When Nasa’s first rover set down on the surface of Mars in 1997, its streamed colour images caused an early internet sensation. After centuries of dreaming, here we were, at eye level to our closest potentially habitable neighbour, and the sight was as bleakly majestic as we could have imagined: a rocky, red desertscape on a scale entirely alien to Earth. One mountain, Olympus Mons, was the largest in our solar system (three times the height of Everest, with a footprint the size of Sweden); dune-seas swept its northern hemisphere while 7km-deep canyons veined the south.

Watching on a clunky desktop computer in the Dutch university town of Twente, 20-year-old Bas Lansdorp’s first thought was one of wonder; his second of longing (“I want to go there!”), then the melancholy realisation that, being Dutch, he could never fly with Nasa. So he’d have to do it himself.

What kind of a person thinks such outlandish thoughts, then tries to make them real? Eighteen years later, Lansdorp and I are on a train en route to Heathrow, discussing Mars One, a real company with real investors and a fledgling astronaut training programme, while our fellow passengers fall silent and pretend not to earwig. Lansdorp has a brusque, crystal-eyed positivity; a boyish charm you see in many entrepreneurs that, combined with his Dutch accent, makes him seem sincere and persuasive. All the same, the woman next to me has been staring at the same smartphone screen for the past 10 minutes, and her thought bubble reads: “This man is talking about going to Mars. Soon. Like he means it. Am I dreaming?”

Lansdorp began by thinking about Mars as an intellectual exercise, a hobby: how might a privately funded Mars mission actually work? He knew that when George Bush Sr ordered Nasa to cost the trip in the early 90s, they came back with a figure of $450bn, after which human travel to Mars became the mad uncle in the shed of space. One Nasa engineer I spoke to identified a “giggle factor” attending its very mention at the agency.

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