On Aug. 9, 1976, the Soviet space program launched its last moon mission.

Luna 24 was a robotic sample return mission and the third of its kind. It lifted off on a Proton-K rocket from the Baikonur Cosmodrome in Kazakhstan and safety landed on the lunar surface nine days later. The probe landed in a dark plain known as Mare Crisium, or the "Sea of Crises" and collected 6 ounces (170.1 grams) of soil samples, which is brought back to Earth on August 22. Scientists then found that the samples from Luna 24 contained tiny traces of water — about 0.1 percent by mass.