Four volunteers are enduring year-long isolation in NASA's Mars habitat simulation to test human endurance for potential future Red Planet exploration. Olivia Palamountain reports

Four volunteers are currently midway through more than a year sealed inside NASA's 3D-printed Mars habitat simulator named Mars Dune Alpha.

The second Crew Health and Performance Exploration Analogue (CHAPEA) mission began in spring 2025, confining the volunteers inside the 1,700 sq ft structure at NASA's Johnson Space Centre in Houston, for 378 days.

The habitat, developed by Danish architecture firm BIG (Bjarke Ingels Group), includes private living quarters, a gymnasium, a vertical farm for growing crops, a medical bay and a robotics work area, alongside a 1,200 sq ft "sandbox" filled with red sand that replicates the Martian surface beneath an inflatable dome.

Participants will experience realistic communication delays of up to 22 minutes each way when contacting mission control or family members, matching the time it takes radio signals to travel between Earth and Mars.

The crew was selected following an application process that closed in April, and represents the middle mission of three planned CHAPEA experiments, with the third scheduled to begin following this mission's completion in 2026. The selected participants will receive compensation for their involvement in the mission.

"Mars is a hostile environment not inherently conducive to human life, so we need to learn how we can support crew to live and work there," Dr Suzanne Bell, a psychologist at NASA and the mission's co-investigator, tells The Times. "The crew we select are incredibly astronaut-like individuals. They aren't just people who didn't have anything to do with their lives for a year." Crew members conduct simulated spacewalks lasting up to six hours using virtual reality headsets whilst walking on special treadmills that replicate Martian terrain. Daily tasks will include operating drones and rovers, maintaining equipment, conducting scientific experiments, exercising and tending the vertical farm to grow crops such as tomatoes and peppers to supplement freeze-dried meals.

The simulation replicates harsh Mars mission conditions including isolation, limited water and food supplies, equipment malfunctions and communication delays. Unlike the International Space Station, which receives regular supply deliveries, the Mars simulation operates under strict resource limitations with no fresh food deliveries during the mission. Water recycling includes processing crew members' urine, mirroring systems planned for actual Mars missions.

NASA selected participants from US citizens or permanent residents aged 30-55 who hold master's degrees in STEM fields with at least two years of professional experience, or equivalent qualifications including medical degrees, doctoral programmes or pilot training with minimum 1,000 flight hours. Candidates were required to be non-smokers and demonstrate strong teamwork abilities."Teamwork is absolutely essential for Mars because there's no abort capability; you can't bring people back, you can't swap out people," Bell explains to The Times. "At the end of the day there will be challenges, there will be things we didn't expect and that crew has to get along and work together to solve it."

The mission addresses critical unknowns about long-duration space missions, particularly the psychological effects of confinement and isolation. The first CHAPEA crew, who completed their mission last year, reported missing natural elements like green grass, blue skies and fresh air on their faces.

Communication delays create particular challenges for emergency responses. "Some of our tech demos have to do with artificial intelligence providing feedback to the crew, in order for them to troubleshoot different medical scenarios," Bell tells The Times, noting that waiting for Earth-based assistance could prove fatal during actual emergencies.Remote research teams will monitor participants' physical and psychological health throughout the mission, collecting extensive data on stress responses, cognitive performance, and overall crew dynamics. The information will inform life support systems, crew selection processes and mission planning for actual Mars expeditions.

The mission forms part of NASA's broader Artemis programme, which aims to return humans to the Moon by 2027 as preparation for eventual Mars exploration. The Mars journey would require seven to ten months travel each way, with crews staying on the planet's surface for up to 18 months.

BIG's 3D-printed habitat, constructed using lavacrete - a concrete-like substance - demonstrates technology that could be used on Mars itself, utilising local dust and rock rather than transporting construction materials from Earth. This approach addresses the impractical costs and logistical challenges of hauling building supplies across millions of miles of space.