The crew has been restricted to a dome as part of a Nasa-backed study into surviving on Mars.
The crew of four men and two women were placed into quarantine on a vast plain below the summit of the world’s largest active volcano in January.
It has sparked speculation that the space agency hopes to send humans to Mars by the 2030s.
Samuel Payler, a doctoral candidate at the University of Edinburgh, became the first UK citizen to participate in the research when he entered the dome in January, on the fifth such mission.
The Hawaii Space Exploration Analog and Simulation (HI-SEAS team), from the University of Hawaii, began sending people into isolation in 2012, in a bid to assess how humans react to it.
Kim Binstead, from the University of Hawaii said: “This is our fifth mission, and we have learned a lot from those five missions.
“The previous three missions, the four, eight and 12 month missions, those were primarily looking at crew cohesion and performance.
“On this mission and going forward we are looking at crew selection and composition.”
Surviving on canned and freeze-dried food, they were only allowed outside in their suits.
The researchers are part of a study designed to better understand the psychological impacts that a long-term manned mission to space would have on astronauts.
The data they gathered will help Nasa better pick crews that have certain traits and a better chance of doing well during a two-to-three year Mars expedition.
All of their communications with the outside world were subjected to a 20-minute delay – the time it takes for signals to get from Mars to Earth.
The Hawaii team wore specially-designed sensors to test their moods and proximity to other people in the small, 1,200 square-foot (111-square meter) dome where they have lived.
The devices monitored, among other things, their voice levels and could sense if people were avoiding one another.
It could also detect if they were next to each other and arguing.
The crew played games designed to measure their compatibility and stress levels.
When they got overwhelmed by being in such close proximity to each other, they could use virtual reality devices to escape to tropical beaches or other familiar landscapes.
The project is the fifth in a series of six Nasa-funded studies at the University of Hawaii facility called the HI-SEAS.
Nasa has pledged about £1.8million to the studies at the facility.