Space travel. Cosmic rays are dangerous to astronauts' brains.

By Jean-Lux Nothias Le Figaro Santé

Irradiation. What would happen to an astronaut's brain during a trip to Mars (and back)? Nothing good, according to a study conducted at the University of California School of Medicine in partnership with a NASA program, the results of which are published in the journal... Science Advances"This is not good news for astronauts," acknowledges Professor Charles Limoli, one of the authors of these studies. "Long-term exposure to cosmic rays causes decreased performance, memory deficits, lack of attention and concentration, which can affect the success of missions during flight."

To obtain this result, scientists conducted studies on mice that were intensely irradiated with particles similar to cosmic rays. These are very high-energy particles, mainly composed of protons originating from interstellar and intergalactic space. On Earth, we are protected by the planet's magnetic field. But in space, this is not the case. The rodents received a dose equivalent to a round trip to Mars in about 900 days.

Researchers were able to observe inflammation in the animals' brains, causing disruption in the transmission of electrical impulses between neurons. The diagnosis through MRI scans shows that all communication within the cortex is scrambled. "The entire central nervous system is affected," explains Professor Limoli, "resulting in global cognitive decline with signs similar to those of dementia."

Protecting the astronauts

Logically, the researchers pointed out, these signs appear very slowly in astronauts, but given the duration of the mission, this seems inevitable. According to data collected by NASA and those collected by Curiosity Rover During their journey from Earth to Mars, astronauts on an 800-day manned mission to Mars would receive a total radiation dose of approximately 1,01 Sieverts (*), including 320 mSv (millisierverts) during their stay on the red planet and two doses of 331 mSv, on the way there and back. By comparison, the average annual dose received on the Earth's surface is 2,5 mSv. The dose received on the International Space Station during 6 months is 75 mSv.

Researchers are trying to find ways to protect astronauts. But escaping cosmic rays is very difficult. That's why they followed the pharmacological lead: molecules could "disarm" cosmic particles and protect neurons.

(*) Sievert = unit that measures the biological effects of radiation