NASA's AIM spacecraft has detected electric-blue clouds forming over Antarctica. These are noctilucent clouds (NLCs), and their apparition marks the beginning of the 2014-2015 season for NLCs in the southern hemisphere.
NLCs are Earth's highest clouds. Seeded by meteor smoke, they form at the edge of space 83 km above Earth's surface. When sunlight hits the tiny ice crystals that make up these clouds, they glow electric blue.
NLCs appear during late spring and summer because, ironically, that is when the upper atmosphere is coldest, allowing the ice crystals of NLCs to form. Northerners reading this story should remember that it is late spring in Antarctica, so the noctilucent clouds are appearing right on time.
Previous results from AIM have shown that NLCs are like a great geophysical light bulb. They turn on every year in late spring, reaching almost full intensity over a period of no more than 10 days. At the moment, only a few puffs and wisps of NLCs are visible over Antarctica. By Dec. 10th, the whole continent could be blanketed in electric blue as the bulb begins to glow in earnest. Stay tuned!
http://buff.ly/v38kkL
More about NLCs: http://science.nasa.gov/science-news/science-at-nasa/2003/19feb_nlc/
Meteor smoke: http://science.nasa.gov/science-news/science-at-nasa/2012/07aug_meteorsmoke/
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