The first of several NASA missions aimed at simulating stays on Mars came to an end in Houston, Texas on Saturday after four volunteers left the NASA-built Mars habitat after more than a year. The two women and two men had spent the last 378 days inside Mars Dune Alpha, a 160-square-metre habitat at Johnson Space Center in Houston designed to mimic conditions on the Red Planet. The mission was the first of a series dubbed Crew Health and Performance Exploration Analog (CHAPEA) that “gives us an opportunity to learn all these critical things about these complex systems and it’s going to make go…