| Piú viste - Mars Reconnaissance Orbiter (MRO) |
PSP_005924_2210_RED_abrowse.jpgFeatures of Cydonia (MULTISPECTRUM; credits: Lunexit)54 visiteThe Cydonia Region on Mars is located in Arabia Terra at the boundary between the Northern Lowlands and Southern Highlands. This Region gained notoriety when Viking imaged a landform that looked like a face.
The “Face” has subsequently been imaged by many orbiters, including HiRISE ( PSP_003234_2210), showing that it is simply a rocky mound, and the face-like appearance was due to a trick of shadows. This observation was taken of a Region slightly to the South-West of that landform.
This Region is characterized by Knobs and Buttes. Knobs are rounded hills and Buttes are hills with steep vertical sides and a flat top. A butte is similar to a plateau, but smaller in scale. These are features that are resistant to erosion, and there are several ways that such features may become more resistant than the surrounding areas. They can be plutonic intrusions or volcanic rocks that are more resistant rock types than the surrounding sedimentary rock. Alternatively, these Regions may be resistant because they have been cemented by water carrying dissolved ions that precipitate as minerals binding the sediment together.
Either way, they provide important information about the geologic history of the Region.
Of note in this image is the interesting pitted and patterned ground. This pitting may have resulted from the sublimation of interstitial ice. Patterned ground is common throughout the Northern Mid-Latitude Plains.MareKromium
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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)54 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. MareKromium
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PSP_003520_1010_RED_abrowse-01.jpgSouth Polar Spiders (edt - MULTISPECTRUM-2; credits: Lunexit)54 visitenessun commentoMareKromium
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PSP_003520_1010_RED_abrowse-00.jpgSouth Polar Spiders (ctx frame - MULTISPECTRUM-2; credits: Lunexit)54 visiteThis image is located in the South Polar Region of Mars and we can see “spiders” likely caused by the sublimation of Carbon Dioxide ice.
As this happens, the gas moves through channels until it reaches the surface and vents out. These vents show up as the dark streaks because they carry dust and dirt up to the surface.MareKromium
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PSP_005410_1115_RED_abrowse.jpgPolar Pit Gullies (MULTISPECTRUM; credits: Lunexit)54 visiteThis image shows Polar Pit Gullies in a depression. The gullies do not appear to have been active recently, as their channels and alcoves are covered with polygonal fractures and ripples that have formed over time. The alcoves contain boulders from eroding layers up-slope. Several of the alcoves extend to the slope rim, suggesting head-ward erosion.
The rest of the scene contains abundant polygonal ground, thought to have formed by processes involving ground ice. This image is at a High Latitude where polygonal terrain is common. This feature is not found in Equatorial Regions, which supports a relationship with ground ice because ground ice is not stable near the equator today.
There are several muted circles on the plains in the lower half of the image; these are possibly relaxed craters. If a crater forms in ice-rich ground, the ice enhances the degradation of the crater and gives the crater a “softened” appearance.MareKromium
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PSP_005817_1515_RED_abrowse.jpgBedrock (MULTISPECTRUM; credits: Lunexit)54 visite
This frame shows part of the floor of an unnamed crater in the Southern Highlands, near Hellas Planitia. It depicts light-colored bedrock and darker wind deposits. The bedrock appears tan-colored and shows subtle signs of layering in places (...).
Layering in terrestrial formations usually indicates that the rock-forming materials were deposited by wind or water.
The bedrock is crisscrossed by a dense network of rectilinear (lines that are parallel or at right angles) fractures; some can be followed for hundreds of meters.
The fractures look bluish in color, indicating that they are occupied by materials that are somehow different from the bedrock. Perhaps wind-carried materials got trapped in the depressed fracture zones.
MareKromium
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PSP_004000_0945_RED_browse~0.jpgThe "South Polar Residual Cap" (natural colors; credits: Lunexit)54 visite
Like Earth, Mars has concentrations of water ice at both poles. Because Mars is so much colder, however, the seasonal ice that is deposited at high latitudes in the winter and is removed in the spring (generally analogous to winter time snow on Earth) is carbon dioxide ice. Around the south pole there are areas of this carbon dioxide ice that do not disappear every spring, but rather survive winter after winter&emdash;this persistent carbon dioxide ice is called the south pole residual cap.
Relatively high-standing smooth material is broken up by circular, oval, and blob-shaped depressions, forming a pattern called "swiss cheese" terrain. The high-standing areas are carbon dioxide ice with thicknesses probably of several meters. The depressions are thought to be caused by the removal of carbon dioxide ice by sublimation (the change of a material from solid directly to gas). By looking at different sized depressions in an image such as this, and by comparing images of the same place from year to year, the development of "swiss cheese" terrain can be observed.
The sublimation process may begin anywhere as a small depression. Once this small depression is formed, it expands laterally in all directions, creating the rounded depressions we see today. As most depressions seem to have a similar depth and have relatively flat bottoms, there is likely some layer below, possibly of water ice, that cannot be as easily removed by sublimation. Thus, while the south polar residual cap as a whole is present every year, there are certainly annual changes taking place within it.
Especially apparent and interesting in this image are the strips of material that parallel the edges of many depressions. Often there are two or more concentric strips that are smooth like the surrounding surface, but seem to be lower than the surrounding surface and in places appear to be tilted down towards the center of the depression. Inner strips are sometimes broken up into chunks. It may be that the uppermost smooth layer is a bit more resistant to sublimation than the material just below it&emdash;the quicker removal of the underlying material might cause the stronger upper layer to detach from the surrounding terrain and settle down towards the center of the depression.
Alternatively, these ringing strips may indicate that many layers are present within the carbon dioxide ice. Another interesting feature is the faint crisscrossing network of ridges on the upper smooth terrain. These may also be complexly involved in the sublimation and deposition of carbon dioxide ice.
With the high resolution capability of HiRISE, we intend to measure the amount of expansion of the depressions over one or more Mars years. Knowing the amount of carbon dioxide removed can give us an idea of the current atmospheric and climate conditions, and possibly how Mars climate may be changing.
MareKromium
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PIA11230.jpgDust Storm in the North Polar Regions54 visiteCaption NASA:"This is an image of Mars taken from orbit by the Mars Reconnaissance Orbiter's Mars Color Imager (MARCI). The Red Planet's Polar Ice-Cap is in the middle of the image. Captured in this image is a 37.000 square-kilometer (almost 23.000 miles) Dust Storm that moved counter-clockwise through the Phoenix Landing Site on Oct 11, 2008, or Sol 135 of the Mission.
Viewing this image as if it were the face of a clock, Phoenix is shown as a small white dot, located at about 10 AM. The storm, which had already passed over the Landing Site earlier in the day, is located at about 9:30 AM".MareKromium
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PIA10148-LizardSkinTerrain~0.jpgLizard-Skin Surface Texture (natural colors; elab. Lunexit)54 visite The South Polar Region of Mars is covered seasonally with translucent CO2 ice.
In the Spring, gas subliming (evaporating) from the underside of the seasonal layer of ice bursts through weak spots, carrying dust from below with it, to form numerous Dust Fans aligned in the direction of the prevailing wind.
The dust gets trapped in the shallow grooves on the surface, helping to define the small-scale structure of the surface. The surface texture is reminiscent of lizard skin.MareKromium
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PSP-20081120_spirit.jpgSpirit from orbit54 visiteThe solar system's most celebrated team of off-planet drivers cheered when they heard the news. Spirit had phoned home from Mars, ending four days of silence. The team had kept the rover safe, with help from a friend named "Marci."
Spirit had survived a fierce and sudden dust storm that had driven solar power to all-time lows. Without being able to notify Earth, Spirit had followed instructions the team sent to protect the rover.
The team had received warning from scientists who keep tabs on Martian weather with MARCI -- short for Mars Color Imager. From orbit, the instrument showed thick, swirling dust clouds advancing from the west. Engineers responded with instructions to conserve energy. They told Spirit to turn off a heater and do only two things each day -- check battery power and dust in the atmosphere.
As directed, Spirit contacted Earth on Nov. 13, 2008. MareKromium
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PSP_006005_2050_RED-00-PCF-LXTT.jpgStreamlined Island in Kasei Valles (Saturated Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)54 visiteIn this picture there is a Streamlined Island: one of many observed in the large outflow channels on Mars. This outflow channel is called Kasei Valles, and is one of the largest catastrophic outflow channels on Mars.
The Streamlined Island forms as water flows through the channel, but is blocked by some sort of obstacle, such as a crater or other topographic landform. In this HiRISE image, we only see the very tail end of the Streamlined Island, which is over 118 Km in length.
The platy surface within the channels has been attributed to either later lava or mud flows along the surface. The island itself is quite dusty and covered in small craters, so the island may be quite old. Along the edge of the island, however, you can see individual layers of rock.
These layers represent individual rock units that may be volcanic or sedimentary in origin.MareKromium
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PSP_004078_2015_RED_browse-00.jpgLayered Deposits in Becquerel Crater (possible natural colors; credits: Lunar Explorer Italia)54 visiteImage PSP_004078_2015 shows light-toned layered deposits along the floor of Becquerel Crater, an impact crater in Arabia Terra. The deposits consist of stacked, repeating layers which consistently appear to be only a few meters thick.
The surface of the deposits also appears to be cracked into blocks a meter or so in length.
Layered deposits, such as these, form from sediments once deposited within the crater. Possible origins for the sediments include windblown debris, volcanic ash falling from the sky, or sediments that accumulated in a lake on the crater floor. The regular thickness of the layers suggests that they were most likely deposited in a water environment or by wind in a cyclic process.
Some of the layering has a dark appearance that produces an alternating bright-dark “zebra” banding. This may be the result of a thin surface layer of coarser and darker basalt sand collected on the more level surfaces, rather than indicating compositional differences in the eroded layered beds. Faults can also be seen displacing portions of the layered bed. An example of this can be seen just left of center in the bottom half of the subimage. The faulting indicates that the deposits have experienced disruption since their emplacement.
MareKromium
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