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 transformations the human body undergoes during prolonged space travel — from developing “chicken legs” and weakened bones to changes in eyesight and even increased radiation exposure.
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.
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.
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.
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.
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 weig
“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.
Former astronaut Mike Massimino emphasized the importance of exercise as well, saying, “We need that stuff to remain healthy, especially when you come back to Earth.” Williams also explained in a video interview:
“Things shift around quite a bit. You probably heard of a fluid shift where folks in space, you know, their heads look a little bit bigger because the fluid evens out along the body.”
She further assured that her weight had remained the same since launch. Wilmore confirmed that both he and Williams dedicated more than two hours each day to exercise, including running, cycling, and weight training.
Despite their situation worrying those on the ground, the pair stuck in space stayed busy with ISS maintenance and scientific research, including studies on the effects of prolonged weightlessness on the human body.
Both had previous experience aboard the ISS and had refreshed their training before launch, allowing them to adapt smoothly to the demands of a prolonged mission.
Throughout nine missions, Williams spent a total of 62 hours outside the station, setting a record for the most time spent spacewalking by a female astronaut.
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.
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 cardiovascular system is also heavily affected. Blood volume shrinks, and circulation patterns change, which can lead to clotting issues. Fluids shift upwards toward the head, causing astronauts to experience persistent congestion and pressure in the skull.
Alan Duffy, an astrophysicist at Swinburne University, further explained, “Fluids build up in their heads, so they feel like they have a constant cold.”
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.
Another unexpected consequence of long-duration spaceflight is increased skin sensitivity — “almost baby-like sensitivity,” Duffy shared. Without clothing constantly pressing against the body, astronauts’ skin becomes much more delicate.
Upon returning to Earth, some astronauts report that their clothes feel like sandpaper against their skin, an uncomfortable side effect of months without gravitational resistance.
Another health risk astronauts face — and perhaps the most concerning — is space radiation exposure. On Earth, the atmosphere and magnetic field provide a natural shield against harmful radiation. But in space, astronauts lack this protection. According to NASA:
“Not only will astronauts be exposed to more radiation in space than on Earth, but the radiation they are exposed to could pose increased risks.”
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.
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.
Their capsule safely splashed down in the Gulf of Mexico, just off the coast of Tallahassee, Florida, in the early evening. Within an hour of landing, Wilmore and Williams were extracted, smiling and waving.
The two had spent an astonishing 286 days in space — 278 days longer than planned — orbiting the Earth 4,576 times and traveling an incredible 121 million miles.
While other astronauts have spent longer periods in space, few have faced such an unpredictable mission extension. NASA astronaut Nick Hague, the commander of their relief crew, said:
“What a ride. I see a capsule full of grins ear to ear.”
Now safely back on Earth, Wilmore and Williams begin their next mission — readjusting to gravity after nearly a year in space.
Reconditioning the Body for Life on Earth
Spending more than nine months in microgravity takes a significant toll on the human body, and Williams and Wilmore could face a difficult adjustment once they return to Earth.
Astronauts undergo strange and sometimes dramatic physical changes at the cellular level while in space. Their bodies stretch out, often making them slightly taller due to spinal elongation in microgravity.
As soon as they emerged from the SpaceX capsule, they were placed on stretchers and transported for immediate medical evaluations.
Since humans are largely made up of fluid, weightlessness also redistributes liquids, resulting in what’s commonly referred to as “chicken legs” and a “puffy head.”
The extensive rehabilitation the astronauts will require, which Dr. Gupta explained could last up to six weeks, is an intense process. It is comparable to the physiotherapy needed for patients who have spent months in a coma.
Doctors have warned that the astronauts stuck in space will not be able to walk on their own immediately after landing on Earth due to severe muscle and bone deterioration.
Since microgravity eliminates the need for balance and coordination, astronauts must retrain their nervous systems to adjust to Earth’s gravity. Studies show that some experience dizziness, motion sickness, and difficulty standing upright in the first days after landing.
As soon as they emerged from the SpaceX capsule, they were placed on stretchers and transported for immediate medical evaluations.
Their recovery began the same day they landed, focusing first on walking, flexibility, and muscle strengthening. This process will include guided exercise routines and a carefully monitored nutritional plan designed to rebuild lost strength.
However, despite these challenges, NASA doctors remain optimistic about Williams and Wilmore’s recovery and the possible side effects of long-term space travel are expected to reverse themselves shortly after they return to Earth. Dr. Joe Dervay, a NASA flight surgeon, said:
“There is some individual variability on how quickly they recover, but it is pretty impressive to see how they will turn the corner and really adapt quickly. Oftentimes, if you look at them a couple days later, you really have no idea what they’ve just done for the last several months.”
The NASA flight surgeon further noted that Williams and Wilmore were in good health ahead of their return, and previous studies suggest that recovery is relatively quick.
“We don’t see any need for any special precaution,” Dina Contella, deputy manager of NASA’s International Space Station Program, added. “Like any astronauts coming back, there is an acclimation period, and so that will vary by crew member.”
After 286 days in space, the astronauts are finally home, but their journey isn’t over. The effects of prolonged weightlessness, radiation exposure, and muscle atrophy mean their recovery will take weeks.
Their experience provides NASA with critical data on how the human body endures extended spaceflight — knowledge that will shape future missions to the Moon, Mars, and beyond.
