Two NASA astronauts are facing months of heightened radiation exposure after Boeing’s Starliner spacecraft left them stranded on the International Space Station (ISS).
Astronauts Sunita Williams and Barry Wilmore have been on the ISS for three months, exposing them to approximately 40 to 80 millisieverts (mSv) of radiation, equivalent to about 120 to 240 chest X-rays. They are not expected to return to Earth until February 2025 at the earliest, which means they could accumulate radiation exposure comparable to 310 to 630 chest X-rays over their extended stay.
NASA warns that such levels of radiation can increase the long-term risk of cancer, cardiovascular disease, and central nervous system damage. Research indicates that high radiation doses can damage cellular DNA, potentially leading to genetic mutations and cancer over time.
Space plasma physicist Martin Archer highlighted the challenges astronauts face, noting that space is an extremely hostile environment. “Space lacks breathable air, exposes astronauts to microgravity, and subjects them to increased radiation from high-energy charged particles,” Archer explained. “These particles can damage cells by disrupting their atomic and molecular structures.”
NASA reports that astronauts on the ISS typically receive between 80 and 160 mSv of radiation during a six-month mission. Williams and Wilmore have already accumulated about 40 to 80 mSv of radiation, and extended exposure can increase risks such as cancer and cardiovascular issues. Radiation can also hinder neurogenesis, potentially leading to cognitive impairments.
The ISS does have shielding to mitigate space radiation, but it still exposes astronauts to about 365 times more radiation than what people on Earth experience. For comparison, individuals on Earth are exposed to an average of 2 mSv of background radiation per year.
There is also concern about acute radiation syndrome (ARS), which can occur with high doses of radiation over a short period, although no astronaut has ever died from ARS.
Williams and Wilmore are scheduled to return to Earth aboard SpaceX’s Crew Dragon mission, which is set to launch no earlier than September 24. Meanwhile, the Starliner mission has been plagued by technical issues, including helium leaks and thruster failures. NASA officials determined that it was too risky to use Starliner for their return, prompting the reliance on the Crew Dragon.
The sun is approaching its solar maximum, an active period in its 11-year cycle that increases the frequency of solar flares and associated radiation risks. This additional factor contributes to the complex risk assessment for astronauts.
NASA continues to monitor the situation closely and has emphasized the need for ongoing research to understand and mitigate the health risks associated with prolonged spaceflight.
