When Mariner 9 arrived and successfully orbited Mars on 14 November 1971, just two weeks prior to Mars 2 and Mars 3, planetary scientists were surprised to find the atmosphere was thick with " a planet-wide robe of dust, the largest storm ever observed.

When Mariner 9 arrived and successfully orbited Mars on 14 November 1971, just two weeks prior to Mars 2 and Mars 3, planetary scientists were surprised to find the atmosphere was thick with " a planet-wide robe of dust, the largest storm ever observed.

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