Invaluable data can at times be overlooked or not fully exploited when first collected. Striking conclusions can often be drawn on the basis of a specific analysis many years later. The Apollo 11 - 17 missions (1961-1972) provided detailed information on lunar basalts which make it possible to measure the iron grains in basalts from microphotographs of thin sections. Analysis of the average size of these grains ( D ) differed as a function of the age of these basalts dated between 3.9 and 3.4 billion years ago, revealed that D increased 1.5 fold, therefore the gravity acceleration g decreased 1.5 fold. The intriguing conclusion can only be that the size of the Moon increased, its mass decreased, or both these factors have changed.
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