Yes, moon rock samples. From Apollo and from the Soviet landers.

The problem with the idea of crustal thicknesses being caused by the moon creation event is that the moon creation event happened very early in the Earth's history, and basically the Earth must have been completely molten -- so there really wasn't a solid crust right after the impact. Think about the huge amount of energy that was imparted by the impact -- where a core of a Mars size planet merged with the core of the proto-earth, and massive quantities of material were splattered out into orbit. That amount of energy would have destroyed any solid crust that already existed.

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