Long-term missions to the Moon and Mars will need a good understanding of the machines, the environment – and the people. Friction among crew members could make a mission much less productive – or even endanger lives.

To minimize the risk, scientists are trying to understand how people get along during long periods of isolation. They’ve conducted test runs in laboratories. They’ve set up habitats on volcanoes and remote islands. They’ve studied research bases in Antarctica. And they’ve sent volunteers into the oceans.

As with space travel, an undersea habitat is isolated and cramped, and the environment can be deadly. So it’s important for the crew to get along.

NASA has conducted quite a few underwater expeditions. For many of them, astronauts spent a few days or weeks in a habitat off the coast of Florida. They conducted experiments both inside and outside the lab. They tested equipment and techniques that might be used in space. And scientists checked out how well they worked as a team.

Recently, the European Space Agency sent 25 volunteers on a two-month trip aboard a submarine. Scientists used questionnaires to check on the volunteers. They also took samples of hair and saliva. The results helped track stress markers, changes in the immune system, and other reactions – better understanding the human factor in long-term missions to other worlds.

Script by Damond Benningfield