metano ed altri elementi di natura organica.
Si noti che alcuni di questi "organic compounds", se riscontrati nell'atmosfera di un corpo celeste simile alla Terra, sarebbero indici forti dell'esistenza di forma di vita indigene. Sulla Terra, infatti, la formazione del metano è legata all'esistenza di forme di vita nel senso che il metano stesso è un sottoprodotto ("by-product") del metabolismo di svariati organismi. E' la Vita stessa, insomma, che sulla Terra contribuisce a ricostituire continuamente le scorte di metano, sostituendo quello andato distrutto per ossidazione. Ma su Titano? Da dove viene tutto il metano che abbiamo scoperto?
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Titan-Rivers-Unnamed_River_and_Tributaries-PIA07236.jpgA "Great River" and several Tributaries on Titan57 visiteCaption NASA originale:"This mosaic of three frames from the Huygens Descent Imager/Spectral Radiometer (DISR) instrument provides unprecedented detail of the high ridge area including the flow down into a major river channel from different sources".
Un fiume di idrocarburi (?) scorre quietamente su Titano, ben alimentato da svariati affluenti. Un'immagine eccezionale e che ci riporta - forse - agli albori del nostro Mondo. Qui, su Titano, forse sta nascendo qualcosa; ma che cosa può riuscire a sopravvivere e ad alimentarsi con una temperatura media di -180°C?
Forse gli orizzonti della Vita sono molto più grandi di quanto la nostra Scienza e la nostra capacità di capire sono pronte ad accettare.
Forse.
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Titan-Channels-Drainage_Channels-PIA07236-01.jpgWater Ice and Methane Springs on Titan57 visiteCaption NASA originale:"A single Huygens DISR image that shows two new features on the surface of Titan. A bright linear feature suggests an area where water ice may have been extruded onto the surface. Also visible are short, stubby dark channels that may have been formed by 'springs' of liquid methane rather than methane rain".
Come mai, qualcuno si è chiesto, gli idrocarburi di Titano non sono completamente ghiacciati? Come mai - almeno a quanto ci è dato vedere - i "fiumi" e le "sorgenti" di idrocarburi di Titano, rispettivamente, scorrono e zampillano? Che cosa permette alla superficie di Titano di essere sufficientemente calda da consentire a questo incredibile mondo di essere - da un certo punto di vista - "vivo e vitale"?
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Titan-Atmosphere-PIA06182.jpgOver the Clouds of Titan57 visiteCaption NASA originale:"This image was taken during Cassini's 3rd close approach to Titan on Feb. 15, 2005.
The image was taken with the Cassini spacecraft narrow angle camera through a filter sensitive to wavelengths of polarized infrared light centered at 338 nanometers. The image was acquired at a distance of approximately 151.000 Km (approx. 94.000 miles) from Titan and at a phase angle of 20°.
Resolution in the image is about 900 meters (approx. 3.000 feet) per pixel".
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