this is your brain on cosmic rays
We knew cosmic rays were a danger to astronauts' bodies, but it turns out they're hazardous to their minds as well.
Back in the day, I argued that if we were going to get serious about space exploration, we also had to budget for large, luxury spacecraft rather than just capsules in which we would cram the brave men and women we'd be sending to other worlds with a pat on the back for agreeing to deal with the discomfort and damage to their bodies. Among the reasons listed were the basic physiological problems of spending many months in zero gravity, and mental health hazards of boredom and cabin fever. But now there's another very important point to add to the list. If you spend too much time out of the Earth's magnetosphere, you will become less competent at the elementary tasks of exploration. Curiosity, focus, determination, situational awareness, the very traits that make humans such good generalists on our own world, and which robots can handle within very limited contexts, which is why we'd want to aid them when exploring new planets, all will become severely diminished after long-term bombardment by cosmic rays.
This is the result of a recent study which exposed mice genetically engineered to have neurons that glow under the right conditions, to lab-generated cosmic rays. After the equivalent of a few months worth of exposure to particles like ionized titanium and oxygen, the mice became a lot less curious, mentally sluggish, and learned slower. The results were comparable to dementia patients, and under the microscope, the reason was readily apparent. Cosmic rays attacked an inordinate number of dendrites, which are the parts of a neuron exchanging neurotransmitters with its neighbors. Fewer connections meant less efficiency and accuracy in communication, so it resulted in what amounts to reduced competency across the board. This is another reason to hold off on planning grand Mars missions. Damaging the minds of astronauts, perhaps for the rest of their lives, is too high of a price to pay just to get a flag-panting moment…
See: Parihar, V. et. al. (2015). What happens to your brain on the way to Mars Science Adv, 1 (4) : https://doi.org/10.1126/sciadv.1400256
