When astronauts Sunita Williams and Butch Wilmore returned to Earth after an unexpected nine-month stay aboard the International Space Station, their faces told a story NASA didn’t need to narrate. The before-and-after pictures said it all: swollen faces, slimmer frames, and the unmistakable look of two people who just spent nearly a year defying gravity. From muscle shrinkage to vision changes, the effects of space on astronauts are wide-ranging and, honestly, pretty wild.
Their mission was supposed to last only a couple of weeks. However, due to delays with Boeing’s Starliner spacecraft, they stayed in orbit far longer than planned. As the headlines rolled in, one question came up again and again: What exactly happens to the human body after so much time in space?
These striking images gave the public a visual glimpse of the toll space takes on the body—but they only scratch the surface. Behind the bloated cheeks and graying hair lies a full-blown science lesson in how the human body responds to life without gravity, constant motion, and cosmic radiation.
So, what really happens to our bodies when we live in space for that long? Let’s break it down.
Bones, Muscles, and the Battle Against Microgravity
Living in microgravity sounds fun—floating around, doing backflips, never needing a chair—but it comes at a cost. Without gravity tugging on muscles and bones all day, the body starts slacking off. Muscles shrink. Bones weaken. Even the heart gets a little lazy.
Astronauts lose muscle mass even with strict exercise routines. In fact, they spend two hours a day working out, and still come back needing help to stand. Wilmore and Williams were no exception. After nine months, their leg and core muscles had noticeably softened, and walking on solid ground felt like a brand-new skill.
Then there’s bone loss. The body sheds bone density in space like it’s on clearance. On Earth, bones are constantly under pressure from walking and standing. But in space? Not so much. That lack of load-bearing means astronauts can lose about 1% of their bone mass each month. The result? Weaker bones, more calcium in the bloodstream, and a higher risk of kidney stones—not exactly a souvenir you want to bring home.
These may be some of the more familiar effects of space on astronauts, but they’re also some of the most serious, especially for longer missions in deep space.
Faces Puff Up, Eyes Blur, and Balance Disappears
One of the most obvious changes in those viral photos? Puffy faces. Without gravity to pull fluids downward, bodily fluids drift upward and settle in the head. That means more pressure in the skull, swollen cheeks, and the sensation of having a constant head cold. At the same time, legs tend to thin out, giving astronauts that cartoonish “top-heavy” look.
The fluid shift doesn’t just mess with appearances—it also causes vision problems. Known as Spaceflight-Associated Neuro-ocular Syndrome (SANS), this condition occurs when extra pressure in the skull pushes on the optic nerve. The eyeball can flatten, and vision can become blurry or distorted. It’s one of the lesser-known but most persistent effects of space on astronauts. For some, the damage is long-term.
Then there’s balance. The inner ear is wired for gravity. In space, it goes haywire. Astronauts often return to Earth feeling dizzy and disoriented. Their brains have to re-learn how to stay upright, walk straight, and not trip over their own feet. It’s like getting off a rollercoaster that lasted for 270 days.
Read More: SpaceX Plans Mars Mission with Starship Next Year, Says Elon Musk
Skin, Hair, and Some Strange Surprises
Turns out, space doesn’t just mess with muscles and bones—it also takes a jab at skin and hair. Many astronauts report their skin feels more sensitive after a mission. Even soft clothes can feel scratchy, like sandpaper on sunburn. Scientists think it might have to do with nerve changes or circulation shifts, but it’s still kind of a mystery.
Then there’s the gray hair. When Wilmore returned, many noted his silvery locks. While there’s no proven link between space and hair color changes, stress, disrupted sleep, and even increased radiation could speed up aging. Whether the gray came from space or from spending months in a pressurized tin can orbiting Earth, we may never know—but it definitely added to the “I’ve just been to space” look.
These less-discussed effects of space on astronauts may not seem dramatic, but they reveal how deeply the body can change—even in ways we don’t fully understand yet.
The Hidden Strain: Mental Health and Radiation
While photos can show swollen faces and tired eyes, they don’t capture what’s going on inside the mind. Space missions, especially long ones, can be mentally draining. Astronauts deal with isolation, tight quarters, a rigid schedule, and no real break. It’s like being on the world’s longest work trip… minus the world.
Even the most experienced space travelers can experience mood swings, trouble sleeping, or concentration issues. NASA builds in support systems to help, including video calls home and mental health check-ins. But the effects are real, and they don’t stop the minute the capsule lands.
Radiation is another silent threat. Earth’s magnetic field usually shields us from cosmic radiation, but astronauts in orbit don’t get that full protection. Over time, this exposure increases cancer risks and may damage organs or DNA. It’s one of the biggest long-term effects of space on astronauts—and one of the toughest to fix.
Beyond the Photos: What Science Learns From Their Return
Those before-and-after pictures gave us a peek into the physical toll of space, but science tells a much deeper story. Williams and Wilmore were tested and scanned from head to toe after landing. NASA’s goal? Learn how to better protect astronauts during future missions—especially as we aim for the Moon and Mars.
The effects of space on astronauts are central to that mission. Every data point from their nine-month flight helps improve spacecraft design, workout routines, and even food planning. New technology, like artificial gravity or advanced shielding, could reduce the stress on the human body.
These space veterans didn’t just return with cool stories and space suits. They brought back crucial insight that will help the next generation of astronauts explore deeper into space—and do it safely.
Looking Forward, One Mission at a Time
So, what do these striking photos really tell us? Space is awesome, but it’s also hard on the body. Floating might look fun, but the price is real—shrinking muscles, blurred vision, weird skin, and gray hair. And let’s not forget the emotional rollercoaster that comes with it all.
But with each mission, we learn more. The effects of space on astronauts won’t stop us from exploring. Instead, they’ll push us to adapt, innovate, and support those bold enough to leave Earth behind.
Sunita Williams and Butch Wilmore didn’t just survive space—they helped us understand it better. And thanks to them, the path forward is a little clearer.
Read More: NASA Gives Startling Explanation for Astronauts’ Extended Stay in Space