The most challenging aspect of the experiment was the monotony.
PIC: A view of the exterior of the HI-SEAS habitat on the northern slope of Mauna Loa in Hawaii. NASA's Hawaii Space Exploration Analogue and Simulation (HI-SEAS) program officially ended Sunday. (AFP/University of Hawaii at Manoa)
The six people who went into isolation for a year in Hawaii to help NASA plan for a mission to Mars emerged Sunday, happy to breathe fresh air and meet new people.
The team was based on a barren, northern slope of Mauna Loa, living inside a dome that is 36 feet (11 meters) in diameter and 20 feet tall.
French astrobiologist Cyprien Verseux said that he was "feeling excited" about being in the open and eating fresh food again.
The most challenging aspect of the experiment was the monotony, he said in a Periscope interview by organizers posted on Twitter.
Crew members experienced no seasons inside the dome, and were able to go outside only dressed in spacesuits.
Nevertheless he was upbeat about the experiment results.
"A mission to Mars in the near future is realistic," he said. "The technical and psychological problems can be overcome."
The crew also included a German physicist and four Americans -- a pilot, an architect, a doctor/journalist and a soil scientist.
The dome was located in a place with no animals and little vegetation around. The team locked themselves in on August 28, 2015.
The men and women had their own small rooms, with space for a sleeping cot and desk, and spent their days eating food like powdered cheese and canned tuna.
They had limited access to the Internet.
NASA's current technology can send a robotic mission to the Red Planet in eight months, but any astronauts that would travel to Mars face a trip that would take between one and three years.
A typical current stint for an astronaut aboard the orbiting International Space Station is six months.