How being stuck in space changes an astronaut’s body

Smaller hearts, poorer vision and added height are among the effects caused by weightlessness.

NASA's Butch Wilmore, Russia’s Alexander Gorbunov, NASA’s Nick Hague and NASA's Suni Williams wait to exit the SpaceX capsule after splashing down. Picture: SpaceX via AP

When astronauts Sunita Williams and Barry Wilmore return to Earth on Tuesday after spending nine months on the International Space Station, their bodies will have undergone significant changes.

The SpaceX capsule carrying the astronauts is expected to splash down off the Florida coast just before 6pm ET (9am AEDT) on Tuesday.

The pair were supposed to spend eight days on the station, but a malfunctioning spacecraft left them stranded without a ride home until now.

This nine-month sojourn will have made them taller, weaker and maybe given them vision trouble, according to medical studies of previous astronauts.

Many astronauts’ bones never fully recover, according to a 2022 study in the journal Scientific Reports.

Often, astronauts must wear prescription glasses upon their return. And, for a time, they will be taller.

When astronaut Scott Kelly returned home in 2016 after spending almost one year in space, he had gained 2 inches (5cm) in height.

Weightlessness also causes body fluids to shift from astronauts’ legs toward the centre of their bodies.

In November, concerns were raised online about the health of Williams, whose face appeared gaunt in several images.

Questions were raised in November about the gaunt appearance of NASA astronaut Sunita Williams, pictured with 'alien'. Picture: X

Williams said that a fluid shift and additional muscle she had built in space changed the way she looked.

“There is a lot of changes that go on up here. I think there is some rumours going on that I’m losing weight,” Williams said during a November 12 interview with New England Sports Network.

“I’m the same weight that I was when I got up here.”

The space station orbits about 250 miles (400km) above the Earth’s surface, putting its occupants at a slightly higher risk of exposure to harmful space radiation.

Astronauts wear radiation-detecting devices called dosimeters to check how much radiation each of them has received during time on the station.

Once astronauts, over their careers, reach a certain level of exposure, the National Aeronautics and Space Administration bars them from returning to space.

NASA doctors will be checking astronauts for signs of cancer for the rest of their lives.

Astronauts exercise on board the station to help lessen some of these physiological problems, and each astronaut responds differently to the rigours of space.

After landing, Williams and Wilmore will be taken to NASA’s Johnson Space Center in Houston, where NASA doctors will check their vital signs and test them for short-term illnesses and potential long-term health effects.

Then, they will go through a 45-day recovery program that includes two hours a day of exercise, medical and performance testing, and scientific tests, according to NASA.

“Generally, most crew members’ physiological systems recover within this time frame,” NASA said in a statement issued Monday.

Dow Jones