The Venus spiral cloudsVenus Express space probe has been eyeing the southern polar region of Venus and has found an atmospheric phenomenon that looks very much like a hurricane with a center resembling an eye like those found in hurricanes on Earth.  This hurricane is causing scientists to scratch their heads as the Venus version seems to morph and change shape rapidly over the course of several days.

The vortex of the hurricane is 2,000 km (1,240 mi) wide and was actually discovered in 1974 by the Mariner 10 spacecraft. A similar entity exists near the north pole of the planet, observed by the Pioneer spacecraft in 1979.

Venus hurrican + 4 hoursScientists have been recently analyzing the southern polar hurricane in the thermal infrared wavelength hoping to understand the temperature in the upper reaches of the clouds. In this analysis, the vortex appears very bright, indicating the downward movement of atmospheric gases through the vortex creating a depression in the upper reaches and generating heat there. Various shapes of the vortex appear in the pictures at left.

Venus hurrican + 24 hrs

In June 2006, the vortex was hourglass shaped matching the earlier observing in the north by the Pioneer mission. The images show the hurricane changes its shape in a matter of days. A video of the phenomenon can be viewed at the European Space Agency web site here:

The changing dynamic of the vortex can be seen quite well in the video. The structure is very complex with different wind dynamics at different altitudes.

Venus hurricane + 48 hours

Scientists are uncertain how to account for the activities of the vortex. One theory is that gases in the atmosphere get heated by the Sun near the equator. These gases rise upward, then migrate to the polar regions. The gases cool, then sink down to the surface. As the gas moves toward the northern and southern poles, they are deflected due to the rotation of the planet. This is similar to the way winds at the center of Earth-born hurricanes operate. The planetary rotation adds to the unpredictability of the hurricane-like winds, just as the rotation of the Earth does for our hurricanes.

Venus polar vortexVenus Express was launched in November 2005 and its mission is scheduled to run through May 2009. Scientists plan to continue to monitor the hurricane and the wind activity in the polar regions of Venus.

A video illustrating the cloud structure of Venus can be found here: