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Moon and Mars

December 4, 2016

The Moon slides past the planet Mars tonight. Mars looks like a bright orange star close to the left of the Moon. Venus, the “evening star,” stands well to their lower right.

In many ways, Mars is the most Earth-like world in the solar system. And one of those ways is the weather. Mars has clouds, cold fronts, dust storms, frost, and even snow.

The biggest and most menacing weather events are the dust storms. They can cover many thousands of square miles — and on rare occasions, they can blanket the entire planet.

These giant storms usually begin around the start of spring in the northern or southern hemisphere. Frozen water and carbon dioxide in the polar ice caps vaporize and enter the atmosphere. This stirs up the powdery orange dust around the poles, then whips it around the planet. A planet-wide dust storm may have doomed two Soviet landers that arrived at Mars in 1971. Storms could prove troublesome to future human explorers as well.

The Martian clouds typically form thin streamers, not the billowy piles we see on Earth. But when a low-pressure system spins across Mars, the clouds form the same spiral pattern as storm systems here. And the clouds occasionally drop a blanket of fresh snow — made not of water, but of carbon dioxide.

And as dawn breaks across Mars, a layer of frost usually coats the landscape. As the Sun climbs into view, though, the frost quickly vaporizes — leaving the Martian surface bone dry.


Script by Damond Benningfield



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