Strange Clouds Spotted at the Edge of Space

A weirdly wonderful sight appeared to astronauts aboard the International Space Station this summer — thin blue clouds hovering at the boundary between Earth's atmosphere and the void.

The noctilucent or "night-shining" clouds are at an altitude of 47 to 53 miles (76 to 85 km), where meteors and bright aurora lights are not uncommon and the atmosphere gives way to the blackness of space. The clouds remain a scientifically baffling phenomenon more than 120 years after their discovery.



source: http://news.yahoo.com/s/space/20080901/sc_space/strangecloudsspottedattheedgeofspace