Deep-space radiation is a serious but largely unquantified threat to astronauts making a long trip to Mars. A new study in mice is discouraging: Space-like levels of radiation exposure damaged their neurons, giving the mice cognitive problems.
High-energy particles from blackholes and stars zip around deep space. We on Earth and even astronauts on the ISS in low-Earth orbit are shielded from space radiation by our planet's magnetic field. Astronauts travelling to Mars, which could take years, would be exposed to space radiation at unprecedented levels.
The new study funded by NASA and carried out by researchers at University of California, Irvine uses mice as a proxy for studying human brains. The mice were irradiated with oxygen and proton ions in a particle accelerator, at levels roughly equal to being in a spacecraft with no shielding on a mission to Mars.
When they followed up six weeks later, the irradiated mice seemed to have trouble remembering familiar versus novel objects. And the neurons in their prefrontal cortex, which is involved in higher-order reasoning, formed fewer connections.
Of course, this isn't a perfect analogue for what might happen in humans, who have bigger brains. A single high-intensity dose might also have a different effect than continuous exposure. In any case, NASA has been working out ideas for shielding a Mars-bound spacecraft. The problem is that the better the shielding, the heavier the spacecraft and the more expensive the fuel necessary. Another strategy is pharmacological, essentially antioxidants that could counteract the effects of radiation.
Whatever the solution, space travel will be dangerous, and we're just getting handle on these unknown dangers.