Gravity is not uniform everywhere on earth, because the Earth's density is not uniform. (This is ignoring the other consideration that the earth is not spherical. Because the Earth bulges at the equator, gravity is also weaker towards the equator and stronger at the poles.) Satellites[1] or humans on the ground can track variance in the gravity field. This is normally done to find underground deposits of valuable minerals or metals, as may be slightly denser or less dense than the equivalent volume of earth/stone.[2] I think OP was wondering if the presence of the impact site would show up on such a survey of Earth's gravity field.
Most of the circular impressions are impact craters.
Variance of the Moon's g field is vastly greater than Earth's. Enough so that long-lived lunar satellites are very difficult to plan as their orbits continuously devolve due to gravitational perturbations, and eventually intersect the Moon at perilune. Often in a matter of weeks or months.
