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Mice exposed for six months to the radiation levels prevalent in interplanetary space exhibited serious memory and learning impairments, and they became more anxious and fearful as well, the study reports.

The trip to Mars takes six to nine months one way with current propulsion technology. So, these results should ring a cautionary bell for NASA and other organizations that aim to send people to the Red Planet, study team members said.

These chronic low-dose-rate, low-dose-exposure scenarios are going to increase the risk of developing, perhaps, mission-critical performance deficits,” Limoli told Space.com. “What exactly those are, we’ll never know until we get out there.”

Researchers investigating the effects of deep-space radiation have historically given lab animals acute doses — high levels over a relatively short period of time. But Limoli and his colleagues — led by Munjal Acharya and Janet Baulch of UCI’s Department of Radiation Oncology and Peter Klein of Stanford University’s Department of Neurosurgery — took a different tack.

Using a neutron-irradiation facility, they exposed 40 mice to 1 milligray of radiation per day (1 mGy/day) for six months, about the same dose and duration that astronauts would experience on a trip to or from Mars. (Astronauts in low Earth orbit are exposed to lower doses, because they’re protected by our planet’s magnetosphere.)

“This is the first study that’s looked at space-relevant dose rates,” Limoli said. “And this is the first study to analyze the consequences of the low dose rate over the course of time on functional endpoints in the brain.”

The researchers analyzed the behavior of these mice over the course of the study, measuring the animals’ ability to learn and remember information, their willingness to interact with new mice introduced into their enclosure, and other variables. And at the end of the six months, the scientists euthanized the mice and studied their brains, looking for physiological changes.

All of these measurements and observations were compared with those gathered from a control group of 40 mice, which did not receive the 1 mGy/day dose.

The results were striking. Radiation-exposed mice exhibited more stress behaviors and a decreased ability to learn and remember. The physiological work bolstered these behavioral findings, identifying impaired cellular signaling in two key areas of the brain: the hippocampus, which is associated with learning and memory, and the prefrontal cortex, the site of many complex cognitive functions. …….https://www.space.com/space-radiation-damage-mars-astronauts-brains.html