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ex·o·sphere  (ĕksō-sfîr′)
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Tweet n. 1. The outermost region of a planet's atmosphere. 2. The outermost region of the earth's atmosphere, lying above the thermosphere and extending thousands of kilometers into space, from which molecules having sufficient velocity can escape the earth's gravitation. ex′o·spheric (-sfîrĭk, -sfĕr-) adj. |
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