Yeah, that's very obvious now. Strange. Maybe it's because of the distance? But it shouldn't be like that.
Btw. something else I noticed, your detail setting is 0.8, which is pretty high (especially for animation I would think). Even for stills I mostly use 0.5, which is very good already. Especially when a lot of the actual planet is covered by objects, it needn't be that high, IMO.