images

Noctilucent clouds

by

D.Anderson/Novapix

Reference

t-met03-49003

Date

2009-10-22

These rare clouds are called noctilucent or "night shining" as they seem to glow in the dark. They are caused by ice crystals at about 80 km altitude. These crystals reflect sunlight when the sun is well below the horizon. They are properly known as polar mesospheric clouds and are under intense study as it remains a mystery as to how they are formed.
Image taken in early August 2009 from Deep Creek on Alaska's Kenai Peninsula.