I love the retro feeling you managed to capture here - the colour palette and design really harkens to a classic era of science fiction artwork that I have always really enjoyed. I do think you could have incorporated the rock photo a little more into the image, as there is a noticeable contrast between your own painting and the photo (the black details, in particular, should have been removed or recoloured), but despite this, I think the image still works quite nicely. I really love your use of the pale pinks and purples in the sky, set against the stronger tones of the foreground. Your design reminds me a little of some of the stuff in the last Star Trek film, which had great art direction, so that’s a good thing.
A bit more work would have improved this, and perhaps you may still decide to work on the rock a little more, but I like your piece anyway simply because of the classic retro feel. I can totally imagine this as a cover to a 1950’s sci fi epic that no-one has ever heard of.