| Piú viste - Venus |
South_Polar_Region-InfraRed-1.jpgVortexes at the South Pole of Venus (infrared) - frame 155 visiteHigh velocity winds are known to spin westwards around the planet, and to take only four days to complete a rotation. This 'super-rotation', combined with the natural recycling of hot air in the atmosphere, would induce the formation of a vortex structure over each pole. But why two vortexes?
"We still know very little about the mechanisms by which the super-rotation and the polar vortexes are linked," said Håkan Svedhem, ESA’s Venus Express Project Scientist. "Also, we are still not able to explain why the global atmospheric circulation of the planet results in a double and not single vortex formation at the poles. However the mission is just at the beginning and it's doing fine; we expect this and many other long-standing mysteries to be addressed and possibly solved by Venus Express" he added. Atmospheric vortexes are very complex structures that are very difficult to model, even on Earth.
Thanks to these first pictures, it has also been possible to observe the presence of a collar of cold air around the vortex structure, possibly due to the recycling of cold air downwards.
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South_Polar_Region-InfraRed-2.jpgVortexes at the South Pole of Venus (infrared) - frame 255 visiteThese 6 (4 in the previous frame plus 2 in this frame) different infrared images (in false colour) were taken by the VIRTIS on board ESA’s Venus Express spacecraft between 12 and 19 April 2006, during the first orbit, or ‘capture orbit’, around the Planet.
The images (taken at 5 microns) were obtained at six different time slots and different distances from Venus (top left - frame 1: 12 April, from 210.000 Km; top centre - frame 1: 13 April, from 280.000 Km; top right - frame 2: 14 April, from 315.000 Km; bottom left - frame 1:16 April, from 315.000 Km; bottom centre - frame 1: 17 April, from 270.000 Km; bottom right - frame 2: 19 April, from 190.000 Km), while the spacecraft moved along a long ellipse around the Planet.
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South_Polar_Vortex-00.jpgVenusian South Polar Vortex (1)55 visiteOriginal ESA caption:"On 20 April 2006, after its first 9-day, elongated orbit around Venus, ESA’s Venus Express started to get closer to the Planet, until it reached its final 24-hour long orbit on 7 May. During this time, and up to today, the spacecraft has been working relentlessly: the new data coming in are already providing first glimpses on planetary features never seen before.
If taking the first ever clear images of the double-eye vortex at Venus’ South Pole - imaged by Venus Express during its very first orbit - was already a first in the history of planetary exploration and a very pleasant surprise for the scientists, nobody could expect that the vortex had a structure even more complicated than possibly foreseen".
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Venusian_Atmosphere-ORB157_03_17_WB_H.jpgVenusian Turbulence: the Near-Equatorial Region55 visiteThis image of the Near-Equatorial Region of Venus was acquired on 24 September 2006 by the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board ESA’s Venus Express, from a distance of about 37.000 Km from the Planet’s surface.
The image, taken on the night-side of Venus at a wavelength of 1,7 micron, provides a close-up view of a highly turbulent region, with irregular and warped clouds, which is common at these low latitudes. This is different from what happens at higher latitudes (pole-ward) where clouds are generally streaky and more regularly shaped.
The gray ‘bubble’ slightly below the centre of the image is located at about 27° Southern Latitude and 7° Western Longitude, and has a diameter of about 300 Km.
The Alpha Regio area is at the bottom left of the image. This area is characterised by a series of troughs, ridges, and faults that are oriented in many directions, with surface features that can be up to 4 Km high. It is not yet clear if atmospheric turbulences may be induced by the rough topography below the clouds.
The grey-scale of the image is such that black means more transparency, therefore less clouds, while white means more opacity, therefore more cloud concentration.MareKromium
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Venusian_Atmosphere_and_the_Solar_Wind-Interaction.jpgInteraction between Venus and the Solar Wind55 visiteCaption ESA:"Mars, Earth and Venus are immersed in a flow of plasma, a ionised and highly variable gas originating from the Sun, called the Solar Wind. While Earth has a Planetary Magnetic Field, which can deviate its flow, Venus (and Mars) don’t.
Gases in the upper atmospheres of these Planets are ionised, and can thus interact with the Solar Wind. Venus is as large as Earth and it is difficult for its Atmosphere to escape due to the Planet’s Gravity. The Solar Wind is the best source of energy to accelerate the upper atmosphere’s charged particles, giving them enough energy to escape. This is why Venus loses its atmosphere due to interaction with the Solar Wind.
To understand this phenomenon, the key questions that the instruments studying plasma on Venus Express must answer are: what and how much of the Atmosphere is lost, and where is it lost? Right now, solar activity is at its minimum in the 11-year cycle, making the Solar Wind weaker than average.
The critical question now is how solar wind interacts with Venus when solar activity is low".MareKromium
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Venus-South_Pole-00.jpgThe South Pole of Venus (False Colors; credits: ESA)55 visiteCaption ESA:"This is a false-colour image taken with the Venus Monitoring Camera (VMC) on board ESA’s Venus Express.
It shows the full view of the Southern Hemisphere from Equator (Dx) to the Pole.
The South Pole is surrounded by a dark oval feature. Moving to the right, away from the Pole and towards the Equator, we see streaky clouds, a bright mid-latitude band and mottled clouds in the convective Sub-Solar Region.
This image was taken in the ultraviolet at 365 nanometres on 23 July 2007 as Venus Express was about 35.000 Km from the Surface of the Planet".MareKromium
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Venusian_Surface-Venera_14-03.jpgVenus, from Venera 14 (Natural Colors; credits: Ted Stryk)55 visiteTed Stryk comments:"...Venera 14, which landed in a much rockier area, took a pretty good partial color pan (again, complete in black and white), but while the other pan was complete in both black and white and through color filters (althoug again the blue was almost useless), the color data in this set was horribly underexposed.
Here is the Venera 14 partial pan, my favorite of the set because of the cool rock right near the lander. It seems to be sitting on the rocky plain...it makes one wonder how it got there. I don't see anything else like it in the Venera pans, although given their limited coverage, it doesnt mean there aren't perhaps a few more rocks like it around. But still , it is lucky it was so close to the lander and in a color zone...".
Nota Lunexit: notate anche Voi una - secondo noi STRAORDINARIA - similitudine fra questa superficie e la superficie di Titano?...MareKromium
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South_Polar_Regions-VI0310_00_5_H-PCF-LXTT.jpgVenus' South Polar Vortex (Absolute Natural Colors; credits for the additional process. and color.: Dr P>aolo C. Fienga - Lunexit Team)55 visiteCaption ESA:"This image, of the ‘Eye of the Hurricane’ on Venus was taken by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express.
This picture shows a Region in the Venusian Atmosphere about 60 Km from the Surface, at a wavelength of about 5 micrometres. In this figure, the dipole assumes an eye-like shape and from here until the last image, it is possible to see how its shape evolves rapidly in a span of only 24 hours.
The yellow dot in the image indicates the location of the South Pole".MareKromium
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South_Polar_Regions-2008-04-03438_Composite_H.jpgThe Southern Hemisphere of Venus55 visiteCaption ESA:In this mosaic, InfraRed images taken at a wavelength of 5 micrometres (in red) are overlaid on UltraViolet images, taken at 0.365 micrometres.
The bright areas in the IR Images represent the temperatures at the cloud tops (dark regions denote lower temperatures). The oval feature that stands out in these images is the giant eye of a hurricane, or the Polar Vortex, at the Planet’s South Pole. Its centre is displaced from the South Pole and the structure measures about 2000 Km across, rotating around the Pole in about 2.5 days.
The Atmosphere rotates counterclockwise in this figure".MareKromium
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Volcanoes-PIA00261.jpgVolcanoes in Guinevere Planitia (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)55 visiteThis image, with radar illumination from West to East, shows three unusual Volcanoes located in the Guinevere Planitia Lowland. At the center of the image is a large feature (approx. 50 Km or about31 miles in diameter) with an unusual shape; very round when viewed from above with steep slides and a flat top.
These Volcanoes are believed to be the result of relatively thick and sticky (viscous) Lava Flows that originated from a point source. Although a faint remnant of its original circular shape is preserved, the Northern Rim of this center Volcano has a steep Scarp.
The Scarp is probably the result of material that has slid away from the Volcano and subsequently has been covered by Lava Flows. This Volcano overlaps another feature to the South-West that is about 45 Km (approx. 28 miles) in diameter and disrupted by many fractures.
The South-Eastern Volcano (about 25 Km or approx. 15,5 miles in diameter) appears to be the highest of the three as its illuminated Western Edge has the brightest radar return. The scalloped Edges give this feature a bottlecap-like appearance. The highly scalloped Edges are probably the result of multiple material slides along the Volcano Margin.MareKromium
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Craters-Unnamed_Crater-PIA00468.jpgUnnamed (and heavily degraded) Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)55 visiteDuring orbits 423 through 424 on 22 September 1990, Magellan imaged this Impact Crater that is located at Latitude 10,7° North and Longitude 340,7° East.
This Crater is shown as a representative of Venusian Craters that are of the proper diameter (about 15 Km) to be 'transitional' in their morphology between 'complex' and irregular'.
Complex Craters account for about 96% of all craters on Venus with diameters larger than about 15 Km; they are thought to have been formed by the impact of a large, more or less intact, mass of asteroidal material that has not been excessively effected during its passage through the dense Venusian Atmosphere.
Complex Craters are characterized by circular Rims, terraced Inner Wall Slopes, well developed Ejecta Deposits, and flat Floors with a Central Peak or Peak Ring.
Irregular Craters make up about 60% of the Craters with diameters less than about 15 Km. Irregular Craters are thought to form as the result of the impact of asteroidal projectiles that have been aerodynamically crushed and fragmented during their passage through the Atmosphere.
Irregular craters are characterized by irregular and/or discontinuous Rims and hummocky or multiple Floors.
The 'Transitional' Crater shown here has a somewhat circular Rim like larger Complex Craters, but has the hummocky Floor and asymmetric Ejecta characteristic of smaller Irregular Craters. MareKromium
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Hestia_Rupes-PIA00469.jpgComplex Network of Narrow Fractures near Hestia Rupes Region (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)55 visiteThis is a Magellan radar image covering an about 105- Km (approx. 63-mile) by 45-Km (approx. 27-mile) Region near Hestia Rupes on the North-Western corner of Aphrodite Terra.
The complex network of narrow (such as <1 Km) Fractures in the center of the image extends for approx. 50 Km (about 31 miles). This network exhibits tributary-like branches similar to those observed in river systems on Earth. However, the angular intersections of the tributaries suggest tectonic control.
These features appear to be due to drainage of lava along preexisting fractures and subsequent collapse of the Surface. The underlying tectonic fabric can be observed in the North-East trending Ridges which predate the Plains.MareKromium
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