| Piú votate - Mars Reconnaissance Orbiter (MRO) |
ESP_011886_1130_RED_abrowse.jpgDark Southern Dunefield (Natural Colors; credits: Lunar Explorer Italia)58 visitenessun commentoMareKromium
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ESP_011913_1720_RED_abrowse.jpgLight-Toned Layering along Plains South of Ius Chasma (Natural Colors; credits: Lunar Explorer Italia)57 visitenessun commentoMareKromium
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ESP_011898_2175_RED_abrowse.jpgUnnamed Crater with Gullies in Acidalia Planitia (Natural Colors; credits: Lunar Explorer Italia)76 visitenessun commentoMareKromium
(3 voti)
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ESP_011732_1595_RED_abrowse-00.jpgLarge Cluster of Small Craters near Maadim Vallis (ctx frame - Natural Colors; credits: Lunar Explorer Italia)58 visitenessun commentoMareKromium
(3 voti)
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ESP_012226_1815_RED_abrowse.jpgDark Sands Deposits or Surfacing Hydrocarbons? (Natural Colors; credits: Lunar Explorer Italia)72 visitenessun commentoMareKromium
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ESP_012265_0950_RED_abrowse.jpgGiza Region (Natural Colors; credits: Lunar Explorer Italia)59 visitenessun commentoMareKromium
(3 voti)
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PSP_010100_2165_RED_abrowse.jpgEjecta Blanket (Natural Colors; credits: Lunar Explorer Italia)58 visiteThis image of a crater in the Utopian Region can be described as what happens when heat produced from an impact comes into contact with Mars’ icy Surface.
Since the Surface Temperature of Mars is well below the freezing point of water, Mars’ soil is a mixture of soil and permafrost. When this impact occurred, a great deal of energy in the form of heat was released onto the Surface, creating a melted feature in the bright icy soil. This melting and then refreezing of the ice (as the impact cooled) caused what is known as a "Periglacial Formation". This is depicted towards the middle of the image where the Ejecta Blanket lays.
This is likely a geologically newer surface since the only impacts disrupting the image are a few small craters that are mostly towards the bottom left-hand side of the full image.
The fact the Ejecta Blanket is still intact and not fully collapsed supports the idea that is it a newer surface feature as it has not been affected by erosional processes.MareKromium
(3 voti)
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ESP_011630_0930_RED_abrowse.jpgFans and Polygons (Natural Colors; credits: Lunar Explorer Italia)60 visitenessun commentoMareKromium
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ESP_011677_1655_RED_abrowse.jpgPit Crater Chain (Natural Colors; credits: Lunar Explorer Italia)59 visiteThis image shows a series of Collapse Craters called Pit Chain; of course, the Chain itself is NOT formed by Impact Craters.
There are a few potential ways that these are formed. The Pit Craters are believed to form by the collapse of Lava Tubes or Magma Chambers. They could also form when the crust of Mars gets pulled apart by extensional forces from a growing volcano Magma Chamber. This leaves structurally weak areas that have a greater chance of collapsing when the area (Lava Tubes or Magma Chamber) no longer contains molten lava or is drained from the chamber.
There is evidence that Mars is not the only Planet that has features like these. Earth also has similar Pit Chains that have formed in Iceland. This Chain was formed on a known fault line and the Pits formed when the Region experienced an earthquake.
This process may be similar to the way the Martian Pit Chains were formed. If "Marsquakes" are the cause of the formation of Pit Chains, this will support the idea that there is still geologic (tectonic) activity occurring on Mars.
The Pit Chains that have been found on Earth are considerably smaller than similar features that are found on Mars. Earth’s are smaller due to higher gravity and weathering makes them smaller and at some point completely erasing them from sight. But Mars has no system to create erosion; therefore the Chains on Mars are better preserved.MareKromium
(3 voti)
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PSP_003608_1510_RED_abrowse-00.jpgThe VERY Deep Zumba Crater (Natural Colors; credits: Lunar Explorer Italia)58 visiteThis image taken at a high Sun Angle (a.k.a. "Phase Angle") shows the relatively unshadowed pristine and youthful rayed crater Zumba.
The crater’s rim-to-rim diameter is approx. 3 Km (about 1,85 miles) with a depth of about 620 mt (approx. 0,4 miles), and its rim rises about 200 mt (656 feet) above the surrounding lava-filled plains of Daedalia Planum, just South-West of the great Tharsis Volcanoes. Zumba is approximately 25% deeper than the average Martian Crater of this size – just one of several attributes that suggests it is a very fresh crater.
One estimate of Zumba’s age, generally accomplished by counting smaller superimposed craters on Zumba itself, suggests it may be 5 MY old. Even if such an estimate is off by 2-4 times, this is still a young geologic feature by Mars standards. Because Zumba is so young and so fresh, it is a perfect example of a simple crater. On Mars, a simple crater is generally less than 6-9 Km (about 3,7-5,6 miles) in diameter with a “simple” conical-bowl shape, minimal wall collapse and lacking a well-developed central feature (exx.: a peak, large pit, or ring).
By impacting into such hard durable rocks, the impact that created Zumba scattered greater than 10 million ejecta blocks at high speeds resulting in far-reaching ray segments and an impressive field of secondary impact craters. This pattern is hard to see in visible-light images, but “lights-up” spectacularly in nighttime thermal InfraRed images taken by THEMIS onboard the Mars Odyssey 2001 Orbiter. Scientists believe that some of these high-speed rocks may have even been expelled from Mars and even traveled to Earth.
Zumba is of considerable interest to scientists, whether it’s a source of Martian meteorites or not, as it possesses interesting features that are typically buried or eroded away in other older Martian Craters, and even within the freshest terrestrial craters (including Meteor crater in Arizona). These preserved and newly recognized features observed at the scale of HiRISE may reveal aspects of the impact process unknown to scientists from previous studies of craters on the terrestrial planets.
What is particularly intriguing is the presence of a pitted deposit giving Zumba the appearance that it has a relatively flat floor despite the pits. These crater-fill deposits are typically composed of lightly to highly damaged rock fragments and impact melts formed from the high temperatures achieved from the energy released by the impact event (on the order several to tens of megatons). The pits in the crater-fill deposits have not been recognized within lunar or terrestrial craters and appear to be unique to crater-fill deposits in only the freshest and best-preserved Martian Craters.
These pits may represent the result of the interactions of the very hot crater-fill deposits with water and water-ice that may have been present in the subsurface prior to impact. It is not well understood whether these pits form explosively (similar to terrestrial volcanic pits/craters formed from the interaction of hot lava with wet sediments/deposits), or by collapse from the drainage of impact melts or volatiles. The presence of pitted deposits in only the freshest and well-preserved craters suggests that they are likely related to the impact process.MareKromium
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PSP_010505_2725_RED_abrowse.jpgNorth Polar Residual Cap (Natural Colors; credits: Lunar Explorer Italia)59 visitenessun commentoMareKromium
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PSP_010462_2505_RED_abrowse.jpgOlivine-rich Terrain in Vastitas Borealis (Natural Colors; credits: Lunar Explorer Italia)79 visitenessun commentoMareKromium
(3 voti)
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