May 31, 2019: A huge blue cloud of frosted meteor smoke is pinwheeling around the Arctic Circle. NASA’s AIM spacecraft spotted its formation on May 20th, and it has since circled the North Pole one and a half times, expanding in size more than 200-fold. “These are noctilucent clouds,” says Cora Randall of the AIM … Continue reading Huge Blue Cloud Circles the North Pole