Thousands of people have volunteered for a potential mission to Mars, but if any of them end up making the trip, they might lose a few brain cells along the way. New research finds that exposure to cosmic rays during the long journey, expected to take about six to eight months, can damage the brain and lead to dementia-like impairment. "This is not positive news for astronauts deployed on a two- to three-year round trip to Mars," Charles Limoli, professor of radiation oncology at the UC Irvine School of Medicine, said in a news release.