Jupiter is by far the largest planet in the solar system. The planet's massive size -- and thus, its massive shadow -- has a profound effect on one of Jupiter's larger moons, Io. Io's atmosphere is composed of sulfur dioxide gas. When Jupiter's shadow passes over, Io's atmosphere freezes and collapses down to the moon's surface. When the eclipse passes and the moon is once again in sunlight, the atmosphere returns to gas form and restructures itself. In this way, Io's atmosphere is constantly undergoing collapse and repair.
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