Once Hera floats into position over a select site, a flexible boom reaches out from the spacecraft. The cutting head and temporary sample-storage chamber is retracted back into the spacecraft. The asteroid material is then transferred into a canister for return to Earth. High hopes The NEAR spacecraft, which has orbited Eros since February, boosts the probability of success for Hera, Sears said. There's a diversity of asteroids that range in composition from iron objects and volcanic-like rock to bits of small stone or gravel loosely clumped together.
Asteroids range all over the map.
While there is much science behind Hera, knowing more about asteroids could also help protect Earth from future run-ins with falling space rocks. While the likelihood of impact is small, the effect is devastating. Also, you can estimate what's going to happen if they hit the Earth. A fluff ball hitting Earth is not quite the same as an iron object.