A NASA spacecraft sent out to collect a sample of rock and dust from an asteroid has nabbed so much that it's created an unexpected problem. NPR science correspondent Nell Greenfieldboyce shares a cautionary tale of a scientific mission that was almost too successful. For additional info and fun links, check out the episode page. Follow Maddie and Nell on Twitter. Maddie's @maddie_sofia and Nell's @nell_sci_NPR. Email the show at [email protected].