1970s mysticism - the same author who wrote "Chariot of the Gods?" that was made into a movie.
"Many people have scoffed at the idea of beings from another universe visiting Earth. But in 1970 we witnessed the drama of a crippled American spacecraft being brought back to Earth. Suppose it had landed on another planet? What would our astronauts teach the inhabitants? What remnants of their efforts to return to Earth would be left behind? How would that planet's inhabitants remember our men in myth and art? The answers we would give fit exactly the vast number of unexplained mysteries that have been found around the world."