🧠 After a long space flight, astronauts' brains are no longer in the same place

Floating in the International Space Station (ISS), freed from the force of gravity, leads to astonishing bodily transformations... in the brain. A recent study reveals that it has deformed and shifted inside the skull after a space mission. This phenomenon, due to the absence of gravity, could have repercussions for future missions.

To understand these changes, scientists analyzed magnetic resonance imaging (MRI) scans of the brains of 26 astronauts. These images were taken before and after their mission, allowing a comparison of the brain's position relative to the skull. By precisely aligning the skulls on the scans, they were able to measure brain movements with great accuracy.


The results indicate that the brain shifts upward and backward during a stay in microgravity. The longer the mission duration, the greater this movement. For example, for astronauts staying one year in space, some brain regions moved by more than 0.08 inches (2 millimeters). Although this distance may seem minimal, it is significant within the confined environment of the skull.

The examination of over one hundred brain regions allowed researchers to observe that areas related to movement and sensation are the most affected. Furthermore, structures located on either side of the brain move closer to the midline, a phenomenon that had gone unnoticed in previous studies. These opposing movements cancel each other out in overall measurements, which explains why they had not been detected before.

After their return to Earth, most of these deformations and shifts gradually subside. Six months later, a large part of the brain returns to its initial position. However, the backward shift persists longer, likely because Earth's gravity acts primarily downward. This slow recovery shows the body's necessary adaptation after a space flight.

These discoveries are valuable for future space explorations, such as NASA's Artemis program. By understanding how the brain adapts to microgravity, it will be possible to design safer missions for astronauts, particularly during prolonged trips to Mars. Research continues to assess long-term risks and develop countermeasures.

These changes do not appear to cause severe symptoms in astronauts, such as headaches or cognitive disorders. However, they correlate with alterations in balance after the flight, highlighting the interest in continuing research.

Microgravity and its impact on the human body

On Earth, gravity plays an important role in the distribution of bodily fluids, pulling them downward. In space, in microgravity, this force disappears, leading to a shift of fluids toward the upper part of the body. Astronauts then experience a puffy face and thinner legs, a phenomenon often called 'moon face and bird legs.'

These fluidic changes also affect the brain and its environment. The brain, normally stabilized by gravity, floats within the skull and experiences different pressures from the surrounding soft tissues. This can lead to deformations and displacements, as observed in recent studies.

In the long term, these alterations could influence astronauts' health, particularly in terms of intracranial pressure and brain function. Although immediate symptoms are limited, understanding these mechanisms is vital for preparing extended space missions.

Research therefore focuses on developing exercises or equipment to minimize these effects, ensuring the safety of space explorers on journeys to the Moon or Mars.