The puzzling 'eye of a hurricane' on Venus   The dynamic nature of the South polar vortex can be seen in this video sequence, composed of images obtained on 7 April 2007. The video is composed of a series of ten images taken over a period of five hours at half-hourly intervals, at a wavelength of 3.9 micrometres. The vortex is rotating with a period of about 44 hours. In video, the point of view of the observer has been rotated at the same rate so that the vortex appears stationary in the centre of the image. These images were obtained as part of the ‘VIRTIS movie’ sequence, previously reported on 7 May 2007. This movie shows that the vortex is very complex, with atmospheric gases flowing in different directions at different altitudes. The bright region at the top-centre appears to be the most active region and its brightness suggests that it is where atmospheric gases are flowing downward. Extending leftward from this point is an ‘S’-shaped feature which is seen frequently in the polar vortex. A very similar feature was observed at the northern polar vortex in 1979 by Pioneer Venus.   This image, of the ‘eye of the hurricane’ on Venus was taken by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express. This picture shows a region in the venusian atmosphere about 60 km from the surface, at a wavelength of about 5 micrometres. In this figure, the dipole assumes an eye-like shape and from here until the last image, it is possible to see how its shape evolves rapidly in a span of only 24 hours. The yellow dot in the image indicates the location of the south pole. The fickle puzzle     This image, of the ‘eye of the hurricane’ on Venus was taken by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express. This picture shows a region in the venusian atmosphere about 60 km from the surface, at a wavelength of about 5 micrometres. This image is taken only 4 hours after the previous one. In this short time, the vortex has already evolved into a different shape. Using two images taken at different times, it is possible to measure the wind speeds and study the dynamics of the region. The yellow dot in the image indicates the location of the south pole. What creates the puzzle?     This image, of the ‘eye of the hurricane’ on Venus was taken by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express. This picture shows a region in the venusian atmosphere about 60 km from the surface, at a wavelength of about 5 micrometres. This image is taken 24 hours after the first of the series, or after one complete Venus Express orbit. Here the vortex has become more circular and less elongated. The yellow dot in the image indicates the location of the south pole.   This image, of the ‘eye of the hurricane’ on Venus was taken by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express. This picture shows a region in the venusian atmosphere about 60 km from the surface, at a wavelength of about 5 micrometres. This image was acquired a day later (after the previous image). Here the shape of the vortex is stretched out in two opposite directions and is almost hourglass-shaped - this shape is called a dipole. The yellow dot in the image indicates the location of the south pole. Notes for editors:     This is a picture of Venus’s atmosphere, taken by the Venus Monitoring Camera (VMC) during Venus Express orbit number 458 on 23 July 2007. The view shows the southern hemisphere of the planet. It clearly shows enormous, spiral cloud features that form at mid-latitudes. One explanation for why the polar vortex forms is that atmospheric gases heated by the Sun at the equator, rise and then move poleward. In the polar regions, they converge and sinks again. As the gases moves towards the poles, they are deflected sideways because of the planet’s rotation. At the top of the cloud layer, this gives rise to cloud features seen in the image. Release date: 15 May 2008