Flying saucers were born in the early summer of 1947, because of the report from a salesman flying onboard his private plane not far from Mount Rainier, Washington. They became nearly instantaneously a mass phenomenon, going deep into the pop culture and remaining in it until today. Sightings of unusual contraptions flying in skies were reported in the USA by the thousands and many abroad too. For a couple of weeks, flying saucers became the topic of the day, or nearly, quickly impacting the common custom, including the advertisement, sports, gags, and much more. Flying saucers have been usually believed to have shown up from out of the blue and to have been taken for wonder secret weapons or delusions, with no contemporary idea about a possible exogenous origin. The very first sighting by Kenneth Arnold happened in the right place (the USA) at the right time (a post-war summer) and involving the right witness (a pilot). An unusual local story coming from a quite remote area of the country got the immediate interest of the likely news-hungry press. It triggered a snowball effect generating a deluge of sightings, following a "me too" path like that you can find in other similar social phenomena. Flying saucers grew, developed steadily, and then remained encapsulated into the pop culture also because of a 70-year process of preparation to the idea that Mars was inhabited by a race far more advanced than us, capable of sending us signals or even visit us.This book shows how the idea that the flying saucers could come from Mars (or elsewhere) was immediately present in the 1947 press, although usually as a way to ridicule the stories or just to emphasize their seemingly "out-of-this-world" features. A small minority of occultists and fans of fringe topics (including many science fiction readers) were ready or open to accept the extraterrestrial origin of those flying discs. The author has surveyed hundreds of 1947 newspapers, collecting over 23,000 news clippings related to the flying saucer, throughout a 13-year research work.The book is enriched by nearly 300 illustrations and nearly 700 footnotes.