The rover made an important discovery on the way to Mars. Its radiation assessment detector took measurements during the flight, identifying levels that exceed NASA's limit for astronauts. RAD measures two forms of natural radiation: galactic cosmic rays, which are particles caused by events such as supernova explosions, and solar energetic particles, which are associated with solar flares. Curiosity continues to take measurements on Mars to determine potential hazards for deep space explorers, who, for instance, may be traveling in the Orion spacecraft currently under development. NASA said it will use the data collected to design systems that protect astronauts from radiation exposure during expeditions.