Volcanoes-Maat_Mons-PIA00487.jpgVolcanic Domes on the Flank of Maat Mons - East Ovda Region (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)53 visiteThis Magellan image is centered at about 3,2° North Latitude and 194,9° East Longitude, in the Eastern Ovda Region of Venus.
The image, which is approx. 90 Km (about 56 miles) in width and approx. 80 Km (such as about 50 miles) in length, shows some small Volcanic Domes on the Flank of the volcano Maat Mons. The bright flows to the East are most likely rough Lava Flows while the darker flows to the West are probably smoother flows. The dark flows do show some roughness, however, as can be seen by the structure in the flows to the South/West.
These dark flows also have some debris that has been deposited on top of them. The debris may be fine material from the surrounding Plains on top of the flow by wind or it may be ash from the volcano.
Small Volcanic Domes are very common features on the Surface of Venus, indicating that there has been (and maybe there still is) much volcanic activity going on almost everywhere.
Assuming that the central Volcanic Cone is symmetrical in shape and knowing the length of the cone's side and the incidence angle, radar foreshortening yields a height and slope of 688 meters and 8,2°, respectively, for the Cone.
These values are similar to heights and slopes of some Volcanic Cones on the Earth. MareKromium
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Craters-Stephania_Crater-PIA00475.jpgStephania Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)53 visiteCrater Stephania is located at 51,3° Norh Latitude and 333,3° East Longitude in Northern Sedna Planitia.
With a diameter of about 11 Km (6,8 miles), Stephania is one of the smaller Craters on Venus.
Because many small meteoroids disintegrate during their passage through the dense Venusian atmosphere, there is an absence of craters smaller than 3 Km (approx. 1,9 miles) in diameter, and even craters smaller than 25 Km (15,5 miles) are relatively scarce.
The apron of ejected material suggests that the impacting body made contact with the Surface from an oblique angle. Upon closer observation it is possible to delineate secondary craters, impact scars from blocks ejected from the primary crater.
A feature associated with this and many other Venusian Craters is a radar-dark halo.
Since dark radar return signifies a smooth surface, it has been hypothesized that an intense shock wave removed or pulverized previously rough surface material or that a blanket of fine material was deposited during or after the impact.MareKromium
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Volcanoes-Sacajawea_Patera-PIA00485.jpgSacajawea Patera (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)53 visiteThis Magellan image reveals Sacajawea Patera, a large, elongate caldera located in Western Ishtar Terra on the smooth plateau of Lakshmi Planum.
The image is centered at 64,5° North Latitude and 337° East Longitude. It is approximately 420 Km (about 252 miles) wide at the base.
Sacajawea is a depression approximately 1-2 Km (0,6-1,2 miles) deep and abo 120 by 215 Km (approx. 74 by 133 miles) in diameter; it is elongate in a S/W-N/E direction.
The depression is bounded by a zone of circumferential curvilinear structures interpreted to be Graben and Fault Scarps. These structures are spaced 0,5-4 Km (0,3-2,5 miles) apart, are 0,6-4 Km (0,4-2,5 miles) in width and up to 100 Km (approx. 62 miles) in length.
Extending up to approximately 140 Km (about 87 miles) in length from the South/East of the Patera, is a system of linear structures thought to represent a flanking rift zone along which the lateral injection and eruption of magma may have occurred.
A shield edifice of approx. 12 Km (about 7 miles) in diameter with a prominent Central Pit, lies along the trend of one of these features.
The Impact crater Zlata, approx. 6 Km (a little less than 4 miles) in diameter is located within the zone of Graben to the N/W of the Patera.
Few flow features are observed in association with Sacajawea, possibly due to age and state of degradation of the flows.
Mottled bright deposits of about 4 to 20 Km (such as 2,5 up to approx. 12 miles) in width are located near the periphery and in the center of the Patera Floor, within local topographic lows. Diffuse patches of dark material approx. 40 Km (such as about 25 miles) in width are observed S/W of the Patera, superposed on portions of the surrounding Graben.
The formation of Sacajawea is thought to be related to the drainage and collapse of a large Magma Chamber. Gravitational relaxation may have caused the resultant Caldera to sag, producing the numerous Faults and Graben that circumscribe the Patera.
Regions of complex, highly deformed tessera-like terrain are located North and East of the Patera and are seen in the upper portion of the image.MareKromium
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Craters-Isabella_Crater-PIA00480.jpgIsabella Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)53 visiteCrater Isabella, with a diameter of approx. 175 Km (such as about 108 miles), seen in this MRI (Magellan Radar Image), is the second largest Impact Crater on Venus.
The feature is named in honor of the 15th Century Queen of Spain, Isabella of Castile. Located at 30° South Latitude and 204° East Longitude, the Crater has two extensive flow-like structures extending to the South and to the S/E.
The end of the Southern Flow partially surrounds a pre-existing 40 Km (approx. 25 mile) circular Volcanic Shield.
The South-Eastern Flow shows a complex pattern of Channels and Flow Lobes, and is overlain at its South-Eastern tip by deposits from a later approx. 20 Km (about 12 mile) diameter Impact Crater, Cohn (for Carola Cohn, Australian artist, 1892-1964).
The extensive Flows, unique to Venusian Impact Craters, are a continuing subject of study for a number of Planetary Scientists. It is thought that the Flows may consist of "Impact Melt", suc as rock melted by the intense heat released in the impact explosion. An alternate hypothesis invokes "Debris Flows", which may consist of clouds of hot gases and both melted and solid rock fragments that race across the landscape during the impact event.
That type of Emplacement Process is similar to that which occurs in violent eruptions on Earth, such as the 1991 Mount Pinatubo eruption in the Philippines.MareKromium
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Volcanic_Features-Lava_Flows-PIA00471.jpgLava Flows (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)53 visiteThis is a full resolution mosaic centered at 25° North Latitude and 351° East Longitude.
The Region is approximately 160 Km (100 miles) across. It shows a series of complex Lava Flows which emerge from the Northern Flank of Sif Mons, a large Southern Venusian Volcano.
Several of the Flows occupy narrow troughs formed by long fractures. A sequence of events that can be inferred from this image is the formation of the dark background Plains by eruptions of extremely fluid volcanic material, and the formation of the small Shield Volcanoes on the Plains' Surface that can be seen in the upper left part of the image.
Next, the Region was domed upward probably by heat from the interior of Venus that ultimately caused magmas to break out from the Surface near the Summit Regions forming the Sif volcanic structure and its associated flank eruptions which can be seen in this image.MareKromium
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Volcanoes-Idunn_Mons-PIA13001-2.jpgIdunn Mons (Perspective View and False Colors; credits: NASA/JPL-Caltech/ESA)53 visiteCaption NASA:"This figure shows the Volcanic Peak Idunn Mons (at about 46° South Lat. and 214,5° East Long.) in the Imdr Regio area of Venus. The topographic backbone derives from data obtained by NASA's Magellan spacecraft, with a vertical exaggeration of 30 times.
Radar data (in brown) from Magellan has been draped on top of the topographic data. Bright areas are rough or have steep slopes. Dark areas are smooth.
The warmest area of Idunn is centered on the Summit, which stands about 2,5 Km (approx. 1,6 miles) above the Datum, and the bright Lava Flows that originate there. Idunn Mons has a diameter of about 200 Km (approx. 120 miles).
The spectrometer data was collected from May 2006 to the end of 2007. A movie featuring 360-degree views of the volcano is based on the same data and can be viewed at JPL's Multimedia".MareKromium
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