Great Display of Rare Electric-Blue Clouds

This image shows one of the first ground sightings of noctilucent clouds in the 2007 season over Budapest, Hungary on June 15, 2007. Credit: Veres Viktor/NASA

On June 11, 2007 the cameras on the AIM satellite returned some of the first data documenting noctilucent clouds over the Arctic regions of Europe and North America. White and light blue represent noctilucent cloud structures. Black indicates areas where no data is available. Credit: Cloud Imaging and Particle Size Experiment data processing team at the University of Colorado Laboratory for Atmospheric and Space Physics

Noctilucent clouds are rare and breathtaking. They form 50 miles above the Earth's surface, in an upper layer of the atmosphere called the mesosphere. The puffs of water vapor and crystals appear during summer months above the Northern Hemisphere's pole as well the Southern Hemisphere's pole in summer.

This has been a banner year for them. "Breathtaking. A crackerjack display. The best in years!" writes Spaceweather.com.

"The electric-blue clouds have been sighted from Belgium, Denmark, Estonia, Latvia, the Netherlands, France, Germany, Poland, Russia and the British Isles," the web site reports.