After the successful completion of the Mercury-Atlas 5 flight that carried Enos, a chimpanzee, in late November 1961, a press conference was held in early December. Reporters asked NASA's Robert Gilruth who would be the first U. S. astronaut in orbit, piloting M-A6. He then announced the team members for the next two Mercury missions. John H. Glenn was selected as prime pilot for the first mission (M-A6), with M. Scott Carpenter as his backup. Donald K. Slayton and Walter M. Schirra were pilot and backup, respectively, for the second mission, Mercury-Atlas 7.