Mars Reconnaissance Orbiter (MRO)
|
|
|
Psp_001700_2505_red-01.jpgThe "Frozen Lake" of Vastitas Borealis...is not a Lake, according to NASA (EDM - Enhanced Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)53 visiteThis EDM shows the Dunes and Frost boundary up-close. The Frost is largely absent over the Dunes and is more stable over the ground that does not have dune-shaped landforms.
|
|
Psp_001697_1390_red.jpgUnnamed (and yet beautiful) Crater with Gullies in Terra Sirenum52 visiteThis image shows part of an unnamed crater, itself located inside the much larger Newton Crater, in Terra Sirenum. This unnamed crater is approx. 7 Km in diameter (over 4 miles) and some 700 mt (about 760 yards) deep.
Numerous gully systems are visible on the East- and South-facing walls of the crater; their characteristics are astonishingly diverse, though.
These troughs are extremely rectilinear, lack tributaries and do not seem to have terminal fan deposits: they terminate rather abruptly, some of them in a spatula-like shape. Their characteristics contrast sharply with those of gully systems elsewhere in this same crater, which are sinuous, have numerous tributaries and show distinct fan deposits.
HiRISE is unveiling the large diversity exhibited by Martian Gully Systems, thanks to its HR, stereo and color capabilities. These diverse types of gullies observed may have been produced by different mechanisms. Current leading hypotheses explaining the origin of gullies include erosion from seepage or eruption of water from a subsurface aquifer, melting of ground ice, or surface snow; and dry landslides. MareKromium
|
|
Psp_001503_2180_red-02.jpgTricks of the Light, Tricks of the Surface... (extra-detail mgnf - 3)52 visitenessun commento
|
|
Psp_001503_2180_red-01.jpgTricks of the Light, Tricks of the Surface... (extra-detail mgnf - 2)57 visitenessun commento
|
|
Psp_001503_2180_red-00.jpgTricks of the Light, Tricks of the Surface... (context image - 1)53 visitenessun commento
|
|
PSP_002136_1920_cut_b.jpgPhotoartifacts?55 visiteThe image shows two portions of the Isidis Planitia image (PSP_002136_1920) with bright noise at top, and 6 examples of bright noise seen in the cruise images; all are from the original, unprocessed images.MareKromium
|
|
Psp_002419_1675_red-02.jpgFrozen Waterfalls or just Layers and Dark Debris in Melas Chasma?52 visiteThis HiRISE sub-image shows layering in a light-toned deposit in Melas Chasma.
The layers are sedimentary in origin, but there are many processes that could have deposited them, such as volcanic airfall from explosive eruptions, dust-size particles settling out of the atmosphere due to cyclic changes and deposition in standing bodies of water.
By looking at the slopes in the layers and how the layers intersect each other, scientists can rule out various origins. A darker material can be seen covering much of the layered deposit. Some of this dark material is loose and can be seen accumulating as debris aprons at the base of steep slopes. Other dark material appears indurated and has been eroded by the wind to form etched edges with topographic expressions.
The lack of impact craters on the layered deposit indicates that it is a relatively young deposit, or the craters have been removed by the wind, or the deposit was quickly buried and is now being exhumed.MareKromium
|
|
Psp_001481_2410_red-00.jpgEolian and Periglacial Activities in Vastitas Borealis (DD Tracks and Polygons)54 visiteThis image shows a region of approximately 7 x 7 km (4.4-by-4.4 miles) located in Vastitas Borealis, part of the Northern Plains.
The surface imaged is relatively young, as indicated by the lack of recent impact craters.
Eolian and Periglacial activity seem to be the dominant geological processes at work, as shown by numerous crisscrossing DD Tracks and ubiquitous polygonal features, respectively.
Dust Devils form when the sun warms up the air near a flat, dry surface. Warm air then rises quickly through the cooler air above and starts spinning, causing a forward motion. The spinning, forward-moving cell may pick up dust and sand as it advances, thus leaving behind a "clean" track. We infer from this image that a thin veneer of light-colored particles of dust and/or fine-grained sand cover relatively darker materials, apparent in the dust devil tracks.
The tracks pictured in this image are in many cases more than 30 mt (27 yards) wide and over 4 Km (2,5 miles) long, surpassing the dimensions of average terrestrial DD tracks.MareKromium
|
|
Psp_002538_1720_red.jpgJust like Thaumasia: more "bright" dunes in Ius Chasma53 visiteIus Chasma is one of several canyons that make up Valles Marineris, the largest canyon system in the Solar System.
The canyons likely formed by extension in association with the development of the Tharsis plateau and volcanoes to the West. Wind and possibly water have modified the canyons after they formed.
This HiRISE image shows the floor of Ius Chasma. The floor is bounded to the North and South by higher standing wallrock, with a few exposures of wallrock seen in the North (Sx) of the picture. Much of the floor is covered by ripples that are oriented approximately North-South, indicating an East to West wind flow, parallel to the orientation of Ius Chasma.
Layered deposits and bright patches of material are also seen along portions of the Ius Chasma floor. The layered deposits appear distinct in morphology from the nearby wallrock. These layered deposits could be lava flows, sediments deposited in a former lake, or fines that settled out from the atmosphere over time, such as dust or volcanic ashes.
The bright outcrops visible further south in the image have been seen elsewhere in Valles Marineris as well as other locations on Mars and tend to have mineral signatures consistent with sulfates. Data from the CRISM instrument (also on Mars Reconnaissance Orbiter) of the composition of these bright patches in Ius Chasma could shed insight into their origin. MareKromium
|
|
Psp_001481_2410_red-01.jpgEolian and Periglacial Activities in Vastitas Borealis (polygons)52 visiteThe polygons shown in this image's subset, which covers approximately 400 x 250 mt (350 x 225 yards), are in the order of 10 mt (0.9 yards) across; in some cases they are delimited by aligned rocks. Similar features in both shape and scale are found in Terrestrial Periglacial Regions such as Antarctica, where ice is present at or near the surface.
Antarctica's polygons and rock alignments are produced by repeated expansion and contraction of the soil-ice mixture due to seasonal temperature oscillations; dry soil falling into the cracks form sand wedges and amplify this effect. This results in polygonal networks of stress fractures and in the resurfacing and sorting of rocks along these fractures.
|
|
Psp_001691_1320_red.jpgGullied Trough in Noachis Terra(False Colors)52 visitePSP_001691_1320 shows gullies in a semi-circular trough in Noachis Terra. The gullies are observed to face all directions.
It is interesting to note that the gully morphology seen here depends on the orientation of the gullies. The morphology differences are most pronounced on the sunlit slope, with the gullies facing South (Dx) being more deeply incised than those facing the West. It is unknown what caused the different gully morphologies, but there are several possibilities.
Gullies are proposed to form at locations determined by the availability of a forming liquid (thought to be water) and/or the amount of insolation the slope receives, among other factors. It is possible that the deeper gullies experienced more erosional events or that their erosional events were more effective for undetermined reasons. It is also possible that the gullies formed at different times such that they did not have the same amount of water either for an individual flow or total available to them.
Also, the underlying topography could make the gullies appear relatively more incised without this actually being the case.
|
|
Psp_001691_1320_red~0.jpgGullied Trough in Noachis Terra (extra-detail mgnf - false colors)53 visiteThe majority of the gullies on both sides of the trough appear to originate at a boulder-rich layer seen in this subimage.
The layer appears dark on the sunlit slope because the boulders sticking out from the slopes cast shadows. If these gullies formed by water from the subsurface, then it is possible that this layer is a permeable layer that conducted water to the surface.
The layer is deteriorating and traveling down slope in the form of boulders.
These boulders can clearly be seen in the alcoves of the gullies on both sides of the trough.
Note that the alternating stripes on the lower right (Dx) side of the image are an artifact from camera noise. They are not real features.
|
|
| 2237 immagini su 187 pagina(e) |
 |
|
|
|
|
10 | |
|
|
|
|
