A new scientific study has revealed that space travel does more than challenge the body; it physically shifts the human brain inside the skull.
Researchers analysing astronauts before and after space missions found that the brain moves “upward and backward” during time in microgravity, with the most dramatic changes seen in regions linked to movement, balance, and sensory processing.
The findings, published in the journal Proceedings of the National Academy of Sciences, add to growing concerns about how long-duration missions could affect astronaut health as space agencies plan for extended stays on the Moon and eventual journeys to Mars.
The Brain Moves When Gravity Disappears
Using MRI scans, scientists studied 26 astronauts before and after spaceflight. Their missions ranged from short shuttle flights lasting weeks to six-month rotations — and in some cases full-year stays — aboard the International Space Station.
After returning to Earth, researchers observed that astronauts’ brains had tilted and shifted within the skull. Sensory and motor regions showed the largest changes, areas already known to be affected by motion sickness and spatial disorientation in orbit.
“There are also regional, nonlinear lateral deformations that differ between the superior and inferior portions of the brain,” the study noted, suggesting the changes are complex rather than uniform.
Longer Missions, Bigger Changes
Duration emerged as the most important factor. Astronauts who spent a year in space experienced the most pronounced brain movement.
Rachael Seidler, a professor at the University of Florida and co-author of the study, said: “There were still some changes evident in people who went for two weeks, but duration seems to be the driving factor.”
Although the shifts measured just a few millimetres, Seidler stressed that this is significant when it comes to brain movement.
Earth-Based Tests Show Similar, But Smaller, Effects
To better understand the cause, researchers compared astronauts with 24 civilians who took part in a long-term “head-down tilt” bed rest experiment designed to mimic microgravity. While similar brain shifts appeared, astronauts experienced a far greater upward movement.
Most of the changes gradually reversed within six months of returning to Earth. However, the study found that some deformations persisted, raising new questions about long-term neurological health.
Why It Matters for the Future of Spaceflight
The findings arrive as NASA pushes ahead with plans for sustained lunar missions and eventual human travel to Mars.
“The health and human performance implications of these brain changes require further study,” the researchers warned, emphasising the need to protect astronauts’ long-term wellbeing.
So far, no serious cognitive impairments have been linked to the shifts. But as humanity prepares to spend longer periods away from Earth’s gravity, understanding how the brain adapts and recovers could prove mission-critical.
Published by Kerry Harrison
Kerry’s been writing professionally for over 14 years, after graduating with a First Class Honours Degree in Multimedia Journalism from Canterbury Christ Church University. She joined Orbital Today in 2022. She covers everything from UK launch updates to how the wider space ecosystem is evolving. She enjoys digging into the detail and explaining complex topics in a way that feels straightforward. Before writing about space, Kerry spent years working with cybersecurity companies. She’s written a lot about threat intelligence, data protection, and how cyber and space are increasingly overlapping, whether that’s satellite security or national defence. With a strong background in tech writing, she’s used to making tricky, technical subjects more approachable. That mix of innovation, complexity, and real-world impact is what keeps her interested in the space sector.