Six scientists have entered a man-made dome on a remote Hawaii volcano as part of a human behaviour study that could help Nasa as it draws up plans for sending astronauts on long missions to Mars.
The four men and two women moved into their new simulated space home on Mauna Loa, settling into the vinyl-covered shelter of 1,200 square feet - about the size of a small, two-bedroom home - for an eight-month stay.
They will have no physical contact with people in the outside world and will work with a 20-minute delay in communications with their support crew - the time it would take for an email to reach Earth from Mars.
The Nasa-funded project will study the psychological difficulties associated with living in isolated and confined conditions for an extended period.
Crammed into a dome with one bathroom, the six carefully selected scientists will spend eight months munching on mostly freeze-dried foods - with a rare treat of Spam - and have only their small sleeping quarters to retreat to for solace.
A video released by the group shows the six scientists in matching red polo shirts arriving and entering the dome to farewell handshakes from programme associates.
Except for the presence of the white van that brought the group, the scene was reminiscent of the Red Planet - the dome set in a barren, rock-strewn and reddish landscape with distant hills giving the feel of a wind-swept and forbidding environment.
"I'm looking forward to building relationships with my crew," said mission commander James Bevington, a space scientist.
"I fully anticipate coming out with five new best friends."
Nasa hopes to send humans to an asteroid in the 2020s and Mars by the 2030s.
"We're hoping to figure out how best to select individual astronauts, how to compose a crew and how to support that crew on long-duration space missions," said principal investigator Kim Binsted, a University of Hawaii science professor.
The team members include engineers, a computer scientist, a doctoral candidate and a biomedical expert. They were selected from 700 applicants subjected to personality tests, background checks and extensive interviews.
"When I started, my biggest fear was that we were going to be that crew that turned out like Biosphere 2, which wasn't a very pretty picture," Mr Bevington said.
The experimental greenhouse-like habitat in Arizona became a debacle in the 1990s. It housed different ecosystems and a crew of eight to try to understand what would be needed for humans to live on other planets.
The participants were supposed to grow their own food and recycle their air inside the sealed glass space, b ut the experiment soon spiralled out of control, with the carbon dioxide level rising dangerously and plants and animals dying.
The crew members grew hungry and squabbled so badly that by the time they emerged two years later, some of them were not speaking to each other.
The University of Hawaii operates the dome, called Hawaii Space Exploration Analogue and Simulation, or HI-SEAS, and Nasa has dedicated more than 2 million dollars to this stage of the project.
Scientists have previously lived in the dome for two other long-term Nasa-funded stays - one of them lasting a year, the other eight months - to study food requirements and crew cohesion.
A number of other Mars simulation projects exist around the world, but one of the chief advantages of the Hawaii experiment is the rugged, Mars-like landscape, on a rocky, red plain below the summit of the world's largest active volcano, the Big Island's Mauna Loa.
The dome has a kitchen, laboratory and bathroom, plus small sleeping quarters for each member. Unlike Biosphere 2, it will not be airtight.
To maintain the crew's sense of isolation, bundles of food, including some canned goods and snacks, will be dropped off a distance from the dome, and the team members will send a robot to retrieve them.
The participants will not be confined but will wear spacesuits whenever they step outside for geological expeditions, mapping studies or other tasks.
They will wear instruments measuring their moods and proximity to other team members and use virtual reality devices to simulate familiar and comforting surroundings.