Infrared Polar Emissions

This composite image shows six infrared views of Venus as seen by the Ultraviolet/Visible/Near-Infrared spectrometer (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 at different distances from Venus: 1, 2, 3, 4, 5, 6.

The infrared radiation coming from Venus was converted in this reddish colour scheme. Thermal radiation comes from the lower atmosphere, (just above the cloud top, located at about 60 kilometres altitude). Solar radiation reflected by the upper atmospheric layers (roughly between 60 and 80 kilometres altitude) and thermal radiation from the layers below contribute to the brightest part of the image.

The south polar vortex structure is visible from different view points close to the centre of the images, mostly in the dark side.

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Infrared of Southern Vortex

This video is composed by six sequences of images (in false colour) taken by the Ultraviolet/Visible/Near-Infrared spectrometer (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 sequences (taken at 5 microns) were obtained during six different time slots and at different distances from Venus. The planet’s globe, imaged at different angles, was mapped onto an electronic mock-up of Venus, so to have the South Pole always plotted at the centre of each single image.

Around the South pole it is possible to see a peculiar double-eye vortex structure, never clearly seen by any other Venusian mission before. The movie shows the rotation and the shape variation of the double vortex over time. It is also possible to see the rotation of the ‘terminator’, the line separating the day side – visible in yellow - from the night side.

The images also show the presence of a collar of cold air around the vortex structure (dark blue), possibly due to the recycling of cold air downwards.

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Southern Vortex

These two images of Venus’s south pole were taken by NASA’s Mariner 10 (during a Venus fly-by on its way to Mercury) and Pioneer Venus missions during the early 1970s and 1980s, respectively. The images provided the first glimpses about a stormy atmospheric behaviour at the south pole of the planet.

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Day & Night (Visible/Infrared)

This sequence of images was taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express spacecraft between 12 and 19 April 2006.

Each image is the composite of the day side of Venus (left, in blue, taken in visible light at 380 nanometres) and the night side (right, in a red colour scheme, taken in infrared light at 1.7 microns).

The visible part shows solar radiation reflected by the atmosphere. The infrared part shows complex cloud structures, revealed by the thermal radiation coming up from different atmospheric depths. Venus Express can resolve these structures by use (for the first time from orbit) of the so so-called ‘infrared windows’ present in the atmosphere of Venus. In fact, if observed at certain wavelengths, it is possible to detect thermal radiation leaking from the deepest atmospheric layers, revealing what lies beneath the dense cloud curtain situated at about 60 kilometres altitude.

In the colour scheme of the presented infrared images, the brighter the colour, the more radiation comes up from the lower layers.

The images were obtained at six different time slots and different distances from the planet (top left: 12 April, from 210 000 kilometres; top centre: 13 April, from 280 000 kilometres; top right: 14 April, from 315 000 kilometres; bottom left:16 April, from 315 000 kilometres; bottom centre: 17 April, from 270 000 kilometres; bottom right: 19 April, from 190 000 kilometres), while the spacecraft moved along a long ellipse around Venus. The separate images can be seen separately here, respectively: 1, 2, 3, 4, 5, 6.

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