Most of the data we have looks at the health effects of radiation like gamma rays and X-rays, which cause damage across the body in a “uniform, spray-bottle kind of pattern,” explained radiation biologist Greg Nelson, who advises NASA on radiation health research. But galactic cosmic rays move through the body in a straight line, like a track. “So you concentrate damage on a microscopic scale, and that damage, because it’s so concentrated, is much more difficult for the body to repair,” Nelson said.

This type of space radiation isn’t like the low-dose exposure of a chest X-ray. Instead, imagine a charged particle traveling at nearly the speed of light, firing straight through your brain, perturbing 10,000 cells all in a row, all within a microsecond. It’s not necessarily damaging those cells, but it is activating them in a highly unusual way. And we don’t yet know what that does.

“It’s that feature, that we would call track structure, that lends itself to the possibility of new and different effects occurring,” Nelson said.

While most radiation on Earth can cause cancer by breaking apart DNA, the latest research suggests these charged particles could be damaging the brain in an entirely different way, such as by disrupting the connections between neurons or the mitochondria within