Apollo 12 Visits Surveyor III
When the Surveyor Program was designed, there was no plan for these spacecraft to be visited by any of the Apollo astronauts. However, in the final planning stages of Apollo 12, landing near the the Surveyor III site was included in the mission plan.
Thirty-one months after Surveyor 3 landed, the crew of Apollo 12 photographed the spacecraft and its landing site, then removed and brought back a number of selected components from the explorer. These parts, which included the television camera, were analyzed to determine the effects on the hardware of the long exposure to the lunar environment.
Engineering studies of the television camera show that the complex electromechanical components, optics, and solid-state electronics were remarkably resistant to the severe lunar surface environment over 32 lunar day / night cycles with their extremes of temperature and long exposure to solar and cosmic radiation. These results indicate that the state of technology was capable of producing reliable hardware that makes feasible long-life lunar and planetary installations.
Although space probes have returned to Earth since Apollo 12, this remains the only occasion in which humans have visited a probe sent to another world.