South-polar features on Venus similar to those near the north pole

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Abstract

Venus has no seasons, slow rotation and a very massive atmosphere, which is mainly carbon dioxide with clouds primarily of sulphuric acid droplets. Infrared observations by previous missions to Venus revealed a bright ‘dipole’ feature surrounded by a cold ‘collar’ at its north pole1,2,3,4. The polar dipole is a ‘double-eye’ feature at the centre of a vast vortex that rotates around the pole, and is possibly associated with rapid downwelling. The polar cold collar is a wide, shallow river of cold air that circulates around the polar vortex. One outstanding question has been whether the global circulation was symmetric, such that a dipole feature existed at the south pole. Here we report observations of Venus’ south-polar region, where we have seen clouds with morphology much like those around the north pole, but rotating somewhat faster than the northern dipole. The vortex may extend down to the lower cloud layers that lie at about 50 km height and perhaps deeper. The spectroscopic properties of the clouds around the south pole are compatible with a sulphuric acid composition.

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Figure 1: The Venus south-polar dipole.
Figure 2: The dipole in its highest-thermal-contrast atmospheric layer.
Figure 3: The deepest view of the dipole seen so far.

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Acknowledgements

We acknowledge the work of the entire Venus Express team, which allowed these data to be obtained. We thank ASI, CNES and the other national space agencies that have supported this research.

Author Contributions G.P. and P.D. coordinated the work as Principal Investigators of VIRTIS. A.S.-L. and R.H. contributed to the dynamics calculation and to Supplementary Fig. 1. F.W.T., C.F.W. and L.Z. contributed to the comparison with earlier data and to the finalization of the paper. D.G. contributed to the temperature retrieval model and calculation, M.M. and A.A. contributed to the thermal structure, and S.L. contributed to the coordination of the dynamics study. All authors contributed equally to the planning of the work and data analysis.

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Correspondence to G. Piccioni.

Supplementary information

Supplementary Figure

The file contains the Supplementary Figure 1. This figure shows the structure of the dipole at different wavelengths on both night and day sides simultaneously. The images have been processed into a polar projection with the same relative size. Spectra in the infrared range from 1 to 5 microns are also shown in two different regions of the southern polar area. (PDF 163 kb)

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Piccioni, G., Drossart, P., Sanchez-Lavega, A. et al. South-polar features on Venus similar to those near the north pole. Nature 450, 637–640 (2007) doi:10.1038/nature06209

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