Neil Armstrong, first man to walk on the moon is recovering after undergoing a heart bypass surgery.
Armstrong, 82, had surgery to relieve four blocked coronary arteries.
NASA administrator Charles Bolden wished the 'true American hero' a quick recovery, the BBC reports
"Neil's pioneering spirit will surely serve him well in this challenging time," Bolden said in a statement.
As commander of the Apollo 11 mission, Armstrong became the first man to set foot on the Moon on 20 July 1969.
Armstrong, along with three other astronauts, received the Congressional Gold Medal, the highest US civilian award, in November.