Vintage 14×36 inch movie poster for Mars Attacks the Earth; a feature film edited together from the original 1938 Flash Gordon's Trip to Mars matinee serial. This is the original vintage half-sheet poster; not a reprint.

From Wikipedia:
This serial, the first sequel to the Flash Gordon serial, was based on the 1936 "Big Little Book" adaptation of the strip "Flash Gordon and the Witch Queen of Mongo". According to Harmon and Glut, the location was changed to Mars to capitalize on Orson Welles' famous War of the Worlds broadcast. According to Stedman, this serial preceded that broadcast, which made Universal hastily release a feature version of the serial as Mars Attacks the World to capitalize on the publicity. The film was a box-office success.