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| Piú votate - Titan: The "Foggy" Moon |
Titan-Seas-PIA09211.jpgJust like California...56 visiteOn May 12, 2007, Cassini completed its 31st Fly-By of Saturn's moon Titan, which the team calls T30. The radar instrument obtained this image showing the coastline and numerous island groups of a portion of a large sea, consistent with the larger sea seen by the Cassini imaging instrument.
Like other bodies of liquid seen on Titan, this feature reveals channels, islands, bays, and other features typical of terrestrial coastlines and the liquid, most likely a combination of methane and ethane, appears very dark to the radar instrument. What is striking about this portion of the sea compared to other liquid bodies on Titan is the relative absence of brighter regions within it, suggesting that the depth of the liquid here exceeds tens of meters.
Of particular note is the presence of isolated islands, which follow the same direction as the peninsula to their lower right, suggesting that they may be part of a mountain ridgeline that has been flooded. This is analogous to, for example, Catalina Island off the coast of Southern California.
MareKromium
(6 voti)
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Titan-Island-PIA09180.jpgTitanian Sea and Islands in it59 visiteCaption NASA:"This radar image, obtained by Cassini's radar instrument during a near-polar flyby on Feb. 22, 2007, shows a big island smack in the middle of one of the larger lakes imaged on Saturn's moon Titan. This image offers further evidence that the largest lakes are at the highest latitudes.
The island is about 90 Km (approx. 62 miles) by 150 Km (approx. 93 miles) across, about the size of Kodiak Island in Alaska or the Big Island of Hawaii.
The island may actually be a peninsula connected by a bridge to a larger stretch of land. As you go farther down the image, several very small lakes begin to appear, which may be controlled by local topography.
This image was taken in synthetic aperture mode at 700 mt (2300 feet) resolution. North is toward the left. The image is centered at about 79° North Lat. and 310° West Long".
(6 voti)
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Titan-Dunes-PIA09115.jpgTitanian Dunes55 visiteCaption NASA:"This radar image of Titan's well-known dunes is distinctive because it may show an age relationship between different classes of features on the surface of this frigid world.
Taken by Cassini's radar mapper on Jan. 13, 2007, during a flyby of Titan, three kinds of terrain can be seen. Throughout the image, the fine striping has been identified as dunes, possibly made from organic material and formed by wind activity. Dunes are a common landform on Titan.
The bright material at the lower right of the image is interpreted as being topographically higher than the dunes that go around it, and several circular features seen at the top center may be craters that are slowly being buried by the dunes. Since the dunes seem to lie over the craters, the dune activity probably occurred later in time.
This image was taken in synthetic aperture mode and has a resolution of approx. 350 mt (1150 feet).
North is toward the top left corner of the image, which is approx. 160 x 150 Km wide".MareKromium
(6 voti)
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Titan-PIA06107-00.jpgThe "True Colors" of Titan, according to Lunexit57 visiteLa NASA, allorchè si tratta di colorizzare Titano, oscilla fra il giallo/arancio (come ben si vede nei frames Voyager), il giallo "canarino", con bordi bluastri (si vedano i primi frames Cassini, tipo PIA06089) ed una colorazione ambigua che potremmo definire giallo/salmonato, con bordi verde chiaro (ultimi frames Cassini, tipo PIA08351). Ma la NASA ha le idee chiare in tema di colori? Diremmo proprio di no, ed a nulla valgono le precisazioni che vengono fatte allorchè la NASA stessa precisa le diverse lunghezze d'onda impiegate per le colorizzazioni (jargon&tecnochiacchiere, nulla di più).
E allora?
E allora subentra - ancora una volta - il buon senso e l'osservazione telescopica (sia da Terra, sia HST). Risultato: Titano è (globalmente) color giallo-pallido, con toni più chiari ed accesi nelle sue Regioni Nord Polari e più sbiaditi in quelle Equatoriali.
Ed i bordi blu e verdi? Ed i bianchi accesi? E gli arancioni? Beh, se la NASA "li vede", vuol dire che ci saranno; ma noi non li "vediamo", neppure filtrando banda-per-banda i loro stessi color-frames e quindi...Questo è Titano, secondo noi, in "colori naturali" (ossìa come li vedremmo se ci trovassimo nei suoi pressi).
(6 voti)
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Titan-Lakes-Unnamed_North_Polar_Lakes-02-PIA01942.jpgTitanian Northern Lakes (3)56 visiteCaption NASA originale:"Using its radar system, the Cassini spacecraft has imaged new lakes on Titan.
The large dark patch seen on this image, at high latitudes surrounding Titan's North Pole, is most likely a hydrocarbon lake. Several dark channels can be seen; the longest one at the left meanders over almost 100 Km (about 62 miles), and appears to drain into the lake. Some dark channels are remarkably straight, suggesting possible faulting in the subsurface. The bright landforms jutting into the lake indicate that old, eroded landforms may have flooded.
This radar image was acquired by the Cassini radar instrument in synthetic aperture mode on Oct. 9, 2006. The image is centered near 73° North Latitude and 343° West Longitude; it measures about 300 by 140 Km (such as about 190 by 90 miles). Smallest details in this image are about 500 mt (approx. 1.640 feet) across".
(6 voti)
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Titan-N00067442.jpgShort "light-streak" in the space of Titan57 visiteCaption NASA:"N00067442.jpg was taken on October 10, 2006 and received on Earth on the same day. The camera was pointing toward Titan that, at the time, was approximately 168.568 Km away.
This image was taken using the CL1 and CB3 filters and it has not been validated or calibrated".
(6 voti)
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Titan-PIA08733.jpgCrescent Titan (HR)68 visiteCaption NASA originale:"This composite image, composed of two images taken with Cassini's Visual and Infrared Mapping Spectrometer (VIMS), shows a crescent view of Saturn's moon Titan.
The data were obtained during a flyby on July 22, 2006, at a distance of 15.700 Km (about 9.700 miles) from Titan. The image was constructed from images taken at wavelengths of 1,26 microns (blue), 2 microns (green) and 5 microns (red)".
(6 voti)
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Titan-Regions-Senkyo_and_Aaru_Regions-PIA08231.jpgAaru and Senkyo82 visiteAs it approached Titan for yet another revealing encounter, the Cassini spacecraft acquired this image showing terrain on the moon's Saturn-facing hemisphere.
Prominent dark areas found in the moon's equatorial region appear to contain vast and continuous dune fields, discovered by the Cassini Radar experiment and likely composed of particles that drop from Titan's unique, smoggy atmosphere.
The Dark Regions seen here are provisionally named Aaru and Senkyo, with parts of Western Fensal and Aztlan showing at left, near the terminator.
The image was taken with the Cassini spacecraft wide-angle camera using a spectral filter sensitive to wavelengths of infrared light centered at 752 nanometers. The view was obtained on July 2, 2006 at a distance of approx. 163.000 Km (about 101.000 miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 62°.
Image scale is roughly 19 Km (such as about 12 miles) per pixel.
(6 voti)
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Titan-Lakes-Unnamed_North_Polar_Lakes-01-PIA08630-2.jpgTitanian Northern Lakes (2)56 visiteCaption NASA originale:"For all these reasons, scientists interpret the dark areas as lakes of liquid methane or ethane, making Titan the only body in the Solar System besides Earth known to possess lakes. Because such lakes may wax and wane over time, and winds may alter the roughness of their surfaces. Repeat coverage of these areas should test whether indeed these are bodies of liquid.
These two radar images were acquired by the Cassini radar instrument in synthetic aperture mode on July 21, 2006.
The image (1) is centered near 80° North Lat. and 92° West Long.; it measures about 380x120 Km.
The image (2) is centered near 78° North Lat. and 18° West Long.; it measures about 425x120 Km.
Smallest details in this image are about 500 mt (roughly 1640 feet) across".
(6 voti)
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Titan-Lakes-Unnamed_North_Polar_Lakes-00-PIA08630.jpgTitanian Northern Lakes (1)55 visiteCaption NASA originale:"The Cassini spacecraft, using its radar system, has discovered very strong evidence for hydrocarbon lakes on Titan.
Dark patches, which resemble terrestrial lakes, seem to be sprinkled all over the high latitudes surrounding Titan's North Pole.
Scientists have speculated that liquid methane or ethane might form lakes on Titan, particularly near the somewhat colder Polar Regions. In the images, a variety of dark patches, some with channels leading in or out of them, appear. The channels have a shape that strongly implies they were carved by liquid. Some of the dark patches and connecting channels are completely black, that is, they reflect back essentially no radar signal, and hence must be extremely smooth. In some cases rims can be seen around the dark patches, suggesting deposits that might form as liquid evaporates. The abundant methane in Titan's atmosphere is stable as a liquid under Titan conditions, as is its abundant chemical product, ethane, but liquid water is not".
(6 voti)
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Titan-Rivers-Unnamed_Rivers_and_Channels-PIA08604-0.jpgCold Rivers56 visiteCaption NASA originale:"A network of river channels is located atop Xanadu, the continent-sized Region on Saturn's moon Titan.
This radar image was captured by the Cassini Radar Mapper on April 30, 2006.
These winding, meandering river channels start from the top of the image and run like a fork in the road, splitting to the right and left of the image. At Titan's chilly conditions, streams of methane and/or ethane might flow across parts of the Region.
The picture is roughly 230 Km (about 143 miles) wide by 340 Km (such as approx. 211 miles) long, and shows features as small as about 500 mt (approx. 1640 feet)".
(6 voti)
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Titan-Rivers-Unnamed_Rivers_and_Channels-PIA08428-0.jpgThe rivers of Titan...56 visiteThis image from the Synthetic Aperture Radar instrument on the Cassini spacecraft shows the radar-bright western margin of Xanadu, one of the most prominent features on Titan.
In radar images, bright regions indicate a rough or scattering material, while a dark region might be smoother or more absorbing. This image was taken during a flyby of Titan on April 30, 2006.
Narrow, sinuous, radar-bright channels, meandering like a maze, are seen on the right-hand-side of the image. These may be river networks that might have flowed onto the dark areas on the left of the image. Vast, dark areas covered by dunes are seen on the equatorial regions of Titan (see PIA03567) and have been referred to as Titan's "sand seas". Near the middle of the image is a radar-bright area that has a boundary with the dark sand seas. Because the radar illumination is coming from the top, this indicates that the bright region, Xanadu, is topographically higher than the sand seas.
(6 voti)
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