Space Jocky in Alien doesn't have to be a Prometheus crewmember

In my opinion, the concept of the SJ in Alien seemed more a fossil or something ancient, eons old. It doesn't seem to follow that in Prometheus a crew member will turn into anything, or transform into something that is the chair/space jockey. Suit or no suit, it just does't jive in the time line happening 30 years before Alien, and I really hope time travel has NO place in this movie concept. It will ruin it. But... the ship in Aliens doesn't have to be the same ship in Prometheus either. Lots of assumptions made in that direction. The derelict ship in Alien could be another ship entirely meant for another purpose, teraforming whatever, and met its demise however it did, and either brought the alien "stuff" to LV-42whatever, or simply have crashed and met this new alien (xeno) on its home planet. Perhaps in this universe the humans find several planets with these derelict craft? Prometheus is the "first contact" and with that discovery we get greedy and start combing the universe for other seed planets, technology and lifeforms. The evil corporation keeps much of these discoveries secret after what it learns through the Prometheus plot, and finds the "second contact" on LV-427. Something clearly went wrong on this planet for the SJ. In Alien the planet appears desolate, the ship appears crashed. There is a malfunction of the SJ seed craft, teraforming doesn't begin. Or perhaps the xeno life form malfunctions in its design. Maybe the Xeno did what it was supposed to do, wipe everything on the planet out, only the SJ died and couldn't seed the planet after the xeno served its purpose. Personally, I've always thought the Xenomorph life form is engineered. I like the theory that the Xenomorph on planet LV is the bio-mech evolved for that particular planet. Humans are the bio-mech evolved for earth. We were not necessarily supposed to meet each other, nor were we meant to have whatever technology is behind the Xeno-bio-mech DNA morphing goop. Prometheus will touch on some of that connection, but as Ridley himself says, "its a much bigger story". I've always been scared, uncomfortable, disgusted, by the Alien concept in these movies which is why I'm so fascinated by it. Add into it a sort of sexual overtone, and its even more uncomfortable. A few times per year I have dreams about running away from these Xeno, sometimes I'm armed, sometimes I'm not. Sometimes I have a motion detector. Sometimes I get turned into one of the creatures. In all cases I'm scared as hell!