Noctilucent Clouds

large image
http://www.nasa.gov/images/content/181083main_NoctilucentWide_lg.jpg
Very little is known about how these clouds form over the poles, why they are being seen more frequently and at lower latitudes than ever before, or why they have been growing brighter.
Full article:
http://www.nasa.gov/mission_pages/aim/multimedia/first_view.html






