MYSTERY OF THE MISSING NOCTILUCENT CLOUDS: Every year in June, far-northern sky watchers see electric-blue tendrils creeping over the western horizon at sunset. These are noctilucent clouds (NLCs) formed by summertime wisps of water vapor crystallizing around bits of meteor smoke at the edge of space. Every year in June ... except this year. NLCs have been mysteriously absent in June 2017, and researchers have just figured out why. A 'heat wave' in the upper atmosphere has temporarily wiped them out. Visit today's edition of Spaceweather.com for the full story and the prognosis for future NLCs.
Above: A comparison of noctilucent clouds in June 2016 vs June 2017. Photo credits: (left) Alan Dyer of Gleichen, Alberta and (right)Heiko Ulbricht of Freital, Saxony, Germany. [full story]
