A Nasa astronaut-in-training has quit for the first time in 50 years.
The last time a trainee quit the prestigious programme was in 1968, the year man first arrived on the moon.
Nasa has not announced why the candidate left and says that it is unable to elaborate on the man’s reasoning.
Robb Kulin resigned halfway through his two years of training at Johnson Space Centre in Houston.
Nasa spokeswoman Brandi Dean said his departure is effective from Friday and that he is leaving for personal reasons that the space agency cannot discuss due to privacy laws.
Mr Kulin was among 12 new astronauts chosen last summer from a record 18,300 applicants.
Mr Kulin, 34, was working as a senior manager at SpaceX when selected and said at the time he was hoping to fly on a vehicle he helped design.
SpaceX and Boeing are developing Nasa’s first commercial crew capsules, due to launch within the next year.
He grew up in Anchorage, Alaska, and worked as a commercial fisherman in Alaska and an ice driller in Antarctica.
The last time astronauts-in-training resigned from Nasa was in 1968.
Additional reporting by Associated Press