A key ingredient of Earth's strangest clouds does not come from Earth. New data from NASA's AIM spacecraft proves that "meteor smoke" is essential to the formation of noctilucent clouds.
Noctilucent Cloud is an unusual phenomenon of the Earth's upper-atmosphere. They are most often seen at times close to the summer solstice, when they appear against the backdrop of deep evening twilights. Read more
Normally too dim to be seen, they may become visible at sunset during late summer when illuminated by sunlight from below. Noctilucent clouds are the highest clouds known and thought to be part of polar mesospheric clouds.