It seems that there's the remains of the large asteroid that caused the crater buried underneath it. If that asteroid was partly metallic, it would have a higher density than the Moon's rock, which would show up as the gravity anomaly.

Iron Sky...

I’m wondering...If a heavy metal asteroid struck anywhere on the moon the moon would suddenly be out of balance. Would that cause a shift in the axis of rotation so that the heavy spot would wind up at one of the poles?

Probably just an alien moon base. All those UFOs have to come from somewhere.

Well, something I said a long time ago . . . . and perhaps they are now starting to realize . . . . We know that mining asteroids could be immensely profitable, and there are a lot of difficulties involved in doing so. However, mining the Moon would be much easier, and, the Moon is full of all kinds of debris from impacts from all kinds of things . . . . this makes the Moon even more fruitful than asteroid mining, so perhaps with more news like this, they will come to this realization. Mars should be second in priority. Not only can the Moon provide many immensely valuable resources, it can also provide a jump off point. Because it rotates around the earth, whenever something is launched from the Moon at the right point in time, it already has the momentum given to it by the Moon, and because the escape velocity of the Moon is so much less, you could not ask for a much better space station. Wake up people, the Moon is much more valuable than mining a fucking asteroid or any trip to Mars, not to mention also, it is much closer.