Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. In this just-released nighttime picture of Jupiter 's moon Io , the red spots clearly show Io 's current volcanically active regions . This telling picture was taken by the automated Galileo spacecraft currently orbiting Jupiter while Io was in Jupiter's shadow. One hypothesis is that the green glow is caused by a different type of aurora resulting from high-energy particles interacting with Io's volcanic plumes .
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