Readings from the Radiation Assessment Detector (RAD) aboard the spaceship that carried the Curiosity rover to Mars reveal that astronauts would receive significant doses of very-high-energy galactic cosmic rays and solar particles.

While the readings are not unexpected given what is known about deep space, the actual measurements are sobering: An astronaut in a spaceship protected to the same level as the International Space Station (ISS) would receive enough radiation to approach or exceed what is considered to be a safe lifetime exposure.