The Moon is pretty boring.
Earth is complex.
Mars is intermediate in size between the Moon and the Earth. And Mars is intermediate in complexity between the Moon and Earth.
Mars even has a couple of small of moons of its own (irregular overgrown boulders the size of uprooted mountains).
So I also expected Pluto to be a yawnfest since its even smaller than the Moon and thus presumably even geologically deader. But tiny pluto has more than one moon of its own (and moons much bigger the Deimos and Phobos around Mars). And its has a more complex geology than the the Earths Moon, and seems to be comparable in complexity to Mars.