We can clearly see in the trailer that the Prometheus crashes into a Jockey ship. The Jockey ship crashes on a flat plain with a ground that opens up, seemingly near to a pyramid.
In Alien, there is no sign of a wrecked Prometheus, or a pyramid, or the flat open area where the Jockey ship crash lands in the Prometheus trailer. Both the original derelict and the Prometheus Jockey ship could indeed be on the same moon in different locations with some sort of explanation for the differences in atmospheric conditions, but it seems pretty clear that they are different ships. Clearly there is a significance for why the two Jockey ships are on or near the same moon or else the story would have just placed things in a different system altogether.