Good Morning Britain guest astronaut Tim Peake spoke to Piers Morgan and Susanna Reid on Monday where he told a story about a blunder he made in space.
European Space Agency astronaut and former International Space Station crew member Tim, 48, revealed that when he was in space, he looked out of the window and saw an unidentified flying object.
He called his colleagues over to show them, and used his years of space training to try to decipher what the object was.
"This was at the end of the mission, and I was quite experienced about what you should see and what you shouldn't see in space," he explained.
"And I saw three lights flying in formation in the daytime, and the only time you see a light in the daytime is if it's another spacecraft coming towards you.
"So I called over my NASA crewmate and we had a look at this, we couldn't work it out - and then we finally realised it was Russian urine that was leaking from the Progress vehicle!"
Piers and Susanna burst out laughing as Tim continued: "It was crystallizing and reflecting the light back at us, so it wasn't quite the first contact experience that we had been hoping for."
Tim also admitted the number one question he is always asked by children and even adults is about how he goes to the toilet in space.
He said this is a simple answer as it's just air flow allowing everything to happen, and people do not realise what the most interesting part is.
He believes the most fascinating thing is the fact that urine is recycled back into drinking water within 24 hours.
Tim also revealed he grew two inches while in space as the spine is less compressed and starts to stretch out so the seats in the spacecraft have to be made slightly bigger to account for the astronauts' new sizes when they land back down on Earth.
But, he added, they shrink back down once they have returned to Earth.
* Good Morning Britain airs weekdays on ITV at 6am
