EXPLAINER

Nine months in space can permanently alter the body, leaving astronauts Sunita Williams and Barry Wilmore with possible long-term health effects.

It was a mission that lasted far longer than planned.

United States astronauts Sunita “Suni” Williams and Barry “Butch” Wilmore went to space on board the Boeing Starliner Calypso on June 5, 2024. They were meant to spend eight days on the International Space Station (ISS).

But as the spacecraft was approaching the station, its thrusters malfunctioned, and NASA ordered the astronauts to remain on the ISS while figuring out how to bring them back.

That lasted nine months, or 288 days, making Williams and Wilmore two of the longest-serving NASA astronauts in space on a single mission.

The ISS orbits at an altitude of 354km (220 miles), while the average distance to Mars from Earth is a staggering 225 million kilometres (140 million miles).

Astronaut Frank Rubio holds the record for NASA’s longest space mission, spending more than a year on the ISS.

The overall record for a single spaceflight belongs to Russian Valeri Polyakov, who spent 437 days on board the Mir space station.

The SpaceX Dragon spacecraft that carried Williams and Wilmore to Earth splashed down at about 5.57pm local time (21:57 GMT) off the coast of Florida, after undocking from the ISS at 05:05 GMT.

On board with Wilmore and Williams was Russia’s Roscosmos astronaut Aleksandr Gorbunov.

NASA provided live coverage of the lead-up to the splashdown.

Now back on land, the crew will have to adjust to being back on Earth, both physically and mentally.

Spending months in microgravity is brutal on the body. Without the Earth’s gravitational pull, muscles shrink, bones weaken and bodily fluids shift.

Astronauts lose muscle mass rapidly because they do not use their legs to support their weight. Their bones become fragile and they lose 1 percent of their bone mass per month – equivalent to an entire year of ageing on Earth.

Radiation is another major concern. Although the ISS is shielded by Earth’s magnetosphere, astronauts on missions lasting six months or longer receive more than 10 times the radiation than what is naturally occurring on Earth. Prolonged exposure is linked to higher cancer risks and potential cognitive decline.

Returning to Earth does not immediately undo months of strain on astronauts’ bodies. As their bodies readjust to gravity, they experience balance issues, dizziness and weakened cardiovascular function.

Even months after landing, not everything recovers. They face long-term health risks, including cancer, nerve damage and degenerative diseases.