Nice showcase of the planetary clouds. A lot of aliasing and/or noise though. There could be a number of reasons for this, and without knowing the render settings it's hard to say. AA is least likely to be responsible since clouds should alias fairly easily, but if it's really low (e.g. 3) then upping that could help. Other possible culprits are needing more samples in the cloud layer(s), or the Cloud Acceleration Cache (try turning it off if it's on for any layers, especially those with small clouds).
Would love to hear feedback on whether any of these suggestions work, if you try them.
- Oshyan