Radiation near the Moon can pass straight through the body, yet preliminary Artemis I measurements suggest a smaller-than-expected increase in exposure compared with low Earth orbit.

Beyond Earth’s protective magnetic field, astronauts face a constant bombardment of high-energy particles from deep space. But how much radiation would they actually absorb during a journey around the Moon? NASA’s Artemis I mission offered a rare opportunity to find out. Aboard the uncrewed Orion spacecraft, two human-shaped mannequins carried more than 10,000 tiny crystal detectors that recorded radiation exposure throughout their simulated bodies.

Surprisingly, radiation doses near the Moon were only moderately higher than those in low Earth orbit, a smaller increase than researchers might have expected.