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This is a composite image of the small moons of Saturn
Click on image for full size version (92K GIF)
Image from: NASA
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The environment of the moons, with the exception of Io, and Titan, is one of little or no atmosphere, which means there is little or no greenhouse effect to moderate the warming of the surface by the sun and little or no surface pressure, which most terrestrial life forms require to hold their bodies intact (recall the movie Total Recall). The lunar surfaces are almost directly exposed to space. Without a greenhouse effect, the lunar surfaces are exposed to extreme swings in temperature (-279 degrees F to +260 degrees; F or 100 K to 400 K). Without an atmosphere, the lunar surfaces are also exposed to ultraviolet light and energetic charged particles. These materials have a tendency to break down biological cells in life as we know it.
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