Exploratour - The Atmosphere of Mars
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Some colors of light bounce off molecules better than others. Blue light bounces the most and red light bounces the least. Since the blue rays of lights bounce the most, they reach our eyes from all directions and we see more blue than any other color. On Earth this means that the sky looks blue.
On Mars, the thin air means that light passes through without bouncing much, so the sky is darker than on Earth. Also, because the atmosphere of Mars contains a lot of dust, and red light bounces better off of dust than it does off of molecules, more red light reaches our eyes than would on Earth. This means that on Mars the sky looks pale red.
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