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Titan-Cryovolcanism-02.jpgCryovolcanism on Titan? (3)53 visiteInsomma: è più "credibile" che la nostra Scienza sia ancora fortemente limitata ed il nostro Sapere ancora - purtroppo - molto lontano dal potersi definire capace di interpretare con assoluta accuratezza una buona parte dei fenomeni che accadono nel nostro (piccolo) Sistema Solare e quindi nell'Universo oppure dobbiamo arrenderci all'idea che ormai 'abbiamo capito tutto' (o 'quasi tutto'...) e che ogni fenomeno è spiegabile facendo ricorso ad una macchina fotografica, ad uno spettrometro ad infrarossi ed a qualche altro aggeggio elettronico dalla sigla impossibile a pronunciarsi?
Scienza non è solo calcolo ma è anche (e forse soprattutto...) riflessione, umiltà, senso comune, capacità di meravigliarsi, capacità di dire - talvolta - "non sappiamo, non abbiamo idea di che cosa stiamo guardando".
Pensateci sopra...
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Titan-Lakes-South_Polar_Lake-00-PIA06240.jpgOntario Lacus and the South Polar Regions of Titan56 visiteThis view of Titan's South Polar Region reveals an intriguing dark feature that may be the site of a past or present lake of liquid hydrocarbons.
The true nature of this feature, seen here at left of center, is not yet known, but the shore-like smoothness of its perimeter and its presence in an area where frequent convective storm clouds have been observed by Cassini and Earth-based astronomers make it the best candidate thus far for an open body of liquid on Titan.
If this interpretation is correct, then other very dark but smaller features seen in the South Polar Region, some of which are captured in this image, may also be the sites of liquid hydrocarbon reservoirs.
In addition to the notion that the dark feature is or was a lake filled with liquid hydrocarbons, scientists have speculated about other possibilities. For instance, it is plausible that the lake is simply a broad depression filled by dark, solid hydrocarbons falling from the atmosphere onto Titan's surface. In this case, the smoothed outline might be the result of a process unrelated to rainfall, such as a sinkhole or a volcanic caldera.
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Titan-Lakes-South_Polar_Lake-01-PIA06241-PCF-LXTT-IPF-000.jpgOntario Lacus and the South Polar Regions of Titan56 visiteCaption NASA originale:"Although it is far too cold for blossoming flowers, summer does bring storm clouds and presumably rain to Titan's south polar region.
The observed persistence of convective storm activity in the region during the Southern Titan Summer has led scientists to speculate that the dark, footprint-shaped feature near the upper left could be a past or present reservoir for Titan's methane rains".
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Titan-IR-PIA07542.jpgInfrared Titan (from approx. 1,2 MKM)53 visiteCaption NASA originale:"Southeast of Xanadu (and above the center in this view) is a peculiar semi-circular feature informally referred to by imaging scientists as "The Smile". This surface feature is the brightest spot on Titan's surface, not only to the Imaging Science Subsystem Cameras, but also to the Visual and Infrared Mapping Spectrometer (VIMS), which sees the surface at even longer wavelengths. "The Smile" is about 560 Km (345 miles) wide.
At the landing site of the successful Huygens probe mission, brighter regions correspond to icy upland areas, while the darker regions are lowlands that possess a higher proportion of the organic byproducts of Titan's atmospheric photochemistry. Those results seem to confirm the long-standing hypothesis that Xanadu is a relatively high region of less contaminated ice. However, the cause of the even brighter Smile is a mystery that is still under study. Farther South, a field of bright clouds arcs around the Pole, moving at a few meters per second".
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Titan-PIA07565.jpgTitan's Terminator...from about 1,3 MKM53 visiteTitan's equatorial latitudes are distinctly different in character from its South Polar Region, as this image shows. The dark terrain, presumably lowland, seen here does not extend much farther south than about 30° South. The successful Huygens probe landed in such a Region. The Huygens probe is rotating into the light here, seeing the dawn of a new day. The bright region toward the right side of Titan's disk is Xanadu. This area is thought to consist of upland terrain that is relatively uncontaminated by the dark material that fills the lowland regions.
Near the South Pole, and just eastward of the terminator, is the dark feature identified by imaging scientists as the best candidate (so far) for a past or present hydrocarbon lake on Titan (see PIA06241). Farther east of the lake-like feature, bright clouds arc around the Pole. These clouds occupy a latitude range that is consistent with previously-seen convective cloud activity on Titan. The phase angle is 60° while the image scale is 7 Km per pixel.
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Titan-IMG001663-br500.jpgTitan from about 209.000 Km (FlyBy n. 6)53 visiteOriginal caption:"This is one of the first images returned from T6, such as the sixth Titan flyby. The image (W00010189.jpg) was taken on August 21, 2005 and received on Earth August 23, 2005. The camera was pointing toward Titan (approx. 209.379 Km away) and the image was taken using the CB3 and IRP90 filters. (...)".
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Titan-PIA07730.jpgTitan, from about 159.000 Km53 visiteThis processed image from Cassini's Aug. 22, 2005, flyby of Titan reveals mid-latitudes on the Moon's Saturn-facing side.
Provisional names recently have been applied to a number of features on Titan. Features within the Region seen here - long known informally as the "H" - now have names like Tsegihi, Aztlan and Quivira.
The bright 215-Km-wide feature provisionally named "Bazaruto Facula" is clearly visible right of center, with its dark, unnamed 80-Km-wide crater at its center.
This view was acquired with the wide-angle camera at a distance of approx. 159.000 Km from Titan using a spectral filter centered on infrared wavelengths at 939 nnmts. The image scale is 9 Km per pixel.
Previous observations indicate that, due to Titan's thick and very hazy atmosphere, the sizes of surface features that can be resolved are a few times larger than the actual pixel scale.
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Titan-PIA07729.jpgTitan, from about 213.000 Km (natural colors)53 visiteAs Cassini approached Titan on Aug. 21, 2005, it captured this natural color view of the moon's orange (nota: veramente, a parte i nostri occhi - che, come tutti sanno, possono sbagliare -, il software che utilizziamo per valutare la densità cromatica dei frames NASA che pubblichiamo e che ci permette altresì di identificare i 'colori maggiori' che sono presenti in essi ci dice che il colore dominante è il "giallo"...), global smog. Titan's hazy atmosphere was frustrating to NASA Voyager scientists during the first tantalizing Titan flybys 25 years ago, but now Titan's surface is being revealed by Cassini with startling clarity (...).
Images taken with the wide-angle camera using red, green and blue spectral filters were combined to create this color view. The images were acquired at a distance of approximately 213.000 Km from Titan and at a Sun-Titan-spacecraft, or phase, angle of 55°. Resolution in the image is about 13 Km per pixel.
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Titan-Regions-Fensal_and_Aztlan_Region-PIA07732.jpgFensal and Aztlan Region on Titan54 visiteDuring its Sept. 7, 2005, flyby of Titan, Cassini acquired images of territory on the moon's Saturn-facing hemisphere that were assembled to create this mosaic. Once known only as "The H" because the Region looks something like the letter on its side, features in this Region now possess provisional names. The Northern Branch of the H is now called Fensal, while the Southern Branch is known as Aztlan.
Fensal is littered with small "islands" ranging in size from 5 to 40 Km across. These landforms currently are thought to be water ice upland areas, surrounded by shallower terrain that is filled-in with dark particulate material from the atmosphere. A few larger islands are also seen, like Bazaruto Facula (near right, containing a dark crater) and several islands in Western Fensal. When viewed in images of Shangri-La (on the other side of Titan), island-like landforms of this size tend to occur in clusters with apparent preferred orientations. The small islands in Fensal appear much more scattered (and most appear roughly circular), although a few islands do have an east-west orientation to their long axis.
Aztlan, on the other hand, appears comparatively devoid of small islands, with three large islands in its western reaches, plus only a few smaller islands. The largest of these islands is called "Sotra Facula" (just right of center in the bottom left mosaic frame), and measures 240 by 120 kilometers (149 to 75 miles) across.
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Titan-Shoreline-PIA03563_modest.jpgShoreline on Titan?53 visiteCaption originale:"This SAR (Synthetic Aperture Radar) image of the surface of Saturn's moon Titan, was obtained by the Cassini spacecraft on Sept. 7, 2005. The bright, rough Region on the left side of the image seems to be topographically "high terrain" that is cut by "channels" and "bays".
The boundary of the bright (rough) Region and the dark (smooth) Region appears to be a "shoreline". The patterns in the dark area indicate that it may once have been flooded, with the liquid having at least partially receded.
The image is 175 Km high and 330 Km wide (about 109 by 205 miles), and is located at 66 degrees south latitude, 356° West Longitude in the Southern Hemisphere of Titan".
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Titan-Channels-Unnamed_Channels-PIA03564.jpgCanyonland on Titan54 visiteFluids have flowed and cut these deeply-incised channels into the icy surface of Titan as seen in this SAR image. The channels are roughly 1 Km across (about 0,6 miles) and perhaps 200 mt deep (about 650 feet); some can be traced as far as 200 Km (about 120 miles). Many of them have angular segments suggesting they may follow faults in Titan's crust.
Taken together with the two other radar passes (October 2004 and February 2005), these very HR images have identified at least two distinct types of drainage and channel formation on Titan. The style shown in this image consists of long valleys following angular patterns without many tributaries, suggesting that fluids flow over great distances.
This Cassini radar image was acquired as a part of the Titan flyby observations taken on Sept. 7, 2005, from a distance of about 2000 Km. The area is located at about 55° South Latitude, 7,5° West Longitude and extends over 300 km (about 186 miles) right to left.
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Titan-Channels-Unnamed_Channels-PIA03565.jpgTitan's rainfall?!?53 visiteIn contrast to the image "Canyonlands on Titan", this bright terrain is cut by channels that are variable in width; they form both radial and branching networks and such patterns are reminiscent of networks formed by rainfall on Earth.
At the bottom of the frame, the channels radiate from a possible source into a dark, smooth region that seems flatter and more plains-like. One interpretation is that the higher, rougher terrain has been cleansed of organic debris and eroded by methane rainfall. The removed material has then been deposited into the lower plains.
This Cassini SAR image of Titan was taken on Sept. 7, 2005, at a distance of 2000 Km from Titan. It is located near 48° South Latitude, 14° West Longitude and extends about 240 Km right to left.
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