Last week, six people entered a two-story, 1,500-square-foot dome on the slopes of Hawaii's Mauna Loa. For the next eight months, they'll have to wear a spacesuit when they leave the dome, and their primary contact with the outside world will be limited to email, to which they'll have to wait 40 minutes for a response.

Why? To train for what conditions would be like on Mars, so scientists can learn how humans respond to the isolation and social effects of a spaceflight journey to the Red Planet, a mission that would take years to complete.

They're part of a NASA-funded study with the University of Hawaii and Cornell University called Hawaii Space Exploration Analog and Simulation, or HI-SEAS, which has already conducted four-month-long missions with several team members in 2013 and earlier this year.

As The New York Times notes, sending astronauts to Mars – a mission NASA plans sometime in the 2030s – will require people who can withstand years of living in a small space, without contact with loved ones.

NASA's plan to date involves a flight to Mars that lasts about six months, a mission on the planet that lasts about 500 days, followed by a six-month flight back to Earth. By contrast, the Apollo 11 mission to the moon in 1969 lasted about eight days, from the time the astronauts blasted off on July 16-24, when they landed safely back on this planet.

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That's why NASA wants to find out how the six team members currently in the dome on Mauna Loa react, especially after they've been there for months.

“Right now, the psychological risks are still not completely understood and not completely corrected for,” said University of Hawaii at Manoa Professor Kimberly Binsted, the principal investigator with the project, in an interview with the New York Times. “NASA is not going to go until we solve this.”

About 150 people applied to participate in the Mauna Loa mission, for which NASA has thought of nearly everything. Solar panels supply power to the dome, which has a 3-D printer that will allow the crew to make anything they forgot "back on Earth," including hair clips or replacement parts for equipment, notes Wired.

They even repurpose their food waste – yes, their poop – in composting toilets to plant food for those on the next mission. And they exercise in shifts to videos like P90X, or play balloon volleyball inside the high ceilings of the 36-ft-diameter dome.

But the main findings NASA hopes to gather are psychological. “This is a fantastic group of people,” mission participant Neil Scheibelhut told the New York Times. “Right now, everything is wonderful.”

He added he knew that conflicts and "unpleasant patches" are inevitable, however. “Eight months — you’re going to have real conflicts you’re going to have to work out,” he added. “Scientifically speaking, it’s going to be really interesting to see what happens.”

Learn more about the mission at Hawaii Space Exploration Analog & Simulation.