
I think I have the "Prometheus" movie figured out….
The "Alien" that we see in the original movie is actually some sort of mutated human.
The "Space Jockey" beings mutate human beings into a killing machine because they feel threatened by humans and their quest to discover/colonize/exploit the galaxy. Obviously the cylindrical vessels we see in the room with the giant "godhead" in the new preview are some sort of proto-eggs that then appear in "Alien", and the green slimy thing that Michael Fassbender pulls out of the cylinder is some sort of face hugger or some sort of parasite that enables humans to be mutated. There is a "mutant" in the teasers and trailers, you can see one of them jump towards the screen. Ridley Scott said there will be NO Xenomorphs in "Prometheus".. My guess is that there is some sort of cliffhanger or tie-in with "Alien" at the end of "Prometheus" showing the Nostromo and then their eventual contact of the end result of the events (mutated humans) in "Prometheus".
So, in "Alien", the Nostromo is actually sent to the planet by the Weyland Yutani corporation because the previous team of explorers disappear… it's not an accident or just a mysterious signal.
I came to this idea by watching the 30 second teasers and the new trailer, and also reading some interviews with Ridley Scott. One of the key things he says is how in the "franchise", only the original "Alien" that he directed is tied into "Prometheus". Jim Cameron's "Aliens" isn't, which means you can throw out the whole Queen alien thing.
edit: Sorry for the sloppy engrish... also REMEMBER the original Alien has a HUMAN skull under the dome!!!