NASA's goal of bringing humans to planet Mars is not just ambitious but also dangerous. Given the extreme conditions on the Red Planet, astronauts who would be sent for a Mars mission face the probability of death.
Findings of a new study suggest of another danger that astronauts on lengthy space missions would face: risk for chronic dementia.
Researchers found that lab animals that had been exposed to highly energetic charged particles just like those found in galactic cosmic rays that astronauts would be exposed to during extended space flights suffered long-term brain damage that can result in cognitive impairments and dementia.
For the study, which was published in Nature's Scientific Reports, researchers from the University of California, Irvine exposed rodents to charged particles at the NASA Space Radiation Laboratory. Six months after exposure, scientists found that the animals still had significant levels of brain inflammation and damage in their brain cells.
Imaging showed damage on the brain's neural network, which include impairments of neural dendrites and spines, disrupting communication among brain cells. The observed deficiencies were comparable to performing poorly in behavioral tasks that test memory and learning.
The researchers said that the resulting brain damage may continue and even progress throughout life.
"Our data provide additional evidence that deep space travel poses a real and unique threat to the integrity of neural circuits in the brain," the researchers wrote in their study, which was published on Oct. 10.
The researchers likewise found that radiation influenced the neural mechanism called "fear extinction," which caused radiation-exposed rodents to lose their ability to get rid of negative memories.
Study researcher Charles Limoli, from UCI's School of Medicine, said deficiency in fear extinction can make an individual vulnerable to anxiety and this could cause a problem for astronauts who would spend years traveling to and from planet Mars.
Limoli said that the space environment exposes astronauts to unique hazards.
"Exposure to these particles can lead to a range of potential central nervous system complications that can occur during and persist long after actual space travel - such as various performance decrements, memory deficits, anxiety, depression and impaired decision-making," Limoli said.
An earlier study, also by scientists from the UCI and published in the journal Science Advances already hints of the dangers of long-term exposure to cosmic ray radiation.
Although NASA is working on ways to shield astronauts and their spacecraft from cosmic rays, no system would completely prevent such exposure.