The second mission to land on the Moon had garbage collection duty: they picked up the remains of a probe that had crashed there two years earlier.
Apollo 12 was the second manned mission to the Moon, and it holds a rare distinction in the annals of space exploration. It was the first (and, so far, only) time that people have gone to the Moon and picked up something left behind by someone else.
The Surveyor 3 probe had landed on the Moon in 1967. Well, actually it bounced onto the Moon because of a radar error, but it got down safely enough. The probe had a little scoop to gather up some lunar soil, not to return it to Earth but just to dig it up, spread it out, and photograph it. The photos would be analysed to work out things like the density of the lunar surface. This would be important information if someone were, for example, planning to land on the Moon and wanted to make sure they weren’t going to sink into the ground. Surveyor 3 also took the first photo of Earth from the surface of the moon (you can see it in the third link below).
Two years later, Apollo 11 made that first human landing on the Moon. It did not sink into the ground. Apollo 12 followed four months later, and for that second visit NASA decided that a little garbage collection was in order. Part of the Apollo 12 mission was to land near the Surveyor 3 probe and bring some of it back with them. This was a good idea for at least a couple of reasons:
- practicing precision landing would give them good experience manoeuvring on the Moon
- bringing back a human-made object that had been on the Moon for a long time would tell them about the potential for weathering and long-term damage
Apollo 12’s lunar module Intrepid landed successfully within walking distance of the probe. The third and fourth men on the Moon, Pete Conrad and Alan Bean, strolled over there and picked up bits of Surveyor 3.
When they got it back to Earth testing showed that the probe parts were infected with bacteria. No, not moon bacteria, but bacteria from Earth that had survived the full lunar round trip. Or so they thought at the time – now we think that the bacteria was actually picked up on the ride home or once it got back.