Shiny Ice Clouds Collecting at Earth's Edge

Feb. 26 -- Lately, astronauts on board the International Space Station have seen some scintillating views.

At the edge of space — the same cold region where space shuttle Columbia broke up into a trail of debris — shiny, silvery blue clouds have been hovering.

The high-altitude ice clouds are called noctilucent or "night-shining" clouds, and astronauts as well as Earth-bound scientists have been puzzled by their growing abundance.

The clouds are visible from space and from the ground over areas that are experiencing summer weather. Astronauts on the space station are seeing them over the southern hemisphere where it's now warm.

"We've seen definite changes," said John Olivero, a professor of physical science at Embry-Riddle Aeronautical University in Daytona Beach, Fla. "It appears the particles that make up the clouds have gotten slightly bigger with time and it appears the clouds are now visible further away from the poles than they have been before."

Volcanic Beginning

The last time these high, shiny clouds appeared in great numbers was after the 1883 eruption of the island volcano, Krakatoa, in Indonesia. The explosion hurled plumes of ash up to 50 miles into the air and caused spectacular sunsets.

The ash particles also served as rare anchors to water vapor at high altitudes and the vapor condensed to ice, forming the brilliant blue clouds. Sky gazers who stayed up late following the eruption reported seeing wispy, glowing streaks in the night sky. Before this incident there were no reported sightings of noctilucent clouds.

But why so many night shining clouds now?

"It's still being debated," says Chester Gardner, an atmospheric scientist at the University of Illinois at Urbana.

One reason scientists are having such a hard time understanding the shimmering clouds is their location. At 30-60 miles above Earth, the mesosphere is also known as the "ignorosphere" due to its inaccessibility. The region is too far to reach by weather balloon and yet it sits below where orbiting satellites or other craft might orbit because its heavier atmosphere would cause too much drag.