Apollo 12 was the first Apollo mission to land astronauts near a previously visited robotic spacecraft, Surveyor 3.
Surveyor 3 had landed in the Ocean of Storms in April 1967 and transmitted thousands of images and engineering measurements. Apollo 12 touched down nearby on 19 November 1969, allowing astronauts Charles Conrad and Alan Bean to walk to the probe during their surface excursions.
The astronauts photographed Surveyor 3 and removed several components, including its television camera and a section of electrical cable. Engineers wanted to examine how long exposure to the lunar environment had affected the hardware. The returned pieces were studied on Earth, although later analysis found no confirmed lunar microorganisms on them.
Apollo 12's precision landing was an important advance over Apollo 11. The mission also deployed scientific instruments and collected samples, but its visit to Surveyor 3 remains its most recognizable robotic-spacecraft investigation.