Dark Planet Saga - Mine the moon

This got me thinking...... an object that large, if it crashed into another far larger object with low enough speed, and then was subjected the the gravitational pull of the other object while stuck on the surface, and exposed to some weathering, the sphere would collapse, right? Would it just look like... mountains after enough time? The crust of the planet (if it had a molten core) would bow inward in response to the mass, so the sphere would sink down a bit... if it didn't full-out penetrate the crust in the initial collision of course.

I wonder if there are any examples of mountain formation of this type within the solar system, or if the impacts of objects of this size are always so high velocity that the bulk of it spins off.