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Sorvolando le nuvole di Venere – aggiornamento scientifico dalla Venus Express   This false-colour movie was built with ultraviolet images taken by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express spacecraft on 22 May 2006. The spacecraft was flying over the northern hemisphere approaching the planet, over distances ranging between about 39 100 and 22 600 kilometres from the surface. The images were taken at 365 nanometres, starting respectively 03:30 and 01:45 hours before reaching the pericentre (point of closest approach of the spacecraft to Venus). The complex atmosphere that surrounds the planet is clearly visible. The true-colour (grey-scale) version of this movie can be downloaded here.  This triple image provides a close-up view of the double-eyed vortex at Venus south pole, as seen by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express. The images were taken on 29 May 2006, from a distance of about 64 000 kilometres from the planet. All the separate images can be downloaded here: - South polar_vortex close up_1_b.gif - South polar_vortex close up_1_b.tif - South polar_vortex close up_3_b.tif - South polar_vortex close up_2_b.tif The vortex is imaged at different infrared wavelengths, corresponding to different atmospheric depths. The left image (taken at 5.05 microns) correspond to an atmospheric altitude of about 59 kilometres, just about the Venusian cloud deck. The central image (taken at 4.65 microns) corresponds to an atmospheric altitude of about 60 kilometres. The right image (taken at 4.08 microns) corresponds to an altitude of about 65 kilometres, just in the upper clouds. The images were taken with a 20º inclination with respect to vertical pointing. The brighter the colour, the more radiation is reaching out from the hot layers below. The brightest spot correspond to the centre of the vortex, where radiation from the deeper layers become clearly visible , like looking through a hole. The dark circular structures surrounding the brighter area belong to the big vortex structure (bottom of the images) - as large as a big portion of Europe (2500 kilometres across) - and are part of the planet atmospheric super-rotation. The left image also clearly shows a complex structure, where many more small structures are visible.  This movie, built with infrared images taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express, provides a close-up view of the double-eyed vortex at Venus south pole. The images (ranging from 4.5 to 5.1 microns) were taken on 29 May 2006, from a distance of about 64 000 kilometres from the planet.
Thanks to the use of different wavelengths, VIRTIS probed the atmosphere at different depths, ranging from 70 kilometres to about 60 kilometres altitude. It is interesting to see how the images contrast and the details increase while approaching the 60 kilometres altitude. Sulle orme di nuvole e vento  This movie was built with ultraviolet images taken by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express spacecraft on 24 April 2006, when the spacecraft was flying over the northern hemisphere, at distances ranging between 7505 and 1570 kilometres from the surface. The images were taken about every 5 minutes at the beginning of the sequence, and less than a minute apart from each other at the end. The sequence allow a first qualitative analysis of the cloud structures. Low-contrast stripe-features are visible, possibly due to the presence of strong winds that produce elongated structures. Set of periodic ‘wave’ patterns in the clouds, possibly due to the local variation of temperature and pressure, or to a kind of tidal forces in action at Venus, can also be seen. The mysterious ‘UV absorbers’, ultraviolet markings on the cloud top, are visible as darker features in this movie. They are so called because they absorb almost half of the solar energy received by the planet. The mysterious substance that causes this absorption still represents a true puzzle for the scientists.
Differently from Earth and other planets, Venus absorbs only the ultraviolet radiation coming from the sun, while it scatters most of the rest of the solar radiation. This is the reason why Venus appears so bright in the sky (high ‘albedo’).  This mosaic is composed of ultraviolet images taken by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express spacecraft on 24 April 2006, when the spacecraft was flying over the northern hemisphere, at distances ranging between 7505 and 1570 kilometres over the surface. The original images (taken at a wavelength of 365 nanometres) were projected on geographical coordinates. While flying over the cloud deck at high speed (from left to right), Venus Express got closer to the deck itself and obtained ever more detailed images (see right-hand side). The sequence allows a first qualitative analysis of the cloud structures. Low-contrast stripe-features are visible, possibly due to the presence of strong winds that produce elongated structures. Set of periodic ‘wave’ patterns in the clouds, possibly due to the local variation of temperature and pressure, or to a kind of tidal forces in action at Venus, can also be seen. The mysterious ‘UV absorbers’, ultraviolet markings on the cloud top, are visible as darker features in this mosaic. They are so called because they absorb almost half of the solar energy received by the planet. The mysterious substance that causes this absorption still represents a true puzzle for the scientists.
Differently from Earth and other planets, Venus absorbs only the ultraviolet radiation coming from the sun, while it scatters most of the rest of the solar radiation. This is the reason why Venus appears so bright in the sky (high ‘albedo’).  This spectacular night image is an infrared view taken at 1.7 microns, as seen by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express on 12 April 2006, during the first orbit around the planet (capture orbit).
The image, covering an area situated between 20º and 90 º south, show clouds being clearly pushed by winds. Using a set of images of the same area acquired at different times, it is possible to make a direct measurement of the wind speed.  These infrared images were taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express on 25 April 2006, while the spacecraft was flying over low planetary latitudes (between 15º and 60º south). The two images on the left panel (taken at 2.3 and 1.7 microns, respectively) show a fine atmospheric structure below the Venusian cloud deck, at about 35 and 20 kilometres altitude, respectively. The right panel is the result of the projection on geographical coordinates of the second image of the left panel. The images at the top where taken from a distance of about 6000 kilometres from the surface, allowing VIRTIS to generate the high resolution details visible at the top of the panel. While Venus Express continued flying over the planet it got farer from the surface – up to 20 000 kilometres distance – allowing VIRTIS to obtain a wider view, but in lower resolution.
Stripe-like features are visible at the bottom of all images. They could be indicative of a wave-like atmospheric motion (due to tidal forces?), but their nature is still unexplained.
The separate images can be downloaded here:
[Cloud_tracking_infrared_b_H.tif,
Cloud_tracking_infrared_c_H.tif,
Wind_tracking_b_H.tif] La sorpresa “in cima” all’atmosfera  This ultraviolet image of the Venus southern hemisphere was taken by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express spacecraft on 15 May 2006, when the spacecraft was flying at about 66500 kilometres distance from the planet.
In this image (taken at 365 nanometres) the South Pole is near the terminator, just above the centre of the image. The complex atmosphere that surrounds the planet is clearly visible. Near the pole we see spiralling clouds surrounding the polar vortex, away from the pole we see cloud features of the upper cloud deck at approximately 70 kilometres altitude.  These two plots where built with data retrieved from ASPERA, the Analyzer of Space Plasma and Energetic Atoms on board ESA’s Venus Express, on 30 May 2006, when the spacecraft was flying through different domains of the interaction region between Venus and the solar wind. The X axis of the plots provides the different position at which the ions (charged atoms) hit the ASPERA detectors. The Y axis provides the energy of the detected ions. The white lines correspond to different ion masses.
The left plot shows the heated solar wind (protons and ‘alfa-particles’) which just passed the Venus bow shock (the region in space separating the unperturbed solar wind from the area where the solar wind interacts with the planetary environment). The right plot shows massive escape of the planetary oxygen ions detected inside the solar wind void which results from the interaction with Venus. Stato della sonda  During the course of its mission, Venus Express communicates with Earth by means of its two high gain antennas, located on two different sides of the spacecraft. Routinely, Venus Express will downlink scientific data for about eight hours once a day, when the spacecraft is around its furthest point from the planet (apocentre) along its 24-hour orbit. Release date: 19 Luglio 2006 |
