NASA's first 50 years have seen both triumph and tragedy as the U.S. space agency sent unmanned probes to other planets and the fringe of our solar system, landed the first astronauts on the moon, built the world's first reusable manned spaceship and worked with other nations to construct the International Space Station. As NASA looks ahead to the next 50 years, here’s a glimpse — by no means comprehensive — at some of the agency’s most memorable milestones.

— Tariq Malik