Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. This active moon of Jupiter is marked with volcanoes spewing lava that is now known to be hotter than any lava on Earth . Above is the highest resolution color-enhanced image yet composed of the most active surface in our Solar System . Features as small as three kilometers are visible. Sulfur compounds cause many of Io 's unusual colors, while darker regions are probably composed of silicate rock .
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