Mars Reconnaissance Orbiter (MRO)
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ESP_012997_1445_RED_abrowse.jpg"8"! (Natural Colors; credits: Lunar Explorer Italia)62 visiteThis image shows two craters in the Southern Hemisphere just South of Sirenum Fossae.
The Northern Crater (the one that is an upper position) is smaller, appears more degraded, and is partially filled with sediments that form a hummocky surface. Dunes have formed subsequently on this Surface. Some incipient gully-like features have formed midway along the Southern Crater Wall and expose Layers that are more resistant to erosion.
The larger crater to the South is eroded by Gullies on its Northern Slope while the Southern Slope Region lacks them. Most Gullies in this scene appear to emanate from more resistant Layers, although the larger Gullies have eroded back almost to the Crater Rim.
The nature of the Layers and their connection to the water that formed the Gullies is unknown.
Gullies typically form when flowing water erodes sediments and soft rocks in a channelized flow. Because Mars is very cold and dry, it is unknown where the water came from to form the Gullies.MareKromium
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ESP_013049_0950_RED_abrowse.jpgSouth Polar Spiders (Natural Colors; credits: Lunar Explorer Italia)52 visiteThis image is part of an ongoing seasonal monitoring effort in this location in the Southern Polar Region of Mars.
Mars South Polar Region changes significantly during the Martian Year. During the Southern Hemispheres Winter, the Polar Cap increases dramatically as the lowered temperatures make a large portion of the Atmosphere freeze out into ice.
As Spring approaches and the Polar Region begins to warm once again, the Cap recedes revealing terrains like those visible in this image. The polygonal features in this image are termed Spiders and their origin is still unknown (although there are several hypotheses).
One possible hypothesis for the black fan-shaped features is that they may be formed by a geyser-like process. As the Sun heats the ground layer below the Carbon Dioxide ice, the ice on the bottom begins to sublimate, or turn directly from a solid to a gas.
This gas then builds up in pressure as more of it sublimates, until a critical pressure is achieved and it erupts through the ice layer much as a geyser would, spewing the debris that is thought to make up the dark fan shaped features.MareKromium
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ESP_013066_1070_RED_abrowse.jpgFault in the South Polar Layered Deposits (Natural Colors; credits: Lunar Explorer Italia)57 visitenessun commentoMareKromium
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ESP_013071_1365_RED_abrowse.jpgCentral Peak Gullies (Natural Colors; credits: Lunar Explorer Italia)55 visitenessun commentoMareKromium
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ESP_013089_2040_RED_abrowse.jpgTooting Crater (Natural Colors; credits: Lunar Explorer Italia)52 visiteThis image is of the Ejecta Blanket of the Tooting Crater in the Northern Hemisphere of Mars.
Tooting is a "rampart" crater that is roughly 29 Km (about 18 miles) in diameter and appears to be one of the youngest craters of this size.
A "rampart crater" is one where the material ejected from the crater during impact forms lobes that end with a low ridge, or rampart. One indication of Tooting Crater's youth is its ratio of depth to width.
As a crater ages, the walls of the crater will tend to erode and debris will accumulate in the crater's floor making its apparent depth less, while also making its width larger.
One of the major features of Tooting Crater are its multiple ejecta layers that build a sequence of ramparts. The shapes of these ramparts suggest that the ejected material acted as a fluid (like mud) as it moved across the surface.
Most researchers think that such fluid ejecta indicates that there was ice in the ground when the crater formed.MareKromium
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ESP_013144_2075_RED_abrowse.jpgCollapse Features on the Flank of Elysium Mons (Natural Colors; credits: Lunar Explorer Italia)52 visiteThis image is of the Flanks of the "Shield Volcano" Elysium Mons. The volcano is considered to be the youngest within the Elysium Mons Province, which also contains the volcanoes Hecates Tholus and Albor Tholus.
Of course, "young" is a relative term. The last eruption of Elysium Mons could well have been a billion years or more ago.
This image shows a series of flat bottomed valleys along the flanks of Elysium Mons. There is considerable debate on exactly how these valleys form. In Hawaii, the classic example of Shield Volcanoes on Earth, similar valleys are carved by prodigious rainfall. While some rain may have fallen in the earliest epochs of Mars' Geologic History, the lack of small drainage networks shows that these Martian Channels were not carved by rain. However, Mudflows and Lava Flows could potentially erode the sides of the Volcano.
An important hint for the origin of the Valleys comes from the Chain of Pits visible in the Northern part of the image. These Pits form as the ground is pulled apart by Marsquakes. Thus it seems that many of these Valleys are first formed by movement along Faults. Then Mud and/or Lava Flows widen the sides of the Valley and give it a flat floor.MareKromium
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ESP_013329_1070_RED_abrowse.jpgSouth Polar Layered Deposits (Natural Colors; credits: Lunar Explorer Italia)52 visiteThe Ice Caps on Mars are surrounded by a thick stack of Layered Deposits. HiRISE and other instruments have shown that these layers are composed of dusty ice. Now imagine this stack of layers as a cake with alternating layers.
What happens if someone comes and takes a big scoop out of the middle of the cake? Well, while our first reaction might be to get mad at them for ruining the cake, take a moment to think what the pattern would look like: it would have rings going round and round the hole. This is what we are seeing in this image of Mars.
The same pattern that you can see HERE!
Therefore, what you see in this frame is just the consequence of some erosional process which has scooped a big hole into the Layered Deposits.MareKromium
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ESP_013348_1185_RED_abrowse-00.jpgDunefield in Noachis Terra (ctx frame - Natural Colors; credits: Lunar Explorer Italia)53 visiteThis Dunefield is on the floor of a small crater in Noachis Terra, a Region located in the Southern Hemisphere of Mars.
The slip faces of the Dunes have multiple directions, indicating that there were several wind directions and changes in wind strength when the Dunes formed. The dominant Dune type are Transverse Dunes (oriented perpendicular to the prevailing wind direction), with modified Barchans (crescent-shaped dunes) in the Northern Region of the Field and incipient Linear Dunes in the Southern Region.
The bright material scattered throughout the Dune Troughs are outcrops of underlying bedrock.
The left side (Sx) of the image clearly displays a mass of Dark Dust Devil Tracks.
Dust Devils are wind funnels that suck up dust as they travel over the surface exposing the dark sandy substrate.MareKromium
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ESP_013348_1185_RED_abrowse-01.jpgDunefield in Noachis Terra (EDM - Natural Colors; credits: Lunar Explorer Italia)89 visitenessun commentoMareKromium
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ESP_013368_1885_RED_abrowse.jpgSmall and (relatively) fresh Impact Crater in Cerberus Palus (Natural Colors; credits: Lunexit)52 visiteThis observation shows a Lava Plain near the Martian Equator. The Lava is superposed by a small, fresh Impact Crater that is itself surrounded by boulders that were ejected from the Surface when the impact occurred.
There are dunes on the Crater Floor, indicating that the Crater has been present long enough on the Plain so that the wind has blown fine material into it and then formed small dunes.MareKromium
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ESP_013499_1650-0.jpgHusband Hill - Gusev Crater (CTX Frame- Natural Colors; credits: Lunexit)52 visitenessun commentoMareKromium
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ESP_013499_1650-1.jpgSpirit near Home Plate (EDM n.1 - Natural - but enhanced - Colors; credits: Lunexit)71 visitenessun commentoMareKromium
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