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| Piú viste - Titan: The "Foggy" Moon |
Titan-N00156684-85-86-87-88-89-MF-LXTT.jpgWatching through the Fog... (False Colors; credits for the additional process. and color.: Dr Marco Faccin - Lunexit Team)74 visitenessun commentoMareKromium
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Titan-PIA14919.jpgTitan's South Polar Vortex (True Colors; credits: NASA/JPL-Caltech/Space Science Institute)74 visiteCaption NASA:"This frame (taken by the NASA - Cassini Spacecraft) shows us a South Polar Vortex or, in other words, a swirling Mass of Gas (and, perhaps, even other - heavier - Elements), which is located in the Upper Atmosphere, and approximately over the South Pole, of the Saturnian moon Titan. This Swirling Mass appears to complete one full rotation in about 9 (nine) hours - meaning a much faster period than the moon's 16 (sixteen)-days Rotation Period. The South Pole of Titan (which is about 3200 miles, or 5150 Km, across) is right under the Vortex.
Since the NASA - Cassini Spacecraft arrived in the Saturnian System, in 2004, Titan has shown a visible "Hood", such as an area of denser (when compared to the rest of the moon's Atmosphere) High Altitude Haze, high above the North Pole, but this is the first time that a similar phenomenon is seen above its South Pole. As a matter of fact, it was Northern Winter on Titan at the time of the arrival of the Cassini Spacecraft, and therefore much of its High Northern Latitudes was then in the darkness. But the Hood was high enough to still be illuminated by Sunlight. However, seasons have been changing since Saturn's August 2009 Equinox, which signaled the beginning of Spring in the Northern Hemisphere and the start of Fall (---> Autumn) in the Southern one, both for Saturn and for its very many moons. As a consequence of this season's changing, now the High Southern Latitudes are the ones moving into darkness, and the formation of this Vortex at Titan's South Pole may be related to the incoming Southern Winter and - maybe - the subsequent beginning of what could well be a South Polar Hood.
These new, more detailed images are only possible because of the NASA - Cassini Spacecraft newly inclined orbits, whose re-definition is part of the next phase of the Cassini Solstice Mission. Previously, Cassini was orbiting along the Equatorial Plane of Titan, and so the imaging team's pictures of the Polar Vortex (in the period between late March and mid-May), were taken from over Titan's Equator. At that time, however, the images taken by the Spacecraft only showed a brightening (or yellowing) of the detached Haze Layer located on the Limb (or Edge) of the Visible Disk of Titan, right over its South Polar Regions".MareKromium
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Titan-Surface-32.pngOn the surface of Titan73 visiteCaption ESA originale:"This raw image was returned yesterday, 14 January 2005, by ESA's Huygens probe during its successful descent to land on Titan. Sizes have been added to indicate scale of these features. 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-PIA12695.jpgThe strange Atmosphere of Titan (possible True Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)73 visiteCaption NASA:"The Cassini Spacecraft examines the characteristics of Titan's Atmosphere as it peers at Saturn's largest moon using a filter sensitive to Visible Violet Light.
This image shows Atmospheric Banding around Titan's North Pole and reveals hints of the moon's seasonal Hemispheric Dichotomy near the Equator. (to learn more about the Northern Bands, please refer to images PIA08868 and PIA08928).
This view looks toward the anti-Saturn side of Titan. North on Titan is up and rotated 23° to the left.
The image was taken in Visible Violet Light with the Cassini Spacecraft wide-angle camera on June 21, 2010. The view was obtained at a distance of approx. 170.000 Km (about 106.000 miles) from Titan and at a Sun-Titan-Spacecraft, or Phase, Angle of 33°.
Image scale is roughly 10 Km (about 6,2 miles) per pixel".MareKromium
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Titan-Regions-Adiri_Region-IMG002645.jpgAdiri Region72 visiteCaption NASA:"Bright mid-latitude clouds near the bottom of this view hint at the ongoing cycling of Methane on Titan. These cloud streaks are near the same latitude as similar clouds observed above different longitudes on Titan.
The view is centered on Titan's Trailing Hemisphere, over the 1.700 Km (such as about 1050 mile) wide bright Region known as "Adiri".
North on Titan is up and rotated 15° to the right.
This view was created by combining multiple images taken using a combination of spectral filters sensitive to wavelengths of infrared light centered at 939 and 742 nanometers
The images were taken with the Cassini spacecraft wide-angle camera on May 13, 2007 at a distance of approx. 104.000 Km (about 65.000 miles) from Titan. Image scale is roughly 12 Km (about 8 miles) per pixel. Due to scattering of light by Titan's hazy atmosphere, the sizes of surface features that can be resolved are a few times larger than the actual pixel scale".MareKromium
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Titan-N00112025.jpgUnknown Object in the Space of Titan (additional process. and color. by Lunexit)72 visiteTutti noi sappiamo riconoscere lo "streak" lasciato su un frame dal transito di un Raggio Cosmico (ormai gli esempi sono migliaia).
In questo caso, come ben si vede nell'inset (un extra-detail mgnf), l'oggetto luminoso evidenzia una "testa", una "coda" e quindi lascia anche intuire una "scia più debole - che si diparte dalla fine della "coda" e che è caratterizzata da perdita di materiale" (o da "scorie" di un qualche tipo).
Un bolide, forse.
Molto probabilmente un O.V.N.I. e, sicuramente, NON un Raggio Cosmico.MareKromium
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Titan-Regions-Senkyo_Region-PIA11577-02.jpgLight and dark Surface Features of Senkyo (possible Natural Colors; credits: Lunexit)72 visiteCaption NASA:"The Cassini Spacecraft peers through the hazy Atmosphere of Titan for a close view of light and dark Terrain on Saturn's largest moon.
This view is centered on Terrain at 28° South Lat. and 334° West Long. and shows a small part of the albedo feature named Senkyo on the Trailing Hemisphere of Titan.
The image was taken with the Cassini Spacecraft narrow-angle camera on July 9, 2009 using a spectral filter sensitive to wavelengths of Near-InfraRed Light centered at 938 nanometers. The view was obtained at a distance of approx. 251.000 Km (such as about 156.000 miles) from Titan and at a Sun-Titan-Spacecraft, or Phase, Angle of 27°.
Image scale is about 1 Km (3281 feet) per pixel".MareKromium
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Titan-Atmosphere-PIA09823-PCF-LXTT.jpgTitan's Upper Atmosphere (Enhanced Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)72 visitenessun commentoMareKromium
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Titan-MF-EB-LXTT-01.jpgNot an Aurora! (False Colors; credits for the additional process. and color.: Elisabetta Bonora and Marco Faccin - Lunar Explorer Italia/IPF)72 visiteDall'ingrandimento del dettaglio controverso (frame superiore) non è possibile ricavare alcuna certezza, se non che il Fenomeno (probabilmente) Atmosferico che interessa le estreme Regioni Sud-Polari di Titano è soggetto a rapidi cambiamenti nel tempo. La sua forma, poi (decisamente irregolare), ci spinge a preferire - diremmo in via definitiva - l'ipotesi transitoria e meteorologica per quanto attiene la natura del Fenomeno in questione (i.e.: nuvola, super-nuvola, nuvola semi-permanente o colonnare da post-impatto che sia).MareKromium
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Titan-PIA09034_H-1.jpgCrescent Titan71 visiteHuygens scored a first in 2005 by measuring the electrical conductivity of Titan’s atmosphere. The results hint at a new way to investigate the subsurface layers of Titan and could provide insight into whether or not Titan has a subsurface ocean.
The Permittivity, Waves and Altimetry (PWA) sensor on the Huygens Atmosphere Structure Instrument (HASI) detected an extremely low frequency (ELF) radio wave during the descent. It was oscillating very slowly for a radio wave, just 36 times a second, and increased slightly in frequency as the probe reached lower altitudes.
If the PWA team confirms that the signal is a natural phenomenon and not an artefact of the way the instrument worked, they will have discovered a powerful new way to probe not just the atmosphere of Titan but its subsurface as well.
The only other world on which ELF waves were detected before was Earth. They are reflected by both the surface of the Earth and its ionosphere, the rarefied region of the atmosphere where most particles are electrically charged. This turns the atmosphere into a giant ‘sound box’ where certain frequencies of ELF waves resonate and are reinforced, whilst other die away.
On Titan, however, the surface is a poor reflector because of its low conductivity and so these waves penetrate the interior. “The wave could have been reflected by the liquid-ice boundary of a subsurface ocean of water and ammonia predicted by theoretical models,” says Fernando Simões, CETP/IPSL-CNRS, France, and a member of the PWA team.
If Simões is right, successful modelling of how ELF waves resonate on Titan could lend support to the ocean’s existence and tell scientists about the depth at which it sits. Understanding the resonance however, is difficult.
Above about 100 kilometres altitude on Earth, the ionosphere provides the upper reflecting layer of the resonating cavity. At Titan, PWA revealed that things are more complicated. Apart from the ionosphere, at a much higher altitude of about 1200 kilometres, Huygens found a layer of ionized particles consisting of electrons, at 63 kilometres. “This does not match any previous prediction for Titan,” says Simões. To some extent, it splits Titan’s atmosphere into two resonating chambers.
With so much at stake, the PWA team are checking to make sure the detection is real and not an artefact generated by the spacecraft. They have already ruled out electrical interference from the instrument itself.
Two small arms, one on either side of Huygens, create an antenna and the team’s next goal is to investigate whether the arms could have oscillated during the descent. Simões and colleagues are building a special chamber to hold a replica of the instrument at the low temperature of Titan’s atmosphere, between 100-200 degrees Kelvin (about -173 to -73 °C), in order to check whether the antenna resonates at 36 hertz. If it does, it probably means that the signal is an artefact. If it does not, confidence in the signal’s reality will increase and the investigation of the atmosphere and subsurface can begin.
But perhaps the biggest mystery is what generated the ELF wave in the first place. On Earth, they are initiated by lightning strikes that make electrons in the atmosphere oscillate, releasing the ELF waves.
The PWA was designed to search for ELF waves on Titan while a microphone on Huygens kept an ear out for thunder – a sure sign of lightning. Cassini has also been watching for lightning using its cameras.
However, Huygens suggests that there is no lightning, or very little. “If there is lightning on Titan, it is significantly less than the amount of lightning that Earth experiences,” says Simões. So what generated Titan’s ELF? No one is quite sure yet. “It might be generated by an interaction with Saturn’s magnetosphere or related to Titan’s intrinsic fields,” suggests Simões. “Titan is proving to be an intriguing environment.”
One thing is certain: there is plenty to investigate. “The measurement of atmospheric electricity is something really new and exciting,” says Jean-Pierre Lebreton, ESA Huygens Project Scientist. “We could send similar instruments to study atmospheric electricity on other celestial bodies, in particular Venus, Mars, and the giant planets,” adds Simões.
The PWA team expect to release more definitive results when their investigation is complete.
MareKromium
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Titan-W00036545.jpgThe "uneven" Haze of Titan (possible Natural Colors - elab. Lunexit)71 visiteNoi osserviamo le immagini e quindi ci poniamo domande. Eccone una, per noi e per Voi: può essere che sia la cosiddetta "super-rotazione" delle nuvole di Titano la (sola o, se non altro, la maggior) causa delle - evidenti - irregolarità che caratterizzano gli strati più alti della sua atmosfera? Avete opinioni al riguardo?
Scriveteci e/o commentate!MareKromium
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Titan-PIA11567.jpgTitan's Atmosphere... (Natural Colors; credits: Lunar Explorer Italia)71 visiteCaption NASA:"The Cassini Spacecraft looks at Saturn's largest moon, Titan, revealing its halo-like ring formed in the upper hazes of the moon's extensive Atmosphere.
This view looks toward the darkened Leading Hemisphere of Titan, but lit terrain seen here is on on the Trailing Hemisphere and anti-Saturn side of the moon.
The moon's North Pole lies on the Terminator between the illuminated and unilluminated parts of the moon. The Pole is rotated 11° to the right in this image.
The image was taken with the Cassini Spacecraft narrow-angle camera on July 5, 2009 using a spectral filter sensitive to wavelengths of UltraViolet light centered at 338 nanometers. The view was acquired at a distance of approx. 1,3 MKM (about 808.000 miles) from Titan and at a Sun-Titan-Spacecraft, or Phase, Angle of 148°.
Image scale is roughly 8 Km (about 5 miles) per pixel".MareKromium
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