Mysterious blue spiral appears in the sky over the UK. Some posted the stunning images on social media, joking that they thought it could be 'aliens' or a portal to another world. But the bizarre shape was caused by illuminated frozen fuel expelled from a SpaceX rocket, experts have said. The light blue spiral is formed when excess fuel that has been released from the fast-spinning rocket turns to ice. It then reflects the sunlight in the upper atmosphere – giving it an otherworldly gleam –