The private Dutch-based Mars One project is proposing to select a group of 40 would-be civilian astronauts this year, aiming to send four of them on a no-return journey to to the red planet in 2022.

Experts have questioned both the financial and practical viability of the mission, but that hasn’t stopped people signing up in droves, including 30,000 Americans, CNN reported.

The estimated cost for the initial mission is $6 billion (£3.87 billion) which Mars One hopes to raise through sponsors and selling broadcasting rights to media companies, including a reality show of the colonisation project.