The U.S. space agency said Friday that it expects to have captured some hundreds of grams in rock samples during a recent visit by a spacecraft to the asteroid Bennu, but added the collector is leaking some of the material.The OSIRIS-REx spacecraft is on the first U.S. mission to carry samples from an asteroid back to Earth. On Tuesday, it unfurled its robotic arm, attached with a disk-shaped sample collector at its end, to touch the surface of Bennu for six seconds.According to the National Aeronautics and Space Administration, images have shown that the sampler, about 30 centimeters in di…READ FULL ARTICLE