(L-R) Apollo 11 crew members, Buzz Aldrin, Michael Collins, Neil Armstrong and former NASA Johnson Space Center director Chris Kraft at the National Air and Space Museum in Washington on July 19. The Apollo 11 astronauts issued a clarion call for Americans to set their sights on Mars as they celebrated the 40th anniversary on Monday of the first moon landing.
(AFP/NASA-HO/Bill Ingalls)