To prepare for the day when humans travel to Mars, NASA is conducting a one-year experiment in a Mars simulation environment. So what's it like to spend a year in CHAPEA, the Crew Health and Performance Exploration Analog? In this season finale episode, travel through the airlock with voice recordings made by the four-person crew, including what it feels like—and smells like—inside their realistic 3-D printed habitat and how virtual reality gives them the sensation of walking on the Red Planet.