Space travel, to go where no human has gone before, presents an alluring challenge. But the cosmic radiation that fills deep space is not brain-friendly.

“Galactic cosmic radiation poses a significant threat to future astronauts,” says researcher M. Kerry O’Banion, M.D., Ph.D. “The possibility that radiation exposure in space may give rise to health problems such as cancer has long been recognized. However, (our) study shows for the first time that exposure to radiation levels equivalent to a mission to Mars could produce cognitive problems and speed up changes in the brain that are associated with Alzheimer’s disease.”

While space is full of radiation, the Earth’s magnetic field generally protects the planet and people in low Earth orbit from these particles. However, once astronauts leave orbit, they are exposed to constant shower of various radioactive particles. With appropriate warning, astronauts can be shielded from dangerous radiation associated with solar flares. But there are also other forms of cosmic radiation that, for all intents and purposes, cannot be effectively blocked.

Several studies have demonstrated the potential cancer, cardiovascular and musculoskeletal impact of galactic cosmic radiation. The most recent study examines the potential impact of space radiation on neuro-degeneration. This harmful process contributes to the development of Alzheimer’s disease. O’Banion, whose research focuses on how radiation affects the central nervous system, and his team have been working with NASA for more than eight years.

The researchers studied the impact of a particular form of radiation called high-mass, high-charged (HZE) particles. These particles — propelled through space at very high speeds by the force of exploding stars — come in many different forms. For this study the researcher chose iron particles. Unlike hydrogen protons, which are produced by solar flares, the mass of iron particles, combined with their speed, enable them to penetrate solid objects such as the wall and protective shielding of a spacecraft.

“Because iron particles pack a bigger wallop it is extremely difficult from an engineering perspective to effectively shield against them,” says O’Banion. “One would have to essentially wrap a spacecraft in a six-foot block of lead or concrete.”