Outer space may look mostly empty, but it’s actually packed with cosmic radiation—gamma rays and charged particles produced by exploding stars, black holes and other violent astrophysical phenomena. Earth’s atmosphere and magnetic field keep us safe from the worst of this steady barrage of subatomic bullets. But cosmic radiation would be a constant concern for astronauts on lengthy interplanetary voyages.

NASA and other space agencies have known for decades that this radiation can cause cancer and other cell damage. However, possible effects on mental functioning have been difficult to test. But a new study shows that, in mice at least, cosmic radiation likely causes cognitive impairment. The research is in the journal Science Advances. [Vipan K. Parihar et al, What happens to your brain on the way to Mars]

The researchers mimicked cosmic-radiation exposure by briefly bombarding the brains of lab mice with high-energy particles. Six weeks later, the mice scored poorly on tests of learning and memory—they displayed less curiosity and more confusion than an unexposed control group. Analysis of their brains revealed inflammation and decreased numbers of dendrites, which transmit signals between nerves.

If humans are similarly susceptible, astronauts on voyages to Mars could suffer permanent cognitive impairment that could hinder their abilities to recall information and to think on their feet. Faster transits, new antiradiation drugs and better spacecraft shielding should help. But until those solutions are developed, sending brain-damaged humans to Mars would be a dim-witted thing to do.

—Lee Billings

[The above text is a transcript of this podcast.]