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Moon and Mars

March 24, 2010

The Moon, the planet Mars, and the twins of Gemini form a beautiful grouping the next couple of nights. They're high in the southeast at nightfall, and remain in view until the wee hours of the morning. Tonight, Mars is to the left of the Moon as darkness falls, with Gemini's twins above them -- the stars Pollux and Castor.

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 and dust devils, frost, and even snow.

The biggest and most menacing weather events are the dust storms. They can cover thousands of square miles -- and at times, they can blanket the entire planet.

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

Mars's 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 -- snow made not of water, but of frozen carbon dioxide.

More about Mars and the Moon tomorrow.

Script by Damond Benningfield, Copyright 2010 Projecting a new image for Mars -- after this.

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