Their extended stay could have health consequences

 On March 14, a journey that was originally supposed to be a little over a week — but was stretched out to nine months — came to an end. NASA astronauts Suni Williams and Butch Wilmore were selected for the first crewed test flight on Boeing's Starliner and were only supposed to stay at the International Space Station for 10 days, but when NASA discovered several helium leaks and propulsion system issues on the spacecraft, the agency decided to send it back empty until another mission could be sent up to get the astronauts. 

This isn't like some low-gravity version of "The Terminal," in which travelers are stuck in limbo due to some administrative glitch. Space can have devastating and profound health effects on astronauts, which means Williams and Wilmore's extended stay on the ISS could result in pronounced impacts on their bodies.

Launching into space requires undergoing g-force more than double that of what we experience on Earth, which former NASA astronaut Dr. Sandy Magnus once described as feeling like having a “70-pound gorilla sitting on your chest.” But that’s the last of gravity astronauts feel before reentering the Earth’s atmosphere once their mission is complete, and once they enter orbit they will spend the rest of their time in space floating in their seats. 

But the effects of gravity — or lack thereof — are just the beginning of how space manipulates the human body. Everything from worsening eyesight to genetic changes to skin rashes that develop upon arrival — even no longer feeling accustomed to the touch of fabric on one's clothes — have been reported in people who have gone to space.

“In general, the environment in space causes an accelerated model for disease, and what we kind of say is an accelerated model for aging,” said Dr. Afshin Beheshti, director of the Center for Space Biomedicine at the University of Pittsburgh. “But you don’t age faster, it’s just that all of the things associated with aging, like cardiovascular risk or cognitive issues … Everything is kind of sped up in space because of that environment."

This week, four astronauts took off to the ISS, where the spacecraft will pick up Williams and Wilmore before returning home. At this point, Williams and Wilmore have been in space for nine months, joining just eight other astronauts who have spent more than 200 days in space. (NASA astronaut Frank Rubio holds the record at 371 days.) From what we know about the impacts of space on health, it will take them some time to recover from the journey.

“When we get back, even to lift a pencil we will feel the weight,” Wilmore said in a CNN interview last month. “That’s the transition back.”

That's in part because on Earth, the force of gravity constantly acts on the skeleton, which stimulates bone-building cells called osteoblasts that maintain our bone density. Without that force, bone density and muscles can atrophy and weaken, with bones becoming 1% less dense for every month spent in space without any measures performed to combat bone loss. 

Although Williams and Wilmore exercise daily to mitigate these effects, they will still likely have experienced significant bone density loss when they get back. Upon landing, Wilmore and Williams will be met with medical teams who can help them get started on a 45-day post-mission recovery program, said NASA's Lead Flight Surgeon Dr. Stevan Gilmore.