Both panels show the oxygen airglow in the night-side atmosphere of Venus, fully detectable only at specific infrared wavelengths. The images are built by a combination of colours: the airglow is blue, corresponding to 1.27 micrometres; yellow corresponds to 1.7 micrometres, and its modulation is due to the different cloud thickness in different areas.

On the right panel the airglow appears in atmospheric structures similar to ‘clouds’. In the left image a slightly different colour scale has been used to emphasize the brightening of the limb (side view of the atmosphere) due to the airglow itself.

The fluorescence of the airglow is produced when oxygen atoms, ‘migrating’ from the day-side to the night-side of the atmosphere of Venus under the push of the so-called sub-solar and anti-solar atmospheric circulation, recombine into molecular oxygen (or ‘O2’) emitting light.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

The scene covers the south pole of Venus (lower-left corner of the image) up to the planet’s equator. It shows the upper cloud deck, as well as a bright haze above it. Venus’ atmospheric super-rotation – by which winds take only four Earth-day to circumnavigate the whole planet - is in anti-clockwise direction. The stormy atmosphere of Venus shows its complexity through the marked variation in the clouds morphology, especially in the polar region, where oval and spiral structures can be observed.

An interactive, mouse-clickable version of this movie can be downloaded here (35 267 kb)

Credits: ESA/MPS, Katlenburg-Lindau, Germany

The image shows the oxygen airglow in the night-side of Venus, appearing as the bright features similar to ‘clouds’ visible at the bottom of the image, and also visible as the white ring surrounding the planet’s disk (limb). The oxygen airglow is fully detectable only at specific infrared wavelengths. This image was obtained at 1.27 micrometres.

The fluorescence of the airglow is produced when oxygen atoms, ‘migrating’ from the day-side to the night-side of the atmosphere of Venus under the push of the so-called sub-solar and anti-solar atmospheric circulation, recombine into molecular oxygen (or ‘O2’) emitting light.

The view was obtained from south, with the south pole at the top of the image. The lower horizon is at about 20 degrees South latitude, while the image centre is at 60 degrees East longitude (coinciding with midnight local time).

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

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 infrared wavelengths.

The images used to produce the sketch were obtained by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) onboard ESA’s Venus Express, and provide a view of the southern hemisphere of the planet.

The left image was obtained at visible wavelengths (400 nanometres) on 19 April 2006, along the capture orbit around Venus.

The right image is a composite of three VIRTIS observations performed on 22 July 2006. Because of this particular viewing geometry, the oxygen airglow appears on the right-hand side of the image (night-side equatorial region) as an area of brightness increase.

Credits: R. Hueso, Grupo de Ciencias Planetarias, Univ. del País Vasco, Spain