After spending an unexpected nine months aboard the International Space Station (ISS), NASA astronauts Barry “Butch” Wilmore and Sunita Williams are preparing for their return to Earth. Originally scheduled for a brief eight-day mission, their stay was significantly prolonged due to technical issues with Boeing’s Starliner spacecraft, which was intended to bring them home. Now, NASA and SpaceX have coordinated a return plan as part of the Crew-10 mission, set to retrieve the stranded astronauts.
Spending extended time in space has profound effects on the human body and mind, including changes in bone density, muscle mass, vision, and even psychological well-being. The return of Wilmore and Williams provides researchers with an opportunity to study the long-term effects of spaceflight, particularly since most ISS missions typically last no more than six months. As they prepare for re-entry, scientists are closely monitoring the physiological and psychological challenges they may face upon their return to Earth.

How returning to Earth affects Sunita Williams and Butch Wilmore’s bodies and minds

Extended stays in microgravity have significant effects on the human body, impacting bones, muscles, circulation, vision, and neurological functions.
1. Bone and muscle loss
Without the resistance of gravity, astronauts experience bone density loss of approximately 1-2% per month and muscle atrophy in the legs, trunk, and even the heart. To counteract this, ISS crew members engage in daily exercise routines, but some loss is unavoidable. Upon returning to Earth, they require months of rehabilitation to regain their strength.
2. Circulatory and cardiovascular changes
In space, the heart works less because it does not need to pump blood against gravity. Blood distribution also shifts, leading to a puffy face and thinner legs. Additionally, fluids accumulate in the head, causing astronauts to feel like they have a constant cold. Changes in circulation can increase the risk of blood clots, which scientists closely monitor upon return.
3. Vision impairment and brain fluid accumulation
Many astronauts develop vision problems due to fluid buildup in the head, which alters the shape of the eyeball. This condition, known as Spaceflight-Associated Neuro-ocular Syndrome (SANS), can lead to blurred vision and may require astronauts to wear glasses permanently.
4. Skin sensitivity
A surprising effect of microgravity is increased skin sensitivity. Because clothing floats away from the skin, astronauts’ skin becomes softer and more sensitive. Upon returning, some report that everyday fabrics feel like sandpaper against their skin.

Silent danger of long-duration space travel

A major concern for long-duration space travel is radiation exposure. Without Earth’s protective atmosphere and magnetic field, astronauts are exposed to higher levels of cosmic radiation, which increases the risk of cancer and neurological disorders.
NASA identifies three primary sources of radiation exposure in space:

Radiation protection remains a key challenge in planning future deep-space missions, such as human exploration of Mars. Studying the long-term effects on Wilmore and Williams could provide valuable insights for future space travel safety measures.

Psychological challenges for Williams and Wilmore: Returning to Earth after nine months

Beyond physical effects, long-duration spaceflight also presents mental and emotional challenges. Astronauts must adapt to isolation, confined spaces, and altered sleep patterns, which can lead to fatigue, anxiety, and mood changes upon return.
1. The “overview effect”
Many astronauts experience a profound cognitive shift known as the “overview effect”, where seeing Earth from space changes their perspective on humanity and the planet. While inspiring, returning to normal life can feel underwhelming and challenging after such an experience.
2. Readjusting to Earth’s environment
Reintegrating into daily life can be difficult, as astronauts must relearn basic movements like walking and adapt to Earth’s gravitational pull. Psychological support is provided to help them transition back to everyday routines.

Scientific significance of the astronauts’ return

The return of Wilmore and Williams presents an important opportunity for scientific research. Most ISS missions last six months, so their nine-month stay allows scientists to study the extended effects of microgravity on the human body.
This research is particularly relevant for:

How Wilmore and Williams became stranded

Wilmore and Williams launched on June 1, 2024, as part of Boeing’s Starliner-1 Crew Flight Test, a mission designed to evaluate the spacecraft’s performance for future NASA missions. The Starliner successfully docked with the ISS, and the astronauts were expected to return within a week. However, significant technical malfunctions with the Starliner—including propulsion system failures and helium leaks—prevented it from being deemed safe for re-entry.
With their return vehicle compromised, NASA made the decision to send the Starliner back to Earth without a crew in September 2024. This left Wilmore and Williams aboard the ISS, awaiting an alternative means of returning home. Their extended stay required additional supplies and adjustments to ISS operations, as they had not originally been scheduled for such a long-duration mission.

Crew-10 mission: The rescue plan

To bring the astronauts back, NASA and SpaceX have incorporated them into the Crew-10 mission, which is set to launch on March 15, 2025. The Crew Dragon spacecraft will travel to the ISS, deliver its new crew, and retrieve Wilmore and Williams, along with NASA astronaut Nick Hague and Roscosmos cosmonaut Aleksandr Gorbunov, who were also scheduled to return.
Upon arrival, the Crew Dragon will: