NASA satellite sees 'night shining' clouds

WASHINGTON, June 28 (UPI) -- U.S. astronomers said a NASA satellite has viewed the first occurrence this year of mysterious iridescent clouds that form 50 miles above Earth.

The first observations of the northern polar clouds by the Aeronomy of Ice in the Mesosphere, or AIM, satellite occurred May 25.

The National Aeronautics and Space Administration said its AIM satellite is the first dedicated to the study of such cloud systems called Polar Mesospheric Clouds.

Often termed "night-shining" clouds when viewed from space -- or noctilucent when viewed from Earth -- the clouds form during the Northern Hemisphere's warmer seasons. They are also visible in the high latitudes of the Southern Hemisphere during those summer months.

Very little is known about how the clouds form, why they are being seen more frequently and at lower latitudes than ever before, or why they have been growing brighter.

"It is clear that PMCs are changing ... and we do not understand how, why or what it means," said AIM principal investigator James Russell III of Hampton University. "These observations suggest a connection with global change in the lower atmosphere and could represent an early warning that our Earth's environment is being altered."