NASA and private space companies like SpaceX plan to send humans to the red planet within the next 15 years but among the major challenges facing future crewed space missions is how to protect astronauts from the dangerous cosmic radiation of deep space. Researchers has identified the first potential treatment for the brain damage caused by exposure to cosmic rays, a drug that prevents memory impairment in mice exposed to simulated space radiation. The study was published in Scientific Reports.

Humans venturing beyond the Earth's protective magnetic fields will be exposed to levels of cosmic radiation estimated to be 1000 times higher than what we experience on Earth or even in the International Space Station's low-earth orbit. Protecting astronauts from this harmful radiation will be key to making deep space exploration and perhaps one day colonization possible.

Researchers has conducted NASA-funded research for the past four years to understand how deep space radiation may affect astronauts' brains. Their team has previously found that exposing mice to simulated space radiation causes problems with memory, social interactions, and anxiety, and has linked these symptoms of radiation exposure to activation of cells called microglia part of the brain's immune system.

Activated microglia drive brain inflammation similar to what is seen in neurodegenerative disorders such as Alzheimer's disease, and also seek out and consume synapses, the information-bearing connections between brain cells.

In the new study, the researchers collaborated with co-authors at Loma Linda University in Southern California to expose mice for a day to a dose of radiation comparable to what they might experience in deep space.

In the present study, the irradiated animals initially displayed no cognitive deficits, but after three months they began showing signs of memory impairment. Normally, when researchers place mice in a room with a familiar and an unfamiliar object, the animals spend more time exploring the new object.

The authors hypothesize that by forcing the brain to replace irritable, radiation-exposed microglia with new, healthy microglia, the drug had allowed the animals avoid the cognitive consequences of radiation. This is really neat evidence, first that rebooting the brain's microglia can protect cognitive function following radiation exposure.

Similar compounds to PLX5622 produced by Plexxikon are already in clinical trials for multiple forms of human cancer, which suggests that the new findings could soon be translated to human use, the researchers say. Beyond spaceflight, these compounds could potentially be used to prevent cognitive impairments following cancer radiation therapy.

NASA is very interested in finding ways of ensuring both astronaut safety and mission success during deep space travel. But astronauts are a small population it's exciting that these findings could potentially help prevent many other forms of cognitive impairment.