Dangerous levels of radiation in space could bar astronauts from a mission to Mars and limit prolonged activity on the moon, experts now caution.
However, more research could reveal ways to handle the risks that radiation poses to space missions.
The magnetic field of Earth protects humanity from radiation in space that can damage or kill cells. Once beyond this shield, people become far more vulnerable.
More: http://www.space.com/missionlaunches/080331-radiation-shielding.html