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Channels-Unnamed_Outflow_Channel-PIA00483.jpgOutflow Channel in South Nawka Vallis (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)54 visiteThis SAR image from the Southern portion of Navka (24,4-25,3° South Latitude and 338,5-340,5° East Longitude) is a mosaic of twelve Magellan orbits that covers approx. 180 Km (about 108 miles) in width and approx. 78 Km (about 47 miles) in length.
In the center of this image are two bright Deposits running North to South.
These Deposits outline an Outflow Channel that flowed from an about 60-Km diameter Crater that is to the South of the Channel itself. Inside the Outflow Channel and outlined by some so-called 'Bathtub Ring' Deposits are small Cones, most likely of volcanic origin.
At the end of the Outflow Channel, where one would expect the smallest particles to be deposited, are specular features which may represent Sand Dunes.
Seasat and space shuttle radar images of sand dunes on Earth also show specular reflections from smooth dune faces that are near-normal to the radar beam.
Other evidence for aeolian activity are the dark and bright Windstreaks running East to West and that formed behind the Cones. Notice how the wind changes direction from a South/East-North/West flow at the right of the image to an East-West flow at the eastern edge of the Outflow Channel.MareKromium
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Craters-Adivar_Crater-0.jpgMagellan Probe: radio image of Adivar Crater134 visiteLa missione che ha ci dato, sino ad ora, i maggiori (e migliori) risultati in termini di mappatura della superficie del Pianeta - operando con l'ausilio di uno speciale strumento radar (il SAR e cioè il Synthetic Aperture Radar) - è stata la Missione Magellano.
Il lancio della Navicella avvenne il 4 Maggio 1989 e l'arrivo su Venere, con inserimento della stessa in un'orbita ellittica definita "presso/circa-polare" (near-polar elliptical orbit), occorse il 10 Agosto 1990.
La mappatura radar di Venere fu, come testimoniano ampiamente le immagini che Vi proponiamo, un grande successo.
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Craters-Adivar_Crater-1.jpgAdivar Crater (Natural Colors; credits: Lunar Explorer Italia)81 visitenessun commentoMareKromium
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Craters-Balch_Crater-0.jpgMagellan Probe: radio image of Balch Crater117 visiteI risultati di tutte queste analisi e studi ci dicono che Venere NON mostra segni di attività tettonica (che sia almeno in parte assimilabile a quella esistente sulla Terra) in corso.
Oltre l'85% della superficie del Pianeta è ricoperta da uno strato di lava (o, comunque, da prodotti derivanti da eventi vulcanici) mentre il 15% residuo è costituito da cinture montuose altamente irregolari ("highly deformed mountain belts", si legge nel rapporto finale).
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Craters-Balch_Crater-1.jpgBalch Crater (Natural Colors; credits: Lunar Explorer Italia)53 visitenessun commentoMareKromium
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Craters-Barton_Crater-PIA00463.jpgBarton Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)54 visiteDuring orbits 404 through 414 on 19-20 September 1990, the Magellan Probe imaged a Peak-Ring Crater that is about 50 Km in diameter located at Latitude 27,4° North and Longitude 337,5° East. The name "Barton" has been proposed by the Magellan Science Team for this Crater, after Clara Barton, founder of the Red Cross; however, the name is tentative pending approval by the International Astronomical Union.
Barton is just at the diameter size that Venus Impact Craters appear to begin to possess Peak-Rings instead of a single Central Peak or Central Peak complex like does about 75% of the craters with diameters between about 50 and 15 Km.
The floor of the Crater is flat and radar-dark, indicating possible infilling by volcanic deposits sometime following the impact event. Barton's Central Peak Ring is discontinuous and appears to have been disrupted or separated during or following the cratering process. The extremely blocky crater deposits (ejecta) surrounding Barton appear to be most extensive on the South-West to South-East (lower left to right) side of it.MareKromium
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Craters-Dickinson_Crater-PIA00479.jpgDickinson Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)59 visiteThis Magellan image is centered at 74,6° North Latitude and 177,3° East Longitude, in the North/Eastern Atalanta Region of Venus.
The image is approximately 185 Km (about 115 miles) wide at the base, and shows Dickinson, an Impact Crater of about 69 Km (approx. 43 miles) in diameter. The Crater is complex, characterized by a partial Central Ring and a Floor flooded by radar-dark and radar-bright materials.
Hummocky, rough-textured ejecta extend all around the Crater, except to the West. The lack of ejecta to the West may indicate that the Impactor that produced the Crater reached the Surface on an oblique angle, and from the West.
Extensive radar-bright flows that emanate from the Crater's Eastern Walls may represent large volumes of impact melt, or they may be the result of volcanic material released from the Subsurface during the cratering event.MareKromium
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Craters-Fossey_Crater-PCF-LXTT-00.jpgMagellan Probe: radio image of Fossey Crater126 visiteNonostante l'elevata temperatura media superficiale (circa 475°C) e la pressione, anch'essa molto alta (in media 92 bars), la totale mancanza di acqua rende i processi erosivi estremamente lenti.
Ne consegue che le caratteristiche superficiali del Pianeta restano sostanzialmente inalterate per milioni di anni salva l'esistenza, in alcune zone, di curiose striature del terreno determinate, probabilmente, da venti (wind streaks) o da getti di materiale (polveri e massi) a seguito del verificarsi di impatti meteorici (dust streaks).
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Craters-Fossey_Crater-PCF-LXTT-01.jpgFossey Crater (Natural Colors; credits: Lunar Explorer Italia)53 visitenessun commentoMareKromium
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Craters-Geopert_Crater-PIA00269.jpgMagellan Probe: radio image of Geopert-Meyer Impact Crater71 visiteCaption NASA originale:"During the third global cycle of Magellan's radar mapping mission, images were obtained at viewing angles that were slightly different than those used in the first two cycles. This strategy was designed to produce stereo image pairs, which take advantage of distortions induced by the different views to provide details of the surface topography. This is a stereo image pair of Crater Geopert-Meyer, named for the 20th Century Polish physicist and Nobel laureate (60° north latitude; 26,5° east longitude). The Crater, 35 Km (22 miles) in diameter, lies above an escarpment at the edge of a ridge belt in southern Ishtar Terra. West of the crater the scarp has more than 1 Km of relief. Perception of relief may be obtained with stereo glasses or a stereoscope".
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Craters-Ghost_Crater_in_Lakshmi_Region-PIA00477-PCF-LXTT-IPF.jpgPossible "Ghost Crater" in Lakshmi Region (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)76 visiteThis NASA - Magellan Spacecraft image covers an area of approximately 100 by 120 Km (such as 62,1 by 74,5 miles) and is located in the Lakshmi Region of Venus, at 47° North Latitude and 334° East Longitude. Due to the extremely dense Venusian Atmosphere, primary Impact Craters of less than a 3 Km (such as 1,863 mileS) diameter are, in fact, nonexistent on the Surface of this Planet. However, the Dark Circular Region and the associated Central Bright Feature visible in this frame are reasonably thought to be the remnants of a Meteoroid that was smaller than the size necessary to create an actual Impact Crater but, anyway, that was big enough to leave some scars on the Venusian Surface.
Entering the Venusian Atmosphere at a low velocity (approximately 350 meters/second - such as about 1260 Km per hour) the Central Bright Feature appears to be a Cluster of Small Secondary Impacts, Ejecta and Debris from the original Meteor that broke up in the Atmosphere and, litterally, fell down in pieces. Even though most of the Meteorite did not hit the Surface, the Atmospheric Shock Wave/s that were generated by the Impact Event, could have been great enough to modify the surrounding Region. One explanation for this radar Dark Circular Formation - called "Dark Margin" -, could be that the Shock Wave/s was/were energetic enough to pulverize some portion of the Venusian Surface (remember that smooth surfaces generally appear radar dark).
Another explanation is that the Surface nere, could be blanketed by a fine material that was formed by the original Meteor's break up through the Atmosphere. Just out of curiosity, more than half of the Impact Craters found on Venus have associated "Dark Margins", and most of them are prominently located left of center of the Craters themselves.
This frame (which is an Original NASA - Magellan Spacecraft Radio-Image published on the NASA - Planetary Photojournal with the n. PIA 00477), since it is just a Radio-Image of the Venusian Surface and NOT a real view of it, has been colorized, according to an educated guess carried out by Dr Paolo C. Fienga (LXTT-IPF), in what they could reasonably be its possible Absolute Natural Colors (such as the colors that a human eye would perceive if someone were onboard the NASA - Magellan Spacecraft and, once the thick layer of Venusian Clouds and Fogs is completely overcome, looked down, towards the Surface of Venus itself), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team.MareKromium
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Craters-Isabella_Crater-PIA00480.jpgIsabella Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)54 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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