Enormous, spiral cloud features

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.