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| Piú votate - Neptune and His Moons |
ZC-Neptune_s Rings-PIA01493_modest.jpgThe Rings of Neptune66 visiteCaption NASA originale:"In Neptune's outermost ring, 39.000 miles out, material mysteriously clumps into 3 arcs.
Voyager 2 acquired this image as it encountered Neptune in August 1989".
(5 voti)
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Triton-PIA02246-PCF-LXTT-IPF.jpgStill in the Abyss (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunar Explorer Italia/Italian Planetary Foundation)98 visiteFeatures as small as approx. 100 Km (such as a little more than 62 miles) across can be seen in this Absolut Color Image of Neptune's moon Triton, photographed by the NASA - Voyager 2 Spacecraft on August 20, 1989, while it was still approx. 5,4 Million KiloMeters (such as about 3,35 Million Miles) from Neptune. Triton's overall light pinkish color may be due to the heavy irradiation (---> the action of the Cosmic Rays and other Charged Particles, including the ones forming the Solar Wind) of the Ice (and, maybe, other Elements which were already) existing on the Surface of this distant Celestial Body.
The dark areas near the top of the image seem to be part of a belt of dark markings observed near Triton's Equator at different Longitudes. However - and generally speaking -, the darker areas visible on Triton appear to be somewhat redder in color than the brighter ones. The central Longitude in the image is 123° East. The South Pole of Triton is at about 6 o'clock of the disk, approximately 1/6th (one sixth) of the way up from its lower limb.
This frame (which is the Original NASA - Voyager 2 color frame published on the NASA - Planetary Photojournal with the ID n. PIA 02246) has been additionally processed and then re-colorized, according to an educated guess carried out by Dr Paolo C. Fienga (LXTT-IPF), in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Voyager 2 Spacecraft and then looked outside, towards the Neptunian moon Triton), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among others, the existence of different Elements present on the Surface of Triton, each having a different Albedo (---> Reflectivity) and Chemical Composition.MareKromium
(4 voti)
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Triton-PIA00317-PCF-LXTT-IPF.jpgThe Southern Regions of Triton (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)107 visiteThis wonderful and highly detailed global Absolute Natural Color image mosaic of Triton was obtained in the AD 1989 by the NASA - Voyager 2 Spacecraft during its Fly-By of the Neptunian System.
With a radius of approx. 1350 Km (such as a little more than 838 miles) and therefore some 22% smaller than Earth's Moon, Triton is by far the largest Natural Satellite of Neptune. Furthermore, Triton is one of the only 3 (three) objects in the Solar System known to have a Nitrogen-dominated Atmosphere (the others are our Home Planet Earth and the Saturnian giant moon, Titan). Triton has the coldest Surface known anywhere in the Solar System (38 K, or about - 391 degrees Fahrenheit, or - 235° Celsius): it is so cold that most of Triton's Nitrogen is condensed as Frost, making it the only Celestial Body in the whole Solar System that is known to have a Surface mainly composed of Nitrogen Ice.
The pinkish deposits constitute a vast South Polar Cap, that is believed to contain Methane Ice, which somehow reacted under Sunlight so to form pink or red Compounds. The Dark Streaks overlying these pink ices are believed to be an Icy and - perhaps - Carbonaceous Dust deposited from huge Geyser-like Plumes, some of which were found to be active during the Voyager 2 Fly-By. The light gray colored band visible in this image extends all the way around Triton, near the Equator and it may consist of relatively fresh Nitrogen Frost Deposits. The vaguely greenish areas of Triton (central and upper right side) include what is known as "The Cantaloupe Terrain", whose origin is still unknown, and a set of "Cryovolcanic" Landscapes apparently produced by Icy-cold Liquids (now totally frozen) that were erupted from Triton's interior.
This frame (which is the Original NASA - Voyager 2 color image mosaic published on the NASA - Planetary Photojournal with the ID n. PIA 00317) has been additionally processed and then re-colorized, according to an educated guess carried out by Dr Paolo C. Fienga (LXTT-IPF), in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Voyager 2 Spacecraft and then looked outside, towards the Neptunian moon Triton), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among others, the existence of different Elements present on the Surface of Triton, each having a different Albedo (---> Reflectivity) and Chemical Composition.MareKromium
(4 voti)
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Triton-PIA12185.jpgVolcanic Plains on Triton65 visiteCaption NASA:"This view of the Volcanic Plains of Neptune's moon Triton was produced using topographic maps derived from images acquired by NASA's Voyager Spacecraft during its August 1989 flyby, 20 years ago this week (August 2009).
Triton, Neptune's largest natural moon, was the last solid object visited by the Voyager 2 Spacecraft on its epic 10-year tour of the Outer Solar System. This view shows a close-up of a prominent chain of Volcanic Features surrounded by smooth Volcanic Plains formed by lavas or ash deposits of water or other ices, such as Methane or Ammonia.
The smaller pits and domes are typically 10 Km (about 6 miles) across and have relief of no more than a few hundred meters (several hundred feet).
The large depressions at the far left and right of the chain are 50 to 80 Km (about 31 to 50 miles) across.
The Surface of Triton is very rugged, scarred by rising blobs of ice (diapirs), faults and volcanic pits and lava flows composed of water and other ices. The Surface is also extremely young and sparsely cratered and could be geologically active today.
This scene is on the order of 500 Km (about 310 miles) across and is taken from a new flyover movie across the Equatorial Regions of Triton commemorating the Voyager anniversary of the Triton flyby.
Vertical relief has been exaggerated by a factor of 25 to aid interpretation".MareKromium
(4 voti)
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Triton-PIA00329.jpgViews of Triton (natural colors - elab. NASA)67 visiteTriton Voyager 2 approach sequence with latitude-longitude grid superposed. The color image was reconstructed by making a computer composite of three black and white images taken through red, green and blue filters. Details on Triton's surface unfold dramatically in this sequence of approach images. South Pole near the bottom of the images at the convergence of lines of longitude. Resolution changes from about 60 Km/pixel (37 mi/pixel) in the image at upper left taken from a distance of 500.000 Km to about 5 Km/pixel (3,1 mi/pixel) for the image at lower right. Global and regional albedo features are visible in all of the images. The albedo features can be tracked in successive images and show that Triton has undergone about 3/4 of a rotation during the 4.3-day interval over which these images were obtained.
A Southern Polar Cap of bright pink, yellow and white materials covers nearly all of the Southern Hemisphere; these materials consist of Nitrogen ice with traces of other substances, including frozen CH4 and CO2. Feeble ultraviolet radiation from the Sun is thought to act on methane to cause chemical reactions to the pinkish yellowish substances. At the time of the Voyager 2 flyby (Jan. 1989) Triton's Southern Hemisphere was starting the Summer Season and the South Pole was canted toward the Sun day and night, such that the Polar Cap was sublimating under the relatively 'hot' summer Sun (surface temperature about 38 K, about -391 degree F). Numerous dark streaks on the Southern Polar Nitrogen-ice cap are thought to consist of dark dust deposited by prevailing winds in Triton's tenuous Nitrogen Atmosphere. A bluish band, seen in all of the images, nearly circumstances Triton's Equator; this band is thought to consist of fairly Nitrogen frost, perhaps deposited in the decade prior to Voyager 2's flyby.MareKromium
(4 voti)
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t Neptune Space.jpgNeptune's System63 visiteUn magnifico e realistico collage che ci mostra Nettuno e le sue Lune maggiori, insieme, per una "Foto Ricordo" di un viaggio indimenticabile...
(4 voti)
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Z-Thalassa.gifThalassa71 visiteThalassa appears to be about 80 Km (about 50 miles) in diameter.
It orbits Neptune in 7 hours and 30 minutes, about 25.200 Km (such as approx. 15.700 miles) above the cloud tops. It is irregularly shaped and shows no sign of any geological modification. Thalassa circles the Planet in the same direction as Neptune rotates. This image has been slightly smeared so that Thalassa appears highly elongated.
(4 voti)
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Triton-PEI.jpgMoments of Triton...64 visiteThis set of images shows the best views of Neptune's moon Triton taken by Voyager 2 as the spacecraft withdrew from the Neptune system on August 25, 1989. The top four images were constructed from various color image bands as Voyager receded from Triton.
The third image from the left is sharper than the other four, because it was taken with the Narrow Angle Camera, with Triton filling two thirds of the frame. The thin crescent first image, while much closer, spanned about a quarter of the frame. The second image was somewhat smaller, and the last was very small. The first of the four images was composed of Blue, Green, and Orange filter images. The second utilized Violet, Green, and Orange Filtered images. In both composites, the Orange image was of poorer quality. In the fourth image, no orange was available, and the green and blue images were badly smeared, though somewhat salvageable. A clear filtered image (also smeared) was substituted for orange. They were combined and used as a color overlay for a slightly overexposed, but sharp clear filtered view. The third image is composed of a Violet and a Green wide-angle image. Like all the images in the first and second composites, and like the images used to color the fourth composite, these images were underexposed. However, they were very sharp. The orange image came from a poor quality wide angle orange image. The resulting color image was combined with a well exposed clear filter image to provide the detail
The Narrow Angle images used in these mosaics were the first obtained after closest approach, with the exception of a single clear filter image obtained while the disk was about twice as big as what could be framed in the camera's field of view. It is very noisy, and by far the worst underexposure of them all, and could not be processed to the point in which the whole image could be made presentable. However, a few sections were salvaged. The first (lower left) was binned to make up for noisiness and sharpened. It was then merged with the color data from the third image above. A cloud can be seen near the limb. To its right is an image of the cloud that has not been as heavily processed. The cloud itself is better presented, as it was far brighter than the surrounding area and hence more securely detected. Its shadow can be faintly made out to its right.
The next two images are the same, but one to the right was merged with color data. The image is towards the center of the crescent, the brightest area, in which white spots can be seen. Although a few of them may be impact craters, this area, as most of the crescent, is over the south polar cap, and thus frost covered, and the appearance of this area most closely resembles the cantaloupe terrain seen on the other hemisphere before closest approach. The final image (lower right) hints of surface topography near the terminator. It seems it is one of the more rugged parts of Triton. The large, foreshortened circular feature slightly below the center of the image is a dimple similar those found in the cantaloupe terrain. The other features are too ambiguous to determine whether or not they are of the same nature.
(4 voti)
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Neptune-crescent-PIA02204_modest.jpgNeptune's bright crescent66 visiteCaption NASA originale:"Neptune's bright crescent taken in six filters (from bottom to top: UV, violet, blue, clear, green, orange) on August, 31, 1989. The images were shuttered in temporal order: violet, blue, UV, clear, green, orange. These images how the bright core of D2, the South Polar feature, and the symmetric structure immediately surrounding the South Pole. The relatively high contrast of the features in these images indicates that they extend above most of the scattering haze and absorbing methane gas in Neptune's atmosphere. [Image processing by D.A. Alexander]"
(4 voti)
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Neptune-clouds-PIA00047_modest.jpgThe clouds of Neptune (b/w) - 162 visiteCaption NASA originale:"The bright cirrus-like clouds of Neptune change rapidly, often forming and dissipating over periods of several to tens of hours. In this sequence Voyager 2 observed cloud evolution in the region around the Great Dark Spot (GDS). The surprisingly rapid changes which occur separating each panel shows that in this region Neptune's weather is perhaps as dynamic and variable as that of the Earth. However, the scale is immense by our standards - the Earth and the GDS are of similar size... - and in Neptune's frigid atmosphere, where temperatures are as low as 55 degrees Kelvin (-360 F), the cirrus clouds are composed of frozen methane rather than Earth's crystals of water ice".
(4 voti)
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Neptune-PIA01286_modest.jpgA new "dark spot" on Neptune, as seen by HST71 visiteCaption NASA originale:"NASA's HST has discovered a new Great Dark Spot, located in the Northern Hemisphere of Neptune. Because the planet's Northern Hemisphere is tilted away from Earth, the new feature appears near the limb of the planet.
The Spot is a near mirror-image to a similar Southern Hemisphere Dark Spot that was discovered in 1989 by the Voyager 2. In 1994, HST showed that the Southern Dark Spot had gone. Like its predecessor, the new Spot has high altitude clouds along its edge, caused by gasses that have been pushed to higher altitudes where they cool to form methane ice crystal clouds. The Dark Spot may be a zone of clear gas that is a window to a cloud deck lower in the atmosphere. Planetary scientists do not know how long this new feature might live. HST's HR images will allow astronomers to follow the spot's evolution and other unexpected changes in Neptune's dynamic atmosphere. This image was taken on 2.11-'94 with HST's Wide Field Planetary Camera 2, when Neptune was 4,5 BKMs from Earth".
(4 voti)
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Triton-PIA01537_modest.jpgGeologic processes on Triton (1)63 visiteCaption NASA originale:"This image of Triton was taken from a distance of about 130.000 Km (80.000 miles) at 12:20 a.m. PDT Aug. 25 1989. The image was received at JPL four hours later at about 4:20 a.m. The smallest detail that can be seen is about 2,5 Km (or 1,5 miles) across. The long linear feature extending vertically across the image is probably a graben (a narrow down dropped fault block) about 35 Km (20 miles) across. The ridge in the center of the graben probably is ice that has welled up by plastic flow in the floor of the graben. The surrounding terrain is a relatively young icy surface with few impact craters".
(4 voti)
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