| Piú viste - Mercury |
ZZ-Mercury-Limb-PIA12306.jpgBehind the Sun64 visiteAs MESSENGER approached Mercury during the Spacecraft's 3rd Mercury flyby, the Solar System's innermost Planet appeared to the imaging system as a sunlit crescent against the blackness of space. About 78 minutes prior to closest approach, the NAC captured this striking high-resolution image of the northernmost Region of Mercury's surface that was visible to the camera and illuminated by sunlight. The brightly lit North-Eastern walls of large impact craters can be seen near the horizon, catching the grazing rays of the Sun. The high Sun angle also accentuates wrinkle ridges winding across the smooth plains. In the foreground, features cast long shadows and the Terminator separates day from night.
Date Acquired: September 29, 2009
Image Mission Elapsed Time (MET): 162744006
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Scale: The crater near the middle of the left edge of the image is approximately 100 Km (about 60 miles) in diameter
Spacecraft Altitude: about 16.200 Km (approx. 10.100 miles)MareKromium
|
|
Craters-PIA02429.jpgRayed Craters on Mercury63 visiteCaption NASA originale:"These two prominent rayed craters are located at 40° North and 124° West. Bright halos extend as far as 2 crater diameters beyond crater rims. Individual rays extend from halo. Bright streak extending from middle top to lower is unrelated to the two craters. Craters are 40 Km in diameter. This image (FDS 275) was taken during the spacecraft's first encounter with Mercury".
|
|
ZZ-Mercury-Limb-208698.jpgMercury's Horizon (HR)63 visiteAs NASA’s MESSENGER drew closer to Mercury for its historic first flyby, the Spacecraft acquired this image showing a variety of surface textures, including smooth plains at the center of the image, numerous impact craters and rough material that appears to have been ejected from the large crater to the lower right.
MESSENGER has acquired over 1200 images of Mercury. These types of images will assist scientists to study, as never before, details to help them learn about the history and evolution of the innermost Planet.MareKromium
|
|
ZZ-Mercury-Craters-Matisse_Crater-209136.jpgMatisse Crater (HR)63 visiteAs NASA’s MESSENGER approached Mercury on January 14, 2008, the Spacecraft took this image of the Crater Matisse. Named for the French artist Henri Matisse, Matisse crater was imaged during the Mariner 10 Mission and is about 130 miles in diameter. Matisse crater is in the Southern Hemisphere and can be seen near the Terminator of the Planet (the line between the sunlit, day side and the dark, night side).
On Mercury, craters are named for people, now deceased, who have made contributions to the Humanities, such as Artists, Musicians, Painters and Authors. The International Astronomical Union (IAU) oversees the official process of naming new craters and other new features discovered on bodies throughout the Solar System. Scientists studying and mapping unnamed features can suggest names for consideration by the IAU. The 1213 images taken by MESSENGER during its first flyby encounter with Mercury cover a large region of Mercury's surface previously unseen by spacecraft, revealing many new craters and other features that will need to be named.
MareKromium
|
|
ZZ-Mercury-Global_View_of_the_Surface-Cratered_Surface-209516.jpgHow many craters do you see?63 visiteOne of many investigations underway includes identifying and measuring the impact craters on Mercury's previously unseen Regions. The density of craters on the surface of a planet can be used to indicate the relative age of different places on the surface; the more craters the surface has accumulated, the older the surface.
By counting craters on different areas of Mercury's Surface, a relative geologic history of the Planet can be constructed, indicating which surfaces formed first and which formed later. However, this process is also time consuming; Mercury has a lot of craters!
This image shows just a portion (276 Km, or 172 miles, wide) of 1 frame taken with the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS). In this image alone, 763 craters have been identified and measured (shown in green) along with 189 hills (shown in yellow).
Altogether, 491 frames were taken by the NAC to create HR mosaics of Mercury's surface.
Of course, simply counting the craters is not enough. Each crater has to be measured and classified to fully interpret the differences in crater density.
Many small craters form as "secondaries," as clumps of material ejected from a "primary" crater re-impact the surface in the regions surrounding the primary.
In order to learn about the history of asteroid and comet impacts on Mercury, scientists have to distinguish between the primary and secondary craters. Once many more craters are measured, MESSENGER researchers will have new insights into the geological history of Mercury.
Image Mission Elapsed Time (MET): 108826672
MareKromium
|
|
ZQ-Mercury-PIA10611.jpgNew Names for Features on Mercury63 visiteThe International Astronomical Union (IAU) recently approved new names for features on Mercury that were all seen for the first time in images taken by MESSENGER during the Spacecraft's first flyby of the Planet.
Read the full press release for additional details about the naming process and the origin of the names, and visit the U.S.G.S. website, the Gazetteer of Planetary Nomenclature, to learn about all of the named planetary features in the Solar System.
This image, produced by mosaicking many Narrow Angle Camera (NAC) images together, shows the locations of the newly named features, along with the craters Basho, Mozart, and Tolstoj, first seen by the Mariner 10 Mission.
Close-up views of many of these features are available in the MESSENGER website image gallery. In particular, look at these previous releases for NAC high-resolution images of Apollodorus, Beagle Rupes, Eminescu, Mozart, Neruda, Pantheon Fossae, Raditladi and Sander.MareKromium
|
|
ZQ-Mercury-PIA11025.jpgWrinkle-Ridge Rings on Mercury and Mars63 visitePlanetary scientists commonly compare and contrast the geologic features found on different planetary bodies, to learn about the similar processes that operated throughout the Solar System and to understand how each planet is different and unique. This figure, recently published in Science magazine, shows wrinkle-ridge rings on both Mercury (upper image) and Mars (lower image) that look quite similar. Wrinkle ridges arrayed in such a ring are interpreted to trace the rim of an impact crater that was nearly or completely flooded by lavas prior to ridge formation. Wrinkle ridges are created by forces that compress the crust horizontally.
A buried crater rim can concentrate the near-surface forces and cause the wrinkle ridges to form a ring. The presence of wrinkle-ridge rings is thus good evidence that volcanism helped to shape the surfaces of both Mars and Mercury.
Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): A: 108826972
Instrument: A: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Mars Image: B: Mars Express High-Resolution Stereo Camera nadir image h2660_0001
MareKromium
|
|
ZU-PIA12038.jpgIn search of the "Vulcanoids"63 visiteIn mid-February 2009, before and after MESSENGER's latest Perihelion (such as the closest approach to the Sun), an imaging campaign was conducted to search for "Vulcanoids": small rocky bodies that have been postulated to exist in orbits between Mercury and the Sun. Those images are still waiting to be transmitted to Earth.
The image here is from the first set of 240 MDIS images taken to look for vulcanoids, acquired in June 2008. It is a 10" exposure taken through the WAC's clear filter. Jupiter is bright and visible in the image. The camera field of view is nearly large enough to capture the entire width of Sagittarius, a constellation of the Zodiac visible low and to the South in Summer from temperate latitudes in the Northern Hemisphere. The Greek letters identify some of the brighter stars in Sagittarius.
During the Vulcanoid search campaign, 4-5 images of the same scene are taken back to back. This procedure allows Cosmic Ray strikes on the camera's detector to be identified and enables fainter objects to be detected. One such Cosmic Ray strike is labeled on this image. In this single image, the Cosmic Ray strike appears similar to the stars, but in the 4 images taken immediately after this one, the Cosmic Ray strike is gone whereas the stars remain. Images are also taken hours and days apart, so the motion of objects in the sky can be determined. If a Vulcanoid were imaged, its motion through the sky would appear very different from motions of the background stars and known Solar System objects.
No Vulcanoids have been found yet, but the latest set of acquired images will expand the volume of the search region examined so far.
Date Acquired: June 4, 2008
Image Mission Elapsed Time (MET): 121050477
Instrument: Wide Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
WAC Filter: 2 (clear filter)
Field of View: The WAC has a 10,5° field of viewMareKromium
|
|
ZZ-Mercury-Craters-Unnamed_Double-Ring_Basin.jpgDouble "Concentric" Basin on Mercury (Natural Colors; credits: Lunexit)63 visiteCaption NASA, da "NASA - Picture of the Day" del giorno 7 Ottobre 2009:"What created the internal second ring of this Double Ringed Basin on Mercury?
No one is sure.
The unusual feature spans approx. 160 Km and was imaged during the robotic MESSENGER Spacecraft's swing past our Solar System's innermost planet. Double and Multiple Ringed Basins, although rare, have also been imaged in years past on Mars, Venus, Earth and Earth's Moon.
Mercury itself has several doubles, including huge Caloris Basin, Rembrandt Basin and enigmatic Raditladi Basin. Most large circular features on planets and moons are caused initially by a forceful impact by a single asteroid or comet fragment. Since it is unlikely that a second impact would occur right in the center of the first, large double rings are usually attributed to a subsequent volcanic lava flow inside the impact crater.
Possibly, though, a second ring could be caused by the melting and flowing of material upon impact. One clue to the origin of the above-imaged double ring is that the basin center appears much smoother than the region between the rings. MESSENGER has now completed its last flyby of Mercury but will return and attempt to enter orbit in March 2011".MareKromium
|
|
ZZ-Mercury-Volcanic_Features-Vent-PIA12370.jpgIrregular Rimless Depression - Candidate for an Explosive Volcanic Vent on Mercury (Natural Colors; credits: Lunexit)63 visiteThis Region of high reflectance was just barely seen on the limb during MESSENGER's 2nd flyby, but without enough detail to characterize it as anything other than a bright spot.
A more favorable viewing angle reveals this bright spot to be an irregular rimless depression approx. 30 Km across surrounded by highly reflective material. Its features are distinctly different from those of impact craters and, though its origin remains ambiguous, it is suspected to be volcanic, possibly the site of an explosive Volcanic Vent. The high-reflectance halo surrounding this enigmatic feature is distinct in color and may represent a pyroclastic deposit greater than 150 Km in diameter.
Date Acquired: September 29, 2009
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Scale: The irregular rimless depression in the center of the image is approx. 30 Km (about 19 miles) acrossMareKromium
|
|
ZZ-Mercury-Craters-Rembrandt_Crater-PIA12395.jpgLow Sun over Rembrandt Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)63 visiteThis NAC image acquired during MESSENGER's third Fly-By of Mercury shows a view of the interior of Rembrandt Basin that emphasizes landforms. Rembrandt was discovered during the Mission's second Fly-By, in October 2008. Its large size (approx. 715 Km, or about 444 miles, in diameter), its relatively young age (as implied by the low number of superposed impact craters), and the radiating extensional and contractional fractures on its Floor, have made it a topic of special interest to the MESSENGER Science Team.
Earlier this year, an article devoted to the first study of the geology of Rembrandt was published in the Science magazine. During Mercury's Fly-By 3, Rembrandt was closer to the Terminator - such as the line between the sunlit dayside and dark nightside of the Planet - and the different viewing geometries between Fly-Bys 2 and 3 enabled a three-dimensional view of this unusual basin. The grazing angle of the light from the setting Sun in this particular NAC image accentuates the topography of the features on the Rembrandt's Floor, including the set of unusual Radiating Fractures.
Date Acquired: September 29, 2009
Image Mission Elapsed Time (MET): 162744327
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 390 meters/pixel (0,24 miles/pixel)
Scale: The prominent crater at center left is about 44 Km (approx. 27 miles) in diameter
Spacecraft Altitude (distance from target): approx. 15.100 Km (about 9400 miles)
MareKromium
|
|
ZZ-Mercury-Craters-Unnamed_Double-Ring_Crater-208672.jpgDouble-Ringed Crater (HR)62 visiteNASA’s MESSENGER Spacecraft’s closest approach to Mercury on January 14, 2008, acquired this image as part of a mosaic that covers much of the sunlit portion of a hemisphere not view by previous spacecraft. Images such as this can be read in terms of a sequence of geological events and provide insight into the relative timing of processes that have acted on Mercury's surface in the past.
The double-ringed crater pictured in the upper right of this image appears to be filled with smooth plains material, perhaps volcanic in nature.
This crater was subsequently disrupted by the formation of a prominent cliff, the surface expression of a major crustal fault system that runs alongside part of its southern rim. This may have led to the uplift seen across a portion of the crater’s floor. A smaller crater in the upper left of the image also has been cut by the cliff, showing that the fault beneath the cliff was active after both of these craters had formed.MareKromium
|
|
| 248 immagini su 21 pagina(e) |
 |
|
|
|
|
|
|
|
19 | |
|
