From MSNBC:
A new NASA satellite has recorded the first detailed images from space of a mysterious type of cloud called “night-shining” or “noctilucent.” The clouds are on the move, brightening and creeping out of polar regions, and researchers don’t know why.
“It is clear that these clouds are changing, a sign that a part of our atmosphere is changing and we do not understand how, why or what it means,” said atmospheric scientists James Russell III of Hampton University in Hampton, Virginia. “These observations suggest a connection with global change in the lower atmosphere and could represent an early warning that our Earth environment is being changed.”
More here.