| Piú votate - Mars Reconnaissance Orbiter (MRO) |
Psp_008216_2325_red.jpgPeriglacial Surface Features in the Northern Plains (natural colors; credits: Lunexit)53 visitenessun commentoMareKromium
(6 voti)
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Psp_008222_1640_red.jpgCollpse Pits along Claritas Rupes (Saturated and Enhaced Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)72 visitenessun commentoMareKromium
(6 voti)
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PSP_008681_2550_RED.jpgTransverse Dunes in Vastitas Borealis (natural colors; credits: Lunexit)53 visiteThe Vastitas Borealis Region, or Northern Lowlands, is a large area of low-lying surface that surrounds Mars’ North Pole.
On average, the Region is 4-5 Km lower in elevation than the mean radius of the Planet. How this basin formed is not known, although researchers have postulated that it could have been the result of a very large-scale impact sometime in Mars’ distant past. As of this writing, it is Summer in the Martian Northern Hemisphere, allowing the HiRISE camera to image this Region in full sunlight.
The sinuous landforms are dunes composed of sand that is made of basalt (a volcanic rock) or gypsum (a hydrous sulfate). There is a transition of modified barchanoid (crescent shaped dunes, generally wider than they are long) and transverse chains into star dunes; the winds change a lot in this area. The orientation of the barchanoid and transverse dunes indicate that the winds that formed them blow from the East (right side of image).
In some areas there are a few linear dunes. The light-toned, smaller bedforms are designated Transverse Aeolian Ridges (TARs).
MareKromium
(6 voti)
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Psp_008779_1905_red.jpgThe Head of Athabasca Valles (natural colors; credits: Lunexit)53 visiteThis observation is located at the head of the Athabasca Valles Channel System, which lies just North of Mars’ Equator, in a low-elevation Region known as Elysium Planitia.
Athabasca Valles has an interesting geologic history. It was probably carved by one or more catastrophic floods of water, but more recently, a flood of lava coursed through the channel system. Both the water and the lava erupted from a few discrete points (or “vents”) along the Cerberus Fossae, a 1600-Km(1000-mile) long network of extensional (or “normal”) faults. The two prominent troughs that cut across the Southern end of this HiRISE image are part of the Cerberus Fossae. They are distinct fault segments that overlap at their tips, as one tapers in and the other pinches out.
They were not always as wide as they are today. Erosional processes have widened the troughs over time. Major eruptions occurred along both of the fault segments seen in this image, though they occurred to either side of the imaged area itself. Lava that erupted from the western vent covers the northern half of the image. The lava has raised, lobate margins and is slightly darker in tone than the older cratered plains it embays. The lava also has a banded appearance of subtly contrasting lighter and darker tones, that correspond to variations in surface roughness.
The bands are concentric to a vent located immediately west of the imaged area. Unfortunately, vents along the Cerberus Fossae are not well preserved.MareKromium
(6 voti)
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PSP_008927_2010_RED-00.jpgPossible MSL Landing Site in Nili Fossae Trough (natural colors; credits: Lunexit)53 visiteNili Fossae Trough is a linear trough about 25 Km wide, formed in response to the creation of the Isidis Basin.
Nili Fossae has diverse deposits, some containing Phyllosilicates (Clay Deposits which typically form in the presence of water), and others with the minerals Olivine and Pyroxene.
This image is part of a series covering the 25 km Landing Ellipse; they are used to determine the safest possible Landing Site for the Mars Science Laboratory Rover. In this frame, relatively smooth rock exposures is visible, as well as sand ripples and some small knobs. There are few large rocks in the area, while the surface seems to be mostly flat, fractured rock.
This landscape is located in the South-Eastern part of the Landing Ellipse.MareKromium
(6 voti)
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PIA10139-FansField~0.jpgFans Field (MULTISPECTRUM; credits: Lunexit)53 visiteAt the very beginning of Spring in the Southern Hemisphere on Mars the ground is covered with a seasonal layer of CO2 ice.
In this image there are 2 lanes of undisturbed ice bordered by 2 lanes peppered with Fans of dark dust.
When we zoom in to the image, we see that the Fans are seen to be pointed in the same direction, dust carried along by the prevailing wind. The Fans seem to emanate from spider-like features.
Image Data: the image is centered at -86,4° Latitude and 99,1° East Long.
The range to the target site was 276,1 Km (about 172,6 miles). At this distance the image scale is 55,2 cm/pixel (with 2x2 binning) so objects ~166 cm across are resolved.
The image was taken at 16:27 MLT (middle afternoon), with the Sun just 2° above the Local Horizon. MareKromium
(6 voti)
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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
(6 voti)
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PSP_007612_2045_RED_abrowse~0.jpgProposed MSL Landing Site in Mawrth Vallis (MULTISPECTRUM; credits: Lunexit)60 visitenessun commentoMareKromium
(6 voti)
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PSP_008792_1410_RED_abrowse.jpgLight-Toned Layers in Crater Wall (MULTISPECTRUM; credits: Lunexit)53 visiteThis approximately 8 Kilometer-diameter Impact Crater is interesting because of the light-toned band visible in the upper slopes of the Inner Crater Wall.
Because the light-toned materials are confined to a distinct elevation within the Crater, it is possible that it represents a well-defined Layer exposed in the Crater Walls.MareKromium
(6 voti)
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PSP_008778_1685_RED_abrowse.jpgMistery Mounds (MULTISPECTRUM; credits: Lunexit)53 visiteThis image was targeted because a previous MGS-MOC image (R1100035) showed an distinctive field of Mounds on the floor of an ancient, large, filled-in Unnamed Crater.
The origin of the Mounds was unclear, so we hoped that a HiRISE image with higher resolution and color would solve the mystery. The HiRISE image shows much more detail on the Mounds and other rough textures, indicating that this is an eroded bedrock surface, perhaps exposed by removal of an overlying layer of fine-grained materials by the wind.
But how did the rocks form, and why did they erode onto Mounds? It could have been lava or impact ejecta or fluvial sediments, perhaps altered and indurated by groundwater.
The Mounds could be due to how it was deposited — like hummocky Impact Ejecta — or how it was indurated. In other words, we haven't solved the mystery!...
Yet we may get new clues from future images of similar terrains in places where the origin is more interpretable, or from other datasets such as the mineral content determined by CRISM.MareKromium
(6 voti)
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PSP_008323_1735_RED_abrowse-00.jpgTARs and Unusual "Star Ripples" (MULTISPECTRUM; credits: Lunexit)61 visiteThis blocky terrain is southwest of Schiaparelli Crater and is surrounded by a field of Transverse Aeolian Ridges (TARs) and unusual "Star Ripples" (dunes).
TARs are linear ripples with crest-ridge morphologies that can vary in shape; these morphologies include forked, sinuous, barchanoid, networked or feathered characteristics. The ridges also appear to transition into star dunes.
Star Dunes are complex features and are not yet fully understood on Earth. They form by multidirectional wind regimes with a dominant Primary Wind. Chains of Star Dunes often appear to have a massive linear appearance, or can be modified linear or Barchan Dunes with the formation of secondary slipfaces (on the steeper slope). On Earth, there are incipient Star Dunes, such as in the Dumont Dune field in the Mojave Desert, that display similar characteristics. The Dumont embryonic Star Dunes may result from dunes merging as they overrun one another, or are modified preexisting dunes, which could also be the case in this image.
Martian weather models predict that the dominate wind comes from a South-Westerly direction. This direction aligns nicely with the Transverse Ripples and the main arms of the Star Ripples.
This suggests that the Star Ripples were also affected by a different wind pattern or "Secondary Winds" or "Secondary Airflow". (Secondary Airflow is the airflow and sediment transport around the slopes of the dune).
Formation of incipient Star Dunes depends on the nature (strength, direction, and duration) of the Primary Wind and the volume of the sand to create the dune. Secondary airflow maintains the dune arms. The last factor is the deposition or removal of the sand by grainfall or grainflow avalanching. Grainfall and grainflow transports material from the main crestline slipface and along-slope or down-slope which maintains the secondary arm crest.MareKromium
(6 voti)
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PSP_006268_1995_RED_abrowse.jpgThe alleged "Bridges" of Chrise Planitia (MULTISPECTRUM; credits: Lunexit)73 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.
MareKromium
(6 voti)
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