You've got the colors quite nicely :-)
I suggest you leave more room for the gradient of near and far color of the distance shader, so that the clouds would begin less abrupt.
Also try reducing the fractal noise amount and cloud roughness.
The crater is too smooth I think. Why not add a nice rim shader to give the outer rim some rough displacements?
Lastly, the flat space before the far mountains shoud have some shape. With it being 100% flat makes it look not well integrated with the rest of the scene. I would like to see how the image looks like with these suggestions implemented.
Regards,
Frank
