Something like 200 tonnes of human-made material sits on the Moon, spread across roughly a hundred sites — landers, rovers, crashed rockets, spent stages and a lot of discarded equipment.

Most of it was left on purpose. Every kilogram lifted off the surface cost fuel, so the Apollo crews jettisoned boots, backpacks, cameras and tools before climbing back in. The single heaviest items are the descent stages and the deliberately crashed upper stages, several of which were aimed at the surface to give the seismometers a bang of known size.