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54-st124520_smart-1_moon_H.jpgBright Impact Crater55 visiteCaption ESA originale:"Screen shot showing a remarkable impact crater (bright circle at top right) and the elongated shapes of ejected material extending radially outward.
Animation sequence captured from SMART-1 star tracker on 1 September 2006, 600 Km above the Moon's surface".
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61-smart-1_data1002887_030_H.jpgDouble Crater53 visiteCaption ESA originale:"This beautiful oblique view was taken on 2 September 2006 by the AMIE camera on board SMART-1 during the last few orbits prior to Moon impact, and shows a double crater.
This view was captured during the imaging session which took place bewteen 15:19 and 17:34 CEST (17:19 - 19:34 UT)".
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APOLLO 14 AS 14-70-9671.jpgAS 14-70-9671 - The "Bright One"53 visiteThis crater on the Lunar Far-Side is similar in age and size to the near- side crater Euler. It is located midway between the craters Becvar and Langemak. About 36 Km in diameter, it was informally called the "Bright One" by the Apollo 14 Astronauts because of its bright ejecta and ray pattern. The bright halo that surrounds the crater is about 150 Km in diameter. Its brightness is not evident in this view because the picture was taken when the Sun angle was low. The radial pattern of dunelike ejecta around the crater is most apparent where the Sun's rays are perpendicular to the direction of ejecta flow, as in the lower part of the picture. The hummocky or bumpy floor of the crater is caused largely by material that has slumped from the walls. Stuart A. Roosa, the Apollo 14 CMP, used a handheld camera with an 80-mm lens for this photograph. Later, using a 500-mm lens, he photographed in much more detail that part of the floor of the crater outlined in this photograph and shown in AS 14-9975.
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APOLLO 14 AS 14-72-9975.jpgAS 14-72-9975 - The "Bright One" (detail mgnf)53 visiteWhen photographed with the 500-mm lens, the abundance of blocks (bright spots with shadows extending to the right) attests to the freshness of the materials on the floor of the "Bright One". Material that has flowed and in some instances formed smooth-surfaced "pools" is evident in much of the area. Arrows mark the edge of a major flow distinguished by its surface texture, color (in the original negative), location in a topographic low, and clearly defined border. Note that the abundance of boulders in the flow is much less than in nearby areas, presumably because the flow has buried most of the boulders in its path. Scientists generally agree that material has flowed here, and on the floors and flanks of many other craters, but the nature of the material that has flowed is a matter of debate.
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APOLLO 15 AS 15-0018.jpgAS 15-0018 - On the rim of Gibbs Crater53 visiteImpact craters with asymmetric ray patterns and profiles can be caused by conditions other than the angle of trajectory. This 5-Km crater was formed when a meteoroid impacted on the North-East rim crest of Gibbs, a very much larger and older crater near the Moon's East limb. In this restricted view, Gibbs' rim is the dark area in the North half of the picture, and its wall is the light area in the south half. The rim crest extends from arrow to arrow. Discrete rays of both light and dark ejecta are well developed around the North half of the small crater where they were deposited on a relatively level surface. They are poorly developed around the South side of the small crater, probably having been partly destroyed by mixing as the ejected materials cascaded down the much steeper wall of the Crater Gibbs. Subsequent erosion has further destroyed the original pattern. The configuration of the small crater's rim has also been affected by topography.
It is sharply defined along the North side but is barely discernible along the south side where large volumes of material have slumped down the wall of the older crater.
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APOLLO 15 AS 15-9254.jpgAS 15-9524 - Bright and Big "Streaks"53 visiteThis elliptical crater is 1 Km long with an unusual, winglike pattern of rays.
This ejecta pattern is similar to those around some small experimental impact craters produced by missiles traveling along low-angle trajectories at White Sands Missile Range, N. Mex.
From the shape of the crater and the distribution of the rays, it is difficult to tell whether the meteoroid was traveling from North to South or South to North.
The higher albedo (brightness) of the North wall and the concentration of high albedo ejecta on the North-West and North-East flanks suggest that it traveled from South to North.
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APOLLO 15 AS 15-9287.jpgAS 15-9287 - A "Middle-aged" Crater53 visiteRemarkable detail is shown in this enlargement of a small part of a panoramic camera frame. In most respects, the crater itself is typical of a great many craters its size-about 1,2 Km. Because it does not have rays, it is believed to be older than most other Lunar craters. Its rounded rim crest and slightly raised rim (extending outward to the arrow, on the West side) also point to its greater age. On the other hand, it is young enough that some of the original dunelike texture of the ejecta blanket is preserved (especially to the West), a great many large blocks of ejecta are still visible, and the original depth of the crater has not been greatly lessened by infalling debris. The largest blocks, which are about 30 mt in size, occur near the rim. The terrace (T) extending partly around the wall about 100 mt below the surface probably marks the top of a resistant rock layer. However, if there were other signs of bedrock stratification within this crater, they have been obscured by the movement of debris down the walls. The very smooth floor is the only unusual feature of this crater. It may consist of a solidified pool of rock melted by heat generated from the impact.
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APOLLO 16 AS 16-5410.jpgAS 16-5410 - Number "8"53 visiteThis 18-km-long ''figure 8" pair of noncircular craters near the crater Guericke probably was not formed by hypervelocity impacts of bodies from space. It could be a secondary impact feature formed by projectiles from the Imbrium Basin, 700 Km to the North. The terrace at the base of the crater walls could be debris from the walls or a "bathtub ring" left by a formerly higher stand of the mare fill. Alternatively, the crater pair and the terrace could have been formed by volcanic eruptions.
The superposed bright crater is younger than and unrelated to either the "figure 8" pair or the mare.
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APOLLO 17 AS 17-2744.jpgAS 17-2744 - Crater's "Rays"53 visiteThis is an oblique view of another crater that probably was formed by a meteoroid following a relatively low-angle trajectory. This crater, 4 Km in diameter, is located in the highlands East of Mare Serenitatis. Compared to the crater described in AS 15-9524, this one is less elliptical and its bilobate ray pattern is much less pronounced. The differences may be attributed to a higher trajectory angle of the impacting body that formed this crater as it struck the surface.
H. J. Moore (1976), in his study of craters formed by impacting missiles at White Sands Missile Range, recognized a characteristic asymmetric profile along the axis of trajectory for craters formed in this manner.
The wall beneath the missile trajectory is typically less steep than the opposite or down-trajectory wall, and its rim crest is lower and more rounded. These observations, when applied to the lunar crater in this photograph, indicate that the impacting body was traveling toward the East when it struck the Moon.
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APOLLO 17 AS 17-2773.jpgAS 17-2773 - Overlapping Craters53 visiteThis pair of overlapping medium-sized craters illustrates some of the criteria used to determine relative ages: material ejected from the larger polygonal crater on the left partially fills the smaller crater on the right; thus, the crater on the left is younger. Furthermore, the wall of the large crater is complete, whereas the West wall of the smaller crater is absent, obviously having been destroyed by the larger crater.
Even if the 2 craters did not overlap, the sharp rim, terraced walls and prominent central peak of the larger crater clearly identify it as the younger of the two. The frames used in the stereogram were selected to show exaggerated relief, a technique very helpful to photointerpreters in determining shapes and relative elevations of surface features.
These 2 craters are located in the rugged terrain of the Far-Side highlands, approx. 250 Km north of Tsiolkovsky.
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APOLLO 17 AS 17-3125.jpgAS 17-3125 - Rimless crater53 visiteThe very young rimless crater near the center of this picture is located near the area where Oceanus Procellarum and Mare Imbrium join. The crater apparently formed in regolith-covered mare basalt. It differs from lunar impact craters of comparable size and age by its lack of a raised rim, surrounding ejecta deposit, or associated secondary impact craters. In addition, its interior walls do not show the steep slopes with craggy outcrops of rock in their upper parts, nor the streams of debris-avalanche deposits and talus that are usually seen in the walls of impact craters of comparable age and size.
Judging from the clear and sharply formed pattern of concentrically curved grooves and scarps that surround the hole, the material near this depression has apparently subsided into a subsurface void. Because of the extreme rarity and inferred short lifetime of steep slopes on the Moon, the latest subsidence must have taken place very recently, after most of the 50- to 300- m diameter craters that densely pepper the nearby mare surface were formed. Movement of the regolithic debris layer during subsidence apparently smoothed out most, if not all, of the craters that must have existed near the depression. Now the depression is surrounded by low, curved fault scarps and narrow, curved grooves that may be fault troughs (grabens) or may represent drainage of regolithic debris into cracks that opened in the underlying sagging basalt rock. The few craters that have formed on the subsided surface compare in density to the craters formed on the cluster (arrow) of Aristarchus secondary impact craters and associated herring- bone ridges; comparable ages for the Aristarchus secondary features and the depression are thus indicated. The subsidence was triggered either by the ground shock or seismic wavetrain generated when Aristarchus was formed 300 km to the west, or by the impacts of the secondary features.
The subdued depression in the upper left may be a similar older feature that was flooded by a later lava flow that now covers the area. The density of craters within the depression and the density on the surrounding lava are comparable. Alternatively, the subsidence there may have been incomplete; however, there is no sign that this subsidence is as young as that in the deeper crater
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Aeolian_Features-Windstreaks-Chrise_Planitia-MGS-00.jpgSigns of the wind in Chryse Planitia (Original NASA/MGS/MSSS b/w Frame)56 visiteCaption NASA originale:"This MGS-MOC image shows two Unnamed Impact Craters of nearly equal size, plus their associated Windstreaks. These occur in far Eastern Chryse Planitia. The Wind streaks point toward the South-West, indicating that the responsible Winds blew from the North-East. One of the two craters is shallower than the other and has a suite of large, windblown Ripples on its Floor. The shallower Unnamed Crater with the Ripples is probably older than the other, deeper Unnamed Crater".
Location near: 20,6° North Lat. and 30,1° West Long.
Image width: ~3 Km (~1,9 mi)
Illumination from: lower left
Season: Northern Winter
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