Astronomy Picture of the Day

Explanation: Bright noctilucent or night shining clouds are not familiar sights from northern France. But these electric-blue waves coursed through skies over the small town of Wancourt in Pas-de-Calais on July 6, just before the dawn. From the edge of space, about 80 kilometers above Earth's surface, the icy clouds still reflect sunlight even though the Sun itself is below the horizon as seen from the ground. Usually spotted at high latitudes in summer months the diaphanous apparitions are also known as polar mesospheric clouds. The seasonal clouds are understood to form as water vapor driven into the cold upper atmosphere condenses on the fine dust particles supplied by disintegrating meteors or volcanic ash. NASA's AIM mission provides projections of the noctilucent clouds as seen from space.