With rubble from an asteroid tucked inside, a NASA spacecraft fired its engines and began the long journey back to Earth, leaving the ancient space rock in its rearview mirror. The trip home for the robotic prospector, Osiris-Rex, will take two years. Osiris-Rex reached asteroid Bennu in 2018 and spent two years flying near and around it, before collecting rubble from the surface last fall. The University of Arizona’s Dante ...