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Night-Shining Clouds

Credit: NASA Earth Observatory
These so-called noctilucent clouds are typically hard to see, since they form 50 to 60 miles (80 to 100 kilometers) above the ground — higher than where…Read More »

clouds typically form in the atmosphere.

Astronauts aboard the International Space Station snapped this photo of these mysterious clouds, known as polar mesospheric clouds, on Aug. 1, as the orbiting outpost flew over southern Ukraine. [Related Gallery: Photos of Mysterious Night-Shining Clouds]   Less «
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