The group of six spent a year living in a dome, on a volcano in Hawaii, with almost no contact at all from the outside world.
The experiment was designed to help scientists understand the human challenges involved in exploration to Mars.
The volcano was chosen because its soil is thought to be similar to the surface of Mars.
To make the 'mission' as realistic as possible, the team had to live without any of their home comforts, and were only allowed to go outside if they were wearing spacesuits.
They each had a small bed and a desk, and their food included things like powdered cheese and canned tuna.
But the biggest challenge was probably the lack of privacy - while they couldn't talk to their friends and family at home, they also couldn't get away from the rest of the team, so it was important to get on well!
The team included scientists - astro-biologist, a physicist, and a soil scientist - as well as a pilot, an architect, and a journalist, and they came from America, France, and Germany.
Pizza and bananas were top of the list of foods they'd missed the most, but the team said that they're confident that a mission to Mars could succeed.
They may not have actually left planet Earth, but a team who've spent a year living as if they were on a mission to Mars say they think they could survive the real thing.