| Piú viste - MOON |
32-Ranger7.jpgMare Nubium, Mare Cognitum and Mare Humorum53 visiteCaption NASA originale:"Second image of the Moon taken by the Ranger 7 spacecraft on 31 July 1964. Ranger 7 was the first U.S. spacecraft to successfully transmit images of the Lunar Surface back to Earth. This image was taken 17,2 minutes before impact from a distance of 2158 km. North is at 12:30. Mare Nubium is at lower right and Mare Humorum at lower left. The image is centered at 13° S, 330° E and is about 950 Km across. The Ranger 7 impact site, at 10.7° S, 339.3° E, is at the center of the upper right quadrant, in Mare Cognitum. Landsberg Crater is against the top of the frame at center, and the 60 Km diameter Bullialdus Crater is just below and right of center, partly obscured by a hash mark (Ranger 7, A001)".
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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 15-9591.jpgAS 15-9591 - Tsiolkovsky53 visiteModerate enlargement of part of a panoramic camera frame provides greater detail of the central peak complex of Tsiolkovsky. A relatively large population of superposed craters has been preserved on level areas of the peaks (near the left-center of the photograph). In contrast, very few craters are present on steep slopes-most have been destroyed by the downslope movement of erosional debris. An intermediate population of craters on the dark mare shows that the mare surface is younger than the level areas of the peak complex but older than the freshly exposed steep slopes of the peaks. The youngest part of the mare surface is the dark, smooth area adjacent to the small angular rifle in the upper left corner. Here small craters have been almost completely filled by the flow and are barely discernible. The rifle may have served as the vent for the young lavas.
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APOLLO 16-0692.jpgAS 16-0692 - Teophilus Crater53 visiteTheophilus is a relatively young crater similar in size but slightly older than Copernicus. It lies on the eastern edge of the Kant Plateau, an elevated area in the Central Highlands along the northwestern margin of Mare Nectaris. Part of Nectaris is visible as the smooth, dark area near the horizon at the left edge. Like Copernicus and Aristarchus, Theophilus has ruggedly terraced walls and a complex central peak protruding through a level floor. Smooth-surfaced material is present in "pools" at various levels on the terraces, on parts of the crater floor, and on the ejecta that blanket the near (North) side of the crater.
As one alternative, the pools may have been emplaced as fluid lava.
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APOLLO 16-4136-B.jpgAS 16-4136 - Cratered Region near Mandel'shtam (2)53 visiteThis enlarged view of part of frame AS 16-4136 shows some of the smooth flows that originate near the crest of the crater rim at the left side of photograph. Arrows point to the lower ends of two flows.
The origin of the flow material is controversial.
It was probably molten material generated by shock-wave compression of lunar rocks and ejected at relatively low velocities during the late stages of the formation of the impact crater; or it may have resulted from the flow of rock debris mixed with a fluidizing agent such as gas or water; or it may have been volcanically generated lava.
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APOLLO 16 AS 16-4511.jpgAS 16-4511 - Crater "Rays"53 visiteThis picture shows the striking bilateral symmetry of the rays of a small (2-Km diameter) crater in the floor of the large crater Daguerre in Mare Nectaris. Continuous areas and narrow filaments of light-gray ejecta extend from the crater across the dark mare surface through 270°, but are entirely absent in the southern 90° sector. Within the crater, dark material occurs on the southern crater wall while the remaining walls are bright. (The reader may wonder about the material whose reflectivity cannot be observed because it lies in shadow on the East wall of this crater. Until the area is observed under high Sun conditions, we are forced to make the simplifying assumption that it is bright because most of the materials visible elsewhere in the walls are bright).
This crater probably resulted from the impact of a projectile traveling from South to North along an oblique trajectory.
Its pattern of ejecta distribution is similar to that of small craters produced by the impact of missiles along oblique trajectories at the White Sands Missile Range, N. Mex. Some observers postulate that the dark material is a talus deposit of mare material that has fallen into the 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 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 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 16 AS 16-4653.jpgAS 16-4653 - Secondary Craters' Clusters53 visiteThese 3 clusters of secondary craters (see arrows) are on the East flank of the larger crater Ptolemaeus near the center of the Moon's Near-Side. Each cluster has a ridged and hummocky appearance. The primary crater has not been identified in this case, but the configuration of the clusters tells us that it must be to the South of Ptolemaeus. Note that the South-facing side of each cluster is more sharply defined than the North-facing side.
This is a consequence of the oblique trajectory of impacting fragments that causes the ejecta of the secondary craters to be propelled away (down range) from the primary crater. Observations of manmade impact craters have shown that the individual fragments within a cluster of secondary debris strike the surface nearly simultaneously.
In the process, ejecta from one secondary collides and interferes with ejecta from adjacent craters, producing a ridged and hummocky surface.
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APOLLO 17 AS 17-149-22838.jpgAS 17-49-22838 - Crater Chain (Far-Side)53 visiteThis oblique view taken with the Hasselblad camera shows a crater chain on the Far-Side, about 500 Km North of Tsiolkovsky. For an idea of the scale, the large crater near the upper left corner is about 26 Km wide. The origin of this chain is controversial. To some geologists, the irregular shape of many of the craters suggests that the chain was formed by the impact of a stream of ejecta from a large primary crater. The presence of herringbone ridges would have strengthened this interpretation, but none are visible; perhaps the high Sun angle and the oblique viewing angle of this scene have obscured them. To others the simple geometry of the chain suggests a volcanic origin. However, there is an apparent lack of faulting to control the alinement of the craters and an apparent absence of a blanket of volcanic ejecta.
The origin of this chain may not be decipherable until, and unless, additional photography becomes available.
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