Before we can send humans to Mars, we’ll need to select people who can live and work together in an extreme and distant environment. So how do we figure that out? One way is to re-create Mars here on Earth.

That’s where HI-SEAS comes in. It’s a fake interplanetary habitat located on an active volcano on Hawaii’s Big Island. From 2013 to 2018, the University of Hawaii operated simulated Martian missions inside the habitat. For months at a time, people would live inside HI-SEAS, re-creating the conditions they might experience during a Mars mission. That meant conserving water, eating preserved foods, and simulating the delay in radio communications between Earth and Mars. They also couldn’t go outside of the habitat unless they were wearing a full suit.

The University of Hawaii ran five successful simulations with HI-SEAS. However, its sixth mission was cut short early in 2018 after a crew member was injured when trying to turn on a backup generator. Now, HI-SEAS is in a state of transition. The owner of the habitat decided to repurpose the structure to do simulated Moon missions since NASA has recently refocused its attention on sending humans to the lunar surface again. However, it’s possible that HI-SEAS may host simulated Mars missions in the future, too, possibly as soon as 2020.

Either way, simulating human missions to Mars will be critical before we do the real thing, and habitats like HI-SEAS could tell us a lot about the people who may be right for the trip.