The eye of the hurricane

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.