In the main menu screen, with the rotating Mars model, the shadows cast by the satellites are vastly oversized (spanning probably 100km or so of the planet's surface). I realise that they are modelled oversized in order to make them visible, but the shadows make that a bit obvious. The shadow casting is a good idea - gives a nice sense of depth - but perhaps they could be made smaller; a few pixels - enough to be noticeable without being obviously oversized?
Very much just a personal aesthetic opinion, of course, and you may well have already tried that and decided it looks better the way it is.