Ideas of what is the Black Goo?

The Engineers create a terrible biological weapon, a species whose life cycle they control (what becomes the Xeno), to purge planets of all life that could threaten them (e.g. Us). But it gets out, grows out of their control and destroys them. Does the changing mural in the ampule room not suggest that the Xeno was always meant to be the end result? Or have the walls of the room merely recorded events, as the ship is obviously able to do? For me, this film answers the question of the blown out chest on the derelict on LV-426: the Engineers were transporting their weapon, it got out, it killed them all. Maybe it destroyed their civilisation, but ultimately, it was of their own making. quote from Bigbibs

I believe the black was a bio-weapon created by the Engineers to create the xenos that we see on the mural. As we all know the substance mutated the worms, Fifield and Holloway. They all had something in common, they wanted to KILL except Holloway volunteered to kill himself (so we couldn't see the true result of his fate). The substance is biological which is at a Primordial stage but it needs a host to for-fill the xeno life cycle. which is substance infects a host, then the host mates, then the female gives birth to a squid-like face-hugger. The face-hugger grows to such a size and then impregnates another host with an embryo, the embryo then bursts outta of the host's chest and is now ready to kill and harvest hosts for more xenos. Basically repeating the life cycle all over again. In the original director's cut version of Alien the xeno actually uses host to metamorph a host into an egg. but in Aliens you have a queen laying eggs. I love the mythos but Prometheus needed to be more of a realistic in terms of science than we skip this and we skip that. too many plot-hole lots of unanswered questions. What a Joke!!!

Did anyone ever consider that at least ONE SJ got away from the "outbreak"? Or at least he thought he did, but developed a bad case of heartburn and had to set down on LV-426... Not such a bad concept is it? I like it a helluva lot more than Shaw being the original Jockey. One thing about plot holes: It leaves a whole lotta room to go wherever you want in PROM2.