Two astronauts stuck in space for 9 months have returned to Earth

After spending more than nine months orbiting Earth, two U.S. astronauts finally returned home on March 18, splashing down at 5:57 p.m. EDT off the coast of Tallahassee, Fla. Suni Williams and Butch Wilmore emerged from the SpaceX Dragon capsule that carried them home, smiling, waving and giving thumbs up. Now they’ll undergo a battery of tests to find out how the longer-than-expected space stay has impacted their health.

The pair left on June 5 for what was supposed to be an eight-day mission to the International Space Station. But the Boeing Starliner that the duo launched in — the spacecraft’s first flight test with crew — experienced technical issues as it neared the ISS. Williams and Wilmore had planned to return to Earth aboard the vehicle, but NASA delayed their flight, bringing back a crewless Starliner.

Months later, the astronauts hitched a ride home with SpaceX. It’s far from the first time people have been stuck in space, or the longest stay there. Frank Rubio holds the American record at 371 consecutive days, while Russian cosmonaut Valeri Polyakov claims the all-time record after spending 437 consecutive days in space. 

Still, such long durations in space are hard on the body. Astronauts often experience bone and muscle loss, vision impairments, shifts in brain structure and immune dysfunction, among other issues. The difference in health impacts between nine months and eight days in space “would be pretty dramatic,” says applied physiologist Rachael Seidler of the University of Florida in Gainesville, who studies spaceflight’s effects on the brain.

“The longer someone has been in space, the larger the magnitude of change,” she says. The rate of change isn’t linear, though. After six months, it seems to slow down, Seidler notes.

Williams and Wilmore will now undergo a series of intense medical tests from NASA called Spaceflight Standard Measures. The agency will extensively examine the astronauts’ cognitive abilities, blood, urine, microbiomes, cardiovascular systems and more, many of which were also assessed preflight and in-flight.

Seidler expects the pair to have some balance problems for the first few days to weeks. The vestibular system in the inner ear, which helps individuals sense where their body parts are, relies on gravity, and the microgravity of space can mess with it. Williams and Wilmore may also have vision changes. About 70 percent of astronauts who spend six months or more in space experience swelling in the backs of their eyes. It’s associated with a cluster of structural changes, including flattened backs of the eyes and kinks in the nerves that carry visual information to the brain, Seidler says.

Another big question is the immune system’s response during spaceflight, says bioastronautics researcher Eliah Overbey of the University of Austin in Texas. She and her colleagues assessed health data from the SpaceX Inspiration4 civilian crew, who spent three days in space. Some of the crew’s immune cells underwent DNA reorganization, she says. “We’re wondering how, over time, this could impact the body’s ability to respond to disease.”

Williams and Wilmore’s tests may help answer such questions. “Our ability to be competitive in space exploration is going to depend on our ability to keep astronauts healthy,” Overbey says.