After a year, four scientists in the United States on Saturday ended an experiment that simulated life on Mars. To loud applause, the four volunteers left NASA-built Mars Dune Alpha, where they had spent the past 378 days completely isolated from the outside world. The 160-square-meter structure at the Johnson Space Center in Houston was designed to mimic conditions on the Red Planet. The habitat is a 3D-printed facility, complete with bedrooms, a gym, common areas, and a vertical farm for growi...