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| Piú viste - Venus |
Craters-Unnamed_Craters-Lakshmi_Region-PIA00477.jpgPossible Remnants of a Meteoroid in Lakshmi Region (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)55 visiteThis full resolution mosaiced image covers an area of approx. 100 by 120 Km (such as about 62 by 74 miles) and is located in the Lakshmi Region of Venus, at 47° North Latitude and 334° East Longitude.
Due to the dense Venusian Atmosphere, Primary Impact Craters of less than a 3 Km (a little less than 2 miles) diameter are nonexistent.
The dark circular region and associated central bright feature in this image are thought to be the remnants of a Meteoroid smaller than the size necessary to create an Impact Crater, and entering the Atmosphere at low velocity (approx. 350 meters/second.)
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.
Even though most of the meteorite did not hit the Surface, the Atmospheric Shock wave could be great enough to modify the surrounding region. One explanation for this radar dark circular formation, called "Dark Margins", could be that the shock wave was energetic enough to pulverize the Surface (smooth surfaces generally appear radar dark).
Another explanation is that the Surface could be blanketed by a fine material that was formed by the original meteor's breakup through the Atmosphere.
More than half of the Impact Craters on Venus have associated Dark Margins, and most of these are prominently located left of center of the rater. This is another effect which could be caused by the extremely dense Atmosphere of Venus. MareKromium
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Craters-Isabella_Crater-PIA00480.jpgIsabella Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)55 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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Volcanoes-Idunn_Mons-PIA13001-2.jpgIdunn Mons (Perspective View and False Colors; credits: NASA/JPL-Caltech/ESA)55 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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South_Polar_Vortex-02.jpgVenusian South Polar Vortex (3)54 visiteOriginal ESA caption:"The reason why the morphology of the vortex varies so extensively along a 'vertical' line is still unexplained.
"This is why we are organizing a campaign to observe the South Polar Vortex, fully dedicated to solve this unexpected puzzle", said Giuseppe Piccioni, VIRTIS co-Principal Investigator.
"First we want to understand how the structure is organized - actually, with VIRTIS we are building a true 3D view of the vortex. Then we hope to be able to better understand what are the driving forces that shape it".
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Venusian_Clouds_tracking_infrared_2_b_H.jpgVenusian cloud structures - Night view (1)54 visiteOriginal ESA caption:"Tracking cloud motion and starting to characterise the wind speed is an exercise that the Venus Express scientists have already started. A spectacular night view of the mid to low atmospheric layers over low latitudes (between 20º and 90 º South) by VIRTIS, show clouds being clearly pushed by winds.
"We can now make a first qualitative assessment of the wind fields and circulation, which is comfortably matching with previous measurement from the Galileo mission over the North Pole", said Giuseppe Piccioni.
"We are now collecting more data from different atmospheric depths, to be able to provide the first precise numbers, possibly in the near future".
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Venusian_Atmosphere-ORB157_02_17_WB_H.jpgVenusian Turbulence: the Alpha Regio Area54 visiteThis image of the Venusian South Polar Region 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 53.000 Km from the Planet’s surface.
The image, taken on the night-side of Venus at a wavelength of 1,7 micron, shows waves structure (faint light vertical streaks at the lower left part of the dark band in the centre-left side of the image) and a highly turbulent region (bottom left).
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-ORB157_00_17_WB_H.jpgVenusian Turbulence: South Polar Region54 visiteThis image of the Venusian South Polar Region 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 60.000 Km from the Planet’s surface.
The image, taken on the night-side of Venus at a wavelength of 1,7 micron, shows waves structure (faint light vertical streaks at the lower left part of the dark band in the centre-left side of the image) and a highly turbulent region (bottom left).
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 kilometres 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-Airglow_VIRTIS_Anticlockwise-00.jpgThe "Airglow" of Venus54 visiteNew infrared data is now available about Venus’ oxygen airglow – a phenomenon detectable on the night-side that makes the planet glow like a ‘space lantern’.
“The oxygen airglow was first discovered thanks to ground observations, and also observed by other missions to Venus such as the Russian Venera spacecraft and the US Pioneer Venus orbiter,” said Pierre Drossart, co-Principal Investigator on Venus Express’ VIRTIS instrument. “However, the global and detailed view we are getting thanks to Venus Express is truly unprecedented.”
The fluorescence of the airglow is produced when oxygen atoms present in the atmosphere ‘recombine’ into molecular oxygen (or ‘O2’) emitting light. Where does the oxygen come from?
“The oxygen in the atmosphere of Venus is a very rare element,” continued Drossart. At high altitudes in the atmosphere, on the day-side of Venus, the strong flux of ultraviolet radiation coming from the Sun ‘breaks’ the molecules of carbon dioxide (‘CO2’) present in large quantity in the atmosphere, liberating oxygen atoms. “These atoms are then transported by the so-called ‘sub-solar’ and ‘anti-solar’ atmospheric circulation towards the night side of the planet. Here the atoms migrate from the high atmosphere to a lower layer, called ‘mesosphere’, where they recombine into O2. By doing this, they emit light at specific wavelengths that can be observed through remote sensing from Earth and with Venus Express,” added Drossart.
The detection of the airglow, and the capability to follow its evolution in time, is extremely important for several reasons.
“First, we can use the distribution and motion of these fluorescent O2 ‘clouds’ to understand how the atmospheric layers below move and behave,” said Giuseppe Piccioni, the other co-Principal Investigator on VIRTIS. “In this sense, the O2 airglow is a real ‘tracer’ of the atmospheric dynamics on Venus.”
“Second, the analysis of this phenomenon will provide new clues on how its global atmospheric chemistry works – a very challenging task indeed, and still an open field of research,” continued Piccioni. “By calculating the speed at which this chemical ‘recombination’ takes place, we might be able – in the future – to understand if there are mechanisms that favour, or catalyze, this recombination, and learn more about the production and recombination of the other chemical species in the Venusian atmosphere.”
“Third, the observation of the oxygen airglow also allows to a better understanding of the global ‘energetic’ exchange between Venus’s mesosphere – at upper boundary of which the airglow is situated, with Venus’ thermosphere, an even higher layer directly influenced by the Sun.”
MareKromium
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Venusian_Atmosphere-Airglow_VIRTIS_Anticlockwise-02.jpgThe "Glowing Oxygen" of Venus (false colors - elab. ESA)54 visite“During one year of observations, we have already collected huge amount of data, which is exactly what we need to decode the secrets of an atmosphere as complex as that of Venus,” said Håkan Svedhem, Venus Express Project Scientist at ESA. “Analysing it is an extreme effort for all science teams, but it is definitively paying back in terms of results.”
The first ever, terrific global views of the double-eyed vortex at Venus’ south pole, the first sets of 3D data about the structure and the dynamics of the sulphuric-acid clouds surrounding the planet in a thick curtain, temperature maps of the surface and the atmosphere at different altitudes, are only a few of the results obtained so far.
“Continuing at today’s rate, and on the basis of what we were able to see so far, there is no doubt that Venus Express will eventually allow a better global understanding of this planet,” continued Svedhem. “Not only will planetary science in general benefit from this, but also understanding Venus – its climate and atmospheric dynamics –will provide a better comprehension of the mechanisms that drive long-term climate evolution on our own Earth.”
MareKromium
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Venusian_Atmosphere-Airglow_VIRTIS_Anticlockwise-01.jpgThe "Airglow" of Venus54 visiteOne year has passed since 11 April 2006, when Venus Express, Europe’s first mission to Venus and the only spacecraft now in orbit around the planet, reached its destination. Since then, this advanced probe, born to explore one of the most mysterious planetary bodies in the Solar System, has been revealing planetary details never caught before.
Intensively visited by several Russian and American probes from the 60s to the early 90s, Venus has always represented a puzzling target for scientists worldwide to observe. Venus Express, designed and built in record time by ESA, was conceived with the purpose of studying Venus - unvisited since 1994 - in the most comprehensive and systematic way ever, to provide a long-due tribute to a planet so interesting, yet cryptic.
Using state-of-the-art instrumentation, Venus Express is approaching the study of Venus on a global scale. The space probe is collecting information about Venus’ noxious and restless atmosphere (including its clouds and high-speed winds, as seen from this video obtained with the VMC camera on board) and its interaction with the solar wind and the interplanetary environment. Last but not least, it is looking for signs of surface activity, such as active volcanism. MareKromium
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Venusian_Atmosphere-ORB157_multiple_H.jpgVenusian Turbulence: Image Mosaic of the (visible) Venusian Cloud System54 visiteThis image is a composite of four different views of the Venusian Cloud System.
The images were acquired on 24 September 2006 by the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board ESA’s Venus Express, from distances of about 65.000 Km (top left), 60.000 Km (top right), 53.000 Km (bottom left), 37.000 Km (bottom right) from the Planet’s surface.
The images, showing a complex cloud system, were taken on the night-side of Venus (04:00 V.L.T.), at a wavelength of 1,7 micron that allows viewing the deep atmospheric layers.
The grey-scale of the images is such that black means more transparency, therefore less clouds, while white means more opacity, therefore more cloud concentration.MareKromium
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South_Polar_Regions-1.gifVenusian South Polar Vortex through Venus Express (2)54 visiteThis composite video sequence was obtained by the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board ESA’s Venus Express.
The single images were taken from 7 to 11 April 2007 over 5 different orbits. In each orbit the images were collected during a time span of 8 hours and were separated by about half an hour. The average distance from the Planet was about 65.000 Km.
The Latitude of the observed area spans from 90 to 50° South. The Longitude spans from about 20 to 150° East.
The video shows details of the Planet’s South Pole with edge-enhanced contrast.
Using specific wavelengths (3.8 and 1.7 microns, respectively), the observations allowed the imaging of the day and night areas around the South Pole simultaneously, at different depths (at about 65 Km and below the cloud deck, respectively) simultaneously. The intersection between the polar atmospheric structures seen at different wavelengths is visible in good detail, due to the optical properties of the clouds.MareKromium
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