Hacker News Reader

Not an expert at all but from skimming Wikipedia

“The appearance of plate tectonics on terrestrial planets is related to planetary mass, with more massive planets than Earth expected to exhibit plate tectonics. Earth may be a borderline case, owing its tectonic activity to abundant water”

https://en.m.wikipedia.org/wiki/Plate_tectonics

It is just that there no objects in the solar system big enough to have plate tectonics. And we currently have no way of detecting them on exoplanets.

> we are the only rocky planet that has both plate tectonics and a natural satellite

We have the oceans to thank for plate tectonics.

https://www.researchgate.net/publication/253303432_Are_Ocean...

I’m under the impression that there were no “plate tectonics” at the time of impact (surface was still nearly molten), and if there were (surface had actually crustified), plates were quickly melted by massive amounts of energy from the collision.