| Ultimi arrivi - Mars Reconnaissance Orbiter (MRO) |
PSP_008130_1745_RED_abrowse-01.jpgSmall but deep Collapse Pit, North of Arsia Mons (extra-detail mgnf n. 1; credits: Dr G. Barca)72 visitenessun commentoMareKromiumGiu 25, 2008
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PSP_008130_1745_RED_abrowse-02.jpgSmall but deep Collapse Pit, North of Arsia Mons (extra-detail mgnf n. 2; credits: Dr G. Barca)68 visitenessun commentoMareKromiumGiu 25, 2008
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PSP_008095_2500_RED_abrowse.jpgLouth Crater, Southern Rim (MULTISPECTRUM; credits: Lunexit)86 visitenessun commentoMareKromiumGiu 24, 2008
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PSP_008161_2505_RED_abrowse.jpgLouth Crater (MULTISPECTRUM; credits: Lunexit)77 visitenessun commentoMareKromiumGiu 24, 2008
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PSP_008197_2655_RED_abrowse.jpgCircular Defrosting Feature (MULTISPECTRUM-2; credits: Lunexit)63 visitenessun commentoMareKromiumGiu 24, 2008
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PSP_008199_1910_RED_abrowse.jpgFeatures of Cerberus Fossae (Enhanced Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team) 56 visitenessun commentoMareKromiumGiu 24, 2008
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PSP_007078_1080_RED_abrowse.jpgThe Dunes of Richardson Crater (MULTISPECTRUM; credits: Lunexit)56 visitenessun commentoMareKromiumGiu 17, 2008
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PSP_006268_1995_RED_abrowse.jpgThe alleged "Bridges" of Chrise Planitia (MULTISPECTRUM; credits: Lunexit)75 visiteThis image shows part of the surface of Chryse Planitia, near the mouth of several of the giant outflow channels carved by massive floods. At this location the channel is much too large to be seen within a HiRISE image, and this shows an area of level plains near the mouth.
Two geologic units are visible at this site: a relatively dark expanse in the southern part of the image (Dx) and a light, slightly higher-standing area along the northern edge. The light unit may be material that has flowed out from below the surface in a process called mud volcanism. However, many aspects of the history of the Northern Plains of Mars remain uncertain.
A few other prominent features are present. A long trough with aeolian ripples runs through the eastern part of the image. This feature likely formed by contraction of the surface layer. This must have occurred after the formation of the light material since it cuts through the light unit in the northwest part of the image.
There is also a large mound which appears to bury part of the trough, and thus is even younger. Alternatively, two troughs could both terminate at the hill.
Despite the resolution of HiRISE, the nature of this mound is still unclear. It has a rugged surface, which might mean that it has been eroded enough to remove indications of its origin.
MareKromiumGiu 16, 2008
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PSP_006006_1715_RED_abrowse.jpgLayering in the Upper Walls of Valles Marineris (Enhanced and Saturated Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)55 visiteThis observation shows parts of the upper walls of Valles Marineris with layered rocks. These layers extend down to a smooth-appearing slope, that is likely material shed from the upper parts of the chasm walls; down-slope stripes are visible, indicating that material has fallen or slid downhill in a process termed Mass Wasting (nota Lunexit: anche noto come Gravity Wasting).
The layers, exposed in most rock outcrops in this image, are most likely lava flows from flood lavas that once erupted across the region. These layers are located in the upper walls of most of Valles Marineris and are sometimes exposed at depths well below the surrounding plateau, recording extensive volcanism in the history of the region. Similar, thick successions of lava flows are found at some sites on Earth (for example, the Columbia River flood basalts in the North-West of the U.S.).
Mass Wasting: is a geologic term that encompasses the rapid downhill movement of rocks and fine particles due to the force of gravity. One of the most common and generic types of mass wasting features on Earth are landslides, but there are many others such as rock falls, debris flows, soil creep, and debris avalanches. Landslides or any other mass wasting feature, require some type of triggering mechanism to induce the movement of particles under gravity. Some of these mechanisms include volume expansion of fractures (i.e. cracks) in rocks by freeze/thaw processes, increase in soil pore pressure (i.e. water content), undermining or removal of less-resistant material below a stronger material layer, and strong vibrational forces produced from above (e.g., meteorite impact) or below ground (e.g., volcanic eruption, earthquake). On Mars, two of the most common Mass Wasting features are landslides and dust avalanches (also referred to as Slope Streaks). Some of the most spectacular landslides in the Solar System are found in the Valles Marineris Canyon System on Mars and exhibit many of the classic characteristics of landslides on Earth. These characteristics include a semi-circular main scarp in the source region, a hummocky (i.e. irregular) or blocky surface in the upper portion of the deposit, surface ridges parallel to landslide flow direction in the middle portion of the deposit, and a lobate outer margin that has some significant thickness (e.g., tens to hundreds of meters). Dust avalanches are common on dune faces, crater interior walls, mesa slopes, and canyon scarps. The streaks are thought to occur when dust and/or other small particles on a sloped surface begins to move due to sublimation of a thin layer of water frost or by the oversteepening of slopes in localized dusty air fall deposits. MareKromiumGiu 14, 2008
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PSP_006237_1460_RED_abrowse.jpgLandforms of Dao Valles (MULTISPECTRUM-2; credits: Lunexit)55 visiteThis image in a section of Dao Valles contains a multitude of landforms that may result from the actions of ice. Aligned ridges on the valley floors are evidence of glacier-like flow of this material as it gets diverted around obstacles such as the valley walls and local mesas and knobs.
In some areas where the flow appears to have traveled over an obstacle instead of around, a series of fractures occur, analogous to crevasses that form in glaciers on Earth when ice flows over obstacles. The surface we see is covered with rocky debris and soil that may be protecting ice from sublimation.
Throughout the Region, the surface has been mantled by a smooth deposit that appears to have been eroded in a few locations. This sort of mantle is common at Martian High Latitudes and is thought to be a mixture of dust and ice, either ice-cemented soil or very dirty snow. The eroded areas could be due to ice loss trough sublimation, leaving the remaining surface to collapse or be eroded by the wind.
Many gullies are observed that appear to be carved into the valley walls by liquid water. Incised channels in places cut deeply into the surface and fans of debris with crisscrossing small channels indicate where the flow of water slowed and deposited material eroded from upstream. The source of water is as yet unknown. One theory has been proposed involving melting of surface ice or ice-rich soil in the cold Martian climate. Another theory suggests that an aquifer a few hundred meters (yards) below ground is feeding the gullies.
MareKromiumGiu 14, 2008
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PSP_006248_1235_RED_abrowse.jpgDark-Reddish Dunes in Terra Cimmeria (MULTISPECTRUM-2; credits: Lunexit)56 visiteThis image shows a set of dark sand dunes within the Northern part of an unnamed crater in the Terra Cimmeria Region.
The dunes have a distinctive shape, with two horns on one end and a rounded edge on the other. The side of the dunes with the horns has a steeper slope and the rounded side a more shallow slope. These types of dunes are called “Barchans” and, by analogy with similar dunes on Earth, form in areas with limited sand supply.
The horns of the barchans point in the downwind direction, thereby indicating that the predominant surface winds in this Region blew from the East (up). Further evidence of this wind regime is apparent when one zooms into the image. “Wind tails” are visible on the Western (down) side of many rocks (many of these rocks may be ejecta from the degraded crater in the Northern part of the image). Wind tails are formed by the accumulation of dust and sand in the lee of rocks, which act as wind shadows. Very small light ripples at a scale of a few meters (yards) are also apparent.
The dark, sinuous forms in the image are tracks left by dust devils, which lift bright dust off the surface, revealing the darker surface. Where dust devils cross the dunes, the fine texture on the dunes is undisturbed, indicating that the particles making up the dunes are coarse and fairly immobile.
MareKromiumGiu 14, 2008
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PSP_008311_1835_RED_abrowse-00.jpgFeatures and Mineralogy of Aram Chaos (context-frame - MULTISPECTRUM; credits: Lunexit)110 visiteThis image is from Aram Chaos, a large crater connected to the Ares Vallis Outflow Channel. It is called “chaos” because of the rough floor topography, large slumped blocks and large fractures that may have been caused by removal of subsurface material.MareKromiumGiu 12, 2008
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