Mascon Basins
Typically, mass deficit associated with large craters (simply big holes) are expected to produce negative free-air gravity anomaly. However, there are numerous large impact basins on the Moon that are associated with positive free-air gravity anomalies and are called mascon (mass concentration) basins. Free-air gravity anomaly associated with mascon basin demonstrates a bull’s-eye pattern in which the center has positive anomaly and is enclosed by a circular negative gravity signature.
Using the following comparison between the lunar gravity and topography you can spot large mascon basins:
Gravity
Topography
The question is why we only see numerous mascon basins on the lunar surface and not elsewhere. We found an answer for it. The manuscript soon will be submitted to JGR-Planet. Meanwhile, you can read the LPSC abstract.
Gravity
Topography
By moving the arrow you can see that the negative topography is associated with positive free-air gravity anomaly. The above illustration is the topography and gravity data of Orientale basin on the Moon.