Which event significantly advanced our understanding of the Moon’s geology?

The Apollo missions' lunar sample return significantly advanced our understanding of the Moon's geology because they allowed scientists to directly analyze lunar rocks and soil brought back from the Moon's surface. These samples provided invaluable insights into the Moon's composition, age, and geological history, revealing information about its formation and evolution. The data gathered from these samples has been fundamental in shaping our current models of lunar geology, including the understanding of impact processes, volcanic activity, and the Moon’s differentiation.

In contrast, while Hubble's observations contributed to our understanding of celestial bodies, including craters, they do not provide direct geological samples. Similarly, the Voyager missions primarily focused on outer planetary bodies and did not gather detailed geological data on the Moon itself. The Lunar Reconnaissance Orbiter, although it has provided high-resolution imagery and topographical maps, does not offer the direct geochemical insights that the Apollo samples do.