Strange Clouds

February 18, 2003: They hover on the edge of space. Thin, wispy clouds, glowing electric blue. Some scientists think they're seeded by space dust. Others suspect they're a telltale sign of global warming.

Astronauts onboard the International Space Station have been observing electric blue "noctilucent" clouds from Earth-orbit.

Sky watchers on Earth have seen them, too, glowing in the night sky after sunset, although the view from Earth-orbit is better. Pettit estimated the height of the noctilucent clouds he saw at 80 to 100 km ... "literally on the fringes of space."

Link - science.nasa.gov...