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More Moon and Venus

June 15, 2010

Big storms rumble across the central and eastern states at this time of year. Their clouds can tower up to 10 miles high, creating the perfect conditions for hail, heavy rains, and even tornadoes.

Clouds cover the planet Venus, too. But they're far different from those on Earth. They're higher in the sky, they're made of different stuff, and they cover the entire planet all the time.

A good bit of what we know about Venus's clouds came from Vega 2, a Soviet mission that arrived at Venus 25 years ago today. A lander sampled the material in the clouds as it plunged toward the surface. And a balloon floated through the clouds for two days, circling a third of the way around the planet.

Vega 2 and other missions showed that Venus's clouds are split into three layers. The top layer tops out at about 50 miles high. It's made of droplets of sulfuric acid that are as tiny as particles of cigarette smoke.

The Vega balloon floated through the middle layer, which consists of slightly larger particles of sulfuric acid.

The bottom layer extends down to an altitude of about 30 miles. It consists of droplets that are the size of raindrops. But it's not clear what those drops are made of. It could be sulfuric acid, chlorine, or a mixture of several substances.

Venus's clouds help make the planet look quite bright. To see how bright, look for Venus in the west this evening. It's the brilliant "evening star" to the lower right of the Moon.

Script by Damond Benningfield, Copyright 2010

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