NASA astronauts Butch Wilmore and Suni Williams are preparing for their return to Earth after an extended nine-month mission aboard the International Space Station (ISS).

Originally intended to last just eight days, their mission faced technical complications that prolonged their stay significantly.

The astronauts launched from Cape Canaveral on June 5, 2024, as part of a test for Boeing's new Starliner capsule but were delayed due to several technical issues, including helium leaks and thruster failures.

A SpaceX Falcon 9 rocket successfully launched on March 15, 2025, with the astronauts' return anticipated later that evening.

They will be replaced by a new team of four astronauts who are also traveling aboard the Falcon 9 to the ISS.

The extended duration of their mission in microgravity presents a number of health concerns for Wilmore and Williams.

For example, astronauts in space face increased exposure to high levels of radiation.

While the Earth’s atmosphere and magnetic field protect against dangerous solar and cosmic radiation, those in space can experience adverse health effects like elevated cancer risk, DNA damage, cardiovascular issues, and potential neurodegenerative effects.

The ISS does benefit from being within the Earth's magnetosphere, providing some level of radiation protection; however, the extended duration still poses significant risks.

Microgravity, defined as a state where gravitational forces are significantly weaker than those on Earth, also adversely affects the human body.

Astronauts commonly experience bone density loss, with studies indicating that bones can weaken by approximately 1% per month unless countermeasures are implemented.

Muscle atrophy is another issue; astronauts may lose muscle mass due to the lack of gravitational resistance.

Additionally, fluid shifts can cause facial swelling and increased intracranial pressure, leading to headaches and vision challenges.

Recent studies indicate that a significant percentage of astronauts who spent over six months in space reported experiencing frequent headaches.

Moreover, psychological challenges arise from the confined living conditions and limited social interactions aboard the ISS.

Astronauts may face stress, sleep disturbances, mood disorders, and cognitive declines during extended missions.

Recovery from such effects can extend for several months after returning to Earth, as noted by former astronauts who have shared their experiences regarding the adjustments needed after long-duration spaceflight.

Productivity in social and familial reintegration can also be challenging for returning astronauts.

The circumstances leading to their extended stay involved cautious decision-making by NASA and Boeing, as safety was prioritized following the Starliner’s technical setbacks.

Initially, NASA mandated an empty return flight of the Starliner, which took place last September after deeming it unsafe to return with crew.

Subsequently, the decision was made to transition Wilmore and Williams to a SpaceX mission, which would allow them to return weeks sooner than their previously scheduled flight back.

Their anticipated recovery process will now begin as they transition back to life on Earth.