Mars Reconnaissance Orbiter (MRO)
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ESP_014424_1845_RED_abrowse.jpgBright Deposits and an anomalous Circular Feature - maybe a VERY fresh Impact Crater or a vertical collapse pit (Natural Colors; credits: Lunexit)52 visitenessun commentoMareKromium
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PSP_003252_1425_RED_browse-00%7E0.jpgBright Gully Deposit in Terra Sirenum (ctx image - MULTISPECTRUM; credits: Lunar Explorer Italia)66 visiteThis HiRISE image shows a bright gully deposit and other gullies within a crater wall in Terra Sirenum (37,7 South Lat. and 229,0 East Long.).
Three images are available:
(context image - A): The full frame HiRISE image, with the crater at left center; the width of the image is 6 Km;
(close-up of the crater's rim - B): an enlargement showing the crater;
(close-up of the bright gully deposit - C).
Frames B and C have been stretched to enhance contrast. The red box in B shows the location of C. MareKromium
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PSP_003252_1425_RED_browse-01.jpgBright Gully Deposit in Terra Sirenum (the "crater" - close-up; false colors)56 visiteAs seen in the context image and here, the appearance of the crater wall differs between the Northern and Southern Sides. On the Northern Pole-Facing Side Walls, prominent gullies with channels and aprons are apparent, with many of these having valley-like alcoves near their tops. The morphology of the gullies is consistent with formation by a fluid, most likely water.
On the pole-facing slopes, ground ice or aquifers may be more stable, being subjected to less heating from sunlight compared to equator-facing slopes.
In contrast, the Southern, Equator-Facing Walls are dominated by rocky debris flows that lack prominent channels.MareKromium
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PSP_003252_1425_RED_browse-02.jpgBright Gully Deposit in Terra Sirenum (the "gully" - close-up; false colors)52 visiteThe bright gully deposit has a very fluid-like appearance, and has not been covered by other gullies or debris flows, indicating a young age. The brightness is a mystery; it could be due to minerals formed from water or ice.
Alternatively, the flow that made the gully may have removed a thin coating of relatively darker dust and soil, revealing a brighter substrate.
In any case, this feature is probably indicative of recent flow of water or water-rich material on Mars.MareKromium
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Juventae_Chasma-PIA12489.jpgBright Layered Deposits near Juventae Chasma (Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)52 visiteThis view shows color variations in bright Layered Deposits on a plateau near Juventae Chasma in the Valles Marineris egion of Mars. A brown mantle covers portions of the bright deposits. The view covers an area about of 1,2 Km (three-fourths of a mile) across.
The image comes from an observation made by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter on May 2, 2007.
Researchers have found that these bright Layered Deposits contain Opaline Silica and Iron Sulfates, consistent with low-temperature, acidic aqueous alteration of basaltic materials. They conclude that aqueous activity affected this plateau after formation of the nearby canyons. Although the source of water and sediment remains uncertain, the strong correlation between fluvial landforms and bright Layered Deposits in this Region argues for sustained precipitation, surface runoff, and fluvial deposition occurring during Mars' Hesperian Era on the plateaus adjacent to Valles Marineris and along portions of the canyon walls.
This image is one product from HiRISE observation PSP_003579_1755, centered at 4,7 South Lat. and 296,4 East Long.MareKromium
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PSP_006673_1600_RED_abrowse.jpgBright Material on the Floor of an Unnamed Crater (natural colors; credits: Lunexit)56 visiteThis image shows part of a crater wall and floor, where the floor is covered by dunes and distinct regions of bright material. The bright material stands higher than the rest of the floor suggesting that it is more resistant to erosion than surrounding materials.
It is possible that more and more bright material will be exposed over time; why the material is bright is unknown.
The material might be evaporites, that form when salt water dries up and leaves behind salt deposits (the evaporites).
Also in this scene is a crater with a ridge running up to its west (left) side. The ridge is lighter and might be evidence that water flowed through it, bleaching the rocks as it went. The water might have cemented the soil, causing it to be more resistant to erosion and high standing as seen today.MareKromium
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ESP_022593_1595_RED_abrowse-PCF-LXTT.jpgBright Southern Dunes (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)122 visitenessun commentoMareKromium
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PIA10144-DarkFans~0.jpgBright Streaks and Dark Fans (MULTISPECTRUM; credits: Lunexit)53 visiteThe South Polar Region of Mars is covered every year by a layer of Carbon Dioxide (CO2) ice. In a Region called the "cryptic terrain", the ice is translucent and sunlight can penetrate through the ice to warm the surface below.
The ice layer sublimates (evaporates) from the bottom. The Dark Fans of dust seen in this image come from the surface below the layer of ice, carried to the top by gas venting from below. The translucent ice is "visible" by virtue of the effect it has on the tone of the surface below, which would otherwise have the same color and reflectivity as the Fans.
Bright streaks in this image are fresh frost. The CRISM team has identified the composition of these streaks to be Carbon Dioxide.
Nota Lunexit: questa la surface feature che ha "stimolato" l'immaginazione di Joseph Skipper e Richard Hoagland. Secondo costoro, le "dark features" sarebbero alberi simili ai "pioppi" terrestri... Ogni ulteriore commento ci sembra davvero inutile.MareKromium
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PIA10140-DarkFans~0.jpgBright Streaks and Dark Fans (MULTISPECTRUM; credits: Lunexit)53 visiteIn a Region of the South Pole known informally as "Ithaca", numerous Fans of dark frost form every Spring. HiRISE collected a time lapse series of these images, starting at Ls = 185 and culminating at Ls = 294. "Ls" is the way we measure time on Mars: at Ls = 180 the Sun passes the Equator on its way South; at Ls = 270 it reaches its maximum subsolar latitude and Summer begins.
We believe that the bright streaks are fine frost condensed from the gas exiting the vent. The conditions must be just right for the bright frost to condense. MareKromium
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PSP_007162_1915_RED_abrowse.jpgBright and Dark "Slope Streaks" in Arabia Terra (MULTISPECTRUM; credits: Lunexit)80 visiteThis observation is of region between large craters in Arabia Terra, which is a large swath of bright (high albedo) terrain in the Martian Cratered Uplands. At the center of this image is a channel with a sinuous, fluvial-like (such as "river-like") morphology, although it has long since been dry.
The floor of the channel is covered with an array of linear dunes, which are accumulations of windblown sediment.
Of special interest in this scene is a series of dark (low albedo) and brighter (higher albedo) discolorations along the channel walls, also known as slope streaks. Most slope streaks are initially dark, gradually brighten with time, and are thought to be due to dust avalanches that remove a thin layer of bright dust to reveal darker material. Here, many streaks appear brighter than the surrounding undisturbed slope surface, and the origin of these bright streaks is not entirely clear.MareKromium
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ESP_020061_1720_RED_abrowse-PCF-LXTT.jpgBright and Dark Plains (Absolute Natural Colors; additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)123 visiteThis HiRISE image shows a mixture of bright and dark Terrain along the plains just West of Ganges Chasma.
The concentration of these bright patches adjacent to an old Impact Crater suggests that the bright patches could represent Ejecta from when the crater formed.
This would be an interesting discovery because it would mean that a different unit underlies the Surface we now see. Alternatively, much of the Plains in this Region seem to have a dark surficial cover (probably aeolian debris). Where this darker debris has been removed by the wind, the underlying brighter substrate would be exposed.
Mineralogic information from the CRISM instrument would be very useful for determining if the bright patches contain minerals indicative of water - such as Clays - or if they are Basalts (produced from Volcanic Eruptions).MareKromium
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PSP_007653_2010_RED_abrowse-00.jpgBright on Dark (MULTISPECTRUM; credits: Lunexit)52 visiteThis image reveals bright Slope Streaks in Bahram Vallis, a long sinuous valley that winds across North-Eastern Lunae Planum and Xanthe Terra to the circum-Chyrse basin.
Typically, dark and light-toned Slope Streaks appear together on light-toned slopes. This scene is a rare case in which only bright streaks are visible on a dark surface. Slope Streaks generally start at a point source and widen downslope as a single streak or branch into multiple streaks. Some of the Slope Streaks show evidence that downslope movement is being diverted around obstacles, such as large boulders, and a few appear to originate at boulders or clumps of rocky material.
Many hypotheses have been proposed for the formation of slope streaks including dry avalanching, geochemical weathering, liquid stains or flows, and moisture wickering. Recent observations from HiRISE images have revealed that the interior of Slope Streaks is lower in elevation than the surroundings indicating that material must have been removed and then deposited in the formation of the streak.
Slope Streak formation is among the few known processes currently active on Mars. Where they appear together, dark Slope Streaks cross cut and lie on top of the older and lighter-toned streaks leading to the belief that lighter-toned streaks are dark streaks that have lightened with time as new dust settled on their surface. Over the course of several years, MOC images from this Region did not reveal any new dark or light-toned Slope Streaks suggesting that streak formation is not currently active here.
HiRISE will continue to monitor this Region for new slope streaks and changes in tone of old streaks.MareKromium
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