Enos the chimpanzee was obtained from Africa in 1960 as part of the Air Force and NASA Mercury program. Soon after his arrival in the United States, he began 1,263 hours of training in psychomotor operations for orbital in-flight performance maneuvers on the Mercury-Atlas rocket. One of the skills Enos would learn required him to differentiate between colors and shapes on a instrument panel - a correct answer earned a drink of water, an incorrect answer resulted in a shock to his foot.

"No one ever held Enos. If you had him he was on a little strap. Enos was a good chimp, he was smart but
he didn't take to people, very little. They said he was a mean chimp, but he wasn't really mean. He just didn't take to cuddling." Senior Master Sergeant Edward Dittmer, former chimp handler

On November 27, 1961 Enos was selected as the chimp for the Mercury-Atlas 2 mission which would attempt three orbits of the Earth. Enos was prepared for his orbital flight and on November 29, 1961 he blasted into outer space and reached orbit. During his flight two malfunctions occurred. The first malfunction occurred in the lever for the motor skills test and Enos was shocked rather then rewarded for each correct answer. As a tribute to Enos, or perhaps his rigorous training, he continued to perform his required operations correctly despite the repeated shocks. The second malfunction occurred in the Atlas rocket's thruster system and, luckily for Enos considering his unfortunate predicament, mission control ended his flight after two orbits of the Earth.

Three hours and 21 minutes after lift off Enos re-entered the Earth's atmosphere and landed in the Atlantic Ocean. He was given a full examination and awarded a clean bill of health. Enos was hailed as a hero by NASA and the press. Thanks to Enos, mission managers concluded that a human could withstand space travel.

Six months after Enos' historic and brave mission he contracted Shigellosis, a rare and potent form of dysentery, and died. His death received almost no media attention. What little attention was given to Enos' death focused not on his courageous mission but rather that Enos had not died as a result from his adventure in space.