"Currently available landing systems, using heat shield and parachutes, might be problematic because jettisoned hardware from these landers normally land within a few hundred meters of the lander. I would imagine a sample return mission would not jettison its parachute in close vicinity of the target sample or the cached sample. The parachute might cover the sample, making its retrieval a problem. Landers using large parachutes or other large devices probably pose the greatest risk as these could be easily blown onto equipment on the surface, damaging or covering it."