The Constantly Changing Vortex on Venus

ESA’s Venus Express has been constantly watching the huge swirling vortex of clouds around Venus’ southern pole. It’s a strange weather feature, morphing and changing shape within just a few days. And scientists, as you can probably imagine, are puzzled about what’s going on.

Venus’ south pole vortex is similar to a hurricane here on Earth. It measures 2,000 km (1,240 miles) across, and was discovered by the Mariner 10 flyby in 1974. A second, similar vortex was found at the planet’s north pole by the Pioneer Venus mission in 1979.

“Simply put, the enormous vortex is similar to what you might see in your bathtub once you have pulled out the plug” says Giuseppe Piccioni, co-Principal Investigator for the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on Venus Express, at IASF-INAF, Rome, Italy.

When Venus express observed the vortex in June 2006, it had a roughly hourglass-shape, similar to what Pioneer Venus saw in the north polar region. But with continued observations from Venus Express, scientists are seeing that the storm is much more fickle than they previously thought.

Over the course of just a single day, scientists watched the shape of the storm’s vortex change from a circle to a oval. It’s believed that atmospheric gases are flowing into the region from different directions at different altitudes. The shape of the vortex is a result of changes in temperature across different parts of the planet.

The actual vortex is created because atmospheric gases are heated by the Sun at the equator. They cool near the polar regions and sink down. The rotation of Venus deflects them sideways so they swirl together, like water going down the drain of a bathtub.

Original Source: ESA News Release