Astronauts Sunita Williams and Barry Wilmore may face health challenges upon return to Earth after 9 months; here's how

NASA astronaut Sunita Williams at the International Space Station. (Photo: NASA)

After spending 9 months and 14 days aboard the International Space Station (ISS), astronauts Sunita Williams and Barry 'Butch' Wilmore, along with another Nasa astronaut and Russian cosmonaut, have returned to Earth safely. The crew-9 splashed down near the coast of Florida, marking the end of an unexpectedly long stay aboard the ISS.

Their mission, which started on June 5, 2024, was supposed to end in eight days, but due to technical difficulties, they stayed in space for more than nine months. Due to this, they are likely to face significant physiological and neurological challenges once back on Earth.

The effects of prolonged exposure to microgravity, radiation and altered lifestyle conditions will require extensive rehabilitation to restore their physical and mental well-being.

Muscle and bone loss

One of the most profound effects of long duration space travel is muscle atrophy and bone density loss. In the absence of gravity, the body does not need to support its weight, leading to weakening of muscles and deterioration of bones. Dr PN Renjen, senior consultant, neurology, Indraprastha Apollo Hospitals, Delhi, explains that this can increase the risk of osteoporosis and make astronauts more vulnerable to fractures.

"Although astronauts engage in rigorous exercise routines to mitigate these effects, they will still need physical therapy and strength training upon their return to regain their pre-flight muscle mass and bone density," Dr Jayanta Thakuria, director, internal medicine and rheumatology, Yatharth Super Speciality Hospitals, Faridabad, says.

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Cardiovascular deconditioning

Extended periods in microgravity also impact the cardiovascular system. Since gravity does not pull blood downward, fluids shift upward, causing facial puffiness and reduced blood volume in the legs. Over time, this leads to a weakened heart that does not have to pump as hard to circulate blood.

"The astronauts may experience dizziness and fainting due to low blood pressure, fatigue as the heart re-adapts to normal circulation and orthostatic intolerance, where they may struggle to stand for long periods," Dr Renjen explains, adding, "To counteract these effects, astronauts undergo cardiovascular rehabilitation, including gradual physical activity and hydration protocols to restore blood pressure regulation."

(L-R) NASA astronaut Butch Wilmore, Roscosmos cosmonaut Aleksandr Gorbunov, NASA astronauts Nick Hague and Sunita Williams inside a SpaceX Dragon spacecraft on board the SpaceX recovery ship MEGAN shortly after having landed in the water off the coast of Tallahassee, Florida. (Courtesy: AFP)

Other health effects

Unlike Earth, space lacks a protective atmosphere, exposing astronauts to cosmic radiation. "Prolonged exposure can increase increased risk of cancer, weaken the immune system and potentially affect cognitive function," Dr Renjen notes.

Space travel also impacts the brain and nervous system. The lack of gravity alters sensory inputs, affecting balance and coordination. According to Dr Thakuria, some astronauts experience "space fog", characterised by difficulty concentrating, slower reaction times, mood changes and fatigue.

Additionally, long-term isolation and the absence of natural Earthly stimuli can impact mental health. "The astronauts may need cognitive therapy, psychological support and balance training to regain their full sensory and neurological functions," Dr Renjen explains.

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While space travel is a remarkable feat, the human body undergoes significant stress in microgravity. The astronauts' recovery will be closely monitored by medical experts, ensuring a safe and healthy transition back to normal life.