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| Ultimi arrivi - Mars Reconnaissance Orbiter (MRO) |
TRA_000823_1720_RED_fault.jpgFault of Jus54 visiteThe sharpness and quality of HiRISE images allows geologists to work out the detailed geometry and sequence of events that have shaped the landscape. For example, this area shows exposures of light- and dark-toned layers of rock that have been faulted and folded. These rocks formed out of sedimentary deposits that originally accumulated in thick horizontal sequences, like a layer cake.
These layers have since been tilted on-end and eroded, exposing the sequence of layers that we now see at the surface. A prominent dark layer extends through the center of the scene from the upper right to the lower left of the image. This dark layer is discontinuous and offset along a fault.
The thin grey zone that extends from the upper left to the lower right of the image delineates the fault plane. This fault was originally a thrust, or compressional fault, that formed prior to the aforementioned tilting event. Tilting of this fault and the surrounding rock reveals a series of drag folds adjacent to the fault plane. These drag folds formed as the layered rock bent in response to friction along the fault plane as the thrust fault formed, prior to the tilting event. This fault offsets the dark layer by a maximum of 70-75 m. Smaller secondary folds and faults are also visible in this scene. The smallest resolved fault offset of an individual rock layer is 1-1.5 m. Also visible in this image are numerous small 4-10-m-diameter impact craters that are surrounded by ejecta of meter-scale boulders.
Ott 18, 2006
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North_Polar_Layered_Deposits-PIA01925.jpgNorth Polar Layers69 visiteCaption NASA originale:"This view shows the basal layers of Mars' north polar layered deposits. The floor of Chasma Boreale is at the bottom of the image. This is a sub-image of a larger view imaged by the High Resolution Imaging Science Experiment (HiRISE) on NASA's Mars Reconnaissance Orbiter on Oct. 1, 2006. The resolution is 64 cm (about 25") per pixel, and the scene is 568 mt (approx. 621 yards) wide". Ott 17, 2006
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Mawrth_Vallis-PIA01924.jpgThe colors of Mawrth Vallis (False Colors; credits: NASA/JPL-Caltech/Univ. of Arizona)59 visiteCaption NASA originale:"This view shows diverse materials and morphologies in the region south of Mawrth Vallis on Mars. The color is composed of infrared, red, and blue-green color images, and has been enhanced to accentuate the color differences. The bright material may be rich in clays and date back to a time when Mars had a wetter environment. This is a sub-image of a larger view imaged by the High Resolution Imaging Science Experiment (HiRISE) on NASA's Mars Reconnaissance Orbiter on Oct. 1, 2006. The resolution is 25 centimeters (10 inches) per pixel, and the scene is 352 meters (385 yards) wide".Ott 17, 2006
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Craters-Becquerel_Crater_mound_6m-04.jpgBeautiful Becquerel Crater (5)57 visitenessun commentoOtt 16, 2006
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Craters-Becquerel_Crater_mound_6m-03.jpgBeautiful Becquerel Crater (4)57 visitenessun commentoOtt 16, 2006
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Craters-Becquerel_Crater_mound_6m-02.jpgBeautiful Becquerel Crater (3)57 visitenessun commentoOtt 16, 2006
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Craters-Becquerel_Crater_mound_6m-01.jpgBeautiful Becquerel Crater (2)57 visitenessun commentoOtt 16, 2006
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Craters-Becquerel_Crater_mound_6m-00.jpgBeautiful Becquerel Crater (1)56 visiteThe mound of layered rock near the center of Becquerel Crater (2,6° North and 8,2° West) is one of the best examples of sedimentary rocks on Mars. This location has been suggested as a possible target for the 2009 Mars Science Laboratory Rover Mission. An interesting attribute of this mound is that most of the actual rock is light-toned. The darker bands seen in this image are actually dark, wind-blown sediment that has been trapped on the surface by the small escarpments associated with each layer. The source of this dark sediment is the sand dune fields to the north and south of the layered mound.
North is towards the top of the 5 images and the Sun is shining from the left.
Ott 16, 2006
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Craters-Unnamed_Crater_in_Terra_Sirenum_12m-01.jpgCrater in Terra Sirenum (2) - natural colors59 visiteDuring its first week of observations from low orbit, NASA's newest Mars spacecraft is already revealing new clues about both recent and ancient environments on the red planet.
Scientists hope the Mars Reconnaissance Orbiter will answer questions about the history and distribution of Mars' water by combining data from the orbiter's high-resolution camera, imaging spectrometer, context camera, ground-penetrating radar, atmospheric sounder, global color camera, radio and accelerometers.
Between Sept. 29 and Oct. 6, science instruments on the spacecraft viewed dozens of sites that reflect different episodes in Mars' history. The diverse sites provide a good test for the capabilities of the spacecraft instruments. The orbiter will begin its primary science mission phase in early November when Mars re-emerges from passing nearly behind the sun.
The instruments are seeing details in the shapes and icy composition of geologically young layering near the Martian north pole. Other views offer details of a mid-latitude valley whose upper layers have been eroded away, revealing an underlying clay layer that formed a few billion years ago, when wet conditions produced the clay. Observations of a southern-hemisphere crater show fine-scale details of more recent gullies, adding evidence that they were carved by flowing water.
"In this opening phase we have tested the instruments, and they are working perfectly," said Dr. Steve Saunders, Mars Reconnaissance Orbiter program scientist at NASA Headquarters, Washington. "The teams are getting amazing science data. They are ready to fulfill the mission's science objectives and to support other Mars missions. One image is already helping the Mars Exploration Rover team choose a route to explore Victoria Crater. Others will help guide the selection of a safe site for the future Phoenix Mars Lander."
In Chasma Boreale, a vast valley that juts into the north polar ice cap, the orbiter's spectrometer sees layers that vary in soil composition and in how much ice is mixed with the soil. A dark underlying layer contains little ice, but just beneath it lies ice-rich material resembling higher layers. The spectrometer takes pictures both in visible-light and infrared wavelengths useful for identifying what a target is made of.
"You see more-ice-rich and less-ice-rich layers, which tells you that conditions changed from the time one layer was deposited to the time another layer was deposited," said Dr. Scott Murchie of Johns Hopkins University Applied Physics Laboratory, Laurel, Md. Murchie is the principal investigator for the spectrometer on the spacecraft. "These layers are geologically young -- on the order of thousands or millions of years -- and may hold clues about climate cycles."
A lower-latitude target was Mawrth Vallis. The European Mars Express spacecraft previously discovered ancient deposits of clay minerals that could form only if water were present for a long time at Mawrth Vallis. The Mars Reconnaissance Orbiter's spectrometer has resolved smaller-scale compositional features and detected differing clay mineral content. The clay-rich areas show some of the best evidence for conditions possibly favorable for life on ancient Mars, Murchie said.
The mission's High Resolution Imaging Science Experiment camera has shown unprecedented detail in orbital images of Mars. An example was released recently showing the Opportunity rover at Victoria Crater. The camera imaged 64 areas on Mars during the testing week. "These images are truly beautiful, and since they resolve features the size of people, you can visualize yourself hiking around in these diverse terrains," said the camera's principal investigator, Dr. Alfred McEwen of the University of Arizona, Tucson.
The high-resolution camera, the imaging spectrometer and the orbiter's wider-looking Context Camera all observed Mawrth Vallis. Details visible in the new observations, such as small channels, are consistent with past wet conditions, McEwen said.
Another observation of an unnamed southern crater shows relatively young gullies, like those seen in many Mars locations viewed by NASA's Mars Global Surveyor orbiter. Braided channels characteristic of sediment-rich streams are visible in the new observations. This reinforces the interpretation that these geologically young gullies formed at least in part from erosion by flowing water. Original discovery of the many geologically young gullies on Martian slopes was by Dr. Michael Malin of Malin Space Science Systems, San Diego.
The Mars Reconnaissance Orbiter is managed by the Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission Directorate, Washington.
Ott 16, 2006
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Craters-Unnamed_Crater_in_Terra_Sirenum_12m-00.jpgCrater in Terra Sirenum (1)56 visiteThe largest number of gullies on Mars occur on the walls of southern hemisphere craters. During southern winter, many of the gullied walls are in shadow. It has been known for many years from Mars Global Surveyor Mars Orbiter Camera images that frost forms on these shadowed slopes and that differences in the amount or nature of the frost deposits highlight the gully floors and deposits. Such differences may occur because the materials are of different particle sizes, or have other differing attributes that affect their thermophysical properties. To investigate this phenomenon, CTX acquired this image of a crater at 39.3°S, 136.5°W, where gullies were known to display frost during winter. To see the gullies, download the image and view it in an image processing program, as they are nearly invisible in the normal contrast image.Ott 16, 2006
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North_Polar_Cap_oct2006.jpgThe "North Polar Cap" of Mars54 visiteDuring the last week of September and the first week or so of October, 2006, the Mars Reconnaissance Orbiter (MRO) scientific instruments were turned on to acquire test information leading up to full science operations to begin the first week of November 2006, following superior conjunction (superior conjunction is where a planet goes behind the sun as viewed from the Earth). Since it is very difficult to communicate with a spacecraft when it is close to the Sun as seen from Earth, this checkout of the instruments was crucial to being ready for the Primary Science Phase (PSP) of the mission.
Throughout the Transition Phase of operations, the Mars Color Imager (MARCI) acquired terminator (transition between nighttime and daytime) to terminator swaths of color images on every dayside orbit, as the spacecraft moved northward in its orbit. The south polar region was deep in winter shadow, but the north polar region was illuminated the entire martian day. During the primary mission, these swaths will be assembled into global maps that portray the state of the martian atmosphere -- its weather -- as seen every day and at every place at about 3 PM local solar time. After the Transition Phase was completed, most of the instruments were turned off, but the Mars Climate Sounder and MARCI have been left on. Their data will be recorded and played back to Earth following the communications blackout associated with conjunction and just prior to the start of the PSP.
Combined with Mars Global Surveryor (MGS) Mars Orbiter Camera (MOC) wide angle image mosaics taken at 2 PM local solar time, the MARCI maps will be used to track motions of clouds.
The image shown above is a composite mosaic of four polar views of Mars, taken at midnight, 6 AM, noon, and 6 PM local martian time. This is possible because during summer the sun is always shining in the polar region. It shows the mostly water ice perennial cap (white area), sitting atop the north polar layered materials (light tan immediately adjacent to the ice), and the dark circumpolar dunes. This view shows the region poleward of about 72 degrees north latitude. The data were acquired at about 900 meters per pixel. Three channels are shown here (425 nm, 550 nm, and 600 nm).
Ott 16, 2006
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T-TRA_000830_1440_RED_NigerVallis_01.jpgNiger Vallis58 visiteThis image shows a portion of the floor of Niger Vallis, an ancient Martian outflow channel. Niger Vallis originates on the flanks of the volcano Hadriaca Patera, and empties into the Hellas impact basin. Outflow channels are observed in many regions of the planet, and may have been carved by brief eruptions of liquid water from beneath the surface. Since Niger Vallis formed, impacts have cratered the channel floor, and fine-grained wind-blown debris has been transported across the surface, eroding and burying all but the freshest craters. The curved ridge in the scene may be the remnant of a large crater rim. At the high resolution of this image, a pattern of parallel dunes and ripples can be seen, as well as individual boulders as large as two meters across.
Ott 08, 2006
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