The cause of the strange blue spiral is actually a SpaceX Falcon 9 rocket that blasted off from Space Launch Complex 40 (SLC-40) at Cape Canaveral Space Force Station in Florida at 1:48 p.m. EDT (1748 GMT) on Monday. The rocket was carrying the secretive NROL-69 mission for the National Reconnaissance Office (NRO).

The United Kingdom’s meteorological service said a SpaceX launch likely caused a blue spiral to appear in skies over the country and Europe on March 24.

A mysterious glowing spiral was spotted in the skies over several European countries, following a SpaceX rocket launch. According to the UK National Meteorological Service, the spiral was likely formed by the rocket’s exhaust interacting with the atmosphere.