Nasa and the Netherlands-based Mars One group bothactively researching how to send people to the red planet Rex

Mars-bound astronauts could develop dementia and an uncontrollable sense of dread – dubbed “space brain” – during the journey, scientists have warned.

Researchers studied the effects of cosmic rays that would bombard astronauts and their results pose a significant problem for those wishing to establish a colony on the distant planet.

Nasa is actively studying how to send humans to Mars, which is nearly 34 million miles away, and the Netherlands-based Mars One group plans to send people there by 2027. US entrepreneur Elon Musk has also talked about sending people by 2022.

However Professor Charles Limoli, an expert in radiation oncology at University of California, Irvine, and colleagues found highly charge particles in cosmic rays caused significant long-term brain damage in test rodents, resulting in cognitive impairments and dementia.

And it also interfered with the “fear extinction” process, which helps people get over scary or stressful incidents so they can, for example, go swimming again after nearly drowning, he reported in the journal Scientific Reports.

“This is not positive news for astronauts deployed on a two- to three-year round trip to Mars,” Professor Limoli said.

“The space environment poses unique hazards to astronauts. 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.
“Many of these adverse consequences to cognition may continue and progress throughout life.”
Alarmingly, the first Martian explorers could also become paranoid during the flight because of the effects on the brain’s normal process of dealing with stressful events. “Deficits in fear extinction could make you prone to anxiety, which could become problematic over the course of a three-year trip to and from Mars,” Professor Limoli said.

While astronauts have lived on the International Space Station for more than a year, they have not faced the same level of cosmic rays because it orbits the Earth inside the planet’s protective magnetosphere.

Areas of the spacecraft could be fitted with extra shielding but it is currently not possible to fully protect the astronauts in this way. There is “really no escaping” the cosmic rays, Professor Limoli said.

Instead he and his team are working on drugs that could protect people from the worst effects of the radiation.

Will astronauts traveling to Mars remember much of it? That’s the question concerning University of California, Irvine scientists probing a phenomenon called “space brain.”

UCI’s Charles Limoli and colleagues found that exposure to highly energetic charged particles — much like those found in the galactic cosmic rays that will bombard astronauts during extended spaceflights — causes significant long-term brain damage in test rodents, resulting in cognitive impairments and dementia.

Their study appears in Nature’s Scientific Reports. It follows one last year showing somewhat shorter-term brain effects of galactic cosmic rays. The current findings, Limoli said, raise much greater alarm.

“This is not positive news for astronauts deployed on a two-to-three-year round trip to Mars,” said the professor of radiation oncology in UCI’s School of Medicine. “The space environment poses unique hazards to astronauts. 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. Many of these adverse consequences to cognition may continue and progress throughout life.”

For the study, rodents were subjected to charged particle irradiation (fully ionized oxygen and titanium) at the NASA Space Radiation Laboratory at New York’s Brookhaven National Laboratory and then sent to Limoli’s UCI lab.

Six months after exposure, the researchers still found significant levels of brain inflammation and damage to neurons. Imaging revealed that the brain’s neural network was impaired through the reduction of dendrites and spines on these neurons, which disrupts the transmission of signals among brain cells. These deficiencies were parallel to poor performance on behavioral tasks designed to test learning and memory.

In addition, the Limoli team discovered that the radiation affected “fear extinction,” an active process in which the brain suppresses prior unpleasant and stressful associations, as when someone who nearly drowned learns to enjoy water again.

“Deficits in fear extinction could make you prone to anxiety,” Limoli said, “which could become problematic over the course of a three-year trip to and from Mars.”

Most notably, he said, these six-month results mirror the six-week post-irradiation findings of a 2015 study he conducted that appeared in the May issue of Science Advances.

Similar types of more severe cognitive dysfunction are common in brain cancer patients who have received high-dose, photon-based radiation treatments. In other research, Limoli examines the impact of chemotherapy and cranial irradiation on cognition.

While dementia-like deficits in astronauts would take months to manifest, he said, the time required for a mission to Mars is sufficient for such impairments to develop. People working for extended periods on the International Space Station, however, do not face the same level of bombardment with galactic cosmic rays because they are still within the Earth’s protective magnetosphere.

Limoli’s work is part of NASA’s Human Research Program. Investigating how space radiation affects astronauts and learning ways to mitigate those effects are critical to further human exploration of space, and NASA needs to consider these risks as it plans for missions to Mars and beyond.

Partial solutions are being explored, Limoli noted. Spacecraft could be designed to include areas of increased shielding, such as those used for rest and sleep. However, these highly energetic charged particles will traverse the ship nonetheless, he added, “and there is really no escaping them.”

Preventive treatments offer some hope. Limoli’s group is working on pharmacological strategies involving compounds that scavenge free radicals and protect neurotransmission.