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Astronauts travelling on long space missions to planets like Mars may suffer brain damage from cosmic rays.

Neuroscientists have found that interstellar radiation can change the structure of neurons in the brain after long periods of exposure.

Mice exposed to highly energetic particles, like those found in galactic cosmic rays, also tended to be more easily confused and less inquisitive.

Neuroscientists have found that interstellar radiation can change the structure of neurons in the brain after long periods of exposure. Astronauts (pictured) are exposed to radiation while in orbit but as they get further from the Earth the doses increase as they are no longer protected by Earth's magnetic field

The scientists warn that if similar impacts occur in human brains it would leave astronauts less able to respond to new situations and solve problems - qualities that will be crucial in dangerous space missions.

They say that spacecraft will need to have shielding to help protect astronauts during long missions.

Professor Charles Limoli, a radiation oncologist at the University of California Irvine, said: 'If the changes seen in mice occur in astronauts, it is likely that space radiation exposure may compromise their ability to problem solve and respond to new situations.'

'This is not positive news for astronauts deployed on a two to three year round trip to Mars.

'Performance decrements, memory deficits and loss of awareness and focus during spaceflight may affect mission-critical activies.

'Exposure to these particles may have long-term adverse consequences to cognition throughout life.'

The findings come as Nasa continues to plan to send astronauts to live in orbit and later on the surface of Mars.

Private ventures like Mars One are also hoping to send humans to the Red Planet.

However, the new study, published in the journalScience Advances, show that mice - the paper does not say how many – were exposed to small doses of high energy charged particle.

Six weeks later the mice were then tested using a series of memory and learning experiments.

Those that had been exposed to the charged particles were more easily confused.

The researchers also found that the number of branched neurons called dendric cells were greatly reduced in those mice that had been exposed.

The scientists behind the study say cosmic rays could pose a considerable risk to astronauts engaging in deep space missions.

The communication delays that would accompany such long distance missions would increase the risk should astronauts be unable to make critical decisions quickly.

The researchers found that the brains of mice exposed to high energy particle similar to those found in cosmic rays had lower levels of branched nerve cells, known as dendric cells. The images above show how as doses (measured in Grays) of different particles increased, the mice had fewer of the branched nerve cells

Missions to Mars (above) involve a two-year round trip, exposing astronauts to dangerous levels of radiation

And they have urged Nasa to make tackling the problem a priority.

Professor Limoli added spacecraft could be designed so that areas used for sleep and rest could have increased shielding against cosmic rays.

He said it may also be possible to protect the brain from damage using drugs.

'We are working on pharmacologic strategies involving compounds that scavenge free radicals and protect neurotransmission. But these remain to be optimised and are under development.'