What returning to lunar space means for human health

Preparing to send astronauts back to the moon is no small feat. Spaceflight exposes the body to both known and unknown risks, some of which are subtle, cumulative and difficult to predict. When humans were last on the lunar surface in 1972, they stayed for just over three days. On that final mission, Apollo astronauts tracked fine gray dust, which they described as smelling like burnt gunpowder, back into their spacecraft on boots, gloves, and suits. The lunar dust particles clung stubbornly to surfaces, irritated their eyes and throats, and left some crew members with what they described as a kind of “lunar hay fever.”