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More Moon and Venus

March 27, 2014

We got an unexpected lesson in meteorology this winter: a primer on the polar vortex. This mass of super-cold air usually stays at high latitudes, but it dipped southward a few times this year, bringing numbing cold to much of the country.

Animation showing motions of Venu's south polar vortexAnimation showing motions of Venu's south polar vortex [ESA]Similar vortexes swirl around the poles of the planet Venus, the brilliant "morning star." It stands to the upper right of the Moon at first light tomorrow.

Venus's atmosphere is quite different from Earth's. It's far denser and hotter, and it's made mainly of carbon dioxide. It's topped by clouds of sulfuric acid. The clouds zoom around Venus at high speed: While the planet itself makes one turn on its axis every 117 Earth days, the clouds whip around the planet once every four days.

That creates vortexes at both poles. They span many hundreds of miles. And like the vortexes on Earth, they sometimes wobble about.

Observations by the Venus Express spacecraft, for example, show that the south vortex can change dramatically from day to day.

The vortex has two centers of rotation — one about a dozen miles above the other. Winds in the higher one are about twice as fast as the lower one. And each layer is chaotic — its size and shape can vary dramatically over periods of many days. There's no apparent pattern in the changes, and no correlation between the upper and lower layers.

So when it comes to unpredictable polar vortexes, Earth has nothing on its turbulent planetary neighbor.


Script by Damond Benningfield, Copyright 2014

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