They're thin, wispy, and shiny. They glow an unmistakable shade of electric blue. Clearly visible to the astronauts on the International Space Station, the mysterious clouds float on the edge of space in the same region where the space shuttle Columbia broke up. What are they?
The official name for these high-altitude ice clouds is "noctilucent clouds" or "night-shining clouds." Some even speculate they may have contributed to the Columbia disaster. Others think they are seeded by space dust, while still others suspect they're a sign of global warming. Whatever they are, they're growing in abundance and are a great puzzle to scientists, reports ABCNews.com and Space.com.
They are visible from Earth only in the summer months, so right now they can be seen in the Southern Hemisphere. "We've seen definite changes," admitted John Olivero, a professor of physical science at Embry-Riddle Aeronautical University in Daytona Beach, Fla., to ABCNews.com reporter Amanda Onion. "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."
The only other reported sighting of such clouds was more than a century ago in 1883 when Krakatoa, an island volcano in Indonesia, erupted. The ash spewed some 50 miles into the air and anchored water vapor at high altitudes. The vapor condensed to ice, and the blue clouds were formed. In addition to enjoying magnificent sunsets, Indonesians who stayed up late enough reported seeing the shimmering, blue clouds. Long after the sunsets returned to normal, the night-shining clouds were still visible. "It's puzzling," Gary Thomas, a professor at the University of Colorado, told Space.com reporter Tony Phillips. "Noctilucent clouds have not only persisted, but also spread."
A volcano eruption caused them in 1883. What has caused them to appear now? Scientists are stumped. They're up too high--some 30 to 60 miles above the Earth--to reach them by weather balloon, but they're too close to our planet for an orbiting satellite to check it out. There are theories. Global warming and the effect of greenhouse gasses on the mesosphere is the most popular one.
Even the space shuttle Columbia astronauts reported seeing them over the Southern Hemisphere. Because so little is understood about the night-shining clouds, some are wondering if they might have played a role in the Columbia disaster. Others dismiss that since Columbia broke up in the Northern Hemisphere, far away from the clouds.
All these questions may be answered in 2006 when NASA launches a small satellite that will take wide angle photographs of the noctilucent clouds, measure their temperatures and chemicals, and more. Until then, enjoy the view.
--Cathryn Conroy
