British astronaut and former Army Air Corps officer Major Tim Peake has said he thought he saw UFOs while in space.
He later discovered they were in fact droplets of liquid leaking out of a Russian probe vehicle.
Major Peake, who spent six months in space, told the BBC's Graham Norton Show: "Space is very black and one day I was looking out and there were three lights moving in formation and then there was a fourth.
"We were perplexed, until we realised that what we thought were the faraway lights of alien spaceships were actually very close small droplets.
"What was happening was liquid leaking out of a Russian probe vehicle, crystallising instantly and reflecting the light. What we were seeing was Russian urine."
When asked if he is ever scared at the thought of going into space, Major Peake said: "There is always a thought at the back of my mind that I am rolling the dice, but the overriding feeling is of adrenalin-fuelled excitement.
"Walking in space feels incredibly exposed and the danger is palpable out there."
He was also asked if he hopes to return to space.
"I’d love to – absolutely. In fact, we are all slated for a second mission between now and 2024. I’m waiting by the phone," he said.
The astronaut also discussed his autobiography Limitless, released in October, saying it's "really the journey from young boy to astronaut", adding: "I feel a bit of a fraud because as a boy I had no ambitions at all of wanting to be an astronaut – I was obsessed with being a pilot."
Major Peake became the first official British astronaut to join the International Space Station crew in 2015.
During his mission, he earned a Guinness World Record for running the fastest marathon in orbit.
Major Peake appeared on the programme alongside Gary Barlow, Nadiya Hussain, Richard Osman and Mariah Carey – who joined from the US virtually.
The Graham Norton Show airs on BBC One on Friday at 10.45pm and is also available on BBC iPlayer.
Cover image: Tim Peake pictured running a 42km marathon while on board the International Space Station in April 2016 (Picture: PA).