A trip to Mars takes about eight months. Round trip, with some time for exploration and sample collection, would be minimum three years. The longest anyone has been in space is one year–NASA astronaut Scott Kelly returned from his year aboard the International Space Station in March of 2016 and is currently being studied to see the effects it has had on his body. In addition to the physiological effects of living in space, there are psychological effects to consider.
NASA has supported the University of Hawii at Manoa to conduct a study with six astronauts living in isolation for eight months on a volcano in Mars-like conditions. They lived in a domed habitat: HI-SEAS. The site was chosen, according to the University, because of its physical isolation and geological similarity to Mars. Communications were stalled so that there was a 20-minute delay on internet communications, the same as would be true on Mars. The astronauts wore space suits every time they went outside, which was usually to conduct geological expeditions.
In a series of five short videos, the last of which premiered in September as the crew exited the habitat, The New York Times chronicled the expedition. The finale is below.