People become astronauts knowing it's a dangerous job, and measures can be taken to minimise their radiation exposure
|Local magnetic fields may provide some radiation protection in particular regions on Mars, but astronauts' living modules will need to be buried. Image: Nasa|
On Earth, we're all exposed to natural radiation from a variety of sources, including brazil nuts, bananas, and invisible radon gas. We'd be exposed to much higher doses from extraterrestrial sources if the Earth wasn't so well protected. The planet's magnetic field is carved into a teardrop-shaped bubble – the magnetosphere — by the solar wind that blows from the Sun. Although it contains some regions of higher radiation, the magnetosphere's overall effect is to shield life on Earth, and astronauts in low Earth orbit, from the harshest effects of cosmic radiation. Earth's atmosphere provides an additional buffer against all but the most energetic of particles. Astronauts travelling outside the magnetosphere, however, have to rely on the shell of their spacecraft to protect them from danger.