Stranded astronauts: How space affects the body

Times of Oman

18-03-2025

Florida: Much was made of the potential health risks that stranded NASA astronauts Barry "Butch" Wilmore and Sunita "Suni" Williams would face in space. Returning to Earth in March 2025, after an unexpected nine months at the International Space Station (ISS), their bodies will have adjusted to radiation and microgravity.
The effects of radiation and microgravity are the same for every astronaut — starting with nausea and bloated faces — but this mission was only meant to last a week. It begged the question: Would the effects be worse for Suni and Butch?
Williams and Wilmore were stranded at the ISS in June 2024 their Boeing Starliner spacecraft experienced technical problems on the way there, and it was deemed too dangerous to send them back in the same vehicle
Both are experienced astronauts, having spent hundreds of days in space prior to their mission from 2024-2025
They will have been prepared and trained for a worst-case scenario, especially since the Starliner launch was a test mission
What it takes to be an astronaut
Humans haven't evolved to live in space — that is, in an environment unprotected by Earth's atmosphere, in near or zero-gravity — so those who travel to space need highly specialized training and careful health monitoring both before, during and afterward.
Astronauts selected for human spaceflight are considered capable of not only undertaking their assigned missions but also of managing complicated and changing situations.
Wilmore and Williams flew as test pilots for the first crewed flight of Boeing's Starliner spacecraft to the ISS. But propulsion issues with their spacecraft meant their eight-day mission had to be extended. They joined a regular crew, known as SpaceX Crew 9.
Soon after they were stranded, retired German astronaut Thomas Reiter said he thought it would be "quite a burden" but that "they can handle it."
Reiter served two missions in space, first on Mir, a Soviet-era space station which de-orbited in 2001, and later as a flight engineer on the ISS. Williams replaced Reiter on her first spaceflight.
"Both of them are not inexperienced, they are familiar with the operations on board [the ISS]," said Reiter.
Radiation: One of the biggest risks of space travel
Space agencies devote entire departments to study the effects of space on the human body — the German Space Agency (DLR), for instance, runs its lab, envihab near Cologne.
In June 2024, the journal Nature published more than 40 studies described as the "largest-ever compendium of data for aerospace medicine and space biology."
Among the studies was one known as TWINS. It involved 10 labs that compared astronaut Scott Kelly, who spent almost a year on the ISS in 2015, and his identical twin Mark, who is also an astronaut but had stayed on Earth. And it's that study that points to one of the major risks of prolonged periods in space — radiation.
"It's going to be space radiation exposure that's going to be the big limiting factor for how well astronauts do or how long they're going to be able to actually be in space," said Susan Bailey, a radiation biologist from Colorado State University. Bailey led research in the TWINS study into the effect of radiation on telomeres, tiny genetic caps on the end of human chromosomes.
"Radiation exposure really is very damaging to our DNA," said Bailey.
That exposure is what increases cancer risk for astronauts. It also raises oxidative stress within the body.
"That's what all of that is about: Sparing them from those really hazardous late effects and some very acute effects," Bailey said. "We have to come up with countermeasures, some way to protect the astronauts not only during spaceflight, but if they're going to be camped out on the moon or even Mars."
Space agencies have specific limits on the amount of radiation that astronauts can be exposed to throughout their careers.
Microgravity: From kidney stones to poor sight
Microgravity in space can cause bone demineralisation — astronauts lose around 1-1.5% bone density for every month spent in space.
This can also lead to changes in mineral levels in the body and result in health risks. For example, increased levels of calcium in the body's excretory system, which removes waste such as urine, can lead to kidney stones.
"When they come back, they [can't] go on the dance floor, like anyone else who's been in weightlessness for many months," Reiter said.
This environment can also cause changes to vision, with fluids in the body shifting to the head and putting pressure on the eyes.
Prolonged pressure can lead to Spaceflight Associated Neuro-ocular Syndrome, which can change the eye's ability to focus, sometimes permanently.
Upon their return to Earth, both Williams and Wilmore will be subject to regular health monitoring.
Plenty of food and water on the ISS
Despite the health risks associated with travelling to space, more immediate needs are well met by the ISS.
"If there are, all of a sudden, two persons more, they are not running short of water, oxygen or food immediately," Reiter said.
Food, water, oxygen and carbon filtration needs are regularly serviced by resupply missions.
And there are six dorms, two bathrooms, and a gymnasium — so, plenty of room for the crew to spread out.
On top of this, psychological care will have been aided by integrating the long-stay astronauts into the ongoing projects at the ISS.
Wilmore and Williams immediately got involved in scientific and support work with the other astronauts.
"But astronauts want to be in space, they train their whole life [for it]." They may well have thought that being stranded in space was "pretty grand," Bailey said.