A crew of 4 NASA volunteers will be locked in a virtual 'Mars' for 378 days. Here's why.

A group of four NASA volunteers have embarked on a 378-day mission in which they will be locked in a ground-based simulation of the planet Mars.

The mission, which began Sunday, is the first of three year-long Mars surface simulations, according to NASA. During the mission, crew members will live and work in a 3D-printed, 1,700-square-foot habitat.

NASA says researchers will simulate the challenges of a human mission to Mars, including resource limitations, equipment failure and communication delays.

The crew will also carry out different types of mission activities, including simulated spacewalks, robotic operations and habitat maintenance.

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The four-person team consists of research scientist Kelly Haston, structural engineer Ross Brockwell, emergency medicine physician Nathan Jones and U.S. Navy microbiologist Anca Selariu. Haston will serve as the crew's commander.

The quartet were selected from a pool of applicants to be part of NASA's Crew Health and Performance Exploration Analog, or CHAPEA.

"Thank you all for your dedication to exploration," said Grace Douglas, the mission's principal investigator at NASA, during a briefing Sunday before the crew entered the habitat.

"The crew has worked so hard this month to get ready for this mission," Haston said. 

"It has been very special to be a part of such a tremendous group of scientists and specialists from a diverse set of backgrounds working together to bring CHAPEA 1, the first of three missions, to reality," she added.

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