Experts Reveal How 9 Months in Space Transformed Astronauts’ Bodies & Health
After an unexpected nine-month mission, NASA astronauts have finally returned to Earth. But their return is only the beginning, as scientists say their bodies could have undergone dramatic changes, and the road to recovery will be grueling.
Experts revealed the stunning rigors the human body undergoes during prolonged space travel — from developing “chicken legs” and weakened bones to changes in eyesight and even increased radiation exposure.
NASA James Free, Ken Bowersox, Steve Stich, and Dana Weigel during a news conference to discuss plans to return two astronauts who remain stranded at the International Space Station, at Johnson Space Center in Houston, Texas, on August 24, 2024. | Source: Getty Images
Now, two NASA astronauts must retrain their bodies to walk, rebuild their strength, and readjust to gravity after spending nearly a year in microgravity. Their story has captivated many, but what happens next may be just as fascinating.
The CST-100 Starliner spacecraft launching from Space Launch Complex 41 at Cape Canaveral Space Force Station on June 5, 2024, in Cape Canaveral, Florida. | Source: Getty Images
A Mission That Stretched Beyond Expectations
When NASA astronauts Sunita Williams and Barry Wilmore launched toward the International Space Station (ISS) in June 2024, they expected to return to Earth in just over a week.
However, while en route to the space station, their spacecraft, the Boeing Starliner, experienced helium leaks and thruster malfunctions, raising concerns about its reliability for a safe return.
Barry Wilmore and Sunita Williams responding to questions during a media briefing on March 22, 2024. | Source: Getty Images
As the situation unfolded, it became clear that the risks were too great. By September 2024, NASA decided to send the Starliner capsule back to Earth empty, leaving Wilmore and Williams aboard the station without a return vehicle and extending their stay to more than nine months.
As their mission stretched far beyond its original timeline, their story became a household one across America. The astronauts gave interviews from space, sharing updates on their experience.
However, amid the widespread attention, concerns surfaced online, with netizens speculating about possible physical changes such as weight loss due to prolonged microgravity exposure.
Despite their situation worrying those on the ground, the pair stuck in space have stayed busy with ISS maintenance and scientific research, including studies on the effects of prolonged weightlessness on the human body.
“Sunita looks exosted ;( I dont think that they are enjoying this prolongation [sic],” one person shared. “WHOA! They ain’t telling us the truth up there. That looks like starvation,” another person commented.
A third netizen wrote, “Hope they’re staying healthy up there,” while a fourth added, “Is she slimmer than before.” To address these concerns, NASA and the astronauts reassured the public that the latter were under constant medical supervision and following strict health protocols.
Dr. JD Polk, NASA’s chief health and medical officer, said, “The crew’s health is regularly monitored by dedicated flight surgeons back on Earth.” He emphasized that Williams and Wilmore followed personalized diet and fitness routines to stay healthy in space and prevent muscle and bone loss.
The Dangers of Space
Microgravity fundamentally alters how the human body functions. The lack of gravitational force causes irreversible bone density loss, which can leave astronauts vulnerable to fractures.
Studies show that astronauts lose approximately one percent of their weight-bearing bone mass each month in space unless they engage in rigorous countermeasures like exercise.
A photo of Sunita Williams in space from a post dated August 24, 2024. | Source: X/NASA
Without gravity constantly pulling on the body, muscles in the arms, legs, and core weaken, including the heart, which does not need to work as hard to pump blood. This atrophy impacts astronauts’ ability to stand and walk immediately after returning to Earth.
The fluid shift also alters the shape of their eyeballs, sometimes resulting in permanent vision impairment. While most vision changes resolve after returning to Earth, some astronauts require corrective lenses for the rest of their lives.
Another unexpected consequence of long-duration spaceflight is increased skin sensitivity — “almost baby-like sensitivity,” Duffy shared. Without clothing constantly pressing against the body, an astronaut’s skin becomes much more delicate.
Within just one week on the ISS, they are exposed to the same amount of radiation that a person on Earth would receive in an entire year. Over nine months, this exposure increases significantly, elevating the risk of developing cancer, cardiovascular disease, and central nervous system damage.
A screenshot of Sunita Suni Williams and Barry Wilmore from a video dated July 10, 2024. | Source: YouTube/@CBSNews
NASA has been studying these risks for years, but prolonged missions like Williams and Wilmore’s provide new data on long-term exposure. Dr. Vinay Gupta, a pulmonologist and Air Force veteran, emphasized the need for long-term monitoring and said:
“If I was their physician, I would think about a more proactive strategy for cancer screening.”
Scientists are still working to understand how radiation affects astronauts at a cellular level, including potential changes to their DNA.
A Triumphant Return to Earth
On March 19, 2025, Wilmore and Williams finally made their long-awaited return to Earth. Rather than returning on Boeing’s Starliner, as originally planned, the duo instead hitched a ride home aboard a SpaceX capsule, bringing an end to a mission that captured global attention.
Spending more than nine months in microgravity takes a significant toll on the human body, and Williams and Wilmore could face a difficult adjustment upon their return to Earth.
