NOCTILUCENT CLOUDS: NASA's AIM spacecraft has spotted a luminous patch
of electric-blue drifting across the Arctic Circle. The sighting marks
the beginning of the 2015 season for northern-hemisphere noctilucent
clouds (NLCs). Long ago, NLCs were a polar phenomenon confined mainly to
the Arctic. In recent years, however, they have intensified and spread,
with sightings as far south as Utah and Colorado.
Learn more about
these exotic clouds and how you might see them this summer on today's