Much of the world is getting fired up about sending astronauts to explore extraplanetary bodies such as Mars or the Moon, but there's one thing to keep in mind: two radiation belts, known as the Van Allen belts, surround our planet.
The Van Allen belts are comprised of a proton-infested inner belt and an electron-infested outer belt. They pose potentially-lethal health risks to deep space astronauts because long-term exposure to the high-energy radiation can damage DNA.
NASA gets around this problem by shielding spacecraft with radiation-resistant armor, but while it keeps most of the radiation out, small amounts still seep through. To protect astronauts even further, NASA ensures that no spacecraft lingers within the radiation belts for too long as to reduce exposure.
Astronauts will need to pass through the Van Allen belts if they ever return to the Moon or explore Mars, but it appears as if NASA has thought things through. This means astronauts shouldn't experience radiation poisoning from traveling through the Van Allen belts when the time comes.