Goals: Surveyor 5 was to support the upcoming Apollo missions by performing a soft landing in Mare Tranquillitatis and then taking pictures of the lunar surface, by firing a rocket engine after landing to see how much the lunar soil is disturbed, and by analyzing the soil.
Accomplishments: When a leak in the thruster system threatened the mission, engineers saved the day by devising and executing an alternate braking sequence. The spacecraft returned over 20,000 pictures taken during 3 lunar days. Soil analysis (the first ever on another world) revealed a basalt-like composition: more than half oxygen, followed by silicon and aluminum. The amount of material sticking to the footpad magnets suggested a mix of pulverized basalt and 10 percent to 12 percent magnetite with no more than 1 percent metallic iron. Firing the main engine for 0.55 second produced no crater or significant dust cloud.