The space exploration activity that has most helped astronomers determine the age of the Moon is the Apollo program, particularly the Apollo 11, 12, and 14 missions. During these missions, astronauts collected lunar samples, including rocks and soil, which were brought back to Earth for analysis.
Radiometric dating techniques, such as uranium-lead dating, were applied to these lunar samples. This analysis has provided crucial insights into the formation and age of the Moon. The findings suggest that the Moon is approximately 4.5 billion years old, which is close in age to the Earth. These lunar samples have been instrumental in understanding the Moon's geological history and its relationship with the early solar system.