Venusian vortex: Infrared images of planetary sibling

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  • Published: Apr 1, 2013
  • Author: David Bradley
  • Channels: Infrared Spectroscopy
thumbnail image: Venusian vortex: Infrared images of planetary sibling

Vortices are from Venus

ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Universidad del País Vasco (I. Garate-Lopez)

The South Polar Vortex of the planet Venus, second planet from the Sun, is a much more chaotic and unpredictable alien weather system than had previously been recognised by astronomers. A new analysis of IR images shows that the axis of rotation of this vortex is nomadic about the pole depending on the particular altitude level in the clouds at which it is observed, revealing a much more unpredictable storm and morphology than thought.

A detailed analysis of infrared images taken by the VIRTIS instrument on board the European Space Agency's Venus Express spacecraft as well as ultraviolet data published in the journal Nature Geoscience tells us much about the foggy and acidic depths of the planet's atmosphere.

All aswhirl

Atmospheric vortices are seen in the atmospheres of most planets across the Solar System, indeed, we repeatedly experience their effects as hurricanes here on Earth, while the famous red spot on Jupiter is an atmospheric vortex we have been observing since at least 1831 and possibly as long ago as 1665.

Venus is a planet of similar to the Earth but its day is much longer at almost 6000 hours (243 Earth days) as opposed to our 24 hours. Intriguingly, the rotation of Venus is counter that of the Earth. Chemically speaking, the atmosphere of Venus is dense carbon dioxide and surface pressures are 90 times those of Earth, which makes the planet the archetype of the runaway greenhouse effect where surface temperatures are as high as 450 Celsius. Where we have frequently annoying rain clouds the Venusian clouds put our concerns about acid rain to shame as at 45 to 70 kilometres above its surface there sits a dense layer of sulfuric acid that envelopes the whole planet and moves at speeds of around 360 kilometres per hour in a super-rotation. Astronomers are yet to explain the mechanism that gives rise to this phenomenon in which a planet's atmosphere can rotate so much faster than the surface of the solid planet below.

Hellish weather

Whereas terrestrial weather systems are rather transient, at the poles of Venus, the atmospheric circulation forms intense and permanent vortices that change shape and size on a daily basis. In this latest analysis, the team show that the winds in the vortex change chaotically from day to day. This not only distinguishes them from polar vortices on Earth but also those observed on Saturn, which are much more stable and predictable.

The team explains that the Venusian vortices are powered by the atmospheric super-rotation and locked to the polar regions by a wide, shallow collar of cold air in sub-polar latitudes. There have been many years of observations, but even the new data cannot yet explain how a vortex can remain stable for prolonged periods or change shape on a daily basis. Venus polar vortices are one of the great mysteries of our sibling planet. Nevertheless, the latest work will ultimately help planetary scientists come up with a precise explanation of the vortex and its relationship with the atmospheric super-rotation.

The team comprises Itziar Garate-Lopez, Ricardo Hueso and Agustín Sánchez-Lavega of the Universidad del País Vasco, in Bilbao, Spain, Javier Peralta of the Lisbon Astronomical Observatory, Portugal, and Pierre Drossart of the Paris Observatory, France.

Related Links

Nature Geosci 2013, online: "A chaotic long-lived vortex at the southern pole of Venus"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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