O.K.
So I'm more of a skeptic than anything else but I just find the features of Iapetus (one of saturn's moons) totally amazing.
Click to view attachment
Not only does it have a straight ridge which runs for hundreds of kilometers. Half of the planet is black as asphalt and the other is white as snow. Also, if you look at the outline of the planet up close. It does not appear smoothly round but rather like a geodesic sphere.
Oh, and the half of the planet that is black is be continually coated with whatever it is that makes it black.
Others have said this moon could be a giant alien craft. While I think that is unlikely, if it was I would bet you would be able to generate a significant about of power because of the temp diferences between the dark half and the light half. It would be cheap, continual, plentiful, safe energy.
Anyway, just a thought