If getting to Mars isn't hard enough, scientists at the UC Irvine say that cosmic radiation could cause astronauts on deep space missions to develop symptoms of dementia. Rodent tests indicate that exposure to high-energy particles produce cases of "space brain" marked by long-term neurological damage, cognitive impairment, and diminished judgment.

Radiation has long been recognized as a constant and very real threat to space travelers, which is the reason why crews on the International Space Station (ISS) are legally classed as radiation workers. Prolonged exposure to cosmic rays can result in an increased chance of cancer, impaired immune systems, and even affect the brain and nervous system. The latter is of particular concern because it's already known that patients undergoing radiation therapy to treat brain tumors can suffer severe neurological symptoms, such as problems with cognition and memory.

For astronauts on the ISS, radiation mainly curtails how long and how many visits crews can make in a lifetime. But outside of the protection of Earth's magnetic field, which means any deep space mission, it's another matter. On long missions, including to Mars, galactic cosmic rays become a major hazard. These immensely high energy charged particles that originate outside the Solar System can shoot through spacecraft hulls and passengers as if they aren't even there. However, when the heavier of these particles, such as the nuclei of oxygen and carbon atoms, strike, they can directly or indirectly cause major damage to living tissue.

As part of NASA's Human Research Program, a UCI team under professor of radiation oncology Charles Limoli used the NASA Space Radiation Laboratory at New York's Brookhaven National Laboratory to approximate cosmic rays using an earthbound particle accelerator. Since real cosmic rays are hard to create if one doesn't have a quasar or exploding galaxy handy, the team used fully ionized oxygen and titanium nuclei to approximate the impact of lighter particles of much higher energies.