Notice the larger impacts in the region. Notice the other smaller crater impact in the top right frame, just up to the left of the cave? The lager impacts and the smaller crater impact in the top right frame, the floor or bottom of the craters can easily been seen. But the bottom or floor of the "caves" cannot be seen. This would seem to indicate that these are not just typical craters.
In addition, the have imaged these with infrared imaging cameras, and during night shots, they show warm areas around the caves, and the daytime images show cooler regions around the caves.