| Piú votate - Neptune and His Moons |
Neptune-HST4.JPGMoments of Neptune (HST - False Colors; credits: NASA, L. Sromovsky and P. Fry - University of Wisconsin-Madison)54 visitenessun commentoMareKromium
(3 voti)
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Neptune-PIA09927.jpgThe "Hot" South Pole of Neptune54 visiteCaption NASA:"These thermal images show a "hot" South Pole on the Planet Neptune. These warmer temperatures provide an avenue for Methane to escape out of the deep atmosphere.
The images were obtained with the Very Large Telescope in Chile, using an imager/spectrometer for mid-infrared wavelengths on Sept. 1 and 2, 2006.
The telescope is operated by the European Organization for Astronomical Research in the Southern Hemisphere (known as ESO).
Scientists say Neptune's South Pole is "hotter" than anywhere else on the Planet by about 10° Celsius (50 degrees Fahrenheit). The average temperature on Neptune is about -200° Celsius (-392 degrees Fahrenheit).
The upper left image samples temperatures near the top of Neptune's troposphere (near 100 millibar pressure, which is 1/10th the Earth atmospheric pressure at sea level). The hottest temperatures are indicated at the lower part of the image, at Neptune's south pole (see the graphic at the upper right).
The lower two images, taken 6.3 hours apart, sample temperatures at higher altitudes in Neptune's stratosphere. They do show generally warmer temperatures near, but not at, the south pole. They also show a distinct warm area which can be seen in the lower left image and rotated completely around the back of the planet and returned to the earth-facing hemisphere in the lower right image".MareKromium
(3 voti)
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Triton-PIA00329.jpgViews of Triton (natural colors - elab. NASA)54 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
(3 voti)
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t Neptune Space.jpgNeptune's System55 visiteUn magnifico e realistico collage che ci mostra Nettuno e le sue Lune maggiori, insieme, per una "Foto Ricordo" di un viaggio indimenticabile...
(3 voti)
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Z-Thalassa.gifThalassa53 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.
(3 voti)
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Triton-PIA00317_modest.jpgTriton (False Colors; credits: NASA/JPL/USGS)56 visiteCaption NASA originale:"The color was synthesized by combining HR images taken through orange, violet and ultraviolet filters; these images were displayed as red, green and blue images and combined to create this color version. With a radius of 1.350 Km, about 22% smaller than Earth's Moon, Triton is by far the largest satellite of Neptune. It is 1 of only 3 objects in the Solar System known to have a nitrogen-dominated atmosphere (the others are Earth and Saturn's giant moon, Titan). Triton has the coldest surface known anywhere in the Solar System (38 K, about -391 degrees F); it is so cold that most of Triton's nitrogen is condensed as frost, making it the only satellite in the Solar System known to have a surface made mainly of nitrogen ice. The pinkish deposits constitute a vast south polar cap believed to contain methane ice, which would have reacted under sunlight 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 flyby. The bluish-green band visible in this image extends all the way around Triton near the equator; it may consist of relatively fresh nitrogen frost deposits. The greenish areas includes what is called the cantaloupe terrain, whose origin is unknown, and a set of "cryovolcanic" landscapes apparently produced by icy-cold liquids (now frozen) erupted from Triton's interior".
(3 voti)
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Triton-PIA01537_modest.jpgGeologic processes on Triton (1)55 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".
(3 voti)
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Triton-PIA01538_modest.jpgGeologic processes on Triton (2)55 visiteCaption NASA originale:"Part of the complex geologic history of icy Triton, Neptune's largest satellite, is shown in this Voyager 2 photo, which has a resolution of 900 meters (2.700 feet) per picture element. The photo was received as part of a Triton-mapping sequence between 3:30 and 5:30 a.m. (PDT). This view is about 500 Km (300 miles) across.
It encompasses 2 depressions, possibly old impact basins, that have been extensively modified by flooding, melting, faulting and collapse. Several episodes of filling and partial removal of material appear to have occurred. The rough area in the middle of the bottom depression probably marks the most recent eruption of material. Only a few impact craters dot the area, which shows the dominance of internally driven geologic processes on Triton".
(3 voti)
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Neptune-PIA21629.jpgNeptune from the Saturnian Sky (Natural Colors; credits: NASA/JPL-Caltech/Space Science Institute)120 visiteCaption NASA:"On August 25, 1989, NASA's Voyager 2 made its historic Fly-By of Neptune and its largest moon, Triton. The Cassini Spacecraft took this image to celebrate the anniversary of that event.
Neptune appears in this Natural Color composite as a pale blue disk (similar to Cassini's image of Uranus from 2014), just below and to the right of image center. Most of the faint specks in the image are background stars, although some are likely Cosmic Rays (charged particles that strike the camera detector).
By imaging Neptune, Cassini's Solar System family portrait-taking is complete. The Mission's Planetary Photojournal includes all of the major Planets except Mercury, which is too close to the Sun to be imaged, as well as dwarf planet Pluto.
This view was acquired by the Cassini narrow-angle camera on Aug. 10, 2017, at a distance of approximately 2,72 Billion Miles (such as approx. 4,38 BKM) from Neptune. Red, blue and green filter images were combined to create this Natural Color image".MareKromium
(2 voti)
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Triton_Mosaic.JPGTriton (photo-mosaic - credits: NASA)54 visiteCaption NASA:"This picture of Triton is a mosaic of the highest resolution images taken by Voyager 2 on Aug. 25, 1989 from a distance of about 40.000 Km (approx. 24.800 miles). The mosaic is superimposed on the lower resolution mapping images taken about 2 hours earlier in order to fill in gaps between high resolution images. The smallest features that can be seen on the images are about 0,8 Km (approx. 0,5 miles) across.
The Terminator (such as the line separating the day from the night) is at the top of the picture and is centered at about 30° North Lat. and 330° East Longitude.
These highest resolution images were targeted for the Terminator Region to show details of the topography by the shadows it casts. Near the center of the picture is a depression filled with smooth plains that are probably ices which were once erupted in a fluid state. The depth of the depression is about 300 meters (900 feet) and the prominent fresh impact crater on its floor is about 20 Km (approx. 12 miles) in diameter and about 1 Km (such as approx. 0,6 mile) deep. On the right is an elongate crater with adjacent dark deposits above it. This feature may be an explosive eruption vent formed by gaps within the ice.
The linear structure on the left is probably a fracture along which fresh ice has been extruded".MareKromium
(2 voti)
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Neptune-HST1.JPGViews of Neptune (from Hubble Space Telescope)76 visitenessun commentoMareKromium
(2 voti)
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Triton-PIA01994.jpgStrange "surface features" on Triton (clouds?!?)55 visiteCaption NASA originale"Already intriguing patterns of unknown origin appear on the surface of Neptune's largest satellite, Triton, in this image returned by Voyager 2. The image was taken Aug. 22, 1989, from a distance of about 4 MKM (approx. 2.5 MMs). Voyager images show that Triton's diameter is about 2.720 Km (approx. 1.690 miles) and that it is one of the brightest objects in the Solar System, reflecting about 70% of the sunlight that strikes it. This is the Hemisphere of Triton that always faces away from Neptune. The South Pole is near the bottom of the image. Triton's rotation axis is tilted so that the latitude at the center of the disk is 55° South. Dark regions at the top of the disk extend from roughly the equator to beyond 20° North. The margin between the bright and dark regions varies with longitude around the satellite. The gray, featureless area just to the right of the center of the disk is due to a reseau (reticule mark) in the camera".
(2 voti)
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