Nothing like erosion has ever troubled asteroid Bennu. It is a pile of broken rocks, a loose conglomerate of jagged rubble 500 meters wide, feebly held together by gravity. In July of 2020, OSIRIS-Rex will take the first souvenirs and then head home for Earth.
You can help NASA pick the spot to sample. After the sample sites are chosen, they will be mapped to centimeter precision and then the lucky bits destined to go to the blue-and-white water planet will be abducted.