The moon curve looks rather blocky, you should stretch out the AA some more. I also think you could add a bit of AA to the Earth.
An edit:
I'd also consider framing the astronaut against a crater or something, so that they don't blend into the moon's surface as much.
I think the craters are a bit distracting, I'd have them use just the light grey. Then, perhaps you could use the dark grey on the astronaut so that they can stand out better.
Here's an edit with all of these suggestions: