| Piú votate - Mars Reconnaissance Orbiter (MRO) |
Juventae_Chasma-PIA12489.jpgBright Layered Deposits near Juventae Chasma (Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)54 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
(5 voti)
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ESP_016036_1370_RED_abrowse-00.jpgDunes in Noachis Terra (CTX Frame - Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)54 visiteDunes of sand-sized materials have been trapped on the floors of many Martian Craters.
This is one example, from an Unnamed Crater located in Noachis Terra, West of the giant Hellas Impact Basin.
The most extensive Linear Dunefields known in the Solar System are on Saturn's largest moon Titan.
But Titan, as to Mars, has a very different environment and composition and so, at a meter-scale resolution (not available yet, unfortunately) the Titanian Dunes should look (better yet: they certainly ARE) very different from the Martian ones.MareKromium
(5 voti)
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ESP_016087_2595_RED_abrowse.jpgFrost-covered Dunes (Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)54 visiteDunes are often found on Crater Floors. In the Winter time, at high Northern Latitudes, the Terrain is covered by Carbon Dioxide Ice (Dry Ice - CO2 Ice). In the Spring, as this seasonal ice evaporates or sublimates, many unusual features - certainly unique to Mars - become visible.
On the Floor of this Crater, where there are no Dunes, the ice forms an uninterrupted layer. On the Dunes, however, Dark Streaks form as surface material from below the ice is mobilized and deposited on top of the ice. In some cases this mobile material probably slides down the steep face of the Dunes, while in other cases it may be literally blown out in a process of gas release similar to the one that we could obtain by removing a cork from a champagne bottle.
Nota Lunexit: ma i commenti NASA ai frames (non tutti, ma certamente alcuni, tipo questo) li fanno scrivere ai bambini ed alle bambine di Scuole Medie e/o Licei, per caso? Lo avevamo già stigmatizzato in passato ma, a volte, repetita juvant: alcuni commenti non solo sono, in sè, piuttosto naif (diciamo "ingenui", valà...) ed alquanto banali ma - e questa è la cosa più grave - essi contengono degli strafalcioni grammaticali (frequenti) e sintattici (meno di frequente) che fanno rabbrividire noi, poveri "ignoranti Italiani".
Bah...MareKromium
(5 voti)
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PSP_002101_1875_red-00~0.jpgMojave Crater Floor and Central Uplift (CTX Frame - Natural Colors; credits: Lunexit)54 visiteThis full HiRISE image shows that the Crater Floor - South of the Central Uplift - is densely pitted and fractured. These Pits, many of which are partially filled with dark sand, lack raised rims and a circular form.
This suggests that they are not impact craters. In fact, very few definite impact craters are seen on the Floor and Walls of Mojave, implying that it is incredibly young and relatively well preserved for a crater of its size.
HiRISE images covering Mojave Crater and the surrounding Region are yielding new insights into impact processes on Mars. MareKromium
(5 voti)
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PSP_002101_1875_red-01.jpgMojave Crater Floor and Central Uplift (EDM - Natural Colors; credits: Lunexit)54 visiteThis HiRISE sub-image shows a portion of the Central Uplift structure in Mojave Crater.
Central Uplifts are a typical feature of large impact craters on the Earth, the Moon and Mars; craters larger than 6 or 7 Km in diameter on Mars typically form this mountain-like peak in the central portion of the crater interior.
This peak consists of rocks originating from several kilometers beneath the pre-impact surface. Mojave has a very prominent Central Uplift as it has a diameter of approx. 60 Km (about 37 miles).
In this image, Boulders as large as 15 mt (50 feet) across have been eroded from the massive uplifted rock and have rolled downslope.
Fine-grained Debris has also collected in the topographic lows and has been shaped by the wind into Dunes and Ripples. Notably absent from this image are the striking Drainage Channels and Alluvial Fans that are abundant on the Wall-Terraces and Ejecta of Mojave Crater (see PSP_001415_1875).
These features were likely formed by Surface Runoff of liquid water, which may have been released from the Subsurface during the impact event that formed Mojave.
Previously, it had been suggested that a brief, torrential downpour over Mojave Crater delivered the water. However, Mars Orbiter Camera's (MOC) images of Mojave's Central Uplift have previously shown no evidence for Surface Runoff, and the higher resolution of this HiRISE image (2.4 MB) confirms that this part of the Crater appears untouched by liquid water.
So the question remains: by what means was the water, in the form of Runoff, supplied to Mojave? This question, in addition to several others regarding this phenomenon, are currently being investigated by the HiRISE team and their collaborators.MareKromium
(5 voti)
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PSP_001456_2010_RED_abrowse.jpgFlood-carved Canyon in Kasei Valles (Natural Colors; credits: Lunexit)57 visiteThis HiRISE image shows a wonderfully complex surface on the floor of this ancient Flood-carved Canyon.
The floor of this Canyon, now, does not show any kind of landform that scientists expect to see from the occurrence of flood erosion phenomena.
Instead, it appears that the floor of the valley has been covered, after the inundation that first designed it, by another flow made by some very dense material that also contained huge ridged plates.
Some of the plates are more than 1 Km (0,6 miles) across. The ridges appear to have formed when the solid crust on the flow crumpled; the plates are pieces of the crust that were rafted apart.
Actually, very large Lava Flows can produce a surface like this, but also water-ice and frozen mud can create similar features.MareKromium
(5 voti)
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PSP_002066_1425_RED_browse-01~0.jpgGullies and Ice-rich Material (EDM - Natural Colors; credits: Lunexit)54 visiteIn this EDM (approx. 500 mt across) we can notice that the crater floor is covered in boulders, dunes and textured material.
The boulders are likely a “sublimation lag” that provides evidence that material on the crater floor is, or once was, ice-rich. A sublimation lag forms when ice-rich material sublimates leaving the boulders and rocks behind. It is possible that the boulders on this crater floor represent such a process.
The pitted texture around boulders may also be an indicator of ice sublimation.MareKromium
(5 voti)
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PSP_007124_1765_RED_abrowse~0.jpgProposed MSL Landing Site in Miyamoto Crater (MULTISPECTRUM; credits: Lunexit)54 visiteMiyamoto Crater is located in South-Western Meridiani Planum (and South-West of the Mars Exploration Rover Opportunity Landing Site).
This image shows fairly smooth plains and some areas covered by Windstreaks.
The streaks suggest that wind is an active process here, depositing surface material downwind in this distinctive form. This Landing Site is adjacent to the Hematite-bearing plains unit where the Opportunity Rover sits.
The CRISM instrument has detected Phyllosilicates (Clay Minerals) at this Landing Site, which scientists believe to have formed in the presence of water.
The Mars Science Laboratory rover would investigate the mineral diversity here, which includes Phyllosilicates and Sulfate Minerals.
MareKromium
(5 voti)
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ESP_014261_0930_RED_abrowse.jpgSouth Polar Residual Cap Monitoring (Natural Colors; credits: Lunexit)57 visiteThis HiRISE image is of a portion of Mars' South Polar Residual Ice Cap. Like Earth, Mars has concentrations of water ice at both Poles.
Because Mars is so much colder, however, the seasonal ice that gets deposited at high latitudes in the Winter and is removed in the Spring (generally analogous to winter-time snow on Earth) is actually Carbon Dioxide Ice. Around the South Pole there are areas of this CO2 ice that do not disappear every Spring, but rather survive Winter after Winter. This persistent Carbon Dioxide Ice is called "South Polar Residual Cap", and is what we are looking at in this HiRISE image.
Relatively high-standing smooth material is broken up by semi-circular depressions and linear, branching troughs that make a pattern resembling those of your fingerprints. The high-standing areas are thicknesses of several meters of CO2 Ice.
The depressions and troughs are thought to be caused by the removal of Carbon Dioxide Ice by Sublimation (the change of a material from solid directly to gas). HiRISE is observing this CO2 Terrain to try to determine how these patterns develop and how fast the depressions and troughs grow.
While the South Polar Residual Cap as a whole is present every year, there are certainly changes taking place within it. With the high resolution of HiRISE, we intend to measure the amount of expansion of the depressions over multiple Mars years.
Knowing the amount of Carbon Dioxide removed can give us an idea of the atmospheric, weather, and climate conditions over the course of a year.
In addition, looking for where CO2 Ice might be being deposited on top of this terrain may help us understand if there is any net loss or accumulation of the CO2 Ice over time, which would be a good indicator of whether Mars' climate is in the process of changing, or not. (Written by: Patrick Russell)MareKromium
(5 voti)
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ESP_013533_2170_RED_abrowse.jpgUnnamed Crater with Gullies (Natural Colors; credits: Lunexit)54 visitenessun commentoMareKromium
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ESP_014356_2090_RED_abrowse.jpgNorth of Tartarus Fossae (Natural Colors; credits: Lunexit)54 visitenessun commentoMareKromium
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ESP_014291_1120_RED_abrowse.jpgSouthern Dunefield (Natural Colors; credits: Lunexit)54 visitenessun commentoMareKromium
(5 voti)
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