The crew of NASA's year-long Mars simulation has switched to living on Martian time. In late September, the four CHAPEA-2 volunteers began following 24-hour-40-minute sols, matching the length of a day on Mars.

The crew members are Ross Elder, Ellen Ellis, Matthew Montgomery and James Spicer. They have been living inside a 3D-printed Mars habitat at the Johnson Space Center, testing what a real Mars mission would demand of its astronauts.

Living on Mars time is one of the mission's toughest psychological tests. Each day starts 40 minutes later than the last, steadily desynchronising the crew from Earth's rhythm. Real Mars astronauts would face the same challenge.

The mission ends on October 31, 2026. Data from CHAPEA-2 will feed into NASA's planning for eventual crewed missions to the Red Planet, including studies of crew health, performance and cohesion. The crew grows its own food and conducts simulated spacewalks in the mock Martian landscape. Every activity is monitored by mission control in Houston.