CAPE CANAVERAL, Fla. (AP) — A NASA spacecraft is descending to the surface of an asteroid to collect a handful of the rubble for return to Earth. The Osiris-Rex spacecraft dropped out of orbit around asteroid Bennu early Tuesday afternoon. It will take more than four hours for the spacecraft to get down to the asteroid’s rough terrain. Bennu’s gravity is too low for the spacecraft to land. So the spacecraft will reach out with its long robot arm and attempt to grab at least 2 ounces of dust and pebbles. It’s the most harrowing part of NASA’s first asteroid-sampling mission, which began with a launch back in 2016.