"I'm just overjoyed," says Nayi Castro, mission operations manager for NASA's OSIRIS-REx mission, as a sample of the 4.5-billion-year-old asteroid Bennu goes on display at the Smithsonian National Museum of Natural History in Washington. Jean Mann, a visitor at the museum, says the sample, though smaller than a fingernail, is "actually much larger" than she expected. IMAGES AND SOUNDBITES