Enos, a chimpanzee, is launched into space.

Enos was a chimpanzee trained by NASA in the early 1960s as part of the Mercury program, which used primates to test systems and conditions before sending humans into orbit. He was carefully selected for his intelligence, responsiveness to training, and calm behavior under pressure. By the time he was chosen for flight, he had completed thousands of hours of conditioning, including simulations of capsule environments, complex task-response training, and exposure to the stresses he would face in space.

His mission took place on November 29, 1961, aboard **Mercury-Atlas 5**, making him the first—and only—chimpanzee to orbit Earth. The plan called for two orbits, but unexpected issues popped up almost immediately: the capsule’s automated conditioning system malfunctioned and repeatedly shocked him despite correct responses. On top of that, the spacecraft experienced mechanical concerns serious enough that mission control cut the flight down to a single orbit. Despite all this, Enos continued performing his tasks, demonstrating remarkable resilience under conditions far more stressful than intended.

After splashdown in the Atlantic, recovery crews brought him aboard the USS *Stormes*, where they found him dehydrated but otherwise in good shape. His flight provided NASA with essential data on orbital conditions, life-support reliability, and spacecraft behavior—data that helped pave the way for John Glenn’s successful orbital mission just a few months later. Enos’s journey is often remembered as a crucial, if sometimes overlooked, stepping stone in the early era of human spaceflight.