‘I was posting the chapters to my website, and people were commenting on it, helping me make the science work. I needed that dust storm to put Watney in the situation he was in. ‘I told everyone there had to be a bit of dramatic licence. I discovered there were a lot of people like me out there.’Īpart from a dust storm near the start (an impossibility thanks to the thin Martian atmosphere), the story is 100 per cent technically accurate. ‘I’d watch a film like Gravity and pick holes in it because the science was wrong. He went back to work as a computer programmer and started a website, Galactanet, gaining a small but loyal following for his short stories that were loaded with technical data. After being laid off from his job at AOL, he tried to make it as a writer for three years ‘but failed abjectly’. Weir, the son of a particle-physicist father and electrical engineer mother (who divorced when he was eight), always wanted to write but trained as a programmer. Weir, 45, is a former computer programmer, who meticulously researched every detail in The Martian to make it scientifically spot-on ‘It’s like a rock band that has a hit first album 20 years in the making and then you get a year to write the follow-up.’

‘I realise The Martian is probably going to be the most successful novel I ever write,’ he says.

For Weir, whose self-confidence and quick wit reminds you of Mark Watney, the central character from The Martian, jokes that his new book is ‘doomed’. Indeed, The Martian is now required reading at Nasa, is taught in science classes in schools across America and has earned him millions of fans, who are all eagerly awaiting his follow-up. Everything in there from the calories it would have taken to survive to the trajectory of the spacecraft, it was all good.’ When he got stuck, in scenes such as how his protagonist would grow potatoes in the planet’s shallow red soil, he sent out questions to his online fanbase, which included real-life astronauts and astrophysicists: ‘They helped me. Weir, 45, a former computer programmer, meticulously researched every detail in The Martian to make it scientifically spot-on. Andy Weir's debut novel The Martian sold more than three million copies in print and earned £480 million at the box office

Andy weir the astronaut