Since November 2000, humans have been living in space on the International Space Station (ISS). Although the ISS is a remarkable engineering achievement, human space exploration has proven dangerous and costly. There is no air, gravity or food, and water has to be recycled from sweat, stale breath and urine. As we return to the Moon and aim for Mars, some argue that space colonisation is also immoral, psychologically and socially damaging and unnecessarily expensive. Beatriz De La Pava talks to astronauts, anthropologists, scientists, doctors and philosophers to investigate if it is time to abandon the dream of human space travel and come back down to Earth.