title: Venus's southern polar vortex reveals precessing circulation.
abstract: Initial images of Venus's south pole by the Venus Express mission have shown 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 Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument, we show the vortex to have a constantly varying internal structure, with a center of rotation displaced from the geographic south pole by ~3 degrees of latitude and that 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.
authors.affiliation: Centro de Astronomia e Astrofísica da Universidade de Lisboa, Observatório Astronómico de Lisboa, 1349-018 Lisboa, Portugal. dluz@oal.ul.pt
authors.forename: D
authors.initials: D
authors.lastname: Luz
authors.forename: D L
authors.initials: DL
authors.lastname: Berry
authors.forename: G
authors.initials: G
authors.lastname: Piccioni
authors.forename: P
authors.initials: P
authors.lastname: Drossart
authors.forename: R
authors.initials: R
authors.lastname: Politi
authors.forename: C F
authors.initials: CF
authors.lastname: Wilson
authors.forename: S
authors.initials: S
authors.lastname: Erard
authors.forename: F
authors.initials: F
authors.lastname: Nuccilli