Headaches, nausea or even swollen hands and feet: the test subjects currently ascending at a rapid pace to Europe’s highest building to voluntarily experience altitude sickness have all of these things coming their way. Ten test subjects will gather at the Margherita Hut in the Valais Alps in Italy, where their bodies will be closely monitored to see how they respond to an altitude of 4554 metres above sea level, oxygen depletion and low air pressure. “If astronauts are stationed in a Mars habitat some time in the future, it is extremely probable that they will live and work in an atmosphere with similar pressure conditions,” explains Ulrich Limper, the mission’s medical director from the German Aerospace Center (DLR). “As things stand, though, we are unable to predict which persons will experience altitude sickness and what the causes may be.” A possible explanation: “The oxygen depletion encountered at high altitudes damages the vascular barrier, allowing fluid and proteins to seep into the connective tissue. In some instances, this will produce dangerous oedema in the body, especially in the lungs and the brain.”