The trials don’t end once astronauts are in orbit. Every mission is high-stakes, with the possibility of making a fatal misstep always lurking ahead. According to NASA’s Human Research Program in Behavioral Health and Performance, severe sleep deprivation, coexisting in confined environments, and performance pressure all put astronauts at high risk for emotional distress and anxiety. “Working during the space walks was very stressful,” says former astronaut, now Columbia professor Dr. Mike Massimino of his shuttle missions to the Hubble Telescope.

“I say I like it — but it was also pretty stressful out there.”