A Swirling Vortex at Venus’ South Pole

Article written: 21 Jan , 2015
Updated: 23 Dec , 2015
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Here’s the latest view of the mass of swirling gas and clouds at Venus’ south pole. The Venus Express’s Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) has been keeping an eye on this polar vortex since the spacecraft arrived and discovered this huge storm in 2006. During the mission, VIRTIS has seen the vortex constantly transform, morphing from a double vortex into a squashed shape and into the eye-like structure seen here.

This image was taken in April 2007 but was just released this week.

Venus has a very choppy and fast-moving atmosphere, even though wind speeds are much slower at the planet’s surface. At the cloud tops about 70 km above the surface, winds can reach 400 km/h. At this altitude, Venus’ atmosphere spins about 60 times faster than the planet itself. Compared to Earth, this is a dizzying speed: even Earth’s fastest winds move at most about 30% of our planet’s rotation speed.

These polar vortices form when heated air from equatorial latitudes rises and spirals towards the poles, carried by the fast winds. As the air converges on the pole and then sinks.

High velocity winds spin westwards around the planet, and take just four days to complete a rotation. This ‘super-rotation’, combined with the natural recycling of hot air in the atmosphere, would induce the formation of a vortex structure over each pole.

A video of the vortex, made from 10 images taken over a period of five hours, can be seen here. The vortex rotates with a period of around 44 hours.

Source: ESA

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3 Responses

  1. Steven says

    I believe the reality of an atmosphere has been pointed out in recent re-apprailals of the habitability of planets orbiting red dwarfs that are likely to be tidally locked facing their star. Curiously the standard argument also maintains that lacking a magnetic field strips away the atmosphere yet here Venus is with a remarkable one.

    As for the vortex of Venus itself it gives the impression one is looking down through a transparent column of Venusian atmosphere to where the clouds lay around the border or wall and it gets brighter as you go down. Is that an accurate understanding or is it an illusion? Could the brightness be “daylight” nearer the surface ( I presume we’ve never actually seen down to the surface if this is really funnel shaped vertically speaking.) Hmm – that would be interesting to see from the side and if it reaches the ground in some form.

    • Member

      “Venus is partially protected by an induced magnetic field.
      As on Earth, solar ultraviolet radiation removes electrons from the atoms and molecules in the upper atmosphere, creating a region of electrically charged gas known as the ionosphere. This ionised layer interacts with the solar wind and the magnetic field carried by the solar wind.
      During the continuous battle with the solar wind, this region of the upper atmosphere is able to slow and divert the flow of particles around the planet, creating a magnetosphere, shaped rather like a comet’s tail, on the lee side of the planet”.
      ~ Tielong Zhang
      Venus Express MAG Principal Investigtor

      And per the “brightness” this image is in the infrared, so the brightness is actually hotness. 😉

  2. Steven says

    Thanks for the reply.

    I did see on the NASA site that it was an infrared image. Missed that here. I still wonder if the vortex ever clears down to the surface enough to make it more specifically visible. The eye of the hurricane as it were.

    About the magnetic field – that is the thinking the differentiates Venus from Mars? Mars is so far away that it could be lacking the ability to generate an ionization level substantial enough to turn aside the solar wind’s erosion?

    I wish we’d hear more about this idea in the various papers and news reports. It certainly would be salient in the discussion of habitable planets.

    Thanks!

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