Exposure to radiation during space travel damages brain tissue and affects performance, a new study has shown.
Space-farers venturing beyond the protective cloak of the Earth's magnetic field are unavaoidably exposed to powerful cosmic radiation. This comprises fast-moving, high-energy, heavy particles.
When these collide with materials, they can rip apart molecules and unleash an atomic domino effect that spits out other forms of radiation that do further, collateral damage locally.
The extent to which this might deleteriously impact on an astronaut's performance in space wasn't known though.
To establish the scale of the threat, University of California, Irvine, scientist Charles Limoli and his colleagues exposed mice over a six week period to streams of oxygen and titanium particles at higher and lower doses equivalent to those encountered in space.
The animals then underwent memory and cognition tests alongside a second group of unexposed, control mice.
At the higher doses, the radiation-exposed animals showed a significant drop in their recall and spatial memory performance.
Samples from the animals' brains showed a dramatic reduction in the density of the connections between nerve cells in the front parts of the animals' brains.
Seen down a microscope, the affected areas resembled trees that had been fiercely pruned and the cells themselves were also devoid of the spine structures that form the physical basis of neural connections, called synapses.
According to the researchers, who have published their findings this week in the journal Science Advances, the neurocognitive deficits observed in the mice, if relevant to humans, represent a significant challenge and a priority for NASA, "as they plan for longer duration missions."
Noteworthy is the recent data returned by the Curiosity rover that journeyed to Mars in 2011, encountering en-route a radiation dose equivalent to two-thirds of an astronaut's safe lifetime exposure.
That journey took nine months, an exposure duration, Limoli and his team point out, which is likely to result in every cell in the brain being hit at least several times, on average, by a particle of cosmic radiation.
"The data also indicate that significant deficits in learning and recall memory persist long after exposure."