NASA image: Night-shining clouds
Monday, June 22, 2015 - 06:00
in Astronomy & Space
In the late spring and summer, unusual clouds form high in the atmosphere above the polar regions of the world. As the lower atmosphere warms, the upper atmosphere gets coooler, and ice crystals form on meteor dust and other particles high in the sky. The result is noctilucent or "night-shining" clouds (NLCs)—electric blue wisps that grow on the edge of space.