What do long trips to space do to your body?

Butch Wilmore and Suni Williams suffer accelerated ageing, DNA damage and muscle loss after nine months aboard ISS

Astronauts Butch Wilmore and Suni Williams were placed in wheelchairs after finally returning to Earth on Tuesday,

forced to confront the physical toll of their nine-month trip to space when they finally returned to Earth on Tuesday, after each were placed in wheelchairs after emerging from their Crew Dragon capsule.

The zero-gravity environment aboard the International Space Station (ISS) had atrophied their muscles and caused their bones to lose density, making it difficult to walk, or even stand.

The pair also appeared gaunt, with some observers noting that they appeared to have aged considerably since setting off last June on what was supposed to be an eight-day trip.

Nasa astronauts Suni Williams, left, and Butch Wilmore ahead of the launch on 5 June, 2024, in Cape Canaveral, Florida (The Associated Press)

It is not the longest anyone has ever spent in space – that record belongs to Russian cosmonaut Valeri Polyakov, who spent 14 months aboard the Mir space station in the 1990s – but it was long enough for their bodies to experience the worst effects of the extreme environment of space.

Here’s what physical changes they would have experienced during their 286-day trip to space.

Accelerated ageing

A lack of gravity means the heart and blood vessels have less work to do, which causes them to gradually weaken over time.

Astronauts also experience bone density loss, muscle atrophy, and cellular changes at a faster rate than normal. Bone density decreases at a rate of up to 1-2 per cent each month, increasing the risk of osteoporosis and fractures upon returning to Earth.

The ISS is equipped with specialised treadmills and exercise bikes to help the astronauts combat this, as well as resistance bands designed to mimic the gravitational forces of Earth.

Studies have shown that exposure to cosmic radiation can also cause DNA damage and oxidative stress, leading to premature ageing at a molecular level.

Impaired vision and increased brain fluid

The absence of gravity also causes bodily fluids to shift towards the head, causing optic nerve swelling, folds in the retina, flattening of the back of the eye, and swelling in the brain.

This can result in impaired vision through something known as Spaceflight-Associated Neuro-ocular Syndrome (SANS), which is one of the most common side effects for long-duration astronauts.

The pressure on the brain and eyes goes back to normal levels after returning to Earth, however the eyesight damage caused can sometimes be permanent.

Weakened immune system

The quarantine period that astronauts go through before launching to the ISS means there are very few germs or viruses on the space station.

A recent study suggested the ISS may be too clean, with the lack of microbes causing immune problems, skin disorders and other conditions.

Butch Wilmore, left, and Suni Williams pose for a portrait inside the vestibule between the forward port on the International Space Station's Harmony module and Boeing's Starliner spacecraft on 13 June, 2024 (Nasa)

Microgravity and radiation can also alter white blood cell production, reducing the body's ability to fight off viruses and bacteria. Astronauts have reported that dormant viruses, like herpes and chickenpox, can reactivate due to stress and immune suppression during stays on the ISS.

Recovery and rehabilitation

The pair will now undergo a 45-day reconditioning programme that will include physical therapy to address the muscle atrophy.

“Crews have previously spent longer durations in space, and Suni Williams and Butch Wilmore’s performance after their return is expected to be consistent with established norms,” a Nasa spokesperson said.

For the first few days of the rehabilitation, the astronauts will feel dizzy as their bodies get used to having to deal with balance in order to stay upright. Their muscle mass should return within a few months, while bone density should return to normal levels after a couple of years.

Some changes to their bodies, such as vision impairment, may be harder to reverse. The US space agency said it hoped to study the physical impacts on the astronauts as part of its preparations for sending humans to Mars – a trip that takes about nine months one way.

“The long-term health outcome from these changes is unknown but actively being investigated,” Nasa said. “The risk of developing SANS is higher during longer-duration missions and remains a top research priority for scientists ahead of a Mars mission.”