Venus’s Southern Polar Vortex Reveals Precessing Circulation

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Science  07 Apr 2011:
DOI: 10.1126/science.1201629


Initial images of Venus's South Pole by the Venus Express mission showed the presence of a bright, highly variable vortex, similar to that at the planet's North Pole. Using high-resolution infrared measurements of polar winds from the Venus Express’s Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument, we show the vortex to have a constantly varying internal structure, with a centre of rotation displaced from the geographic South Pole by ~3 degrees of latitude, and which drifts around the pole with a period of 5 to 10 Earth days. This is indicative of a nonsymmetric and varying precession of the polar atmospheric circulation with respect to the planetary axis.