The Moon is the only body in the solar system outside of the Earth that has been visited by humans. More than 440 pounds of lunar material are brought by NASA and Soviet space missions to Earth for study. The information gleaned about the Moon from this relatively small pile of rocks is mind-boggling and stands as the greatest proof that Martian planetary science would be greatly enhanced by returning samples to Earth. Compositional studies of lunar rocks show that the Moon and the Earth are made of similar material, and because lunar material has not been reworked through erosion and plate tectonics, it sheds light on the early formation of the Moon and its internal evolution.