Mars Reconnaissance Orbiter (MRO)
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PSP_010219_2785_RED_abrowse-01.jpgDunes in Abalos Undae (edm - possible True Colors; credits: Lunexit)53 visiteThis enhanced-color close-up (1,2 Km across) shows an example of dunes in Abalos Undae.
The enhanced color data illuminate differences in composition: the dunes appear of a green/bluish color because of their basaltic composition, while the reddish-white areas are probably covered in dust and residual ice. Upon close inspection, tiny ripples and grooves are visible on the surface of the dunes (both ripples and grooves are formed by wind action, as are the dunes themselves).
It is possible that these dunes are no longer migrating (the process of dune formation forces dunes to move in the direction of the main winds) and that the tiny ripples are the only active parts of the dunes today.MareKromium
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PSP_010221_1420_RED_abrowse-00.jpgAeolian Features (CTX Frame - Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)145 visitenessun commentoMareKromium
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PSP_010221_1420_RED_abrowse-01.jpgAeolian Features (EDM - False Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)53 visiteThis image is particularly interesting because of the occurrence of seasonal frost on the South-facing slopes (the image is relevant to the Southern Hemisphere, so South faces the Pole and gets little Winter light). This is particularly apparent in this natural colors view, as the frost forms pale, blue-grey-silver patterns. On the dunes, this highlights some of the regular patterns, as the frost forms only on parts of the ripples. The result is an intricately textured pattern of color.MareKromium
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PSP_010222_1815_RED.jpgLight-toned Bedrock in Terra Meridiani (possible True Colors; credits: Lunexit)53 visiteThis observation shows part of a broad expanse of bare rock in Terra Meridiani. This is a large area with abundant sedimentary rocks forming a stack hundreds of meters thick, and now being eroded into a landscape reminiscent of the South-Western United States.
The timescale involved in depositing and eroding these layers is evident from the remnant impact craters preserved here. The large arc in the image is the rim of one crater; the smaller, circular dark spots are traces of other impacts. Light sediments are found both inside and outside the large crater, indicating that this crater formed during the period of sediment deposition. It is likely that this depression, which was probably more than a kilometer deep when it formed, was completely filled and buried and is now being exhumed. Crater densities are often used to estimate the age of surfaces on Mars, but here the rate of erosion is enough to erase small craters, reducing the apparent age of the surface. These rocks probably date from an early era of Martian History, but no fresh, pristine craters are visible.
The smaller circular patches are also impact craters seen somewhere in a complex cycle of burial and erosion. They are filled with dark material which probably mantled the region at one point, most likely after all of the light material was deposited. In some places this appears to have been hardened into rock, as in the large dark circle in the north-central part of the image. Material eroded from this hardened mantle may now be forming the ripples seen in many places as it is blown by the wind; the color of the ripples is similar to the slabs of dark mantle.
At the finest scale, the light sediments are intricately textured. A diverse assortment of fine cracks called joints are visible. The scale and density of these joints varies across the image; this suggests variations in the properties of the rocks. Although the image as a whole is a relatively flat plain, at small scale the surface is intricately rough. The balance between erosion and rock strength has left a surface with many small knobs, mesas, cliffs, and bumpy textures.
Further evidence for the diversity of rocks here comes from the enhanced color. The dark mantling materials are generally blue in the RGB color image while the sediments are generally pale, but a diverse range of hues indicates variations in the composition (or in the amount of sand and dust trapped on the surface by textures of varying roughness). This helps to highlight layering and shows which rocks are most similar to each other.MareKromium
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PSP_010222_1815_RED_abrowse.jpgLight-Toned Rock and Dunes in Meridiani Planum (Natural Colors; credits: Lunexit)54 visiteNote Lunexit: in questo frame, un esempio di come il processing in Natural Colors (cioè i colori che percepirebbe un essere umano il quale si trovasse in loco) possa condurre a risultati radicalmente differenti rispetto al processing in (possible) True Colors (frame precedente).
ATTENZIONE: entrambi i processing sono veritieri (nel senso di eseguiti "A Regola d'Arte" e senza alterazioni intenzionali dei dati), eppure i colori che si vedono sono PROFONDAMENTE diversi!
E' - anche - per questo motivo che la diatriba sui "Colori Veri" di un Mondo (un qualsiasi Mondo) è intrinsecamente complessa, contraddittoria e, per certi versi, anche fuorviante - oltre che, a nostro avviso, tendenzialmente infinita...).
Pensateci sopra...MareKromium
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PSP_010252_2550_RED-PCF-LXTT.jpgSmall Snow-filled Depression in Vastitas Borealis (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)64 visitenessun commentoMareKromium
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PSP_010269_1900_RED.jpgVolcanic Fissure Vent in Elysium Planitia (natural colors; credits: Lunexit)53 visiteThis observation shows lava-covered plains in the Elysium Planitia region of Mars, located near the equator.
Two distinct lavas are visible in this image. The darker lava to the north (top) is the edge of the youngest major lava flow on Mars; it was fed by a voluminous eruption that coursed through the Athabasca Valles channel system.
The lighter-toned lava that covers the remainder of this image is older and dustier. It has a striped appearance due to slender dunes or ripples composed of windblown materials that are oriented northwest-southeast.
The most prominent feature in this image is the discontinuous line of pits and troughs that cuts across its center. It is an ancient volcanic fissure vent. Lava once erupted through this fracture onto the surface. The irregular depressions around the troughs may either be due to near-vent erosion by the lava or to the ponding and drain-back of the lava around the vent.
MareKromium
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PSP_010281_1510_RED_abrowse-00.jpgSedimentary Layers in Columbus Crater (ctx frame - possible True Colors; credits: Lunar Explorer Italia)53 visiteThis image covers a portion of the North-Eastern Inner Wall of Columbus Crater, located in the Southern Hemisphere of Mars and is approx. 100 Km (about 60 miles) in diameter.
Layered sedimentary rocks are found on the Crater Walls and Floor, and may have been deposited by water or by wind. These rocks have subsequently been eroded to expose their successive layers in cross-section.
The near-infrared spectrometer CRISM has revealed that these layers contain various hydrated minerals.
Mars Local Time: 15:42 (middle afternoon)
Coord. (centered): 28,6° South Lat. and 194,3° East Long.
Spacecraft altitude: 256,0 Km (such as about 160,0 miles)
Original image scale range: 25,6 cm/pixel (with 1 x 1 binning) so objects ~77 cm across are resolved
Map projected scale: 25 cm/pixel
Map projection: EQUIRECTANGULAR
Emission Angle: 0,5°
Phase Angle: 70,9°
Solar Incidence Angle: 70° (meaning that the Sun is about 20° above the Local Horizon)
Solar Longitude: 137,3° (Northern Summer)
Credits: NASA/JPL/University of Arizona
Additional process. and coloring: Lunar Explorer ItaliaMareKromium
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PSP_010281_1510_RED_abrowse-01.jpgSedimentary Layers in Columbus Crater (edm - possible True Colors; credits: Lunar Explorer Italia)53 visiteVisible in this edm is a north-facing slope (roughly 250 meters, or 800 feet, across) exposing finely layered sedimentary rock.
In this possibly true-color view, layers with a dark silver-gray appearance may be intrinsically darker, or may have a texture that more effectively collects dark sand particles, than adjacent layers with a brighter appearance.MareKromium
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PSP_010334_1760_RED.jpgYardangs in Southern Amazonis Planitia (natural colors; credits: Lunexit)53 visiteThis image shows Yardangs, or Ridges formed from wind abrasion, in the Southern Amazonis Planitia, which is located between the Tharsis and Elysium Volcanic Provinces on Mars.
Yardangs typically form in dry, desert environments with strong prevailing winds that are unidirectional and carry an abrasive sediment load. Abrasive winds erode the surface into parallel elongate landforms, or ridges, that are often three or more times longer than they are wide. When viewed from above, these landforms resemble the hull of a boat. Yardangs typically form in easily-eroded material, most likely sedimentary rock or volcanic ash deposits that contain some amount of sand. Sometime after the formation of these landforms, they were covered by a relatively thin, uniform coating of dust giving the area a monotone appearance. Dark slope streaks, interpreted as forming by avalanching of the dry dust, are visible on several of the slopes.
Yardangs are found on both Earth and Mars and are common on Mars in the Regions West and South-West of Olympus Mons, such as the area in this image in the southern Amazonis Planitia.MareKromium
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PSP_010344_2655_RED_abrowse.jpgScarp-fed Dark Dunes and NPLD (Natural Colors; credits: Lunexit)54 visiteMultiple levels within the North Polar Layered Deposits (NPLD) are visible in this HiRISE image.
The NPLD are a stack of dusty water-ice layers that are thought to record information about past Martian climates in the same way that Ice-Caps on the Earth record variations in our climate. These Martian layers are visible in the walls of troughs and scarps eroded into the stack.
One such scarp-face is visible on the far left of the full image and decreases in height from left to right.
Scientists continue to debate the length of time required to accumulate this stack of layers with estimates ranging from a few million years to about a billion years. Although we don’t yet know which layer corresponds to which time in Mars’ History, we can still use these layers to try to understand how the climate has changed over this period.
The topmost layers, which are the most recent (far left of the image), are brighter and appear gray-ish in this Natural Color view. They are interpreted to be a mixture of water ice and dust. The lower layering is more complex and appears to be a mixture of bright whiteiish layers (that we think are ice) and dark blue-ish layers (which we think are mostly sand).
A large pit in the center of the image penetrates deeply into this stack of layers and shows these alternating sandy and icy layers extending to depths of hundreds of meters (about 1000 feet).
Erosion of the dark sandy layers releases sandy material which collects into dunes such as the linear example that stretches across the middle of this image.MareKromium
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PSP_010345_2510_RED_abrowse.jpgUnnamed Crater in Vastitas Borealis (Natural Colors; credits: Lunar Explorer Italia)54 visitenessun commentoMareKromium
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