One of America's next big space missions is to go where no man has gone before: the red planet. Your head may be filling with images of astronauts maneuvering Mars' mountainous terrain and harsh climate, but the greater challenge is getting there.

A big one is radiation, and astronauts would be exposed to high levels of it in open space. They'd encounter electrons, protons, and alpha particles traveling near light speed, passing through their body, breaking DNA chains, and mutating and killing cells. We have long known this level of bombardment on the body increases cancer risks, and now it appears there is an increased risk for Alzheimer's Disease as well.

Researchers exposed mice to doses of highly charged, high mass particles of iron at levels comparable to a Mars Trip. Six months after exposure, the mice had cognitive impairment including memory issues. Male mice had changes in brain blood supply and higher build up of beta amyloid which is associated with the start of Alzheimer's. It's hard to tell if their poorer memory was caused by the radiation or the beta-amyloid accumulation or both.

A roundtrip to Mars, predicted to take three years, would expose astronauts to four times NASA's recommended lifetime radiation exposure. At this level, an astronaut's lifetime cancer fatality risk increases by 2.4 percent and for women by almost 17 percent. How much this level of radiation raises an astronaut's risk for Alzheimer's is unclear. As we better understand the risks of space travel, it is obvious NASA must develop a spacecraft that can protect its astronauts from radiation.