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| Piú viste - Mars Reconnaissance Orbiter (MRO) |
PSP_006969_1725_RED_abrowse-01.jpgThe Floor of Noctis Labyrinthus (extra-detail mgnf - MULTISPECTRUM; credits: Lunexit)55 visiteThe most striking feature of many of these knobs is a thin, bright band which often wraps around the edges near the bottom, as in this extra-detail mgnf. This image was acquired in order to investigate whether this is an exposed layer of rock or the shoreline of a former body of water.
HiRISE resolves details of the bright band that indicate that this is an unusual layer of rock, rather than an old shoreline. In several places, the band is broken up along cracks, sometimes forming boulders. This indicates that the band is solid rock, while material left on a shoreline should be loose sediments. It is now exposed as rings and arcs where erosion has cut deeply enough to expose the layer.
This band must indicate some unusual event in the geologic history of the region when a different type of rock was deposited; it is strikingly different in color from the other rocks. Although it is not a shoreline, it could be material that was deposited on the floor of a much older lake or sea and then buried by other rock; it could also have been laid down by other sedimentary processes or as volcanic ash.
MareKromium
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PSP_007338_2640_hires.jpgCaught in Action: Avalanches on North Polar Scarps (false colors; credits: NASA)55 visiteAmazingly, this image has captured at least four Martian avalanches, or debris falls, in action. It was taken on February 19, 2008, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.
The image to the left shows the context of where these avalanches occurred, with white boxes indicating the locations of the more detailed image portions shown to the right. All images are false color. Material, likely including fine-grained ice and dust and possibly including large blocks, has detached from a towering cliff and cascaded to the gentler slopes below. The occurrence of the avalanches is spectacularly revealed by the accompanying clouds of fine material that continue to settle out of the air. The largest cloud (upper images) traces the path of the debris as it fell down the slope, hit the lower slope, and continues downhill, forming a billowing cloud front. This cloud is about 180 meters (590 feet) across and extends about 190 meters (625 feet) from the base of the steep cliff. Shadows to the lower left of each cloud illustrate further that these are three dimensional features hanging in the air in front of the cliff face, and not markings on the ground. Sunlight is from the upper right.
Cameras orbiting Mars have taken thousands of images that have enabled scientists to put together pieces of Mars' geologic history. However, most of them reveal landscapes that haven't changed much in millions of years. Some images taken at different times of year do show seasonal changes from one image to the next, however, it is extremely rare to catch such a dramatic event in action. (Another, unrelated, active process that has been captured by Mars cameras are dust devils.) Observing currently active processes is often a useful tool in unlocking puzzles of the past for scientists studying the Earth. Working from primarily still images, it is harder for scientists studying Mars to rely on this tool. The HiRISE image of avalanching debris is a very rare opportunity to directly do so.
The scarp in this image is on the edge of the dome of layered deposits centered on Mars' north pole. From top to bottom this impressive cliff is over 700 meters (2300 feet) tall and reaches slopes over 60 degrees. The top part of the scarp, to the left of the images, is still covered with bright (white) carbon dioxide frost which is disappearing from the polar regions as spring progresses. The upper mid-toned (pinkish-brownish) section is composed of layers (difficult to see here) that are mostly ice with varying amounts of dust. The darkest deposits below form more gentle slopes, less than 20 degrees, and are mainly composed of two materials: mid-toned layers, possibly ice-rich, that form small shelves, and more mobile, wide-spread, sand-sized dark material. The wavy forms on the flatter areas to the right are dunes.
The upper, steepest section, which appears highly fractured due to blocks pulling away from the wall, is the likely source zone for the falls. The precise trigger mechanism is not yet known, although the disappearance of the carbon dioxide frost, the expansion and contraction of the ice in response to temperature differences, a nearby Mars-quake or meteorite impact, and vibrations caused by the first fall in the area, are all possible contributors.
By comparing images taken before the fall (such as HiRISE image PSP_007140_2640) and after the fall, we may be able to see where material has disappeared from the steep scarp and where it has appeared on the gentler slopes below, possibly as larger blocks, diffuse streaks, or other debris deposits. By imaging this scarp throughout the polar summer, we may be able to determine how much material falls over a given time period. These observations would help determine how much, and at what rate, ice is being eroded from the cliff. Understanding the processes and rates of erosion will help determine how the polar landscape has evolved, and help reveal how volatiles, such as water and carbon dioxide ices and gases, move around Mars.
The precise composition of the ice-dust mixture making up layers in the upper, steepest section of scarp is not known. However, detailed measurements of the volume of material removed, the configuration of the source area, and the steepness of the slope can be used to estimate physical properties of the material that may relate to composition.
The complete image, HiRISE PSP_007338_2640, is centered at 83.7 degrees latitude, 235.8 degrees east longitude. The image was taken at a local Mars time of 1:05 PM and the scene is illuminated from the west with a solar incidence angle of 70 degrees, thus the sun was about 20 degrees above the horizon. At a solar longitude of 34.0 degrees, the season on Mars is northern spring.
NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The High Resolution Imaging Science Experiment is operated by the University of Arizona, Tucson, and the instrument was built by Ball Aerospace and Technology Corp., Boulder, Colo.
MareKromium
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PSP_007219_1720_RED_abrowse-01.jpgFinely-Layered Rocks in Ius Chasma (extra-detail mgnf - MULTISPECTRUM; credits: Lunexit)55 visiteMuch of this Region has been covered by dust and sand, which appears brownish-red. This material is eroded by wind over time and allows us to see the light-toned rock underneath the surface.
There are also dunes that obscure portions of the outcrop.
Many outcrops within Ius Chasma and elsewhere on Mars are covered by such dunes and dust, but the high spatial resolution of instruments such as HiRISE and CRISM allow us to see the Geology and Mineralogy of regions between these dunes to help unravel the Geologic History of Mars.MareKromium
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PSP_007769_9010_15.jpgPhobos in 3D (credits: NASA)55 visitenessun commentoMareKromium
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PSP_007738_2145_RED_abrowse.jpgStreamlined Islands in Hrad Vallis (possible natural colors; credits: Lunexit)55 visiteThis image shows a portion of Hrad Vallis, an approx. 400 mt (1300 feet) deep and about 800 Km (approx. 500 mile) long depression located in the Elysium Planitia.
Hrad Vallis is one of several channel systems that are found just West of the Elysium volcanoes. The scoured floor of Hrad Vallis shows the effects of erosion, presumably by water.
Flowing water in the past has carved and sculpted rocky masses into streamlined shapes or islands. The streamlined islands often have sharp edges and are narrower at the downstream end and wider at the upstream end. The streamlined islands visible here are located in an area where the flow condensed from the fractured terrain of the Hrad Valles headwaters (to the South-East) to a more regular channel (to the North-West).MareKromium
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SHARAD-1.gifUnder the Ice... (1)55 visiteRadar Sounder Instruments orbiting Mars have looked beneath the Martian Surface and opened up the Third Dimension for Planetary Exploration.
The technique's success is prompting scientists to think of all the other places in the Solar System where they would like to use Radar Sounders.
The first Radar Sounder at Mars was the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on the European Space Agency's Mars Express Orbiter. It has been joined by the complementary Shallow Subsurface Radar (SHARAD), operating at a different wavelength aboard NASA's Mars Reconnaissance Orbiter.
The data in this animation are from SHARAD.MareKromium
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PSP_007338_2640.jpgNorth Polar Landslide (Special Processing by Dr M. Faccin)55 visitenessun commentoMareKromium
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PSP_007673_2575_RED_abrowse.jpgFrosted North Polar Crater (MULTISPECTRUM; credits: Lunexit)55 visiteThis image was taken over the North Polar Region of Mars, just South of the Layered Ice Cap.
The image shows a 10 Km diameter impact crater during Northern Spring, still covered by Carbon Dioxide ice/frost, and perhaps some water ice/frost.
There are color variations due to the presence of reddish dust mixed with the ice/frost in different proportions, and the dark and relatively blue spots form when CO2 is released in small jets from beneath the ice.
There are no clear examples of small impact craters superimposed on the large crater, although there are many shallow depressions that might be degraded craters.
This seems puzzling because small (approx. 10 meters in diameter) craters form much more frequently than 10 Km craters.
In fact, they form about a billion times more frequently! The reason why there aren’t any sharp small craters is due to the fact that the ice destroys them, and does so rapidly, compared with the cratering rate.
Ice on Mars does not melt in the current climate, but it does expand and contract with temperature variations and it can flow.MareKromium
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PSP_008585_2915_.jpgPhoenix Lander "Hardware" (Night-Time Frame)55 visiteCaption NASA:"MRO's HiRISE camera acquired this image of the Phoenix Landing Site 11 hours after landing. The image shows 3 unusual features, which were not present in the earlier, pre-landing HiRISE image.
We expect to find three main pieces of hardware: the Parachute attached to the Back-Shell, the Heat-Shield, and the Lander itself. The Parachute (lower right) is easy to identify because it is especially bright, although this image doesn't clearly reveal the Back-Shell.
The double dark marking at upper right seems most consistent with disturbance of the ground from impact and bouncing of the Heat-Shield, which fell from a height of about 13 Km.
The last object (upper left) appears to be a about the right size and height for the Lander and with dark objects on each side (to the East and West) consistent with the solar arrays.
This image was acquired in the nighttime, when the Arctic Sun was only 12° above the horizon to the North-East. Later images will be acquired in the daytime with the Sun higher in the sky and to the South-West, and could confirm our initial interpretations. North is about 7° to the left of straight up in this image.
These objects were later confirmed on the subsequent HiRISE observation acquired 22 hours after landing".MareKromium
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PSP_008591_2485_cut_e.jpgPhoenix Lander "Hardware" (Day-Time Frame; MULTISPECTRUM process.)55 visitenessun commentoMareKromium
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PSP_008244_2645_RED_abrowse.jpgNorth Polar Layered Deposits (MULTISPECTRUM; credits: Lunexit)55 visiteThe North Polar Layered Deposits of Mars form a layered stack of dusty ice up to 3 Km (about 2 miles) thick. The differences from layer to layer are thought to reflect differences in the climate of Mars that existed when the layers were formed.
We can see these internal layers exposed on the faces of the many troughs and scarps that cut through these deposits.
One of these scarp faces is shown here; it is situated at the head of a large canyon (named Chasma Boreale) that cuts through these Polar Layered Deposits.
The terrain on the upper side of the picture is higher and consists of the upper surface of the icy layered deposits in this area while the terrain on the lower side of the frame consists of the rocky ground that underlies the layered deposits. The cliff that separates these two areas runs down the center of the image with a relief of about 700 meters (about 2300 feet).
The section of the Layered Deposits that is exposed on this cliff face is unusual in that, as well layers of dusty ice, there are also layers of sand present. Small structures, called cross-beds, visible in the sandy layers indicate that each layer was originally a dune field that only later became covered with ice. Some of this sandy material is being removed from the cliff face and is forming new dunes at the foot of the cliff.MareKromium
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Psp_001736_2605_red.jpgThe Dunes of Olympia Undae (MULTISPECTRUM; credits: Lunexit)55 visiteThis HiRISE image shows dark dunes and light polygonal terrain in Olympia Undae, also known as the North Polar Erg.
Two sets of dunes are obvious. The major set trends ~North-South, indicating winds from the East or West. Between the crests of these dunes is a second set oriented mostly East-West.
Zooming in on the dunes, a rippled texture is apparent, probably due to redistribution of sand at the scale of meters and less. Near the crests of some dunes are channel-like features, with some branching downslope.
The origin of these channels is unknown, but they may result from the flow and displacement of sand that was fluidized by sublimating CO2 or water frost.
Bright patches of ground are found in some inter-dune areas, with many having a polygonal texture. Polygons on Earth form from contraction induced by stresses from dehydration, cooling, and other processes, so these features may have a similar origin.
The CRISM instrument on MRO and OMEGA on Mars Express indicates that many dunes in Olympia Undae are rich in the mineral gypsum. MareKromium
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