There is an interesting corelation between art and UFO mythology. I have a big history of Science Fiction Art, and early on in the book they show a cover from "Astounding" or one of those early pulp rags. It shows a circular (actually spherical) UFO, complete with leering "little green men" swooping in to abduct terrified Earthlings... This was 1936 or so, just prior to the war and the boom in UFO sightings that followed.
These images were in newstands all over the country, at a time when folks got their news from same. The author makes a pretty good case that such images would have been in the public consciousness for some time.