Astronaut Tim Peake has revealed he thought he saw lights of suspected UFOs “moving in formation” in space, only to later realise they were, in fact, droplets of Russian urine leaking from a probe vehicle. Major Peake became the first official British astronaut to join the International Space Station crew in 2015, and during his mission he earned a Guinness World Record for the fastest marathon in orbit. One day, while staring out of the window into the dark abyss, he saw “three lights moving in formation and then there was a fourth,” he told The Graham Norton Show. "We were perplexed, until we realised that what we thought were the far away lights of alien spaceships were actually very close small droplets,” he said. "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." The astronaut, who has released his autobiography Limitless, appeared on the programme alongside Gary Barlow, Nadiya Hussain, Richard Osman and Mariah Carey - who joined from the US virtually. Major Peake said Limitless is "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." Asked by Take That star Barlow if he was scared 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. Major Peake has previously said there is a “high chance” we will soon discover if there is other life in our solar system. "I would be very surprised if there wasn't life elsewhere in the universe,” he said in 2016.