Neil Armstrong, the first man to walk on the Moon, is recovering after undergoing heart bypass surgery.
Armstrong, who celebrated his 82nd birthday on Sunday, had an operation to relieve four blocked coronary arteries on Tuesday after failing a stress test on his heart.
His wife Carol was reported by NBC news as saying that her husband was "doing great" following the surgery.
The astronaut wrote his name in history on July 20, 1969 when, as commander of the Apollo 11 mission, he climbed out of the Eagle module he had piloted to the moon and declared: "That's one small step for a man, one giant leap for mankind."
Buzz Aldrin, who accompanied him on the mission, wrote on Twitter: "Sending my best wishes for a speedy recovery- we agreed to make it the 50th Apollo Anniv in 2019".