A program of unmanned space missions designed for planetary exploration. There were a number of such missions in the program, but the most notable were Pioneer 10 and Pioneer 11, which explored the outer planets and left the solar system. Both carry a golden plaque (see Pioneer plaque), depicting a man and a woman and information about the origin and the creators of the probes, should any Extraterrestrials find them someday.
... Pizarro, (1471-1541), conqueror of the Inca Empire
Marco Polo, (1254-1323), travelled to China in the 13th century.
John Wesley Powell, (1834-1902), explorer, ...