Enos was purchased from the Miami Rare Bird Farm in April 3, 1960. He completed more than 1,250 hours of training for his mission at the University of Kentucky and Holloman Air Force Base. His training was more intense than that of Ham, the Americans' first chimp in space, because Enos would be exposed to weightlessness and a higher g for longer periods of time. His training included psychomotor training and aircraft flights.
Enos was selected to make the first orbital animal flight only three days before the launch. Two months before allowing a chimp to be launched into orbit, NASA had launched Mercury Atlas 4 on September 13, 1961, to conduct the same mission with a "crewman simulator" in the spacecraft. Enos flew into space on board Mercury Atlas 5 on November 29, 1961. He completed his first orbit in 1 hour, 28.5 minutes.
Enos was originally scheduled to complete three orbits, but was brought back after the second orbit because the spacecraft was not maintaining proper attitude. According to observers, Enos jumped for joy and ran around the deck of the recovery ship enthusiastically shaking the hands of his rescuers. Enos' flight was a full dress rehearsal for the next Mercury launch on February 20, 1962, which would make Lt. Colonel John Glenn the first American to orbit the Earth, after astronauts Alan Shepard, Jr. and Gus Grissom's successful suborbital space flights.
On November 4, 1962, Enos died of dysentery caused by shigellosis, which was resistant to antibiotics of the time. He had been under constant observation for two months before his death. Pathologists reported that they found no symptom that could be attributed or related to his space flight a year before.
- Yuri Gagarin, the first person to orbit the Earth
- One Small Step: The Story of the Space Chimps. Documentary on History of Primates Used in Space Travel