NASA runs fake space missions on Earth. These simulations — called analog missions — allow scientists to study what a long space mission would be like for the crew. Some analog missions study the use of specialized technology or the effects of zero gravity on the body, but others focus primarily on psychological effects.

The HI-SEAS mission, or Hawaii Space Exploration Analog and Simulation, takes place near the Mauna Loa volcano in Hawaii and is designed to simulate living on Mars. Crew members live in isolation for about 8 months and aren't allowed to stray further than a mile or two from their small, dome-shaped habitat. Scientists study the impact this has on the crew's mental and emotional state. Following is a transcript of the video.

If we ever send a manned mission to Mars, everyone aboard will travel further from Earth than anyone ever has. They’ll set foot on land no human has ever seen, touched, or explored. It would be a life-changing opportunity for whoever gets chosen.

Elon Musk: "It would be an incredible adventure. I think it would be the most inspiring thing that I could possibly imagine."

Getting to Mars is going to be a really long trip. And it will require living in extremely cramped quarters — no bigger than a motor home — with just five other people for at least nine months. And then living and working in small, specially-designed habitats once they get there.

But before the countdown to launch can begin, NASA is studying what it would be like to live there. Enter Analog missions — scenarios created to simulate living in an extreme environment. These allow scientists to study how a crew might behave on a real space mission. And it’s a way for the crew to troubleshoot problems in a place that is safer than outer space. A place like … Earth.

Joshua Ehrlich: "It's always been a little bit of a dream of mine. I mean I — my dream is to become an astronaut and head to Mars."

That’s Joshua Ehrlich. He was the biologist on the crew of the HI-SEAS Mission — a NASA analog designed to simulate living on Mars. The HI-SEAS mission has happened five times so far, always in a remote part of Hawaii.

Like Matt Damon’s character, Mark Watney, in “The Martian,” Ehrlich’s focus was to grow vegetables inside the habitat.

Joshua Ehrlich: "Hi everybody, this is Josh Ehrlich calling to you live— 20 minutes live that is — from the HI-SEAS habitat."

The crew could go outside of the habitat, but not without wearing hazmat suits, meaning no fresh air, and the only plant life the crew saw, touched, or ate, came from Josh’s little garden.

Joshua Ehrlich: “To see and just to watch the crew members eat a vegetable for the first time — like a real vegetable, not something that’s dehydrated or freeze-dried — it was truly worthwhile experience as a crew member because you’re providing to them.”

Not only is it logistically challenging to live inside a geodesic dome for eight months even if you’re on Earth, it can also do a number on your psychological state. One of the biggest concerns with a long space mission is the impact it has on the crew’s mental and emotional well-being. It’s one big psychological experiment.

So, what’s it actually like living in isolation with just five other people for eight months?

Joshua Ehrlich: “It slowly adds up till you realize, man, I miss feeling the wind. I miss getting a sunburn. I miss jumping into the ocean.”

Josh’s duty to his crew and to the mission kept him invested in the project, but dedication in itself can’t be enough to keep everyone sane and on good terms with each other, right? Conflicts will come up. People will inevitably get on each other’s nerves.

Joshua Ehrlich: “Communication, when you are all on the same page, man, you can do anything. If there’s something bothering you just say it. A few words can go miles to getting things done — to accomplishing.”

What Josh learned on this mission, he says, can be applied to anyone. These aren’t just rules to live by when you’re trapped in a dome in Hawaii pretending you’re on Mars.

Joshua Ehrlich: “Always keep it in the back of your mind that we’re all in this together, so that can be spoken for HI-SEAS and also here on Earth. How we treat our planet, how we interact with each other, how we live with family members and friends, we’re all in this together so let’s focus on going forward, not backward.”