It has to be LV-426....and that ship is the derelict...

Here is my thoughts on why the planet they are on is LV-426/Acheron. The planetoid has a molten lava base, when it was visited by the nostromo. So who is to say that the planet in the time after the events of the Prometheus mission didn't under go severe geographic change? Perhaps certain events during the Prometheus mission caused those changes to happen. Maybe a self destruct sequence was activated to destroy where the derelict was stationed? Causing the faults in the area to have massive quakes, thus having the molten lava come to the surface making the land we see in Alien and Aliens? Constant eruptions on the planet and or in that area could cause what we see in Alien. The eruptions would deplete the atmosphere to the point it wouldn't be breathable to humans. As for some people saying that the ship trying to escape is NOT the derelict, doesn't make sense. I would see no viable reason for Ridley Scott to move away from the story of the derelict and LV-426. Those two things together would just mess up future events. Why would some people even want the movie to be on a different planet? I have always wanted to know more about the derelict and LV-426, that for me was one of the main reasons I watched the movies. Those two things themselves are what keeps bringing me back. Of course the space jockey, that is a no brainer. Well thanks for reading the rant.