| Piú viste - Venus |
South_Polar_Regions-0.gifVenusian South Polar Vortex through Venus Express (1)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 over 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 50 to 90° South. The Longitude spans about 20 to 150° East.
The video shows details of the Planet’s South Pole in RGB colour. The data obtained at 1.7 microns is shown in blue, while those obtained at 3.8 microns is represented in red.
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 well, due to the optical properties of the clouds.
MareKromium
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Venusian_Clouds-VI410_411_23_tot.gifVenusian Cloud Structure (GIF-movie)54 visiteCaption ESA:"This movie consists of a sequence of six images obtained by the VIRTIS imaging spectrometer on board ESA’s Venus Express on 5 and 6 June 2007, before and after NASA MESSENGER’s closest approach to the Planet. The image sequence, obtained by VIRTIS, provides a night-side view of the same region that Messenger flew over and imaged.
They were obtained at 1,7 micrometres, revealing atmospheric details down to an altitude of 50 Km from the surface".MareKromium
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Venusian_Atmosphere-ORB410_411_tot_H1.jpgThe Venusian Atmosphere under the Messenger54 visiteCaption ESA:"The images in this panel were obtained by the VIRTIS imaging spectrometer on board Venus Express on 5 and 6 June 2007, before and after MESSENGER’s closest approach to the Planet. These panels from VIRTIS provide a night-side view of the same Region that Messenger flew over and imaged.
The images where obtained at 1,7 micrometres, revealing atmospheric details down to an altitude of 50 Km from the surface".MareKromium
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Thermal_Map-ORB410_01_surf_comp_H1.jpgThermal Map of Venusian Surface (comparison ESA/NASA)54 visiteCaption ESA:"An unprocessed thermal map of the Venusian Surface obtained by VIRTIS on 5 June 2007 (left) is compared here with a radar image of the same area obtained by NASA’s Magellan Spacecraft in the 1990s (right).
VIRTIS, the imaging spectrometer on board Venus Express, obtained this image at 1 micrometre, a wavelength that allows detection of radiation originating from the surface. The imaged region is that which NASA’s MESSENGER flew over as it made its closest approach to the Planet.
Magellan’s radar imaging and altimetry maps made it possible to measure the elevation and the radio-optical properties of the surface. Venus Express’ VIRTIS is providing the first complete set of thermal maps of the surface of Venus.
Correlations between topographic and thermal data similar to the ones shown in this image-composite will allow the scientists to understand if the measured temperature of the surface depends only on the altitude – where higher altitudes simply corresponds to colder, temperatures such as on Earth – or if it depends on the presence of previously undetected sources of heat such as active volcanoes".MareKromium
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Venus-PIA10125.jpgFarewell to Venus54 visiteCaptio NASA:"After acquiring hundreds of HR images during close approach to Venus, the MESSENGER Spacecraft turned its wide-angle camera back to the Planet and acquired a departure sequence. These images provide a spectacular good-bye to the cloud-shrouded Planet while also providing valuable data to the camera calibration team. The MESSENGER Spacecraft was 60.688 Km (about 37.710 miles) from the Planet at the start of the sequence and 89.310 Km (approx. 55.495 miles) at the end. Initially, images were acquired at a rate of one of every 20', and then as Venus shrank the timing interval was increased to 60'.
The first image was taken on June 6, 2007, at 12:58 UTC (8:58 p.m. EDT on June 5), and the final image on June 7 at 02:18 UTC (10:18 p.m. EDT on June 6). During this 25 h, 20' period the Spacecraft traveled 833.234 Km (about 517.748 miles-more than twice the distance from the Earth to the Moon) with respect to Venus at an average speed of 9,13 Km-per-second (such as 5,67 miles-per-second).
These images represent the last view of Venus by the MESSENGER Spacecraft, but they also point toward the spacecraft's first encounter with Mercury in January 2008".MareKromium
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Venus-PIA10123.jpgApproaching Venus54 visiteCaption NASA:"On Oct. 24, 2006, the MESSENGER Spacecraft came within 2990 Km (such as about 1860 miles) of Venus during its second planetary encounter.
Twenty days before closest approach to Venus the MESSENGER Dual Imaging System snapped pictures of the Planet from a distance of about 16,5 MKM (about 10,3 MMs). Despite the low resolution of the image on the left, one can see that Venus is shrouded in a thick blanket of clouds that hides its surface.
The picture on the right is the same image expanded 4 times, clearly showing the dense Venusian cloud cover".MareKromium
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Venus-PIA10124.jpgVenus (natural colors; credits: NASA)54 visiteCaption NASA:"The Planet Venus is enshrouded by a global layer of clouds that obscures its surface to the MESSENGER Dual Imaging System (MDIS) cameras.
This single frame is part of a color sequence taken to help the MESSENGER team calibrate the camera in preparation for the spacecraft's first flyby of Mercury on January 14, 2008. Over the next several months the camera team will pore over the 614 images taken during this Venus encounter to ascertain color sensitivity and other optical properties of the instrument. These tasks address two key goals for the camera at Mercury: understanding surface color variations and their relation to compositional variations in the crust, and ensuring accurate cartographic placement of features on Mercury's surface.
Preliminary analysis of the Venus flyby images indicates that the cameras are healthy and will be ready for next January's close encounter with Mercury".MareKromium
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Venus-South_Polar_Vortex-13_VIRTIS_vortex_movie_H.gifThe restless South Pole of Venus (GIF-Movie - credits: ESA)54 visiteCaption ESA:"This video is composed of a set of images acquired by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on board ESA’s Venus Express, during two observations slots in August 2007. The spacecraft was flying at a distance of about 65.000 Km from the Planet.
The video was obtained at 3.8-micrometre wavelength, allowing the instrument to see the cloud top thermal emission at an altitude of about 60-65 Km.
The South Polar "Dipole", a complex atmospheric vortex-like feature situated over the South Pole of the Planet, can be clearly seen".MareKromium
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Venusian_Clouds-29_VM_Pericentre_mosaic_H.jpgChaotic "Cloud Patterns" at Venus54 visiteCaption ESA:"This mosaic of Venus’ cloud tops was put together with several images obtained by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express. The images where taken in the ultraviolet (365-nanometre wavelength) on 15 August 2006 at distances from 5000 to 1000 Km from the Planet.
The picture clearly shows streaks, wave trains and convection cells. The elongated orbit of Venus Express allows one to zoom into the cloud features as the Spacecraft approaches the Planet. This mosaic shows that mottled and chaotic cloud patterns at low latitudes give way to oriented streaks at about 15° South.
This behaviour indicates transition between two different cloud motion regimes – a ‘dynamic’ regime dominated by local convection where the Sun light hits the Planet perpendicularly (so-called "Sub-Solar Point") - and a more regular, quasi-laminar-flow regime".
MareKromium
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Venusian_Clouds_and_Haze-27_VMC_polar_views_H.jpgVenusian "Variable Clouds" and "Hazes"54 visiteCaption ESA:"This is a composite of several ultraviolet (365-nnmts) images taken with the Venus Monitoring Camera (VMC) on board ESA’s Venus Express.
These images show variability of the clouds and hazes in Venus’ South Polar Region.
The South Pole is at the Terminator in the bottom-left of the images.
Super-Rotation, a phenomenon where cloud layers on Venus rotate much faster than the surface below, is in the anticlockwise direction. The period of Super-Rotation varies between 3 and 5 days, depending on the latitude.
The images a, b and c in the top row were taken between 27 and 30 June 2006, at a distance of about 65.000 Km from the Planet.
It is obvious from the pictures that the near-polar features vary from one day to another.
An extreme case of such variability is shown in Figure d (obtained on 13 January 2007, from about 35.000 Km). The bright haze located above the absorbing cloud layer has expanded to 35º South and has also become denser, masking all features except the oval. This dense haze disappeared within a day, probably due to very quick coagulation of aerosols making up the haze.
The figure in panel e (obtained on 27 December 2006, from about 38.000 Km) shows the full view of the Southern Hemisphere from the Equator (right) to the Pole".MareKromium
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Venus-South_Pole-01.jpgThe South Pole of Venus (false colors; credits: ESA)54 visiteDa "NASA - Picture of the Day", del 26 Febbraio 2006:"Why did an acidic haze spread across Venus? The unusual clouds were discovered last July by ESA's robotic Venus Express Spacecraft currently orbiting Venus. The bright and smooth haze was found by Venus Express to be rich in Sulfuric Acid (H2SO4), created when an unknown process lifted Water Vapor and Sulphur Dioxide (SO2) from lower levels into Venus' upper Atmosphere.
There, sunlight broke these molecules apart and some of them recombined into the volatile Sulfuric Acid. Over the course of just a few days last July, the smooth acidic clouds spread from the South Pole of Venus across half the Planet.
The above false-color picture of Venus was taken last July 23rd (2007) in UV (Ultraviolet Light), and shows the unusual haze as relatively smooth regions across the image bottom. The cause of the dark streaks in the clouds is also not yet understood and is being researched".MareKromium
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Venus-South_Pole-02.jpgThe South Pole of Venus (Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)54 visitenessun commentoMareKromium
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