<http://schema.org/alternativeHeadline>
"The space agency will study the effects of living in space for a year using astronaut Scott Kelly and his retired twin brother Mark as the test subjects."^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.mnn.com/earth-matters/space/stories/nasa-turns-to-its-own-for-unprecedented-astronaut-twin-study>