The six people who went into isolation for a year in Hawaii to help NASA plan for a mission to Mars has completed their work.
The team was based on a barren, northern slope of Mauna Loa, living inside a dome that is 36 feet (11 meters) in diameter and 20 feet tall.
Crew members experienced no seasons inside the dome, and were able to go outside only dressed in spacesuits.
The dome was located in a place with no animals and little vegetation around. The team locked themselves in on August 28, 2015.
The men and women had their own small rooms, with space for a sleeping cot and desk, and spent their days eating food like powdered cheese and canned tuna.
They had limited access to the Internet.
NASA’s current technology can send a robotic mission to the Red Planet in eight months, but any astronauts that would travel to Mars face a trip that would take between one and three years.