Former NASA astronaut Buzz Aldrin believes American swimmer Katie Ledecky could make a good austronaut. Aldrin, the second man to ever walk on the moon, was in the stands at the Olympic Aquatics Stadium on Tuesday to watch U.S. swimmers Katie Ledecky and Michael Phelps win gold.

SOUNDBITE: (English) Buzz Aldrin, former NASA astronaut: (On his favourite Olympic event)

"I probably haven't seen it yet, and I may not, because we got to leave before the track and field. But I did pole vaulting, and they changed the game completely, it's a lot more acrobatic, with brute force."

SOUNDBITE: (English) Buzz Aldrin, former NASA astronaut: (On performance enhancing drugs in sport)

"You have an obligation to represent your country in the best possible light and getting involved in certain things that are not following the rules is not too good. Not too good for your country, it's not too good for the whole world, because you are looked up to, and you have responsibility. Military, astronauts, all have an image and we just don't want to mess it up. And athletes have temptations, they just do that to be above and enhance performance. We are looking for a human being, not an artificial robot."

SOUNDBITE: (English) Buzz Aldrin, former NASA astronaut: (On his impression of the Rio Olympic Games)

"Well everybody is in the same city, and whatever the conditions are, if the diving pool is green, it's green for everybody, until they clean it up. And then it becomes new, or clear."

SOUNDBITE: (English) Buzz Aldrin, former NASA astronaut: (On which athlete could be a good astronaut)

"I don't know that many. Katie Ledecky? Yeah, she's got a way to go, she already exhibited a pretty good talent, but I don't think she wants to retire from that business."