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| Piú votate - Mercury |
Mercury-PIA11013.jpgMapping a "Volcano"68 visiteMESSENGER Science Team members are busy studying in detail the newly discovered volcanoes on Mercury (see also PIA10942). This figure, recently published in Science magazine, shows a NAC mosaic of the largest volcano currently identified on Mercury and a geologic sketch map of the major features in the surrounding area.
The “irregularly-shaped depressions” are believed to correspond to volcanic vents, and the “margin of the dome-like feature” marks the outer limits of lava flows from the vents that are thought to have covered up the underlying surface of “hummocky plains”.
The unlabeled double line outlines bright material associated with the volcano, believed to be pyroclastic deposits ejected during volcanic eruptions at the vents. A “highly-embayed impact crater” also appears to have had lava flow up to its rim, while a slightly more distant impact crater is “relatively fresh” and unchanged by any lava.
The volcano is located just inside the rim of the Caloris Impact Basin (see also PIA10383), labeled as “Caloris Basin Rim Units” on this map. Maps such as this are aiding scientists as they work to understand the history of volcanism on Mercury.
Date Acquired: January, 14th, 2008
Image Mission Elapsed Time (MET): Mosaic of 108826812 and 108826877
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Spacecraft Altitude: about 10.500 Km (approx. 6500 miles)MareKromium
(5 voti)
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ZZ-Mercury-Limb-PIA10936.jpgDürer Basin (natural colors; credits: Lunexit)62 visiteMESSENGER snapped this image of Mercury’s horizon about 56 minutes before the Spacecraft’s closest pass by the Planet. The distinctive peak-ring basin Dürer (named from Mariner 10 photos for the German artist Albrecht Dürer) is visible.
The smaller crater Mickiewicz (named for the Polish poet Adam Mickiewicz) can also be seen, with a smaller central peak-ring structure in the middle of its crater floor.
Craters form ring structures during the impact process that creates the crater, and the number and characteristics of the rings depend on the crater’s size. Raditladi, imaged for the first time by MESSENGER and recently named, also shows a pronounced peak-ring structure.
Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): 108821505
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Scale: Dürer crater is about 190 Km (approx. 120 miles) in diameter
Spacecraft Altitude: about 18.300 Km (approx. 11.400 miles)MareKromium
(5 voti)
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ZP-Mercury-PIA10396.jpgMercury's "Sodium Tail"88 visiteCaption NASA:"This plot shows the intensity of emission of light associated with Sodium (Na) Atoms in the vicinity of Mercury. The observations were made with the Ultraviolet and Visible Spectrometer (UVVS) section of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS). The intensity (up to 40 kiloRayleighs) indicates the relative abundance of material - in this case Sodium Atoms - along the observational line of sight back to the Spacecraft.
While Sodium from Mercury has been observed with Earth-based telescopes, this is the highest-spatial-resolution image ever made.
The geometry and observing circumstances have to be disentangled to infer the true spatial distribution, but the observations do confirm a North-South asymmetry that has previously been observed in ground-based Sodium images.
The Sodium emission is at 589 nm (in the visible part of the spectrum and the same wavelength, or color, as in sodium lamps and street lights on Earth). Because Sodium Atoms have intense emission, they are easy to detect, and this makes sodium a good tracer for other volatile elements in Mercury's Exosphere".MareKromium
(5 voti)
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ZP-Mercury-PIA10381.jpgTopographic "Close-up"64 visiteCaption NASA:"A close-up of the Mercury Laser Altimeter (MLA) profile of Mercury acquired during MESSENGER's first Mercury flyby on January 14, 2008.
Comparison with an Arecibo radar image mosaic (bottom) provided by Harmon and co-workers shows that the two largest depressions are adjacent impact craters.
The craters have rim-to-rim diameters of 107 Km (left) and 122 Km (right).
The root mean square roughness of the floor the larger crater is ~35 m.
The vertical exaggeration in the figure is equal to 35:1".MareKromium
(5 voti)
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ZZ-Mercury-Global_View_of_the_Surface-PIA10607.jpgMercurian Symphony (MULTISPECTRUM-2; credits: Lunexit)72 visiteCaption NASA:"When Mariner 10 flew by Mercury in 1974, morning sunlight was just striking Mozart Crater so that most of the feature was hidden in darkness near the Terminator. During MESSENGER's Mercury flyby on January 14, 2008, Mozart was in full sunlight, allowing the Crater to be seen in detail for the first time, as shown in this image snapped by the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS). Named in honor of the classical composer Wolfgang Amadeus Mozart, Mozart is the large crater near the center of the image. The Crater's diameter is about 225 Km (such as approx. 140 miles). The arc of dark hills visible on the Crater's floor probably represents remnants of a central peak ring, similar to that shown in the January 30 image release (PIA10378). Clues to the origin of the dark material on the peak ring and the curious dark streaks radiating outward from the Crater will be provided by 11-color image data collected by the Spacecraft's Wide Angle Camera (WAC).
A close inspection of the area around Mozart Crater shows many long chains of secondary craters, formed by impact of material thrown out during the formation of the main crater.
Mozart Crater is located just South of the Caloris Basin and can be identified in the false color image previously released (PIA10398).
Members of the MESSENGER Science Team are currently studying and characterizing the small craters on Mercury in order to provide new insight into the cratering process as it operates on the different planets in the Solar System.
Image Mission Elapsed Time (MET): 108830250
MareKromium
(5 voti)
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ZO-Mercury21_Messenger-big.jpgCrescent Mercury (in Accentuated Colors; credits: NASA)65 visiteCaption NASA:"The colors of Mercury are subtle but beautiful. At first glance, our Solar System's innermost Planet appears simply black and white, but images that include IR colors normally beyond human vision accentuate a world of detail. One such image, shown above, was acquired by the robotic MESSENGER Spacecraft that swung by Mercury in mid-January 2008.
Here, most generally, the hot world itself acquires a slightly more brown hue. Many craters that appear on top of other craters - and so surely have formed more recently - appear here as bright with bright rays that include a slightly blue tint, indicating that soil upended during the impact was light in color. A few craters, such as some in the huge Caloris Basin impact feature visible on the upper right, appear unexpectedly to be ringed with a dark material, the nature of which is being researched.
MESSENGER continues to glide through the inner Solar System and will pass Mercury again this October and next September, before entering orbit around the desolate world in 2011".MareKromium
(5 voti)
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ZZ-Mercury-Caloris_Basin.jpgCaloris Basin: fascinating "Rayed Crater" or an extremely old "Shield Volcano"?75 visiteThe NAC of the MDIS on the MESSENGER Spacecraft obtained HR images of the floor of the Caloris Basin on January 14, 2008. Near the center of the basin, an area unseen by Mariner 10, this remarkable feature – nicknamed “The Spider” by the Science Team – was revealed. A set of troughs radiates outward in a geometry unlike anything seen by Mariner 10. The radial troughs are interpreted to be the result of extension (breaking apart) of the floor materials that filled the Caloris Basin after its formation. Other troughs near the center form a polygonal pattern. This type of polygonal pattern of troughs is also seen along the interior margin of the Caloris Basin. An impact crater about 40 Km (~25 miles) in diameter appears to be centered on “The Spider.” The straight-line segments of the crater walls may have been influenced by preexisting extensional troughs, but some of the troughs may have formed at the time that the crater was excavated.
Nota Lunexit: portando il massimo rispetto per quanto esposto e dedotto nella caption NASA, noi riteniamo - dopo aver ATTENTAMENTE ESAMINATO le differenti ed intricate surface features di "Spider Crater" - che il rilievo ripreso dalla Sonda NASA Messenger potrebbe NON ESSERE un impact crater con raggiatura intensa ed estesa, bensì quello che resta di un antichissimo Shield Volcano (probabilmente simile, per certi versi, al gigante Ascraeus Mons) oppure il remnant di una Caldera Vulcanica la quale è ormai quasi completamente collassata (es.: la Summit Caldera del Vulcano Marziano Hecates Tholus). In effetti, se si eccettua il Central Peak (a nostro avviso l'unica evidenza che ha "suggerito" l'ipotesi "craterica" come ipotesi base), le fattezze dello "Spider" sono, da un lato, molto lontane dalle fattezze proprie e tipiche dei crateri da impatto ed invece molto simili, dall'altro, alle fattezze proprie e tipiche dei vulcani (osservate le ripide e scoscese pareti Nord del rilievo le quali sono assolutamente analoghe alle pareti delle Summit Calderae di Olympus ed Ascraeus nonchè MOLTO SIMILI alla Culann-Tohill Patera di Io). Osservate le tracce di "Lava Flows" visibili sul versante Sud dello "Spider" ad ore 07:00 ed 08:00 e, quale intrigante ed ulteriore evidenza della possibile origine vulcanica del rilievo, la colorizzazione e la texture dei dintorni del medesimo (nettamente più scura del resto del paesaggio e, anche da e per questo aspetto, molto simile alle textures e colorizzazioni dei dintorni dei già menzionati Vulcani Marziani (e non solo).
Insomma: noi non stiamo dicendo che gli Scienziati di Pasadena hanno sbagliato...Vi stiamo solo suggerendo una "visione alternativa" (e, a nostro avviso, non "campata per aria"...) del medesimo rilievo. I Vostri commenti e le Vostre riflessioni saranno, come sempre, tenute in considerazione.MareKromium
(5 voti)
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ZZ-Mercury-North_Pole-209526.jpgThe North Pole of Mercury74 visiteAs MESSENGER sped by Mercury on January 14, 2008, the NAC of the Mercury Dual Imaging System (MDIS) captured this shot looking toward Mercury's North Pole.
The surface shown in this image is from the side of Mercury not previously seen by spacecraft.
The top right of this image shows the limb of the Planet, which transitions into the Terminator on the top left of the image.
Near the Terminator, the Sun illuminates surface features at a low angle, casting long shadows and causing height differences of the surface to appear more prominent in this Region.
It is interesting to compare MESSENGER's view to the North with the image looking toward the South Pole, released on January 21. Comparing these two images, it can be seen that the terrain near the South Pole is more heavily cratered while some of the Regions near the North Pole show less cratered, smooth plains material, consistent with the general observations of the poles as made by Mariner 10.
This image was acquired about 94' after MESSENGER's closest approach to Mercury, when the spacecraft was at a distance of about 32.000 Km (such as approx. 20.000 miles).
Mission Elapsed Time (MET) of image: 108830513MareKromium
(5 voti)
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ZZ-Mercury-Cliffs_and_Ridges-208889-MZO-MESSENGER_012008.jpgRidges and Cliffs64 visiteBoth it and the lighter-colored ridge that extends downward from it resemble wrinkle ridges that are common on the large Volcanic Plains, or "Maria," on the Moon.
The MESSENGER science team is studying what features like these reveal about the interior cooling history of Mercury.
Ghostly remnants of a few craters are seen on the right side of this image, possibly indicating that once-pristine, bowl-shaped craters (like those on the large crater’s floor) have been subsequently flooded by volcanism or some other plains-forming process.
A complex history of geological evolution is recorded in this frame from the Narrow Angle Camera (NAC), part of the Mercury Dual Imaging System (MDIS) instrument, taken during MESSENGER’s close flyby of Mercury on January 14, 2008.
Part of an old, large crater occupies most of the lower left portion of the frame. An arrangement of ridges and cliffs in the shape of a "Y" crosses the crater’s floor.
The shadows defining the ridges are cast on the floor of the crater by the Sun shining from the right, indicating a descending stair-step of plains. The main, right-hand branch of the "Y" crosses the crater floor, the crater rim, and continues off the top edge of the picture; it appears to be a classic “lobate scarp” (irregularly shaped cliff) common in all areas of Mercury imaged so far. These lobate scarps were formed during a period when Mercury’s crust was contracting as the planet cooled. In contrast, the branch of the Y to the left ends at the crater rim and is restricted to the floor of the crater.
This image was taken 18 minutes after close approach, when MESSENGER was about 5000 Km (about 3000 miles) away from Mercury.
The image is about 200 Km (approx. 125 miles) across, and features as small as about 400 mt (about 400 yards) can be resolved. MareKromium
(5 voti)
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ZZ-Mercury-Craters-Crater_Cluster-208907.jpgCraterland62 visiteMESSENGER's Narrow Angle Camera (NAC) on the Mercury Dual Imaging System (MDIS) acquired this view of Mercury’s surface illuminated obliquely from the right by the Sun. The unnamed crater (about 52 Km in diameter) in the center of the image displays a telephone-shaped collapse feature on its floor.
Such a collapse feature, not seen on the floors of other craters in this image, could reflect past volcanic activity at and just below the surface of this particular crater.
The crater is located in the Southern Hemisphere of Mercury, on the side that was not viewed by Mariner 10 during any of its three flybys (1974-1975).
This scene was imaged while MESSENGER was departing from Mercury from a distance of 19.300 Km (approx. 12.000 miles), about 1 hour after the spacecraft's closest encounter with Mercury.
The image is of a region approx. 236 Km (about 147 miles) across, and craters as small as 1,6 Km (1 mile) can be seen. MareKromium
(5 voti)
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ZZ-Mercury-Craters-Crater_Field-208852.jpgFresh Primary Impact Crater and Secondary Craters (HR)75 visiteOn January 14, 2008, NASA’s MESSENGER spacecraft observed about half of the hemisphere not seen by Mariner 10. This image shows part of a large, fresh crater with secondary crater chains located near Mercury’s Equator on the side of the Planet newly imaged by MESSENGER.
Large, flat-floored craters show terraced rims from post-impact collapse of their newly formed walls. The hundreds of secondary impactors that are excavated from the Planet’s surface by an incoming object, create long, linear crater chains radial to the main crater.
These chains, in addition to the rest of the ejecta blanket, create the complicated, hilly terrain surrounding the primary crater in the image. By counting craters that have formed since the impact event, the age of the crater can be estimated.
This count can then be compared with a similar count for the crater floor to determine whether any material has partially filled the crater since its formation. With their large size and production of abundant secondary craters, these flat-floored craters both illuminate and confound the study of the geological history of Mercury. MareKromium
(5 voti)
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ZZ-Mercury-Craters-Unnamed_Rayed_Crater-208635.jpgUnnamed Crater with Bright Ejecta Rays (HR)70 visiteDuring its flyby of Mercury on Jan. 14, 2008, NASA’s MESSENGER spacecraft acquired High-Resolution (HR) images of the Planet's surface. This image shows a previously unseen crater with distinctive bright rays of ejected material extending outward from the crater's center.
A chain of craters nearby is also visible. Studying impact craters provides insight into the history and composition of Mercury as well as dynamical processes that occurred throughout our Solar System.
This image is one of 99 taken by the Spacecraft to enable the creation of a large, HR mosaic of the northeast quarter of the Region.MareKromium
(5 voti)
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