Astronauts Williams, Wilmore brace for their toughest challenge after Earth touchdown—Here’s why

NASA astronauts Sunita Williams and Butch Wilmore are finally set to return to Earth on 19 March 2025 after spending over eight months in microgravity. Initially planned as a 10-day mission aboard Boeing’s Starliner, their stay on the International Space Station (ISS) was unexpectedly prolonged due to thruster malfunctions that delayed their return. Their homecoming not only brings relief but also marks the start of a grueling battle against Earth's gravity. Stranded in space since June last year due to technical glitches in Boeing’s spacecraft, the duo will soon face one of the toughest physical challenges of their careers.

Gravity’s brutal return

Adapting back to Earth’s gravity after prolonged exposure to weightlessness is no easy feat. Wilmore has admitted that even the simplest actions—like lifting a pencil—will feel exhausting in the first few days after touchdown. "Gravity is really tough," he told CNN, explaining how fluids in the body will be pulled down abruptly, causing discomfort and weakness. Williams echoed similar concerns, acknowledging that her body will have to relearn how to function under gravitational pressure after months of floating weightlessly.

The European Space Agency (ESA) has previously warned of the potential long-term consequences of extended space travel. A recent study found that prolonged inactivity in microgravity can lead to cartilage degradation and cellular clustering—early signs of arthritis. This could make the return even more challenging for the astronauts as they work to rebuild their physical strength.

A body transformed by space

Long-duration space travel drastically alters human physiology. In microgravity, bodily fluids shift toward the upper body, often causing what is known as "puffy face syndrome." However, once astronauts return to Earth, these fluids redistribute downward, leading to swelling in the legs and a sensation of heaviness.

Another major concern is muscle atrophy and bone density loss. Studies suggest that astronauts can lose up to 1-2% of their bone mass per month in space. Without the need to support body weight, muscles also weaken, making movement difficult upon reentry. Cardiovascular adjustments further add to the struggle. The heart, which adapts to reduced effort in microgravity, suddenly has to work harder in Earth's gravity, often resulting in dizziness and fatigue. Additionally, changes in the vestibular system—the part of the inner ear responsible for balance—can lead to temporary disorientation and difficulty walking.

The road to recovery

NASA has devised a rigorous rehabilitation plan to help Williams and Wilmore regain their strength and mobility. Their recovery will involve intensive physical therapy, including resistance training and balance exercises, to rebuild muscle strength. Cardiovascular conditioning will also be crucial, with astronauts engaging in activities such as cycling and treadmill workouts to restore heart function.

Dietary support will play a key role in counteracting bone loss. Nutrition plans rich in calcium and vitamin D will aid bone recovery, while neurological training will help them regain balance and coordination. Recent research published in npj Microgravity suggests that jumping exercises could help mitigate cartilage damage, potentially offering insights into better rehabilitation techniques for astronauts returning from long-term space missions.

On the other hand, Williams and Wilmore have rejected the 'stranded' label. NASA and Boeing decided to bring Starliner back uncrewed, leading to changes in astronaut assignments. Williams and Wilmore were moved to SpaceX’s Crew-9 return mission, which extended their time in space until Crew-10’s arrival. Their situation gained further attention when former U.S. President Donald Trump criticised the delay, but Wilmore emphasised, in an interview with CNN, that they are not stuck, stating, “We are fully prepared and committed.” Williams, meanwhile, expressed her continued enthusiasm for space travel.

Williams and Wilmore are prepared to board SpaceX’s Dragon spacecraft for their return journey home.