When NASA astronaut Sunita Williams returned to Earth a few days ago after , her transformation was striking.
The 59-year-old, who had set off on what was meant to be an eight-day mission, looked noticeably older and frailer upon her return.
Her dark hair had turned completely white - and this wasn’t just a cosmetic change—her body had undergone a level of strain equivalent to years of ageing.
Spending nearly nine months in orbit takes an extreme toll on both the body and brain.
Astronauts face physical and physiological changes that mimic accelerated ageing, and Williams’ unexpected extended stay serves as a stark reminder of the harsh realities of space travel.
The visible and invisible effects of space travel
One of the most noticeable changes was her hair. While missing nine months of hair appointments is something many can relate to, the rapid whitening of Williams' hair could be due to more than just skipping salon visits.
Stress has been linked to premature greying, with heightened levels of adrenaline and cortisol depleting the stem cells responsible for hair pigmentation plus bodily fluids shift upwards, increasing pressure in the scalp.
Her physical condition also showed signs of the toll taken by space travel.
Williams appeared significantly weaker—a common effect among astronauts. In the absence of gravity, muscles and bones weaken rapidly. Astronauts can lose up to 1% of their bone density per month, the equivalent of ageing an entire year on Earth.
Although they take vitamin D supplements, the lack of weight-bearing activity in space means their bones don’t regenerate at the same rate.
A struggle to reacclimatise to Earth
Williams and her fellow astronaut Barry Wilmore had to be stretchered off their capsule, a standard procedure for returning space travellers who struggle to walk after months in zero gravity.
Without gravity to work against, the heart also weakens, as it doesn’t have to pump blood as forcefully. This can lead to a condition known as Spaceflight Venous Thrombosis, where blood flow slows in certain areas, increasing clotting risks.
The effects extend to the rest of the body, too. In space, fluids don’t drain downwards as they do on Earth, which can make astronauts’ faces appear puffy while their legs and feet become thinner.
Meanwhile, the combination of nausea, reduced appetite, and a diet of rehydrated packaged food often results in significant weight loss.
DNA damage and radiation exposure
Perhaps the most concerning effect of long-term space travel is the exposure to high levels of radiation.
While Earth’s atmosphere and magnetic field shield us from harmful cosmic rays, astronauts don’t have that protection.
Those who spend six months or longer in space are exposed to more than ten times the natural radiation levels on Earth. This increases the risk of DNA damage, which can lead to serious conditions such as cancer and Alzheimer’s disease.
Williams’ return highlights just how much space travel pushes the human body to its limits.
As NASA and other space agencies prepare for longer missions—including potential trips to Mars—understanding these effects is crucial.
For now, Williams’ experience serves as a reminder that while space exploration is a remarkable achievement, it comes with significant costs to our bodies.
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