You might not want to book that trip to Mars just yet. Researchers have published a study estimating that the risk of cancer from cosmic rays is twice as high as previously thought. They've determined that conventional risk models are incomplete. While NASA and other groups believe that radiation-based cancer stems only from direct cell damage and mutations, the new model accounts for the possibility that heavily damaged cells will increase the cancer risk for "bystander" cells. There's a knock-on effect that would be difficult to escape.