The above image shows the differences of the lunar gravity field. These measurements were taking by NASA’s Gravity Recovery and Interior Laboratory (GRAIL.) These images were taking as a result of it’s primary mapping mission that took place from March to May in 2012.
NASA took it’s microwave measurements from two spacecraft, the Ebb and Flow. The spacecraft were used to map gravity of the Moon with high precision and high spatial resolution. The picture was formed from blocks on the surface of about 12 miles. These measurements were three to five times better then the previous data. The map shows more small-scale detail for the far side of the moon because the far side has many more small craters.