Noctilucent Clouds Taken by Christopher Martin on July 2, 2011 @ Redwood Meadows, Alberta, Canada
Astronauts on board the ISS took this picture of noctilucent clouds near the top of Earth’s atmosphere on July 13, 2012.
Noctilucent clouds are a mystery dating back to the late 19th century. Northern sky watchers first noticed them in 1885 about two years after the eruption of Krakatoa. Ash from the Indonesian volcano caused such splendid sunsets that evening sky watching became a worldwide past time. One observer in particular, a German named T.W. Backhouse who is often credited with the discovery of NLCs, noticed something odd. He stayed outside longer than most people, long enough for the twilight to fully darken, and on some nights he saw wispy filaments glowing electric blue against the black sky. Scientists of the day figured they were some manifestation of volcanic dust. (via Meteor Smoke Makes Strange Clouds - NASA Science)
Noctilucent Clouds in Motion Stockholm Sweden 7-17-2012 (by sheepleification)