the humans inside the spacecraft. the primary purpose of hera is to learn about the effects of isolation and confinement on people. so a lot of the studies that we do are behavioural or psychological in nature, looking at the type of isolation from people. so you're really only talking to or in contact with the other crew members that are in the vehicle with you or mission control that's supporting you. yeah, astronauts on future missions to mars have more to worry about than the toxic soil, the deadly atmosphere and high levels of radiation. they also have to worry about each other. and it's hard to say which of these would be more likely to result in someone�*s death. and it's consistent, low—level stress over time. little things start to grate