Suni Williams and NASA Astronauts Return After 9-Month Space Stay: The Physical Toll of Extended Spaceflight

NASA astronauts Sunita Williams, Butch Wilmore, Nick Hague, and Roscosmos cosmonaut Aleksandr Gorbunov, safely landed off Tallahassee, Florida on March 18, 2025. Their return completed NASA’s ninth commercial crew rotation mission to the International Space Station (ISS). The SpaceX Dragon spacecraft “Freedom” splashed down at 5:57 p.m. EDT in the Gulf of America, bringing to close a mission that was extended far beyond its original plan due to technical issues.

Williams and Wilmore, who originally launched aboard Boeing’s Starliner spacecraft on June 5, 2024, for what was planned as an eight-day Boeing Crew Flight Test, ended up spending 286 days in space—nearly nine months—after NASA decided to return the Starliner uncrewed due to propulsion problems and helium leaks. They were integrated into the regular ISS crew and returned with Crew-9.

“We are thrilled to have Suni, Butch, Nick, and Aleksandr home after their months-long mission conducting vital science, technology demonstrations, and maintenance aboard the International Space Station,” said NASA acting Administrator Janet Petro. She stated that at President Trump’s direction, NASA and SpaceX coordinated to adjust the schedule, allowing the crew to return a month earlier than initially planned.

For Williams, this marked her third spaceflight, bringing her total time in space to 608 days, making her second among U.S. astronauts for cumulative time in space. She also set a new record for the most spacewalking time by a female astronaut, with 62 hours and 6 minutes, which makes her fourth on the all-time spacewalk duration list. Wilmore has now logged 464 days in space across three flights, while Hague has accumulated 374 days over two missions. For Gorbunov, this was his first spaceflight.

The mission saw the astronauts conduct more than 150 unique scientific experiments and technology demonstrations, accumulating over 900 hours of research. Their work included investigations on plant growth and quality, the potential of stem cell technology for treating blood diseases and cancers, testing lighting systems to help astronauts maintain circadian rhythms, and loading the first wooden satellite for deployment.

During their stay, Williams conducted two spacewalks, one with Wilmore and another with Hague, during which they removed a radio frequency group antenna assembly, collected samples from the station’s external surface, and installed patches to cover damaged areas of light filters on an X-ray telescope.

Moreover, Sarah Walker, director of the SpaceX Dragon Mission Management announced that after six years of successful recovery operations off the coast of Florida, they would now be moving Dragon recovery operations back to the West coast.

A memorable moment during the splashdown was when a pod of dolphins surrounded the capsule as it floated in the Gulf of Mexico. The sight which was captured on live video feeds, added a special touch to the astronauts’ return, without interfering with recovery operations.

Physiological Challenges of Extended Spaceflight

The extended mission of Sunita and Butch offers valuable insights into the effects of long-duration spaceflight on human-health. Microgravity may trigger a variety of physiological changes that affect astronauts after they return to Earth’s gravity.

Without the continuous pull of gravity, muscles- particularly in the back, neck, calves, and thighs- tend to weaken. A 2021 study found that despite vigorous workout routines on the ISS, muscle loss can’t be completely prevented. Factors such as baseline muscle mass, hormonal fluctuations, and metabolic shifts contribute to variations in muscle deterioration among astronauts.

Bone mineral density (BMD) declines at a rate of approximately 1-1.5% per month in space. This bone loss can continue even after rehabilitation. While the risk of fractures may not increase significantly, the release of calcium can raise the risk of developing kidney stones. Research published in 2022 indicated that some ISS astronauts, who spent an average of five and a half months on mission, exhibited reduced bone mineral density even a year after returning to Earth.

Another concern is Spaceflight Associated Neuro-ocular Syndrome (SANS), a condition that affects vision due to the redistribution of blood and cerebrospinal fluid toward the head in microgravity, increasing intracranial pressure. Some astronauts experience lasting vision impairment requiring corrective lenses.

Other physiological changes include fluid redistribution causing facial puffiness, weakened immune response, temporary height increase due to spinal disc expansion, and “gravity sickness” upon return (dizziness and orthostatic hypotension). Astronauts may also experience “baby feet”—softened foot soles from lack of walking pressure—and even changes in gene expression.

Recovery Process and Medical Protocol

Steve Stich, Manager, NASA’s Commercial Crew program, noted, “They all looked healthy you could tell, they all looked like they were feeling about normal for the landing and recovery phase and their bodies trying to readapt.”

British astronaut Tim Peake suggested that Williams and Wilmore would likely experience nausea, dizziness, and vertigo as they readjust to Earth’s gravity. As a precaution, both astronauts were assisted out of the spacecraft and transported on stretchers.

Though initial two to three days after return involve rapid physiological adjustment, regaining full physical strength generally takes two to three months. The recovery process focuses on rebuilding small stabilizing muscles in the lower back and core, which cannot be adequately exercised in microgravity.

Frank Rubio, who spent 371 days in space, previously shared that his first few months back on Earth were dedicated to reintegrating himself into daily life and rehabilitating his body. He noted that while the human body adapts quickly to space, readjusting to Earth’s strong gravitational force can be more challenging.

Upon arrival at NASA’s Johnson Space Center, Williams and Wilmore will undergo several days of health evaluations, including laboratory tests, physical examinations, sensorimotor assessments, and ocular and cardiovascular assessments. NASA’s Lifetime Surveillance of Astronaut Health program ensures long-term monitoring of their health and well-being.

They will then begin NASA’s structured 45-day post-mission rehabilitation program, consisting of two-hour daily sessions, seven days a week. This program is divided into three phases: initial recovery of strength, flexibility, and walking ability; proprioceptive exercises for balance and coordination with cardiovascular reconditioning; and functional development to restore optimal physical performance. The program is tailored to each astronaut’s individual needs based on medical evaluations and test results.

While many astronauts return to their pre-mission fitness levels after the 45-day program, full recovery can take longer, and some effects, especially in terms of bone density, may persist. Psychological assessments and support are also essential for the rehabilitation process.

Research Gaps and Future Focus Areas

Despite decades of human spaceflight experience, significant gaps remain about spaceflight’s impact on human health. One area still under study is lung function as relatively little is known about the effect of microgravity on it. Space radiation is known to increase cancer risk, accelerate aging, and cause cellular damage, but the precise biological mechanisms remains unclear.

Research suggests mitochondria—the cell’s power generators—plays a crucial role in spaceflight-induced health effects. However, how they adapt and potentially dysfunction in space is still under investigation. Scientists are also studying the broader impacts of microgravity, radiation exposure, and isolation on cognitive function, mental health, and neuroplasticity over extended periods.

The NASA Twins Study, which compared astronaut Scott Kelly during her year in space, to his twin brother Mark who was on Earth, provided valuable insights, besides highlighting how much remains unknown. Ongoing research is examining the phenomenon of “accelerated aging phenotype” potentially caused by the harsh space environment and its effects on mitochondrial function.

As space missions to the Moon and Mars become a reality, and as civilian space travel increases, understanding how a broader population responds to the space environment becomes increasingly important.

Records and Historical Context

The return of Williams and Wilmore adds to the history of long-duration spaceflight. While their 286-day mission was substantial, several astronauts have spent even longer periods in orbit:

• Russian cosmonaut Valeri Polyakov holds the record for the longest continuous time in space: 437 days aboard the Mir space station
• NASA astronaut Frank Rubio holds the record for the longest single mission on the ISS: 371 days
• NASA astronaut Peggy Whitson holds the record for most cumulative time in space by a U.S. astronaut: 675 days across four missions
• With her recent return, Suni Williams now holds second place for cumulative time in space for a U.S. astronaut: 608 days across three spaceflights

The data gathered from Williams and Wilmore’s unexpectedly prolonged mission will contribute to our understanding of long-duration spaceflight effects and help develop countermeasures for future extended missions to the Moon, Mars, and beyond. Their experience demonstrates both the challenges of space travel and the remarkable adaptability of the human body and spirit.