As if boredom, cramped conditions, and limited company were not enough to worry about on a voyage to Mars, future astronauts will face brain damage from cosmic rays too.

Researchers in the US exposed mice to streams of high energy particles– similar to those found in galactic cosmic rays - and found they produced nervous system damage that caused the animals’ performance to plummet.



“This is not positive news for astronauts deployed on a two- to three-year round trip to Mars,” said Charles Limoli, a professor of radiation oncology at the University of California, Irvine.



“Performance decrements, memory deficits, and loss of awareness and focus during spaceflight may affect mission-critical activities, and exposure to these particles may have long-term adverse consequences to cognition throughout life,” he added.

“This is not a deal breaker but it represents an issue Nasa needs to prepare for,” Limoli told the Guardian. “It could develop into performance-based decrements and elevated anxiety and affect the ability to problem solve. These effects are likely to be subtle, however, and would not preclude our efforts to plan future manned deep space missions.”

Facebook Twitter Pinterest A SpaceX Falcon 9 rocket lifts off from Cape Canaveral carrying a craft on its way to resupply the International Space Station, where research will help prepare Nasa astronauts for future missions to Mars. Photograph: Kim Shiflett/Rex Shutterstock

The technological hurdles of sending humans to Mars are formidable, but Nasa has its eye on a mission to the planet in the 2030s. Speaking at a hearing of the US house committee on science, space and technology in April, Nasa’s chief, Charles Bolden, said: “Our ultimate focus is the journey to Mars and everything comes back to that.

The US space agency is not the only organisation with Mars in its sights. The Dutch group, Mars One, aims to start a permanent colony on the planet in the 2020s and is interviewing candidates who would – should the project get off the ground – become the first crews. But some are sceptical: last year, scientists at MIT calculated that, as the mission is planned, the first Mars One pioneers would suffocate in 68 days.

In the latest study, rodents were briefly placed in a single beam of high-energy oxygen and titanium particles at Nasa’s space radiation laboratory before being sent back to Limoli’s lab for examination. In space, the particles that make up galactic cosmic rays are typically blasted from exploding stars.



Mars One mission: a one-way trip to the red planet in 2024 Read more

Exposure to the particles left the mice with brain inflammation, which affected how well signals passed along their neurons. Images of the animals’ brains found that the communication network was impaired.



Six weeks after their encounter with the energetic particles, the mice had fewer dendritic synapses, which are structures that protrude from neurons and carry electrochemical signals. The charged particles appeared to hit these neural branches and knock them off, creating similar effects to neurodegenerative diseases such as Alzheimer’s.



To study the impact of the brain changes on the animals’ behaviour, the scientists put the mice in containers with toys and then changed the types of toys, or their positions in the enclosure. The mice that had been hit by charged particles were less curious and less active than control mice, and became more easily confused.



“The present data do demonstrate that there is some likelihood of developing certain radiation-induced cognitive deficits,” the authors write in the journal Science Advances.

“Although the impairment of neurocognitive performance is undesirable in any circumstance, the impact of such decrements on the success of a deep space mission is likely to be especially problematic,” they add.



Similar cognitive problems could take a while to build up in astronauts, but space-farers on a long duration round trip to Mars could be at risk, said Limoli.



Researchers have documented other curious effects of cosmic rays since humans first began to fly in space. In 1974, Nasa scientists revealed that astronauts onboard the last seven Apollo missions reported bright flashes, caused by cosmic ray particles penetrating their head and eyes.

The latest study builds on previous work in animals, and suggests that spacecraft bound for long voyages are likely to need special shielding from cosmic rays. But such shielding might only lessen the problem. “There is really no escaping them,” said Limoli.

Other options are in development, including medicines that could help to protect the brain from the rays.

