<http://schema.org/alternativeHeadline>
"If radiation exposure over the course of a Mars mission increases cancer risk for astronauts by at least 3 percent, NASA deems the mission too dangerous."^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.mnn.com/earth-matters/space/stories/mars-bound-astronauts-will-face-high-risk-of-cosmic-radiation>