If you were traveling to Mars solely by spacecraft, your health might take a serious hit during the 18-month or so round-trip journey–and you might not even be able to see your home by the time you got back. Throughout the journey, high-energy particles known as cosmic rays would course through your body, not only damaging your eyesight, but also increasing your risk of cancer by up to 20 percent.
Luckily, one scientist has an answer: Don’t fly a spaceship to Mars, hop on an asteroid instead.
Cosmic rays zing into our solar system from interstellar space; here on Earth our planet’s magnetic field protects us from them, and astronauts aboard the International Space Station are mostly protected by the Earth’s bulk and its magnetic field as well. But astronauts on a long-haul trip to Mars would be in more danger.